/*
 * Copyright 2016 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.nativescript.widgets;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.SparseIntArray;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

import androidx.annotation.IntDef;
import androidx.annotation.NonNull;
import androidx.core.view.ViewCompat;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * A layout that arranges its children in a way its attributes can be specified like the
 * CSS Flexible Box Layout Module.
 * This class extends the {@link ViewGroup} like other layout classes such as {@link LinearLayout}
 * or {@link RelativeLayout}, the attributes can be specified from a layout XML or from code.
 * <p>
 * The supported attributes that you can use are:
 * <ul>
 * <li>{@code flexDirection}</li>
 * <li>{@code flexWrap}</li>
 * <li>{@code justifyContent}</li>
 * <li>{@code alignItems}</li>
 * <li>{@code alignContent}</li>
 * <li>{@code showDivider}</li>
 * <li>{@code showDividerHorizontal}</li>
 * <li>{@code showDividerVertical}</li>
 * <li>{@code dividerDrawable}</li>
 * <li>{@code dividerDrawableHorizontal}</li>
 * <li>{@code dividerDrawableVertical}</li>
 * </ul>
 * for the FlexboxLayout.
 * <p>
 * And for the children of the FlexboxLayout, you can use:
 * <ul>
 * <li>{@code layout_order}</li>
 * <li>{@code layout_flexGrow}</li>
 * <li>{@code layout_flexShrink}</li>
 * <li>{@code layout_flexBasisPercent}</li>
 * <li>{@code layout_alignSelf}</li>
 * <li>{@code layout_minWidth}</li>
 * <li>{@code layout_minHeight}</li>
 * <li>{@code layout_maxWidth}</li>
 * <li>{@code layout_maxHeight}</li>
 * <li>{@code layout_wrapBefore}</li>
 * </ul>
 */
public class FlexboxLayout extends LayoutBase {

	@IntDef({FLEX_DIRECTION_ROW, FLEX_DIRECTION_ROW_REVERSE, FLEX_DIRECTION_COLUMN,
		FLEX_DIRECTION_COLUMN_REVERSE})
	@Retention(RetentionPolicy.SOURCE)
	public @interface FlexDirection {

	}

	public static final int FLEX_DIRECTION_ROW = 0;

	public static final int FLEX_DIRECTION_ROW_REVERSE = 1;

	public static final int FLEX_DIRECTION_COLUMN = 2;

	public static final int FLEX_DIRECTION_COLUMN_REVERSE = 3;

	/**
	 * The direction children items are placed inside the Flexbox layout, it determines the
	 * direction of the main axis (and the cross axis, perpendicular to the main axis).
	 * <ul>
	 * <li>
	 * {@link #FLEX_DIRECTION_ROW}: Main axis direction -> horizontal. Main start to
	 * main end -> Left to right (in LTR languages).
	 * Cross start to cross end -> Top to bottom
	 * </li>
	 * <li>
	 * {@link #FLEX_DIRECTION_ROW_REVERSE}: Main axis direction -> horizontal. Main start
	 * to main end -> Right to left (in LTR languages). Cross start to cross end ->
	 * Top to bottom.
	 * </li>
	 * <li>
	 * {@link #FLEX_DIRECTION_COLUMN}: Main axis direction -> vertical. Main start
	 * to main end -> Top to bottom. Cross start to cross end ->
	 * Left to right (In LTR languages).
	 * </li>
	 * <li>
	 * {@link #FLEX_DIRECTION_COLUMN_REVERSE}: Main axis direction -> vertical. Main start
	 * to main end -> Bottom to top. Cross start to cross end -> Left to right
	 * (In LTR languages)
	 * </li>
	 * </ul>
	 * The default value is {@link #FLEX_DIRECTION_ROW}.
	 */
	private int mFlexDirection = FLEX_DIRECTION_ROW;


	@IntDef({FLEX_WRAP_NOWRAP, FLEX_WRAP_WRAP, FLEX_WRAP_WRAP_REVERSE})
	@Retention(RetentionPolicy.SOURCE)
	public @interface FlexWrap {

	}

	public static final int FLEX_WRAP_NOWRAP = 0;

	public static final int FLEX_WRAP_WRAP = 1;

	public static final int FLEX_WRAP_WRAP_REVERSE = 2;

	/**
	 * This attribute controls whether the flex container is single-line or multi-line, and the
	 * direction of the cross axis.
	 * <ul>
	 * <li>{@link #FLEX_WRAP_NOWRAP}: The flex container is single-line.</li>
	 * <li>{@link #FLEX_WRAP_WRAP}: The flex container is multi-line.</li>
	 * <li>{@link #FLEX_WRAP_WRAP_REVERSE}: The flex container is multi-line. The direction of the
	 * cross axis is opposed to the direction as the {@link #FLEX_WRAP_WRAP}</li>
	 * </ul>
	 * The default value is {@link #FLEX_WRAP_NOWRAP}.
	 */
	private int mFlexWrap = FLEX_WRAP_NOWRAP;


	@IntDef({JUSTIFY_CONTENT_FLEX_START, JUSTIFY_CONTENT_FLEX_END, JUSTIFY_CONTENT_CENTER,
		JUSTIFY_CONTENT_SPACE_BETWEEN, JUSTIFY_CONTENT_SPACE_AROUND})
	@Retention(RetentionPolicy.SOURCE)
	public @interface JustifyContent {

	}

	public static final int JUSTIFY_CONTENT_FLEX_START = 0;

	public static final int JUSTIFY_CONTENT_FLEX_END = 1;

	public static final int JUSTIFY_CONTENT_CENTER = 2;

	public static final int JUSTIFY_CONTENT_SPACE_BETWEEN = 3;

	public static final int JUSTIFY_CONTENT_SPACE_AROUND = 4;

	/**
	 * This attribute controls the alignment along the main axis.
	 * The default value is {@link #JUSTIFY_CONTENT_FLEX_START}.
	 */
	private int mJustifyContent = JUSTIFY_CONTENT_FLEX_START;


	@IntDef({ALIGN_ITEMS_FLEX_START, ALIGN_ITEMS_FLEX_END, ALIGN_ITEMS_CENTER,
		ALIGN_ITEMS_BASELINE, ALIGN_ITEMS_STRETCH})
	@Retention(RetentionPolicy.SOURCE)
	public @interface AlignItems {

	}

	public static final int ALIGN_ITEMS_FLEX_START = 0;

	public static final int ALIGN_ITEMS_FLEX_END = 1;

	public static final int ALIGN_ITEMS_CENTER = 2;

	public static final int ALIGN_ITEMS_BASELINE = 3;

	public static final int ALIGN_ITEMS_STRETCH = 4;

	/**
	 * This attribute controls the alignment along the cross axis.
	 * The default value is {@link #ALIGN_ITEMS_STRETCH}.
	 */
	private int mAlignItems = ALIGN_ITEMS_STRETCH;


	@IntDef({ALIGN_CONTENT_FLEX_START, ALIGN_CONTENT_FLEX_END, ALIGN_CONTENT_CENTER,
		ALIGN_CONTENT_SPACE_BETWEEN, ALIGN_CONTENT_SPACE_AROUND, ALIGN_CONTENT_STRETCH})
	@Retention(RetentionPolicy.SOURCE)
	public @interface AlignContent {

	}

	public static final int ALIGN_CONTENT_FLEX_START = 0;

	public static final int ALIGN_CONTENT_FLEX_END = 1;

	public static final int ALIGN_CONTENT_CENTER = 2;

	public static final int ALIGN_CONTENT_SPACE_BETWEEN = 3;

	public static final int ALIGN_CONTENT_SPACE_AROUND = 4;

	public static final int ALIGN_CONTENT_STRETCH = 5;

	/**
	 * This attribute controls the alignment of the flex lines in the flex container.
	 * The default value is {@link #ALIGN_CONTENT_STRETCH}.
	 */
	private int mAlignContent = ALIGN_CONTENT_STRETCH;

	/**
	 * The int definition to be used as the arguments for the {@link #setShowDivider(int)},
	 * {@link #setShowDividerHorizontal(int)} or {@link #setShowDividerVertical(int)}.
	 * One or more of the values (such as
	 * {@link #SHOW_DIVIDER_BEGINNING} | {@link #SHOW_DIVIDER_MIDDLE}) can be passed to those set
	 * methods.
	 */
	@IntDef(flag = true,
		value = {
			SHOW_DIVIDER_NONE,
			SHOW_DIVIDER_BEGINNING,
			SHOW_DIVIDER_MIDDLE,
			SHOW_DIVIDER_END
		})
	@Retention(RetentionPolicy.SOURCE)
	public @interface DividerMode {

	}

	/**
	 * Constant to how no dividers
	 */
	public static final int SHOW_DIVIDER_NONE = 0;

	/**
	 * Constant to show a divider at the beginning of the flex lines (or flex items).
	 */
	public static final int SHOW_DIVIDER_BEGINNING = 1;

	/**
	 * Constant to show dividers between flex lines or flex items.
	 */
	public static final int SHOW_DIVIDER_MIDDLE = 1 << 1;

	/**
	 * Constant to show a divider at the end of the flex lines or flex items.
	 */
	public static final int SHOW_DIVIDER_END = 1 << 2;

	/**
	 * The drawable to be drawn for the horizontal dividers.
	 */
	private Drawable mDividerDrawableHorizontal;

	/**
	 * The drawable to be drawn for the vertical dividers.
	 */
	private Drawable mDividerDrawableVertical;

	/**
	 * Indicates the divider mode for the {@link #mDividerDrawableHorizontal}. The value needs to
	 * be the combination of the value of {@link #SHOW_DIVIDER_NONE},
	 * {@link #SHOW_DIVIDER_BEGINNING}, {@link #SHOW_DIVIDER_MIDDLE} and {@link #SHOW_DIVIDER_END}
	 */
	private int mShowDividerHorizontal;

	/**
	 * Indicates the divider mode for the {@link #mDividerDrawableVertical}. The value needs to
	 * be the combination of the value of {@link #SHOW_DIVIDER_NONE},
	 * {@link #SHOW_DIVIDER_BEGINNING}, {@link #SHOW_DIVIDER_MIDDLE} and {@link #SHOW_DIVIDER_END}
	 */
	private int mShowDividerVertical;

	/**
	 * The height of the {@link #mDividerDrawableHorizontal}.
	 */
	private int mDividerHorizontalHeight;

	/**
	 * The width of the {@link #mDividerDrawableVertical}.
	 */
	private int mDividerVerticalWidth;

	/**
	 * Holds reordered indices, which {@link LayoutParams#order} parameters are taken into account
	 */
	private int[] mReorderedIndices;

	/**
	 * Caches the {@link LayoutParams#order} attributes for children views.
	 * Key: the index of the view ({@link #mReorderedIndices} isn't taken into account)
	 * Value: the value for the order attribute
	 */
	private SparseIntArray mOrderCache;

	private List<FlexLine> mFlexLines = new ArrayList<>();

	/**
	 * Holds the 'frozen' state of children during measure. If a view is frozen it will no longer
	 * expand or shrink regardless of flexGrow/flexShrink. Items are indexed by the child's
	 * reordered index.
	 */
	private boolean[] mChildrenFrozen;

	public FlexboxLayout(Context context) {
		this(context, null);
	}

	public FlexboxLayout(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

	public FlexboxLayout(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);

		// NOTE: We do not support android xml.
		// TypedArray a = context.obtainStyledAttributes(
		//         attrs, R.styleable.FlexboxLayout, defStyleAttr, 0);
		// mFlexDirection = a.getInt(R.styleable.FlexboxLayout_flexDirection, FLEX_DIRECTION_ROW);
		// mFlexWrap = a.getInt(R.styleable.FlexboxLayout_flexWrap, FLEX_WRAP_NOWRAP);
		// mJustifyContent = a
		//         .getInt(R.styleable.FlexboxLayout_justifyContent, JUSTIFY_CONTENT_FLEX_START);
		// mAlignItems = a.getInt(R.styleable.FlexboxLayout_alignItems, ALIGN_ITEMS_STRETCH);
		// mAlignContent = a.getInt(R.styleable.FlexboxLayout_alignContent, ALIGN_CONTENT_STRETCH);
		// Drawable drawable = a.getDrawable(R.styleable.FlexboxLayout_dividerDrawable);
		// if (drawable != null) {
		//     setDividerDrawableHorizontal(drawable);
		//     setDividerDrawableVertical(drawable);
		// }
		// Drawable drawableHorizontal = a
		//         .getDrawable(R.styleable.FlexboxLayout_dividerDrawableHorizontal);
		// if (drawableHorizontal != null) {
		//     setDividerDrawableHorizontal(drawableHorizontal);
		// }
		// Drawable drawableVertical = a
		//         .getDrawable(R.styleable.FlexboxLayout_dividerDrawableVertical);
		// if (drawableVertical != null) {
		//     setDividerDrawableVertical(drawableVertical);
		// }
		// int dividerMode = a.getInt(R.styleable.FlexboxLayout_showDivider, SHOW_DIVIDER_NONE);
		// if (dividerMode != SHOW_DIVIDER_NONE) {
		//     mShowDividerVertical = dividerMode;
		//     mShowDividerHorizontal = dividerMode;
		// }
		// int dividerModeVertical = a
		//         .getInt(R.styleable.FlexboxLayout_showDividerVertical, SHOW_DIVIDER_NONE);
		// if (dividerModeVertical != SHOW_DIVIDER_NONE) {
		//     mShowDividerVertical = dividerModeVertical;
		// }
		// int dividerModeHorizontal = a
		//         .getInt(R.styleable.FlexboxLayout_showDividerHorizontal, SHOW_DIVIDER_NONE);
		// if (dividerModeHorizontal != SHOW_DIVIDER_NONE) {
		//     mShowDividerHorizontal = dividerModeHorizontal;
		// }
		// a.recycle();
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		CommonLayoutParams.adjustChildrenLayoutParams(this, widthMeasureSpec, heightMeasureSpec);

		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		if (isOrderChangedFromLastMeasurement()) {
			mReorderedIndices = createReorderedIndices();
		}
		if (mChildrenFrozen == null || mChildrenFrozen.length < getChildCount()) {
			mChildrenFrozen = new boolean[getChildCount()];
		}

		// TODO: Only calculate the children views which are affected from the last measure.

		switch (mFlexDirection) {
			case FLEX_DIRECTION_ROW: // Intentional fall through
			case FLEX_DIRECTION_ROW_REVERSE:
				measureHorizontal(widthMeasureSpec, heightMeasureSpec);
				break;
			case FLEX_DIRECTION_COLUMN: // Intentional fall through
			case FLEX_DIRECTION_COLUMN_REVERSE:
				measureVertical(widthMeasureSpec, heightMeasureSpec);
				break;
			default:
				throw new IllegalStateException(
					"Invalid value for the flex direction is set: " + mFlexDirection);
		}

		Arrays.fill(mChildrenFrozen, false);
	}

	/**
	 * Returns a View, which is reordered by taking {@link LayoutParams#order} parameters
	 * into account.
	 *
	 * @param index the index of the view
	 * @return the reordered view, which {@link LayoutParams@order} is taken into account.
	 * If the index is negative or out of bounds of the number of contained views,
	 * returns {@code null}.
	 */
	public View getReorderedChildAt(int index) {
		if (index < 0 || index >= mReorderedIndices.length) {
			return null;
		}
		return getChildAt(mReorderedIndices[index]);
	}

	@Override
	public void addView(View child, int index, ViewGroup.LayoutParams params) {
		// Create an array for the reordered indices before the View is added in the parent
		// ViewGroup since otherwise reordered indices won't be in effect before the
		// FlexboxLayout's onMeasure is called.
		// Because requestLayout is requested in the super.addView method.
		mReorderedIndices = createReorderedIndices(child, index, params);
		super.addView(child, index, params);
	}

	/**
	 * Create an array, which indicates the reordered indices that {@link LayoutParams#order}
	 * attributes are taken into account. This method takes a View before that is added as the
	 * parent ViewGroup's children.
	 *
	 * @param viewBeforeAdded          the View instance before added to the array of children
	 *                                 Views of the parent ViewGroup
	 * @param indexForViewBeforeAdded  the index for the View before added to the array of the
	 *                                 parent ViewGroup
	 * @param paramsForViewBeforeAdded the layout parameters for the View before added to the array
	 *                                 of the parent ViewGroup
	 * @return an array which have the reordered indices
	 */
	private int[] createReorderedIndices(View viewBeforeAdded, int indexForViewBeforeAdded,
																			 ViewGroup.LayoutParams paramsForViewBeforeAdded) {
		int childCount = getChildCount();
		List<Order> orders = createOrders(childCount);
		Order orderForViewToBeAdded = new Order();
		if (viewBeforeAdded != null
			&& paramsForViewBeforeAdded instanceof FlexboxLayout.LayoutParams) {
			orderForViewToBeAdded.order = ((LayoutParams) paramsForViewBeforeAdded).order;
		} else {
			orderForViewToBeAdded.order = LayoutParams.ORDER_DEFAULT;
		}

		if (indexForViewBeforeAdded == -1 || indexForViewBeforeAdded == childCount) {
			orderForViewToBeAdded.index = childCount;
		} else if (indexForViewBeforeAdded < getChildCount()) {
			orderForViewToBeAdded.index = indexForViewBeforeAdded;
			for (int i = indexForViewBeforeAdded; i < childCount; i++) {
				orders.get(i).index++;
			}
		} else {
			// This path is not expected since OutOfBoundException will be thrown in the ViewGroup
			// But setting the index for fail-safe
			orderForViewToBeAdded.index = childCount;
		}
		orders.add(orderForViewToBeAdded);

		return sortOrdersIntoReorderedIndices(childCount + 1, orders);
	}

	/**
	 * Create an array, which indicates the reordered indices that {@link LayoutParams#order}
	 * attributes are taken into account.
	 *
	 * @return @return an array which have the reordered indices
	 */
	private int[] createReorderedIndices() {
		int childCount = getChildCount();
		List<Order> orders = createOrders(childCount);
		return sortOrdersIntoReorderedIndices(childCount, orders);
	}

	private int[] sortOrdersIntoReorderedIndices(int childCount, List<Order> orders) {
		Collections.sort(orders);
		if (mOrderCache == null) {
			mOrderCache = new SparseIntArray(childCount);
		}
		mOrderCache.clear();
		int[] reorderedIndices = new int[childCount];
		int i = 0;
		for (Order order : orders) {
			reorderedIndices[i] = order.index;
			mOrderCache.append(i, order.order);
			i++;
		}
		return reorderedIndices;
	}

	@NonNull
	private List<Order> createOrders(int childCount) {
		List<Order> orders = new ArrayList<>();
		for (int i = 0; i < childCount; i++) {
			View child = getChildAt(i);
			LayoutParams params = (LayoutParams) child.getLayoutParams();
			Order order = new Order();
			order.order = params.order;
			order.index = i;
			orders.add(order);
		}
		return orders;
	}

	/**
	 * Returns if any of the children's {@link LayoutParams#order} attributes are changed
	 * from the last measurement.
	 *
	 * @return {@code true} if changed from the last measurement, {@code false} otherwise.
	 */
	private boolean isOrderChangedFromLastMeasurement() {
		int childCount = getChildCount();
		if (mOrderCache == null) {
			mOrderCache = new SparseIntArray(childCount);
		}
		if (mOrderCache.size() != childCount) {
			return true;
		}
		for (int i = 0; i < childCount; i++) {
			View view = getChildAt(i);
			if (view == null) {
				continue;
			}
			LayoutParams lp = (LayoutParams) view.getLayoutParams();
			if (lp.order != mOrderCache.get(i)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Invalidates the cache of the orders so that they are recalculated.
	 */
	public void invalidateOrdersCache() {
		if (this.mOrderCache != null) {
			this.mOrderCache.clear();
		}
	}

	/**
	 * Sub method for {@link #onMeasure(int, int)}, when the main axis direction is horizontal
	 * (either left to right or right to left).
	 *
	 * @param widthMeasureSpec  horizontal space requirements as imposed by the parent
	 * @param heightMeasureSpec vertical space requirements as imposed by the parent
	 * @see #onMeasure(int, int)
	 * @see #setFlexDirection(int)
	 * @see #setFlexWrap(int)
	 * @see #setAlignItems(int)
	 * @see #setAlignContent(int)
	 */
	private void measureHorizontal(int widthMeasureSpec, int heightMeasureSpec) {
		int widthMode = MeasureSpec.getMode(widthMeasureSpec);
		int widthSize = MeasureSpec.getSize(widthMeasureSpec);
		int childState = 0;

		mFlexLines.clear();

		// Determine how many flex lines are needed in this layout by measuring each child.
		// (Expand or shrink the view depending on the flexGrow and flexShrink attributes in a later
		// loop)
		{
			int childCount = getChildCount();
			int paddingStart = ViewCompat.getPaddingStart(this);
			int paddingEnd = ViewCompat.getPaddingEnd(this);
			int largestHeightInRow = Integer.MIN_VALUE;
			FlexLine flexLine = new FlexLine();

			// The index of the view in a same flex line.
			int indexInFlexLine = 0;
			flexLine.mMainSize = paddingStart + paddingEnd;
			for (int i = 0; i < childCount; i++) {
				View child = getReorderedChildAt(i);
				if (child == null) {
					addFlexLineIfLastFlexItem(i, childCount, flexLine);
					continue;
				} else if (child.getVisibility() == View.GONE) {
					flexLine.mItemCount++;
					flexLine.mGoneItemCount++;
					addFlexLineIfLastFlexItem(i, childCount, flexLine);
					continue;
				}

				FlexboxLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams();
				if (lp.alignSelf == LayoutParams.ALIGN_SELF_STRETCH) {
					flexLine.mIndicesAlignSelfStretch.add(i);
				}

				int childWidth = lp.width;
				if (lp.flexBasisPercent != LayoutParams.FLEX_BASIS_PERCENT_DEFAULT
					&& widthMode == MeasureSpec.EXACTLY) {
					childWidth = Math.round(widthSize * lp.flexBasisPercent);
					// Use the dimension from the layout_width attribute if the widthMode is not
					// MeasureSpec.EXACTLY even if any fraction value is set to
					// layout_flexBasisPercent.
					// There are likely quite few use cases where assigning any fraction values
					// with widthMode is not MeasureSpec.EXACTLY (e.g. FlexboxLayout's layout_width
					// is set to wrap_content)
				}
				int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,
					getPaddingLeft() + getPaddingRight() + lp.leftMargin
						+ lp.rightMargin, childWidth < 0 ? LayoutParams.WRAP_CONTENT : childWidth);
				int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec,
					getPaddingTop() + getPaddingBottom() + lp.topMargin
						+ lp.bottomMargin, lp.height < 0 ? LayoutParams.WRAP_CONTENT : lp.height);

				child.measure(childWidthMeasureSpec, childHeightMeasureSpec);

				// Check the size constraint after the first measurement for the child
				// To prevent the child's width/height violate the size constraints imposed by the
				// {@link LayoutParams#minWidth}, {@link LayoutParams#minHeight},
				// {@link LayoutParams#maxWidth} and {@link LayoutParams#maxHeight} attributes.
				// E.g. When the child's layout_width is wrap_content the measured width may be
				// less than the min width after the first measurement.
				checkSizeConstraints(child);

				childState = View.combineMeasuredStates(childState, child.getMeasuredState());
				largestHeightInRow = Math.max(largestHeightInRow,
					child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin);

				if (isWrapRequired(widthMode, widthSize, flexLine.mMainSize,
					child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin, lp,
					i, indexInFlexLine)) {
					if (flexLine.getLayoutVisibleItemCount() > 0) {
						addFlexLine(flexLine);
					}

					flexLine = new FlexLine();
					flexLine.mItemCount = 1;
					flexLine.mMainSize = paddingStart + paddingEnd;
					largestHeightInRow = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
					indexInFlexLine = 0;
				} else {
					flexLine.mItemCount++;
					indexInFlexLine++;
				}
				flexLine.mMainSize += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
				flexLine.mTotalFlexGrow += lp.flexGrow;
				flexLine.mTotalFlexShrink += lp.flexShrink;
				// Temporarily set the cross axis length as the largest child in the row
				// Expand along the cross axis depending on the mAlignContent property if needed
				// later
				flexLine.mCrossSize = Math.max(flexLine.mCrossSize, largestHeightInRow);

				// Check if the beginning or middle divider is required for the flex item
				if (hasDividerBeforeChildAtAlongMainAxis(i, indexInFlexLine)) {
					flexLine.mMainSize += mDividerVerticalWidth;
					flexLine.mDividerLengthInMainSize += mDividerVerticalWidth;
				}

				if (mFlexWrap != FLEX_WRAP_WRAP_REVERSE) {
					flexLine.mMaxBaseline = Math
						.max(flexLine.mMaxBaseline, child.getBaseline() + lp.topMargin);
				} else {
					// if the flex wrap property is FLEX_WRAP_WRAP_REVERSE, calculate the
					// baseline as the distance from the cross end and the baseline
					// since the cross size calculation is based on the distance from the cross end
					flexLine.mMaxBaseline = Math
						.max(flexLine.mMaxBaseline,
							child.getMeasuredHeight() - child.getBaseline()
								+ lp.bottomMargin);
				}
				addFlexLineIfLastFlexItem(i, childCount, flexLine);
			}
		}

		determineMainSize(mFlexDirection, widthMeasureSpec, heightMeasureSpec);

		// TODO: Consider the case any individual child's alignSelf is set to ALIGN_SELF_BASELINE
		if (mAlignItems == ALIGN_ITEMS_BASELINE) {
			int viewIndex = 0;
			for (FlexLine flexLine : mFlexLines) {
				// The largest height value that also take the baseline shift into account
				int largestHeightInLine = Integer.MIN_VALUE;
				for (int i = viewIndex; i < viewIndex + flexLine.mItemCount; i++) {
					View child = getReorderedChildAt(i);
					LayoutParams lp = (LayoutParams) child.getLayoutParams();
					
					if (mFlexWrap != FLEX_WRAP_WRAP_REVERSE) {
						int marginTop = flexLine.mMaxBaseline - child.getBaseline();
						marginTop = Math.max(marginTop, lp.topMargin);
						largestHeightInLine = Math.max(largestHeightInLine,
							child.getMeasuredHeight() + marginTop + lp.bottomMargin);
					} else {
						int marginBottom = flexLine.mMaxBaseline - child.getMeasuredHeight() +
							child.getBaseline();
						marginBottom = Math.max(marginBottom, lp.bottomMargin);
						largestHeightInLine = Math.max(largestHeightInLine,
							child.getMeasuredHeight() + lp.topMargin + marginBottom);
					}
				}
				flexLine.mCrossSize = largestHeightInLine;
				viewIndex += flexLine.mItemCount;
			}
		}

		determineCrossSize(mFlexDirection, widthMeasureSpec, heightMeasureSpec,
			getPaddingTop() + getPaddingBottom());
		// Now cross size for each flex line is determined.
		// Expand the views if alignItems (or alignSelf in each child view) is set to stretch
		stretchViews(mFlexDirection, mAlignItems);
		setMeasuredDimensionForFlex(mFlexDirection, widthMeasureSpec, heightMeasureSpec,
			childState);
	}

	/**
	 * Sub method for {@link #onMeasure(int, int)} when the main axis direction is vertical
	 * (either from top to bottom or bottom to top).
	 *
	 * @param widthMeasureSpec  horizontal space requirements as imposed by the parent
	 * @param heightMeasureSpec vertical space requirements as imposed by the parent
	 * @see #onMeasure(int, int)
	 * @see #setFlexDirection(int)
	 * @see #setFlexWrap(int)
	 * @see #setAlignItems(int)
	 * @see #setAlignContent(int)
	 */
	private void measureVertical(int widthMeasureSpec, int heightMeasureSpec) {
		int heightMode = MeasureSpec.getMode(heightMeasureSpec);
		int heightSize = MeasureSpec.getSize(heightMeasureSpec);
		int childState = 0;

		mFlexLines.clear();

		// Determine how many flex lines are needed in this layout by measuring each child.
		// (Expand or shrink the view depending on the flexGrow and flexShrink attributes in a later
		// loop)
		int childCount = getChildCount();
		int paddingTop = getPaddingTop();
		int paddingBottom = getPaddingBottom();
		int largestWidthInColumn = Integer.MIN_VALUE;
		FlexLine flexLine = new FlexLine();
		flexLine.mMainSize = paddingTop + paddingBottom;
		// The index of the view in a same flex line.
		int indexInFlexLine = 0;
		for (int i = 0; i < childCount; i++) {
			View child = getReorderedChildAt(i);
			if (child == null) {
				addFlexLineIfLastFlexItem(i, childCount, flexLine);
				continue;
			} else if (child.getVisibility() == View.GONE) {
				flexLine.mItemCount++;
				flexLine.mGoneItemCount++;
				addFlexLineIfLastFlexItem(i, childCount, flexLine);
				continue;
			}

			FlexboxLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams();
			if (lp.alignSelf == LayoutParams.ALIGN_SELF_STRETCH) {
				flexLine.mIndicesAlignSelfStretch.add(i);
			}

			int childHeight = lp.height;
			if (lp.flexBasisPercent != LayoutParams.FLEX_BASIS_PERCENT_DEFAULT
				&& heightMode == MeasureSpec.EXACTLY) {
				childHeight = Math.round(heightSize * lp.flexBasisPercent);
				// Use the dimension from the layout_height attribute if the heightMode is not
				// MeasureSpec.EXACTLY even if any fraction value is set to layout_flexBasisPercent.
				// There are likely quite few use cases where assigning any fraction values
				// with heightMode is not MeasureSpec.EXACTLY (e.g. FlexboxLayout's layout_height
				// is set to wrap_content)
			}

			int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,
				getPaddingLeft() + getPaddingRight() + lp.leftMargin
					+ lp.rightMargin, lp.width < 0 ? LayoutParams.WRAP_CONTENT : lp.width);
			int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec,
				getPaddingTop() + getPaddingBottom() + lp.topMargin
					+ lp.bottomMargin, childHeight < 0 ? LayoutParams.WRAP_CONTENT : childHeight);

			child.measure(childWidthMeasureSpec, childHeightMeasureSpec);

			// Check the size constraint after the first measurement for the child
			// To prevent the child's width/height violate the size constraints imposed by the
			// {@link LayoutParams#minWidth}, {@link LayoutParams#minHeight},
			// {@link LayoutParams#maxWidth} and {@link LayoutParams#maxHeight} attributes.
			// E.g. When the child's layout_height is wrap_content the measured height may be
			// less than the min height after the first measurement.
			checkSizeConstraints(child);

			childState = View
				.combineMeasuredStates(childState, child.getMeasuredState());
			largestWidthInColumn = Math.max(largestWidthInColumn,
				child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);

			if (isWrapRequired(heightMode, heightSize, flexLine.mMainSize,
				child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin, lp,
				i, indexInFlexLine)) {
				if (flexLine.getLayoutVisibleItemCount() > 0) {
					addFlexLine(flexLine);
				}

				flexLine = new FlexLine();
				flexLine.mItemCount = 1;
				flexLine.mMainSize = paddingTop + paddingBottom;
				largestWidthInColumn = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
				indexInFlexLine = 0;
			} else {
				flexLine.mItemCount++;
				indexInFlexLine++;
			}
			flexLine.mMainSize += child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
			flexLine.mTotalFlexGrow += lp.flexGrow;
			flexLine.mTotalFlexShrink += lp.flexShrink;
			// Temporarily set the cross axis length as the largest child width in the column
			// Expand along the cross axis depending on the mAlignContent property if needed
			// later
			flexLine.mCrossSize = Math.max(flexLine.mCrossSize, largestWidthInColumn);

			if (hasDividerBeforeChildAtAlongMainAxis(i, indexInFlexLine)) {
				flexLine.mMainSize += mDividerHorizontalHeight;
			}
			addFlexLineIfLastFlexItem(i, childCount, flexLine);
		}

		determineMainSize(mFlexDirection, widthMeasureSpec, heightMeasureSpec);
		determineCrossSize(mFlexDirection, widthMeasureSpec, heightMeasureSpec,
			getPaddingLeft() + getPaddingRight());
		// Now cross size for each flex line is determined.
		// Expand the views if alignItems (or alignSelf in each child view) is set to stretch
		stretchViews(mFlexDirection, mAlignItems);
		setMeasuredDimensionForFlex(mFlexDirection, widthMeasureSpec, heightMeasureSpec,
			childState);
	}

	/**
	 * Checks if the view's width/height don't violate the minimum/maximum size constraints imposed
	 * by the {@link LayoutParams#minWidth}, {@link LayoutParams#minHeight},
	 * {@link LayoutParams#maxWidth} and {@link LayoutParams#maxHeight} attributes.
	 *
	 * @param view the view to be checked
	 */
	private void checkSizeConstraints(View view) {
		boolean needsMeasure = false;
		LayoutParams lp = (LayoutParams) view.getLayoutParams();
		int childWidth = view.getMeasuredWidth();
		int childHeight = view.getMeasuredHeight();

		if (view.getMeasuredWidth() < lp.minWidth) {
			needsMeasure = true;
			childWidth = lp.minWidth;
		} else if (view.getMeasuredWidth() > lp.maxWidth) {
			needsMeasure = true;
			childWidth = lp.maxWidth;
		}

		if (childHeight < lp.minHeight) {
			needsMeasure = true;
			childHeight = lp.minHeight;
		} else if (childHeight > lp.maxHeight) {
			needsMeasure = true;
			childHeight = lp.maxHeight;
		}
		if (needsMeasure) {
			view.measure(MeasureSpec.makeMeasureSpec(childWidth, MeasureSpec.EXACTLY),
				MeasureSpec.makeMeasureSpec(childHeight, MeasureSpec.EXACTLY));
		}
	}

	private void addFlexLineIfLastFlexItem(int childIndex, int childCount, FlexLine flexLine) {
		if (childIndex == childCount - 1 && flexLine.getLayoutVisibleItemCount() != 0) {
			// Add the flex line if this item is the last item
			addFlexLine(flexLine);
		}
	}

	private void addFlexLine(FlexLine flexLine) {
		// The size of the end divider isn't added until the flexLine is added to the flex container
		// take the divider width (or height) into account when adding the flex line.
		if (isMainAxisDirectionHorizontal(mFlexDirection)) {
			if ((mShowDividerVertical & SHOW_DIVIDER_END) > 0) {
				flexLine.mMainSize += mDividerVerticalWidth;
				flexLine.mDividerLengthInMainSize += mDividerVerticalWidth;
			}
		} else {
			if ((mShowDividerHorizontal & SHOW_DIVIDER_END) > 0) {
				flexLine.mMainSize += mDividerHorizontalHeight;
				flexLine.mDividerLengthInMainSize += mDividerHorizontalHeight;
			}
		}
		mFlexLines.add(flexLine);
	}

	/**
	 * Determine the main size by expanding (shrinking if negative remaining free space is given)
	 * an individual child in each flex line if any children's flexGrow (or flexShrink if remaining
	 * space is negative) properties are set to non-zero.
	 *
	 * @param flexDirection     the value of the flex direction
	 * @param widthMeasureSpec  horizontal space requirements as imposed by the parent
	 * @param heightMeasureSpec vertical space requirements as imposed by the parent
	 * @see #setFlexDirection(int)
	 * @see #getFlexDirection()
	 */
	private void determineMainSize(@FlexDirection int flexDirection, int widthMeasureSpec,
																 int heightMeasureSpec) {
		int mainSize;
		int paddingAlongMainAxis;
		switch (flexDirection) {
			case FLEX_DIRECTION_ROW: // Intentional fall through
			case FLEX_DIRECTION_ROW_REVERSE:
				int widthMode = MeasureSpec.getMode(widthMeasureSpec);
				int widthSize = MeasureSpec.getSize(widthMeasureSpec);
				if (widthMode == MeasureSpec.EXACTLY) {
					mainSize = widthSize;
				} else {
					mainSize = getLargestMainSize();
				}
				paddingAlongMainAxis = getPaddingLeft() + getPaddingRight();
				break;
			case FLEX_DIRECTION_COLUMN: // Intentional fall through
			case FLEX_DIRECTION_COLUMN_REVERSE:
				int heightMode = MeasureSpec.getMode(heightMeasureSpec);
				int heightSize = MeasureSpec.getSize(heightMeasureSpec);
				if (heightMode == MeasureSpec.EXACTLY) {
					mainSize = heightSize;
				} else {
					mainSize = getLargestMainSize();
				}
				paddingAlongMainAxis = getPaddingTop() + getPaddingBottom();
				break;
			default:
				throw new IllegalArgumentException("Invalid flex direction: " + flexDirection);
		}

		int childIndex = 0;
		for (FlexLine flexLine : mFlexLines) {
			if (flexLine.mMainSize < mainSize) {
				childIndex = expandFlexItems(flexLine, flexDirection, mainSize,
					paddingAlongMainAxis, childIndex);
			} else {
				childIndex = shrinkFlexItems(flexLine, flexDirection, mainSize,
					paddingAlongMainAxis, childIndex);
			}
		}
	}

	/**
	 * Expand the flex items along the main axis based on the individual flexGrow attribute.
	 *
	 * @param flexLine             the flex line to which flex items belong
	 * @param flexDirection        the flexDirection value for this FlexboxLayout
	 * @param maxMainSize          the maximum main size. Expanded main size will be this size
	 * @param paddingAlongMainAxis the padding value along the main axis
	 * @param startIndex           the start index of the children views to be expanded. This index
	 *                             needs to
	 *                             be an absolute index in the flex container (FlexboxLayout),
	 *                             not the relative index in the flex line.
	 * @return the next index, the next flex line's first flex item starts from the returned index
	 * @see #getFlexDirection()
	 * @see #setFlexDirection(int)
	 * @see LayoutParams#flexGrow
	 */
	private int expandFlexItems(FlexLine flexLine, @FlexDirection int flexDirection,
															int maxMainSize, int paddingAlongMainAxis, int startIndex) {
		int childIndex = startIndex;
		if (flexLine.mTotalFlexGrow <= 0 || maxMainSize < flexLine.mMainSize) {
			childIndex += flexLine.mItemCount;
			return childIndex;
		}
		int sizeBeforeExpand = flexLine.mMainSize;
		boolean needsReExpand = false;
		float unitSpace = (maxMainSize - flexLine.mMainSize) / flexLine.mTotalFlexGrow;
		flexLine.mMainSize = paddingAlongMainAxis + flexLine.mDividerLengthInMainSize;
		float accumulatedRoundError = 0;
		for (int i = 0; i < flexLine.mItemCount; i++) {
			View child = getReorderedChildAt(childIndex);
			if (child == null) {
				continue;
			} else if (child.getVisibility() == View.GONE) {
				childIndex++;
				continue;
			}
			LayoutParams lp = (LayoutParams) child.getLayoutParams();
			if (isMainAxisDirectionHorizontal(flexDirection)) {
				// The direction of the main axis is horizontal
				if (!mChildrenFrozen[childIndex]) {
					float rawCalculatedWidth = child.getMeasuredWidth() + unitSpace * lp.flexGrow + accumulatedRoundError;
					int roundedCalculatedWidth = Math.round(rawCalculatedWidth);
					if (roundedCalculatedWidth > lp.maxWidth) {
						// This means the child can't expand beyond the value of the maxWidth attribute.
						// To adjust the flex line length to the size of maxMainSize, remaining
						// positive free space needs to be re-distributed to other flex items
						// (children views). In that case, invoke this method again with the same
						// startIndex.
						needsReExpand = true;
						roundedCalculatedWidth = lp.maxWidth;
						mChildrenFrozen[childIndex] = true;
						flexLine.mTotalFlexGrow -= lp.flexGrow;
					} else {
						accumulatedRoundError = (rawCalculatedWidth - roundedCalculatedWidth);
					}
					child.measure(MeasureSpec.makeMeasureSpec(roundedCalculatedWidth, MeasureSpec.EXACTLY),
						MeasureSpec
							.makeMeasureSpec(child.getMeasuredHeight(),
								MeasureSpec.EXACTLY));
				}
				flexLine.mMainSize += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
			} else {
				// The direction of the main axis is vertical
				if (!mChildrenFrozen[childIndex]) {
					float rawCalculatedHeight = child.getMeasuredHeight() + unitSpace * lp.flexGrow;
					int roundedCalculatedHeight = Math.round(rawCalculatedHeight);
					if (roundedCalculatedHeight > lp.maxHeight) {
						// This means the child can't expand beyond the value of the maxHeight
						// attribute.
						// To adjust the flex line length to the size of maxMainSize, remaining
						// positive free space needs to be re-distributed to other flex items
						// (children views). In that case, invoke this method again with the same
						// startIndex.
						needsReExpand = true;
						roundedCalculatedHeight = lp.maxHeight;
						mChildrenFrozen[childIndex] = true;
						flexLine.mTotalFlexGrow -= lp.flexGrow;
					} else {
						accumulatedRoundError = rawCalculatedHeight - roundedCalculatedHeight;
					}
					child.measure(MeasureSpec.makeMeasureSpec(child.getMeasuredWidth(),
						MeasureSpec.EXACTLY),
						MeasureSpec.makeMeasureSpec(roundedCalculatedHeight, MeasureSpec.EXACTLY));
				}
				flexLine.mMainSize += child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
			}
			childIndex++;
		}

		if (needsReExpand && sizeBeforeExpand != flexLine.mMainSize) {
			// Re-invoke the method with the same startIndex to distribute the positive free space
			// that wasn't fully distributed (because of maximum length constraint)
			expandFlexItems(flexLine, flexDirection, maxMainSize, paddingAlongMainAxis, startIndex);
		}
		return childIndex;
	}

	/**
	 * Shrink the flex items along the main axis based on the individual flexShrink attribute.
	 *
	 * @param flexLine             the flex line to which flex items belong
	 * @param flexDirection        the flexDirection value for this FlexboxLayout
	 * @param maxMainSize          the maximum main size. Shrank main size will be this size
	 * @param paddingAlongMainAxis the padding value along the main axis
	 * @param startIndex           the start index of the children views to be shrank. This index
	 *                             needs to
	 *                             be an absolute index in the flex container (FlexboxLayout),
	 *                             not the relative index in the flex line.
	 * @return the next index, the next flex line's first flex item starts from the returned index
	 * @see #getFlexDirection()
	 * @see #setFlexDirection(int)
	 * @see LayoutParams#flexShrink
	 */
	private int shrinkFlexItems(FlexLine flexLine, @FlexDirection int flexDirection,
															int maxMainSize, int paddingAlongMainAxis, int startIndex) {
		int childIndex = startIndex;
		int sizeBeforeShrink = flexLine.mMainSize;
		if (flexLine.mTotalFlexShrink <= 0 || maxMainSize > flexLine.mMainSize) {
			childIndex += flexLine.mItemCount;
			return childIndex;
		}
		boolean needsReShrink = false;
		float unitShrink = (flexLine.mMainSize - maxMainSize) / flexLine.mTotalFlexShrink;
		float accumulatedRoundError = 0;
		flexLine.mMainSize = paddingAlongMainAxis + flexLine.mDividerLengthInMainSize;
		for (int i = 0; i < flexLine.mItemCount; i++) {
			View child = getReorderedChildAt(childIndex);
			if (child == null) {
				continue;
			} else if (child.getVisibility() == View.GONE) {
				childIndex++;
				continue;
			}
			LayoutParams lp = (LayoutParams) child.getLayoutParams();
			if (isMainAxisDirectionHorizontal(flexDirection)) {
				// The direction of main axis is horizontal
				if (!mChildrenFrozen[childIndex]) {
					float rawCalculatedWidth = child.getMeasuredWidth() - unitShrink * lp.flexShrink + accumulatedRoundError;
					int roundedCalculatedWidth = Math.round(rawCalculatedWidth);
					if (roundedCalculatedWidth < lp.minWidth) {
						needsReShrink = true;
						roundedCalculatedWidth = lp.minWidth;
						mChildrenFrozen[childIndex] = true;
						flexLine.mTotalFlexShrink -= lp.flexShrink;
					} else {
						accumulatedRoundError = rawCalculatedWidth - roundedCalculatedWidth;
					}

					int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(roundedCalculatedWidth, MeasureSpec.EXACTLY);

					// NOTE: for controls that support internal content wrapping (e.g. TextView) reducing the width
					// might result in increased height e.g. text that could be shown on one line for larger
					// width needs to be wrapped in two when width is reduced.
					// As a result we cannot unconditionally measure with EXACTLY the current measured height
					int childHeightMeasureSpec = getChildMeasureSpec(this.getMeasuredHeightAndState(),
						getPaddingTop() + getPaddingBottom() + lp.topMargin
							+ lp.bottomMargin, lp.height < 0 ? LayoutParams.WRAP_CONTENT : lp.height);

					child.measure(childWidthMeasureSpec, childHeightMeasureSpec);

					// make sure crossSize is up-to-date as child calculated height might have increased
					flexLine.mCrossSize = Math.max(
						flexLine.mCrossSize,
						child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin
					);
				}
				flexLine.mMainSize += child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
			} else {
				// The direction of main axis is vertical
				if (!mChildrenFrozen[childIndex]) {
					float rawCalculatedHeight = child.getMeasuredHeight() - unitShrink * lp.flexShrink + accumulatedRoundError;
					int roundedCalculatedHeight = Math.round(rawCalculatedHeight);
					if (roundedCalculatedHeight < lp.minHeight) {
						needsReShrink = true;
						roundedCalculatedHeight = lp.minHeight;
						mChildrenFrozen[childIndex] = true;
						flexLine.mTotalFlexShrink -= lp.flexShrink;
					} else {
						accumulatedRoundError = rawCalculatedHeight - roundedCalculatedHeight;
					}
					child.measure(MeasureSpec.makeMeasureSpec(child.getMeasuredWidth(),
						MeasureSpec.EXACTLY),
						MeasureSpec.makeMeasureSpec(roundedCalculatedHeight, MeasureSpec.EXACTLY));
				}
				flexLine.mMainSize += child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
			}
			childIndex++;
		}

		if (needsReShrink && sizeBeforeShrink != flexLine.mMainSize) {
			// Re-invoke the method with the same startIndex to distribute the negative free space
			// that wasn't fully distributed (because some views length were not enough)
			shrinkFlexItems(flexLine, flexDirection, maxMainSize, paddingAlongMainAxis, startIndex);
		}
		return childIndex;
	}

	/**
	 * Determines the cross size (Calculate the length along the cross axis).
	 * Expand the cross size only if the height mode is MeasureSpec.EXACTLY, otherwise
	 * use the sum of cross sizes of all flex lines.
	 *
	 * @param flexDirection         the flex direction attribute
	 * @param widthMeasureSpec      horizontal space requirements as imposed by the parent
	 * @param heightMeasureSpec     vertical space requirements as imposed by the parent
	 * @param paddingAlongCrossAxis the padding value for the FlexboxLayout along the cross axis
	 * @see #getFlexDirection()
	 * @see #setFlexDirection(int)
	 * @see #getAlignContent()
	 * @see #setAlignContent(int)
	 */
	private void determineCrossSize(int flexDirection, int widthMeasureSpec,
																	int heightMeasureSpec, int paddingAlongCrossAxis) {
		// The MeasureSpec mode along the cross axis
		int mode;
		// The MeasureSpec size along the cross axis
		int size;
		switch (flexDirection) {
			case FLEX_DIRECTION_ROW: // Intentional fall through
			case FLEX_DIRECTION_ROW_REVERSE:
				mode = MeasureSpec.getMode(heightMeasureSpec);
				size = MeasureSpec.getSize(heightMeasureSpec);
				break;
			case FLEX_DIRECTION_COLUMN: // Intentional fall through
			case FLEX_DIRECTION_COLUMN_REVERSE:
				mode = MeasureSpec.getMode(widthMeasureSpec);
				size = MeasureSpec.getSize(widthMeasureSpec);
				break;
			default:
				throw new IllegalArgumentException("Invalid flex direction: " + flexDirection);
		}
		if (mode == MeasureSpec.EXACTLY) {
			int totalCrossSize = getSumOfCrossSize() + paddingAlongCrossAxis;
			if (mFlexLines.size() == 1) {
				mFlexLines.get(0).mCrossSize = size - paddingAlongCrossAxis;
				// alignContent property is valid only if the Flexbox has at least two lines
			} else if (mFlexLines.size() >= 2 && totalCrossSize < size) {
				switch (mAlignContent) {
					case ALIGN_CONTENT_STRETCH: {
						float freeSpaceUnit = (size - totalCrossSize) / (float) mFlexLines.size();
						float accumulatedError = 0;
						for (int i = 0, flexLinesSize = mFlexLines.size(); i < flexLinesSize; i++) {
							FlexLine flexLine = mFlexLines.get(i);
							float newCrossSizeAsFloat = flexLine.mCrossSize + freeSpaceUnit;
							if (i == mFlexLines.size() - 1) {
								newCrossSizeAsFloat += accumulatedError;
								accumulatedError = 0;
							}
							int newCrossSize = Math.round(newCrossSizeAsFloat);
							accumulatedError += (newCrossSizeAsFloat - newCrossSize);
							if (accumulatedError > 1) {
								newCrossSize += 1;
								accumulatedError -= 1;
							} else if (accumulatedError < -1) {
								newCrossSize -= 1;
								accumulatedError += 1;
							}
							flexLine.mCrossSize = newCrossSize;
						}
						break;
					}
					case ALIGN_CONTENT_SPACE_AROUND: {
						// The value of free space along the cross axis which needs to be put on top
						// and below the bottom of each flex line.
						int spaceTopAndBottom = size - totalCrossSize;
						// The number of spaces along the cross axis
						int numberOfSpaces = mFlexLines.size() * 2;
						spaceTopAndBottom = spaceTopAndBottom / numberOfSpaces;
						List<FlexLine> newFlexLines = new ArrayList<>();
						FlexLine dummySpaceFlexLine = new FlexLine();
						dummySpaceFlexLine.mCrossSize = spaceTopAndBottom;
						for (FlexLine flexLine : mFlexLines) {
							newFlexLines.add(dummySpaceFlexLine);
							newFlexLines.add(flexLine);
							newFlexLines.add(dummySpaceFlexLine);
						}
						mFlexLines = newFlexLines;
						break;
					}
					case ALIGN_CONTENT_SPACE_BETWEEN: {
						// The value of free space along the cross axis between each flex line.
						float spaceBetweenFlexLine = size - totalCrossSize;
						int numberOfSpaces = mFlexLines.size() - 1;
						spaceBetweenFlexLine = spaceBetweenFlexLine / (float) numberOfSpaces;
						float accumulatedError = 0;
						List<FlexLine> newFlexLines = new ArrayList<>();
						for (int i = 0, flexLineSize = mFlexLines.size(); i < flexLineSize; i++) {
							FlexLine flexLine = mFlexLines.get(i);
							newFlexLines.add(flexLine);

							if (i != mFlexLines.size() - 1) {
								FlexLine dummySpaceFlexLine = new FlexLine();
								if (i == mFlexLines.size() - 2) {
									// The last dummy space block in the flex container.
									// Adjust the cross size by the accumulated error.
									dummySpaceFlexLine.mCrossSize = Math
										.round(spaceBetweenFlexLine + accumulatedError);
									accumulatedError = 0;
								} else {
									dummySpaceFlexLine.mCrossSize = Math
										.round(spaceBetweenFlexLine);
								}
								accumulatedError += (spaceBetweenFlexLine
									- dummySpaceFlexLine.mCrossSize);
								if (accumulatedError > 1) {
									dummySpaceFlexLine.mCrossSize += 1;
									accumulatedError -= 1;
								} else if (accumulatedError < -1) {
									dummySpaceFlexLine.mCrossSize -= 1;
									accumulatedError += 1;
								}
								newFlexLines.add(dummySpaceFlexLine);
							}
						}
						mFlexLines = newFlexLines;
						break;
					}
					case ALIGN_CONTENT_CENTER: {
						int spaceAboveAndBottom = size - totalCrossSize;
						spaceAboveAndBottom = spaceAboveAndBottom / 2;
						List<FlexLine> newFlexLines = new ArrayList<>();
						FlexLine dummySpaceFlexLine = new FlexLine();
						dummySpaceFlexLine.mCrossSize = spaceAboveAndBottom;
						for (int i = 0, flexLineSize = mFlexLines.size(); i < flexLineSize; i++) {
							if (i == 0) {
								newFlexLines.add(dummySpaceFlexLine);
							}
							FlexLine flexLine = mFlexLines.get(i);
							newFlexLines.add(flexLine);
							if (i == mFlexLines.size() - 1) {
								newFlexLines.add(dummySpaceFlexLine);
							}
						}
						mFlexLines = newFlexLines;
						break;
					}
					case ALIGN_CONTENT_FLEX_END: {
						int spaceTop = size - totalCrossSize;
						FlexLine dummySpaceFlexLine = new FlexLine();
						dummySpaceFlexLine.mCrossSize = spaceTop;
						mFlexLines.add(0, dummySpaceFlexLine);
						break;
					}
				}
			}
		}
	}

	/**
	 * Expand the view if the {@link #mAlignItems} attribute is set to {@link #ALIGN_ITEMS_STRETCH}
	 * or {@link LayoutParams#ALIGN_SELF_STRETCH} is set to an individual child view.
	 *
	 * @param flexDirection the flex direction attribute
	 * @param alignItems    the align items attribute
	 * @see #getFlexDirection()
	 * @see #setFlexDirection(int)
	 * @see #getAlignItems()
	 * @see #setAlignItems(int)
	 * @see LayoutParams#alignSelf
	 */
	private void stretchViews(int flexDirection, int alignItems) {
		if (alignItems == ALIGN_ITEMS_STRETCH) {
			int viewIndex = 0;
			for (FlexLine flexLine : mFlexLines) {
				for (int i = 0; i < flexLine.mItemCount; i++, viewIndex++) {
					View view = getReorderedChildAt(viewIndex);
					LayoutParams lp = (LayoutParams) view.getLayoutParams();
					if (lp.alignSelf != LayoutParams.ALIGN_SELF_AUTO &&
						lp.alignSelf != LayoutParams.ALIGN_SELF_STRETCH) {
						continue;
					}
					switch (flexDirection) {
						case FLEX_DIRECTION_ROW: // Intentional fall through
						case FLEX_DIRECTION_ROW_REVERSE:
							stretchViewVertically(view, flexLine.mCrossSize);
							break;
						case FLEX_DIRECTION_COLUMN:
						case FLEX_DIRECTION_COLUMN_REVERSE:
							stretchViewHorizontally(view, flexLine.mCrossSize);
							break;
						default:
							throw new IllegalArgumentException(
								"Invalid flex direction: " + flexDirection);
					}
				}
			}
		} else {
			for (FlexLine flexLine : mFlexLines) {
				for (Integer index : flexLine.mIndicesAlignSelfStretch) {
					View view = getReorderedChildAt(index);
					switch (flexDirection) {
						case FLEX_DIRECTION_ROW: // Intentional fall through
						case FLEX_DIRECTION_ROW_REVERSE:
							stretchViewVertically(view, flexLine.mCrossSize);
							break;
						case FLEX_DIRECTION_COLUMN:
						case FLEX_DIRECTION_COLUMN_REVERSE:
							stretchViewHorizontally(view, flexLine.mCrossSize);
							break;
						default:
							throw new IllegalArgumentException(
								"Invalid flex direction: " + flexDirection);
					}
				}
			}
		}
	}

	/**
	 * Expand the view vertically to the size of the crossSize (considering the view margins)
	 *
	 * @param view      the View to be stretched
	 * @param crossSize the cross size
	 */
	private void stretchViewVertically(View view, int crossSize) {
		LayoutParams lp = (LayoutParams) view.getLayoutParams();
		int newHeight = crossSize - lp.topMargin - lp.bottomMargin;
		newHeight = Math.max(newHeight, 0);
		view.measure(MeasureSpec
				.makeMeasureSpec(view.getMeasuredWidth(), MeasureSpec.EXACTLY),
			MeasureSpec.makeMeasureSpec(newHeight, MeasureSpec.EXACTLY));
	}

	/**
	 * Expand the view horizontally to the size of the crossSize (considering the view margins)
	 *
	 * @param view      the View to be stretched
	 * @param crossSize the cross size
	 */
	private void stretchViewHorizontally(View view, int crossSize) {
		LayoutParams lp = (LayoutParams) view.getLayoutParams();
		int newWidth = crossSize - lp.leftMargin - lp.rightMargin;
		newWidth = Math.max(newWidth, 0);
		view.measure(MeasureSpec
				.makeMeasureSpec(newWidth, MeasureSpec.EXACTLY),
			MeasureSpec.makeMeasureSpec(view.getMeasuredHeight(), MeasureSpec.EXACTLY));
	}

	/**
	 * Set this FlexboxLayouts' width and height depending on the calculated size of main axis and
	 * cross axis.
	 *
	 * @param flexDirection     the value of the flex direction
	 * @param widthMeasureSpec  horizontal space requirements as imposed by the parent
	 * @param heightMeasureSpec vertical space requirements as imposed by the parent
	 * @param childState        the child state of the View
	 * @see #getFlexDirection()
	 * @see #setFlexDirection(int)
	 */
	private void setMeasuredDimensionForFlex(@FlexDirection int flexDirection, int widthMeasureSpec,
																					 int heightMeasureSpec, int childState) {
		int widthMode = MeasureSpec.getMode(widthMeasureSpec);
		int widthSize = MeasureSpec.getSize(widthMeasureSpec);
		int heightMode = MeasureSpec.getMode(heightMeasureSpec);
		int heightSize = MeasureSpec.getSize(heightMeasureSpec);
		int calculatedMaxHeight;
		int calculatedMaxWidth;
		switch (flexDirection) {
			case FLEX_DIRECTION_ROW: // Intentional fall through
			case FLEX_DIRECTION_ROW_REVERSE:
				calculatedMaxHeight = getSumOfCrossSize() + getPaddingTop()
					+ getPaddingBottom();
				calculatedMaxWidth = getLargestMainSize();
				break;
			case FLEX_DIRECTION_COLUMN: // Intentional fall through
			case FLEX_DIRECTION_COLUMN_REVERSE:
				calculatedMaxHeight = getLargestMainSize();
				calculatedMaxWidth = getSumOfCrossSize() + getPaddingLeft() + getPaddingRight();
				break;
			default:
				throw new IllegalArgumentException("Invalid flex direction: " + flexDirection);
		}

		int widthSizeAndState;
		switch (widthMode) {
			case MeasureSpec.EXACTLY:
				if (widthSize < calculatedMaxWidth) {
					childState = View
						.combineMeasuredStates(childState, View.MEASURED_STATE_TOO_SMALL);
				}
				widthSizeAndState = View.resolveSizeAndState(widthSize, widthMeasureSpec,
					childState);
				break;
			case MeasureSpec.AT_MOST: {
				if (widthSize < calculatedMaxWidth) {
					childState = View
						.combineMeasuredStates(childState, View.MEASURED_STATE_TOO_SMALL);
				} else {
					widthSize = calculatedMaxWidth;
				}
				widthSizeAndState = View.resolveSizeAndState(widthSize, widthMeasureSpec,
					childState);
				break;
			}
			case MeasureSpec.UNSPECIFIED: {
				widthSizeAndState = View
					.resolveSizeAndState(calculatedMaxWidth, widthMeasureSpec, childState);
				break;
			}
			default:
				throw new IllegalStateException("Unknown width mode is set: " + widthMode);
		}
		int heightSizeAndState;
		switch (heightMode) {
			case MeasureSpec.EXACTLY:
				if (heightSize < calculatedMaxHeight) {
					childState = View.combineMeasuredStates(childState,
						View.MEASURED_STATE_TOO_SMALL
							>> View.MEASURED_HEIGHT_STATE_SHIFT);
				}
				heightSizeAndState = View.resolveSizeAndState(heightSize, heightMeasureSpec,
					childState);
				break;
			case MeasureSpec.AT_MOST: {
				if (heightSize < calculatedMaxHeight) {
					childState = View.combineMeasuredStates(childState,
						View.MEASURED_STATE_TOO_SMALL
							>> View.MEASURED_HEIGHT_STATE_SHIFT);
				} else {
					heightSize = calculatedMaxHeight;
				}
				heightSizeAndState = View.resolveSizeAndState(heightSize, heightMeasureSpec,
					childState);
				break;
			}
			case MeasureSpec.UNSPECIFIED: {
				heightSizeAndState = View.resolveSizeAndState(calculatedMaxHeight,
					heightMeasureSpec, childState);
				break;
			}
			default:
				throw new IllegalStateException("Unknown height mode is set: " + heightMode);
		}
		setMeasuredDimension(widthSizeAndState, heightSizeAndState);
	}

	/**
	 * Determine if a wrap is required (add a new flex line).
	 *
	 * @param mode          the width or height mode along the main axis direction
	 * @param maxSize       the max size along the main axis direction
	 * @param currentLength the accumulated current length
	 * @param childLength   the length of a child view which is to be collected to the flex line
	 * @param lp            the LayoutParams for the view being determined whether a new flex line
	 *                      is needed
	 * @return {@code true} if a wrap is required, {@code false} otherwise
	 * @see #getFlexWrap()
	 * @see #setFlexWrap(int)
	 */
	private boolean isWrapRequired(int mode, int maxSize, int currentLength, int childLength,
																 LayoutParams lp, int childAbsoluteIndex, int childRelativeIndexInFlexLine) {
		if (mFlexWrap == FLEX_WRAP_NOWRAP) {
			return false;
		}
		if (lp.wrapBefore) {
			return true;
		}
		if (mode == MeasureSpec.UNSPECIFIED) {
			return false;
		}
		if (isMainAxisDirectionHorizontal(mFlexDirection)) {
			if (hasDividerBeforeChildAtAlongMainAxis(childAbsoluteIndex,
				childRelativeIndexInFlexLine)) {
				childLength += mDividerVerticalWidth;
			}
			if ((mShowDividerVertical & SHOW_DIVIDER_END) > 0) {
				childLength += mDividerVerticalWidth;
			}
		} else {
			if (hasDividerBeforeChildAtAlongMainAxis(childAbsoluteIndex,
				childRelativeIndexInFlexLine)) {
				childLength += mDividerHorizontalHeight;
			}
			if ((mShowDividerHorizontal & SHOW_DIVIDER_END) > 0) {
				childLength += mDividerHorizontalHeight;
			}
		}
		return maxSize < currentLength + childLength;
	}

	/**
	 * Retrieve the largest main size of all flex lines.
	 *
	 * @return the largest main size
	 */
	private int getLargestMainSize() {
		int largestSize = Integer.MIN_VALUE;
		for (FlexLine flexLine : mFlexLines) {
			largestSize = Math.max(largestSize, flexLine.mMainSize);
		}
		return largestSize;
	}

	/**
	 * Retrieve the sum of the cross sizes of all flex lines including divider lengths.
	 *
	 * @return the sum of the cross sizes
	 */
	private int getSumOfCrossSize() {
		int sum = 0;
		for (int i = 0, size = mFlexLines.size(); i < size; i++) {
			FlexLine flexLine = mFlexLines.get(i);

			// Judge if the beginning or middle dividers are required
			if (hasDividerBeforeFlexLine(i)) {
				if (isMainAxisDirectionHorizontal(mFlexDirection)) {
					sum += mDividerHorizontalHeight;
				} else {
					sum += mDividerVerticalWidth;
				}
			}

			// Judge if the end divider is required
			if (hasEndDividerAfterFlexLine(i)) {
				if (isMainAxisDirectionHorizontal(mFlexDirection)) {
					sum += mDividerHorizontalHeight;
				} else {
					sum += mDividerVerticalWidth;
				}
			}
			sum += flexLine.mCrossSize;
		}
		return sum;
	}

	private boolean isMainAxisDirectionHorizontal(@FlexDirection int flexDirection) {
		return flexDirection == FLEX_DIRECTION_ROW
			|| flexDirection == FLEX_DIRECTION_ROW_REVERSE;
	}

	@Override
	protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
		int layoutDirection = ViewCompat.getLayoutDirection(this);
		boolean isRtl;
		switch (mFlexDirection) {
			case FLEX_DIRECTION_ROW:
				isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
				layoutHorizontal(isRtl, left, top, right, bottom);
				break;
			case FLEX_DIRECTION_ROW_REVERSE:
				isRtl = layoutDirection != ViewCompat.LAYOUT_DIRECTION_RTL;
				layoutHorizontal(isRtl, left, top, right, bottom);
				break;
			case FLEX_DIRECTION_COLUMN:
				isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
				if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
					isRtl = !isRtl;
				}
				layoutVertical(isRtl, false, left, top, right, bottom);
				break;
			case FLEX_DIRECTION_COLUMN_REVERSE:
				isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
				if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
					isRtl = !isRtl;
				}
				layoutVertical(isRtl, true, left, top, right, bottom);
				break;
			default:
				throw new IllegalStateException("Invalid flex direction is set: " + mFlexDirection);
		}

		CommonLayoutParams.restoreOriginalParams(this);
	}

	/**
	 * Sub method for {@link #onLayout(boolean, int, int, int, int)} when the
	 * {@link #mFlexDirection} is either {@link #FLEX_DIRECTION_ROW} or
	 * {@link #FLEX_DIRECTION_ROW_REVERSE}.
	 *
	 * @param isRtl  {@code true} if the horizontal layout direction is right to left, {@code
	 *               false} otherwise.
	 * @param left   the left position of this View
	 * @param top    the top position of this View
	 * @param right  the right position of this View
	 * @param bottom the bottom position of this View
	 * @see #getFlexWrap()
	 * @see #setFlexWrap(int)
	 * @see #getJustifyContent()
	 * @see #setJustifyContent(int)
	 * @see #getAlignItems()
	 * @see #setAlignItems(int)
	 * @see LayoutParams#alignSelf
	 */
	private void layoutHorizontal(boolean isRtl, int left, int top, int right, int bottom) {
		int paddingLeft = getPaddingLeft();
		int paddingRight = getPaddingRight();
		// Use float to reduce the round error that may happen in when justifyContent ==
		// SPACE_BETWEEN or SPACE_AROUND
		float childLeft;
		int currentViewIndex = 0;

		int height = bottom - top;
		int width = right - left;
		// childBottom is used if the mFlexWrap is FLEX_WRAP_WRAP_REVERSE otherwise
		// childTop is used to align the vertical position of the children views.
		int childBottom = height - getPaddingBottom();
		int childTop = getPaddingTop();

		// Used only for RTL layout
		// Use float to reduce the round error that may happen in when justifyContent ==
		// SPACE_BETWEEN or SPACE_AROUND
		float childRight;
		for (int i = 0, size = mFlexLines.size(); i < size; i++) {
			FlexLine flexLine = mFlexLines.get(i);
			if (hasDividerBeforeFlexLine(i)) {
				childBottom -= mDividerHorizontalHeight;
				childTop += mDividerHorizontalHeight;
			}
			float spaceBetweenItem = 0f;
			switch (mJustifyContent) {
				case JUSTIFY_CONTENT_FLEX_START:
					childLeft = paddingLeft;
					childRight = width - paddingRight;
					break;
				case JUSTIFY_CONTENT_FLEX_END:
					childLeft = width - flexLine.mMainSize + paddingRight;
					childRight = flexLine.mMainSize - paddingLeft;
					break;
				case JUSTIFY_CONTENT_CENTER:
					childLeft = paddingLeft + (width - flexLine.mMainSize) / 2f;
					childRight = width - paddingRight - (width - flexLine.mMainSize) / 2f;
					break;
				case JUSTIFY_CONTENT_SPACE_AROUND: {
					int visibleCount = flexLine.getLayoutVisibleItemCount();
					if (visibleCount != 0) {
						spaceBetweenItem = (width - flexLine.mMainSize)
							/ (float) visibleCount;
					}
					childLeft = paddingLeft + spaceBetweenItem / 2f;
					childRight = width - paddingRight - spaceBetweenItem / 2f;
					break;
				}
				case JUSTIFY_CONTENT_SPACE_BETWEEN: {
					int visibleCount = flexLine.getLayoutVisibleItemCount();
					float denominator = visibleCount != 1 ? visibleCount - 1 : 1f;

					childLeft = paddingLeft;
					spaceBetweenItem = (width - flexLine.mMainSize) / denominator;
					childRight = width - paddingRight;
					break;
				}
				default:
					throw new IllegalStateException(
						"Invalid justifyContent is set: " + mJustifyContent);
			}
			spaceBetweenItem = Math.max(spaceBetweenItem, 0);

			for (int j = 0; j < flexLine.mItemCount; j++) {
				View child = getReorderedChildAt(currentViewIndex);
				if (child == null) {
					continue;
				} else if (child.getVisibility() == View.GONE) {
					currentViewIndex++;
					continue;
				}
				LayoutParams lp = ((LayoutParams) child.getLayoutParams());
				childLeft += lp.leftMargin;
				childRight -= lp.rightMargin;
				if (hasDividerBeforeChildAtAlongMainAxis(currentViewIndex, j)) {
					childLeft += mDividerVerticalWidth;
					childRight -= mDividerVerticalWidth;
				}

				if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
					if (isRtl) {
						layoutSingleChildHorizontal(child, flexLine, mFlexWrap, mAlignItems,
							Math.round(childRight) - child.getMeasuredWidth(),
							childBottom - child.getMeasuredHeight(), Math.round(childRight),
							childBottom);
					} else {
						layoutSingleChildHorizontal(child, flexLine, mFlexWrap, mAlignItems,
							Math.round(childLeft), childBottom - child.getMeasuredHeight(),
							Math.round(childLeft) + child.getMeasuredWidth(),
							childBottom);
					}
				} else {
					if (isRtl) {
						layoutSingleChildHorizontal(child, flexLine, mFlexWrap, mAlignItems,
							Math.round(childRight) - child.getMeasuredWidth(), childTop,
							Math.round(childRight), childTop + child.getMeasuredHeight());
					} else {
						layoutSingleChildHorizontal(child, flexLine, mFlexWrap, mAlignItems,
							Math.round(childLeft), childTop,
							Math.round(childLeft) + child.getMeasuredWidth(),
							childTop + child.getMeasuredHeight());
					}
				}
				childLeft += child.getMeasuredWidth() + spaceBetweenItem + lp.rightMargin;
				childRight -= child.getMeasuredWidth() + spaceBetweenItem + lp.leftMargin;
				currentViewIndex++;

				flexLine.mLeft = Math.min(flexLine.mLeft, child.getLeft() - lp.leftMargin);
				flexLine.mTop = Math.min(flexLine.mTop, child.getTop() - lp.topMargin);
				flexLine.mRight = Math.max(flexLine.mRight, child.getRight() + lp.rightMargin);
				flexLine.mBottom = Math.max(flexLine.mBottom, child.getBottom() + lp.bottomMargin);
			}
			childTop += flexLine.mCrossSize;
			childBottom -= flexLine.mCrossSize;
		}
	}

	/**
	 * Place a single View when the layout direction is horizontal ({@link #mFlexDirection} is
	 * either {@link #FLEX_DIRECTION_ROW} or {@link #FLEX_DIRECTION_ROW_REVERSE}).
	 *
	 * @param view       the View to be placed
	 * @param flexLine   the {@link FlexLine} where the View belongs to
	 * @param flexWrap   the flex wrap attribute of this FlexboxLayout
	 * @param alignItems the align items attribute of this FlexboxLayout
	 * @param left       the left position of the View, which the View's margin is already taken
	 *                   into account
	 * @param top        the top position of the flex line where the View belongs to. The actual
	 *                   View's top position is shifted depending on the flexWrap and alignItems
	 *                   attributes
	 * @param right      the right position of the View, which the View's margin is already taken
	 *                   into account
	 * @param bottom     the bottom position of the flex line where the View belongs to. The actual
	 *                   View's bottom position is shifted depending on the flexWrap and alignItems
	 *                   attributes
	 * @see #getAlignItems()
	 * @see #setAlignItems(int)
	 * @see LayoutParams#alignSelf
	 */
	private void layoutSingleChildHorizontal(View view, FlexLine flexLine, @FlexWrap int flexWrap,
																					 int alignItems, int left, int top, int right, int bottom) {
		LayoutParams lp = (LayoutParams) view.getLayoutParams();
		if (lp.alignSelf != LayoutParams.ALIGN_SELF_AUTO) {
			// Expecting the values for alignItems and alignSelf match except for ALIGN_SELF_AUTO.
			// Assigning the alignSelf value as alignItems should work.
			alignItems = lp.alignSelf;
		}
		int crossSize = flexLine.mCrossSize;
		switch (alignItems) {
			case ALIGN_ITEMS_FLEX_START: // Intentional fall through
			case ALIGN_ITEMS_STRETCH:
				if (flexWrap != FLEX_WRAP_WRAP_REVERSE) {
					view.layout(left, top + lp.topMargin, right, bottom + lp.topMargin);
				} else {
					view.layout(left, top - lp.bottomMargin, right, bottom - lp.bottomMargin);
				}
				break;
			case ALIGN_ITEMS_BASELINE:
				if (flexWrap != FLEX_WRAP_WRAP_REVERSE) {
					int marginTop = flexLine.mMaxBaseline - view.getBaseline();
					marginTop = Math.max(marginTop, lp.topMargin);
					view.layout(left, top + marginTop, right, bottom + marginTop);
				} else {
					int marginBottom = flexLine.mMaxBaseline - view.getMeasuredHeight() + view
						.getBaseline();
					marginBottom = Math.max(marginBottom, lp.bottomMargin);
					view.layout(left, top - marginBottom, right, bottom - marginBottom);
				}
				break;
			case ALIGN_ITEMS_FLEX_END:
				if (flexWrap != FLEX_WRAP_WRAP_REVERSE) {
					view.layout(left,
						top + crossSize - view.getMeasuredHeight() - lp.bottomMargin,
						right, top + crossSize - lp.bottomMargin);
				} else {
					// If the flexWrap == FLEX_WRAP_WRAP_REVERSE, the direction of the
					// flexEnd is flipped (from top to bottom).
					view.layout(left, top - crossSize + view.getMeasuredHeight() + lp.topMargin,
						right, bottom - crossSize + view.getMeasuredHeight() + lp.topMargin);
				}
				break;
			case ALIGN_ITEMS_CENTER:
				int topFromCrossAxis = (crossSize - view.getMeasuredHeight()) / 2;
				if (flexWrap != FLEX_WRAP_WRAP_REVERSE) {
					view.layout(left, top + topFromCrossAxis + lp.topMargin - lp.bottomMargin,
						right, top + topFromCrossAxis + view.getMeasuredHeight() + lp.topMargin
							- lp.bottomMargin);
				} else {
					view.layout(left, top - topFromCrossAxis + lp.topMargin - lp.bottomMargin,
						right, top - topFromCrossAxis + view.getMeasuredHeight() + lp.topMargin
							- lp.bottomMargin);
				}
				break;
		}
	}

	/**
	 * Sub method for {@link #onLayout(boolean, int, int, int, int)} when the
	 * {@link #mFlexDirection} is either {@link #FLEX_DIRECTION_COLUMN} or
	 * {@link #FLEX_DIRECTION_COLUMN_REVERSE}.
	 *
	 * @param isRtl           {@code true} if the horizontal layout direction is right to left,
	 *                        {@code false}
	 *                        otherwise
	 * @param fromBottomToTop {@code true} if the layout direction is bottom to top, {@code false}
	 *                        otherwise
	 * @param left            the left position of this View
	 * @param top             the top position of this View
	 * @param right           the right position of this View
	 * @param bottom          the bottom position of this View
	 * @see #getFlexWrap()
	 * @see #setFlexWrap(int)
	 * @see #getJustifyContent()
	 * @see #setJustifyContent(int)
	 * @see #getAlignItems()
	 * @see #setAlignItems(int)
	 * @see LayoutParams#alignSelf
	 */
	private void layoutVertical(boolean isRtl, boolean fromBottomToTop, int left, int top,
															int right, int bottom) {
		int paddingTop = getPaddingTop();
		int paddingBottom = getPaddingBottom();

		int paddingRight = getPaddingRight();
		int childLeft = getPaddingLeft();
		int currentViewIndex = 0;

		int width = right - left;
		int height = bottom - top;
		// childRight is used if the mFlexWrap is FLEX_WRAP_WRAP_REVERSE otherwise
		// childLeft is used to align the horizontal position of the children views.
		int childRight = width - paddingRight;

		// Use float to reduce the round error that may happen in when justifyContent ==
		// SPACE_BETWEEN or SPACE_AROUND
		float childTop;

		// Used only for if the direction is from bottom to top
		float childBottom;

		for (int i = 0, size = mFlexLines.size(); i < size; i++) {
			FlexLine flexLine = mFlexLines.get(i);
			if (hasDividerBeforeFlexLine(i)) {
				childLeft += mDividerVerticalWidth;
				childRight -= mDividerVerticalWidth;
			}
			float spaceBetweenItem = 0f;
			switch (mJustifyContent) {
				case JUSTIFY_CONTENT_FLEX_START:
					childTop = paddingTop;
					childBottom = height - paddingBottom;
					break;
				case JUSTIFY_CONTENT_FLEX_END:
					childTop = height - flexLine.mMainSize + paddingBottom;
					childBottom = flexLine.mMainSize - paddingTop;
					break;
				case JUSTIFY_CONTENT_CENTER:
					childTop = paddingTop + (height - flexLine.mMainSize) / 2f;
					childBottom = height - paddingBottom - (height - flexLine.mMainSize) / 2f;
					break;
				case JUSTIFY_CONTENT_SPACE_AROUND: {
					int visibleCount = flexLine.getLayoutVisibleItemCount();
					if (visibleCount != 0) {
						spaceBetweenItem = (height - flexLine.mMainSize)
							/ (float) visibleCount;
					}
					childTop = paddingTop + spaceBetweenItem / 2f;
					childBottom = height - paddingBottom - spaceBetweenItem / 2f;
					break;
				}
				case JUSTIFY_CONTENT_SPACE_BETWEEN: {
					int visibleCount = flexLine.getLayoutVisibleItemCount();
					float denominator = visibleCount != 1 ? visibleCount - 1 : 1f;

					childTop = paddingTop;
					spaceBetweenItem = (height - flexLine.mMainSize) / denominator;
					childBottom = height - paddingBottom;
					break;
				}
				default:
					throw new IllegalStateException(
						"Invalid justifyContent is set: " + mJustifyContent);
			}
			spaceBetweenItem = Math.max(spaceBetweenItem, 0);

			for (int j = 0; j < flexLine.mItemCount; j++) {
				View child = getReorderedChildAt(currentViewIndex);
				if (child == null) {
					continue;
				} else if (child.getVisibility() == View.GONE) {
					currentViewIndex++;
					continue;
				}
				LayoutParams lp = ((LayoutParams) child.getLayoutParams());
				childTop += lp.topMargin;
				childBottom -= lp.bottomMargin;
				if (hasDividerBeforeChildAtAlongMainAxis(currentViewIndex, j)) {
					childTop += mDividerHorizontalHeight;
					childBottom -= mDividerHorizontalHeight;
				}
				if (isRtl) {
					if (fromBottomToTop) {
						layoutSingleChildVertical(child, flexLine, true, mAlignItems,
							childRight - child.getMeasuredWidth(),
							Math.round(childBottom) - child.getMeasuredHeight(), childRight,
							Math.round(childBottom));
					} else {
						layoutSingleChildVertical(child, flexLine, true, mAlignItems,
							childRight - child.getMeasuredWidth(), Math.round(childTop),
							childRight, Math.round(childTop) + child.getMeasuredHeight());
					}
				} else {
					if (fromBottomToTop) {
						layoutSingleChildVertical(child, flexLine, false, mAlignItems,
							childLeft, Math.round(childBottom) - child.getMeasuredHeight(),
							childLeft + child.getMeasuredWidth(), Math.round(childBottom));
					} else {
						layoutSingleChildVertical(child, flexLine, false, mAlignItems,
							childLeft, Math.round(childTop),
							childLeft + child.getMeasuredWidth(),
							Math.round(childTop) + child.getMeasuredHeight());
					}
				}
				childTop += child.getMeasuredHeight() + spaceBetweenItem + lp.bottomMargin;
				childBottom -= child.getMeasuredHeight() + spaceBetweenItem + lp.topMargin;
				currentViewIndex++;

				flexLine.mLeft = Math.min(flexLine.mLeft, child.getLeft() - lp.leftMargin);
				flexLine.mTop = Math.min(flexLine.mTop, child.getTop() - lp.topMargin);
				flexLine.mRight = Math.max(flexLine.mRight, child.getRight() + lp.rightMargin);
				flexLine.mBottom = Math.max(flexLine.mBottom, child.getBottom() + lp.bottomMargin);
			}
			childLeft += flexLine.mCrossSize;
			childRight -= flexLine.mCrossSize;
		}
	}

	/**
	 * Place a single View when the layout direction is vertical ({@link #mFlexDirection} is
	 * either {@link #FLEX_DIRECTION_COLUMN} or {@link #FLEX_DIRECTION_COLUMN_REVERSE}).
	 *
	 * @param view       the View to be placed
	 * @param flexLine   the {@link FlexLine} where the View belongs to
	 * @param isRtl      {@code true} if the layout direction is right to left, {@code false}
	 *                   otherwise
	 * @param alignItems the align items attribute of this FlexboxLayout
	 * @param left       the left position of the flex line where the View belongs to. The actual
	 *                   View's left position is shifted depending on the isRtl and alignItems
	 *                   attributes
	 * @param top        the top position of the View, which the View's margin is already taken
	 *                   into account
	 * @param right      the right position of the flex line where the View belongs to. The actual
	 *                   View's right position is shifted depending on the isRtl and alignItems
	 *                   attributes
	 * @param bottom     the bottom position of the View, which the View's margin is already taken
	 *                   into account
	 * @see #getAlignItems()
	 * @see #setAlignItems(int)
	 * @see LayoutParams#alignSelf
	 */
	private void layoutSingleChildVertical(View view, FlexLine flexLine, boolean isRtl,
																				 int alignItems, int left, int top, int right, int bottom) {
		LayoutParams lp = (LayoutParams) view.getLayoutParams();
		if (lp.alignSelf != LayoutParams.ALIGN_SELF_AUTO) {
			// Expecting the values for alignItems and alignSelf match except for ALIGN_SELF_AUTO.
			// Assigning the alignSelf value as alignItems should work.
			alignItems = lp.alignSelf;
		}
		int crossSize = flexLine.mCrossSize;
		switch (alignItems) {
			case ALIGN_ITEMS_FLEX_START: // Intentional fall through
			case ALIGN_ITEMS_STRETCH: // Intentional fall through
			case ALIGN_ITEMS_BASELINE:
				if (!isRtl) {
					view.layout(left + lp.leftMargin, top, right + lp.leftMargin, bottom);
				} else {
					view.layout(left - lp.rightMargin, top, right - lp.rightMargin, bottom);
				}
				break;
			case ALIGN_ITEMS_FLEX_END:
				if (!isRtl) {
					view.layout(left + crossSize - view.getMeasuredWidth() - lp.rightMargin,
						top, right + crossSize - view.getMeasuredWidth() - lp.rightMargin,
						bottom);
				} else {
					// If the flexWrap == FLEX_WRAP_WRAP_REVERSE, the direction of the
					// flexEnd is flipped (from left to right).
					view.layout(left - crossSize + view.getMeasuredWidth() + lp.leftMargin, top,
						right - crossSize + view.getMeasuredWidth() + lp.leftMargin,
						bottom);
				}
				break;
			case ALIGN_ITEMS_CENTER:
				int leftFromCrossAxis = (crossSize - view.getMeasuredWidth()) / 2;
				if (!isRtl) {
					view.layout(left + leftFromCrossAxis + lp.leftMargin - lp.rightMargin,
						top, right + leftFromCrossAxis + lp.leftMargin - lp.rightMargin,
						bottom);
				} else {
					view.layout(left - leftFromCrossAxis + lp.leftMargin - lp.rightMargin,
						top, right - leftFromCrossAxis + lp.leftMargin - lp.rightMargin,
						bottom);
				}
				break;
		}
	}

	@Override
	protected void onDraw(Canvas canvas) {
		if (mDividerDrawableVertical == null && mDividerDrawableHorizontal == null) {
			return;
		}
		if (mShowDividerHorizontal == SHOW_DIVIDER_NONE
			&& mShowDividerVertical == SHOW_DIVIDER_NONE) {
			return;
		}

		int layoutDirection = ViewCompat.getLayoutDirection(this);
		boolean isRtl;
		boolean fromBottomToTop = false;
		switch (mFlexDirection) {
			case FLEX_DIRECTION_ROW:
				isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
				if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
					fromBottomToTop = true;
				}
				drawDividersHorizontal(canvas, isRtl, fromBottomToTop);
				break;
			case FLEX_DIRECTION_ROW_REVERSE:
				isRtl = layoutDirection != ViewCompat.LAYOUT_DIRECTION_RTL;
				if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
					fromBottomToTop = true;
				}
				drawDividersHorizontal(canvas, isRtl, fromBottomToTop);
				break;
			case FLEX_DIRECTION_COLUMN:
				isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
				if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
					isRtl = !isRtl;
				}
				drawDividersVertical(canvas, isRtl, false /* fromBottomToTop */);
				break;
			case FLEX_DIRECTION_COLUMN_REVERSE:
				isRtl = layoutDirection == ViewCompat.LAYOUT_DIRECTION_RTL;
				if (mFlexWrap == FLEX_WRAP_WRAP_REVERSE) {
					isRtl = !isRtl;
				}
				drawDividersVertical(canvas, isRtl, true /* fromBottomToTop */);
				break;
		}
	}

	/**
	 * Sub method for {@link #onDraw(Canvas)} when the main axis direction is horizontal
	 * ({@link #mFlexDirection} is either of {@link #FLEX_DIRECTION_ROW} or
	 * {@link #FLEX_DIRECTION_ROW_REVERSE}.
	 *
	 * @param canvas          the canvas on which the background will be drawn
	 * @param isRtl           {@code true} when the horizontal layout direction is right to left,
	 *                        {@code false} otherwise
	 * @param fromBottomToTop {@code true} when the vertical layout direction is bottom to top,
	 *                        {@code false} otherwise
	 */
	private void drawDividersHorizontal(Canvas canvas, boolean isRtl, boolean fromBottomToTop) {
		int currentViewIndex = 0;
		int paddingLeft = getPaddingLeft();
		int paddingRight = getPaddingRight();
		int horizontalDividerLength = Math.max(0, getWidth() - paddingRight - paddingLeft);
		for (int i = 0, size = mFlexLines.size(); i < size; i++) {
			FlexLine flexLine = mFlexLines.get(i);
			for (int j = 0; j < flexLine.mItemCount; j++) {
				View view = getReorderedChildAt(currentViewIndex);

				if (view == null || view.getVisibility() == View.GONE) {
					continue;
				}

				LayoutParams lp = (LayoutParams) view.getLayoutParams();

				// Judge if the beginning or middle divider is needed
				if (hasDividerBeforeChildAtAlongMainAxis(currentViewIndex, j)) {
					int dividerLeft;
					if (isRtl) {
						dividerLeft = view.getRight() + lp.rightMargin;
					} else {
						dividerLeft = view.getLeft() - lp.leftMargin - mDividerVerticalWidth;
					}

					drawVerticalDivider(canvas, dividerLeft, flexLine.mTop, flexLine.mCrossSize);
				}

				// Judge if the end divider is needed
				if (j == flexLine.mItemCount - 1) {
					if ((mShowDividerVertical & SHOW_DIVIDER_END) > 0) {
						int dividerLeft;
						if (isRtl) {
							dividerLeft = view.getLeft() - lp.leftMargin - mDividerVerticalWidth;
						} else {
							dividerLeft = view.getRight() + lp.rightMargin;
						}

						drawVerticalDivider(canvas, dividerLeft, flexLine.mTop,
							flexLine.mCrossSize);
					}
				}
				currentViewIndex++;
			}

			// Judge if the beginning or middle dividers are needed before the flex line
			if (hasDividerBeforeFlexLine(i)) {
				int horizontalDividerTop;
				if (fromBottomToTop) {
					horizontalDividerTop = flexLine.mBottom;
				} else {
					horizontalDividerTop = flexLine.mTop - mDividerHorizontalHeight;
				}
				drawHorizontalDivider(canvas, paddingLeft, horizontalDividerTop,
					horizontalDividerLength);
			}
			// Judge if the end divider is needed before the flex line
			if (hasEndDividerAfterFlexLine(i)) {
				if ((mShowDividerHorizontal & SHOW_DIVIDER_END) > 0) {
					int horizontalDividerTop;
					if (fromBottomToTop) {
						horizontalDividerTop = flexLine.mTop - mDividerHorizontalHeight;
					} else {
						horizontalDividerTop = flexLine.mBottom;
					}
					drawHorizontalDivider(canvas, paddingLeft, horizontalDividerTop,
						horizontalDividerLength);
				}
			}
		}
	}

	/**
	 * Sub method for {@link #onDraw(Canvas)} when the main axis direction is vertical
	 * ({@link #mFlexDirection} is either of {@link #FLEX_DIRECTION_COLUMN} or
	 * {@link #FLEX_DIRECTION_COLUMN_REVERSE}.
	 *
	 * @param canvas          the canvas on which the background will be drawn
	 * @param isRtl           {@code true} when the horizontal layout direction is right to left,
	 *                        {@code false} otherwise
	 * @param fromBottomToTop {@code true} when the vertical layout direction is bottom to top,
	 *                        {@code false} otherwise
	 */
	private void drawDividersVertical(Canvas canvas, boolean isRtl, boolean fromBottomToTop) {
		int currentViewIndex = 0;
		int paddingTop = getPaddingTop();
		int paddingBottom = getPaddingBottom();
		int verticalDividerLength = Math.max(0, getHeight() - paddingBottom - paddingTop);
		for (int i = 0, size = mFlexLines.size(); i < size; i++) {
			FlexLine flexLine = mFlexLines.get(i);

			// Draw horizontal dividers if needed
			for (int j = 0; j < flexLine.mItemCount; j++) {
				View view = getReorderedChildAt(currentViewIndex);

				if (view == null || view.getVisibility() == View.GONE) {
					continue;
				}

				LayoutParams lp = (LayoutParams) view.getLayoutParams();

				// Judge if the beginning or middle divider is needed
				if (hasDividerBeforeChildAtAlongMainAxis(currentViewIndex, j)) {
					int dividerTop;
					if (fromBottomToTop) {
						dividerTop = view.getBottom() + lp.bottomMargin;
					} else {
						dividerTop = view.getTop() - lp.topMargin - mDividerHorizontalHeight;
					}

					drawHorizontalDivider(canvas, flexLine.mLeft, dividerTop, flexLine.mCrossSize);
				}

				// Judge if the end divider is needed
				if (j == flexLine.mItemCount - 1) {
					if ((mShowDividerHorizontal & SHOW_DIVIDER_END) > 0) {
						int dividerTop;
						if (fromBottomToTop) {
							dividerTop = view.getTop() - lp.topMargin - mDividerHorizontalHeight;
						} else {
							dividerTop = view.getBottom() + lp.bottomMargin;
						}

						drawHorizontalDivider(canvas, flexLine.mLeft, dividerTop,
							flexLine.mCrossSize);
					}
				}
				currentViewIndex++;
			}

			// Judge if the beginning or middle dividers are needed before the flex line
			if (hasDividerBeforeFlexLine(i)) {
				int verticalDividerLeft;
				if (isRtl) {
					verticalDividerLeft = flexLine.mRight;
				} else {
					verticalDividerLeft = flexLine.mLeft - mDividerVerticalWidth;
				}
				drawVerticalDivider(canvas, verticalDividerLeft, paddingTop,
					verticalDividerLength);
			}
			if (hasEndDividerAfterFlexLine(i)) {
				if ((mShowDividerVertical & SHOW_DIVIDER_END) > 0) {
					int verticalDividerLeft;
					if (isRtl) {
						verticalDividerLeft = flexLine.mLeft - mDividerVerticalWidth;
					} else {
						verticalDividerLeft = flexLine.mRight;
					}
					drawVerticalDivider(canvas, verticalDividerLeft, paddingTop,
						verticalDividerLength);
				}
			}
		}
	}

	private void drawVerticalDivider(Canvas canvas, int left, int top, int length) {
		if (mDividerDrawableVertical == null) {
			return;
		}
		mDividerDrawableVertical.setBounds(left, top, left + mDividerVerticalWidth, top + length);
		mDividerDrawableVertical.draw(canvas);
	}

	private void drawHorizontalDivider(Canvas canvas, int left, int top, int length) {
		if (mDividerDrawableHorizontal == null) {
			return;
		}
		mDividerDrawableHorizontal
			.setBounds(left, top, left + length, top + mDividerHorizontalHeight);
		mDividerDrawableHorizontal.draw(canvas);
	}

	@Override
	protected LayoutParams generateDefaultLayoutParams() {
		return new FlexboxLayout.LayoutParams();
	}

	@Override
	protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
		return p instanceof FlexboxLayout.LayoutParams;
	}

	@Override
	public LayoutParams generateLayoutParams(AttributeSet attrs) {
		return new FlexboxLayout.LayoutParams();
	}

	@Override
	protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams from) {
		if (from instanceof FlexboxLayout.LayoutParams)
			return new FlexboxLayout.LayoutParams((FlexboxLayout.LayoutParams) from);

		if (from instanceof CommonLayoutParams)
			return new FlexboxLayout.LayoutParams((CommonLayoutParams) from);

		if (from instanceof FrameLayout.LayoutParams)
			return new FlexboxLayout.LayoutParams((FrameLayout.LayoutParams) from);

		if (from instanceof ViewGroup.MarginLayoutParams)
			return new FlexboxLayout.LayoutParams((ViewGroup.MarginLayoutParams) from);

		return new FlexboxLayout.LayoutParams(from);
	}

	@FlexDirection
	public int getFlexDirection() {
		return mFlexDirection;
	}

	public void setFlexDirection(@FlexDirection int flexDirection) {
		if (mFlexDirection != flexDirection) {
			mFlexDirection = flexDirection;
			requestLayout();
		}
	}

	@FlexWrap
	public int getFlexWrap() {
		return mFlexWrap;
	}

	public void setFlexWrap(@FlexWrap int flexWrap) {
		if (mFlexWrap != flexWrap) {
			mFlexWrap = flexWrap;
			requestLayout();
		}
	}

	@JustifyContent
	public int getJustifyContent() {
		return mJustifyContent;
	}

	public void setJustifyContent(@JustifyContent int justifyContent) {
		if (mJustifyContent != justifyContent) {
			mJustifyContent = justifyContent;
			requestLayout();
		}
	}

	@AlignItems
	public int getAlignItems() {
		return mAlignItems;
	}

	public void setAlignItems(@AlignItems int alignItems) {
		if (mAlignItems != alignItems) {
			mAlignItems = alignItems;
			requestLayout();
		}
	}

	@AlignContent
	public int getAlignContent() {
		return mAlignContent;
	}

	public void setAlignContent(@AlignContent int alignContent) {
		if (mAlignContent != alignContent) {
			mAlignContent = alignContent;
			requestLayout();
		}
	}

	/**
	 * @return the flex lines composing this flex container. This method returns a copy of the
	 * original list excluding a dummy flex line (flex line that doesn't have any flex items in it
	 * but used for the alignment along the cross axis).
	 * Thus any changes of the returned list are not reflected to the original list.
	 */
	public List<FlexLine> getFlexLines() {
		List<FlexLine> result = new ArrayList<>(mFlexLines.size());
		for (FlexLine flexLine : mFlexLines) {
			if (flexLine.getLayoutVisibleItemCount() == 0) {
				continue;
			}
			result.add(flexLine);
		}
		return result;
	}

	/**
	 * @return the horizontal divider drawable that will divide each item.
	 * @see #setDividerDrawable(Drawable)
	 * @see #setDividerDrawableHorizontal(Drawable)
	 */
	public Drawable getDividerDrawableHorizontal() {
		return mDividerDrawableHorizontal;
	}

	/**
	 * @return the vertical divider drawable that will divide each item.
	 * @see #setDividerDrawable(Drawable)
	 * @see #setDividerDrawableVertical(Drawable)
	 */
	public Drawable getDividerDrawableVertical() {
		return mDividerDrawableVertical;
	}

	/**
	 * Set a drawable to be used as a divider between items. The drawable is used for both
	 * horizontal and vertical dividers.
	 *
	 * @param divider Drawable that will divide each item for both horizontally and vertically.
	 * @see #setShowDivider(int)
	 */
	public void setDividerDrawable(Drawable divider) {
		setDividerDrawableHorizontal(divider);
		setDividerDrawableVertical(divider);
	}

	/**
	 * Set a drawable to be used as a horizontal divider between items.
	 *
	 * @param divider Drawable that will divide each item.
	 * @see #setDividerDrawable(Drawable)
	 * @see #setShowDivider(int)
	 * @see #setShowDividerHorizontal(int)
	 */
	public void setDividerDrawableHorizontal(Drawable divider) {
		if (divider == mDividerDrawableHorizontal) {
			return;
		}
		mDividerDrawableHorizontal = divider;
		if (divider != null) {
			mDividerHorizontalHeight = divider.getIntrinsicHeight();
		} else {
			mDividerHorizontalHeight = 0;
		}
		setWillNotDrawFlag();
		requestLayout();
	}

	/**
	 * Set a drawable to be used as a vertical divider between items.
	 *
	 * @param divider Drawable that will divide each item.
	 * @see #setDividerDrawable(Drawable)
	 * @see #setShowDivider(int)
	 * @see #setShowDividerVertical(int)
	 */
	public void setDividerDrawableVertical(Drawable divider) {
		if (divider == mDividerDrawableVertical) {
			return;
		}
		mDividerDrawableVertical = divider;
		if (divider != null) {
			mDividerVerticalWidth = divider.getIntrinsicWidth();
		} else {
			mDividerVerticalWidth = 0;
		}
		setWillNotDrawFlag();
		requestLayout();
	}

	@FlexboxLayout.DividerMode
	public int getShowDividerVertical() {
		return mShowDividerVertical;
	}

	@FlexboxLayout.DividerMode
	public int getShowDividerHorizontal() {
		return mShowDividerHorizontal;
	}

	/**
	 * Set how dividers should be shown between items in this layout. This method sets the
	 * divider mode for both horizontally and vertically.
	 *
	 * @param dividerMode One or more of {@link #SHOW_DIVIDER_BEGINNING},
	 *                    {@link #SHOW_DIVIDER_MIDDLE}, or {@link #SHOW_DIVIDER_END},
	 *                    or {@link #SHOW_DIVIDER_NONE} to show no dividers.
	 * @see #setShowDividerVertical(int)
	 * @see #setShowDividerHorizontal(int)
	 */
	public void setShowDivider(@DividerMode int dividerMode) {
		setShowDividerVertical(dividerMode);
		setShowDividerHorizontal(dividerMode);
	}

	/**
	 * Set how vertical dividers should be shown between items in this layout
	 *
	 * @param dividerMode One or more of {@link #SHOW_DIVIDER_BEGINNING},
	 *                    {@link #SHOW_DIVIDER_MIDDLE}, or {@link #SHOW_DIVIDER_END},
	 *                    or {@link #SHOW_DIVIDER_NONE} to show no dividers.
	 * @see #setShowDivider(int)
	 */
	public void setShowDividerVertical(@DividerMode int dividerMode) {
		if (dividerMode != mShowDividerVertical) {
			mShowDividerVertical = dividerMode;
			requestLayout();
		}
	}

	/**
	 * Set how horizontal dividers should be shown between items in this layout.
	 *
	 * @param dividerMode One or more of {@link #SHOW_DIVIDER_BEGINNING},
	 *                    {@link #SHOW_DIVIDER_MIDDLE}, or {@link #SHOW_DIVIDER_END},
	 *                    or {@link #SHOW_DIVIDER_NONE} to show no dividers.
	 * @see #setShowDivider(int)
	 */
	public void setShowDividerHorizontal(@DividerMode int dividerMode) {
		if (dividerMode != mShowDividerHorizontal) {
			mShowDividerHorizontal = dividerMode;
			requestLayout();
		}
	}

	private void setWillNotDrawFlag() {
		setWillNotDraw(mDividerDrawableHorizontal == null && mDividerDrawableVertical == null);
	}

	/**
	 * Check if a divider is needed before the view whose indices are passed as arguments.
	 *
	 * @param childAbsoluteIndex           the absolute index of the view to be judged
	 * @param childRelativeIndexInFlexLine the relative index in the flex line where the view
	 *                                     belongs
	 * @return {@code true} if a divider is needed, {@code false} otherwise
	 */
	private boolean hasDividerBeforeChildAtAlongMainAxis(int childAbsoluteIndex,
																											 int childRelativeIndexInFlexLine) {
		if (allViewsAreGoneBefore(childAbsoluteIndex, childRelativeIndexInFlexLine)) {
			if (isMainAxisDirectionHorizontal(mFlexDirection)) {
				return (mShowDividerVertical & SHOW_DIVIDER_BEGINNING) != 0;
			} else {
				return (mShowDividerHorizontal & SHOW_DIVIDER_BEGINNING) != 0;
			}
		} else {
			if (isMainAxisDirectionHorizontal(mFlexDirection)) {
				return (mShowDividerVertical & SHOW_DIVIDER_MIDDLE) != 0;
			} else {
				return (mShowDividerHorizontal & SHOW_DIVIDER_MIDDLE) != 0;
			}
		}
	}

	private boolean allViewsAreGoneBefore(int childAbsoluteIndex,
																				int childRelativeIndexInFlexLine) {
		for (int i = 1; i <= childRelativeIndexInFlexLine; i++) {
			View view = getReorderedChildAt(childAbsoluteIndex - i);
			if (view != null && view.getVisibility() != View.GONE) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Check if a divider is needed before the flex line whose index is passed as an argument.
	 *
	 * @param flexLineIndex the index of the flex line to be checked
	 * @return {@code true} if a divider is needed, {@code false} otherwise
	 */
	private boolean hasDividerBeforeFlexLine(int flexLineIndex) {
		if (flexLineIndex < 0 || flexLineIndex >= mFlexLines.size()) {
			return false;
		}
		if (allFlexLinesAreDummyBefore(flexLineIndex)) {
			if (isMainAxisDirectionHorizontal(mFlexDirection)) {
				return (mShowDividerHorizontal & SHOW_DIVIDER_BEGINNING) != 0;
			} else {
				return (mShowDividerVertical & SHOW_DIVIDER_BEGINNING) != 0;
			}
		} else {
			if (isMainAxisDirectionHorizontal(mFlexDirection)) {
				return (mShowDividerHorizontal & SHOW_DIVIDER_MIDDLE) != 0;
			} else {
				return (mShowDividerVertical & SHOW_DIVIDER_MIDDLE) != 0;
			}
		}
	}

	private boolean allFlexLinesAreDummyBefore(int flexLineIndex) {
		for (int i = 0; i < flexLineIndex; i++) {
			if (mFlexLines.get(i).getLayoutVisibleItemCount() > 0) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Check if a end divider is needed after the flex line whose index is passed as an argument.
	 *
	 * @param flexLineIndex the index of the flex line to be checked
	 * @return {@code true} if a divider is needed, {@code false} otherwise
	 */
	private boolean hasEndDividerAfterFlexLine(int flexLineIndex) {
		if (flexLineIndex < 0 || flexLineIndex >= mFlexLines.size()) {
			return false;
		}

		for (int i = flexLineIndex + 1; i < mFlexLines.size(); i++) {
			if (mFlexLines.get(i).getLayoutVisibleItemCount() > 0) {
				return false;
			}
		}
		if (isMainAxisDirectionHorizontal(mFlexDirection)) {
			return (mShowDividerHorizontal & SHOW_DIVIDER_END) != 0;
		} else {
			return (mShowDividerVertical & SHOW_DIVIDER_END) != 0;
		}

	}

	/**
	 * Per child parameters for children views of the {@link FlexboxLayout}.
	 */
	public static class LayoutParams extends CommonLayoutParams {

		private static final int ORDER_DEFAULT = 1;

		private static final float FLEX_GROW_DEFAULT = 0f;

		private static final float FLEX_SHRINK_DEFAULT = 1f;

		public static final float FLEX_BASIS_PERCENT_DEFAULT = -1f;

		public static final int ALIGN_SELF_AUTO = -1;

		public static final int ALIGN_SELF_FLEX_START = ALIGN_ITEMS_FLEX_START;

		public static final int ALIGN_SELF_FLEX_END = ALIGN_ITEMS_FLEX_END;

		public static final int ALIGN_SELF_CENTER = ALIGN_ITEMS_CENTER;

		public static final int ALIGN_SELF_BASELINE = ALIGN_ITEMS_BASELINE;

		public static final int ALIGN_SELF_STRETCH = ALIGN_ITEMS_STRETCH;

		private static final int MAX_SIZE = Integer.MAX_VALUE & View.MEASURED_SIZE_MASK;

		/**
		 * This attribute can change the ordering of the children views are laid out.
		 * By default, children are displayed and laid out in the same order as they appear in the
		 * layout XML. If not specified, {@link #ORDER_DEFAULT} is set as a default value.
		 */
		public int order = ORDER_DEFAULT;

		/**
		 * This attribute determines how much this child will grow if positive free space is
		 * distributed relative to the rest of other flex items included in the same flex line.
		 * If not specified, {@link #FLEX_GROW_DEFAULT} is set as a default value.
		 */
		public float flexGrow = FLEX_GROW_DEFAULT;

		/**
		 * This attributes determines how much this child will shrink is negative free space is
		 * distributed relative to the rest of other flex items included in the same flex line.
		 * If not specified, {@link #FLEX_SHRINK_DEFAULT} is set as a default value.
		 */
		public float flexShrink = FLEX_SHRINK_DEFAULT;

		/**
		 * This attributes determines the alignment along the cross axis (perpendicular to the
		 * main axis). The alignment in the same direction can be determined by the
		 * {@link #mAlignItems} in the parent, but if this is set to other than
		 * {@link #ALIGN_SELF_AUTO}, the cross axis alignment is overridden for this child.
		 * The value needs to be one of the values in ({@link #ALIGN_SELF_AUTO},
		 * {@link #ALIGN_SELF_STRETCH}, {@link #ALIGN_SELF_FLEX_START}, {@link
		 * #ALIGN_SELF_FLEX_END}, {@link #ALIGN_SELF_CENTER}, or {@link #ALIGN_SELF_BASELINE}).
		 * If not specified, {@link #ALIGN_SELF_AUTO} is set as a default value.
		 */
		public int alignSelf = ALIGN_SELF_AUTO;

		/**
		 * The initial flex item length in a fraction format relative to its parent.
		 * The initial main size of this child View is trying to be expanded as the specified
		 * fraction against the parent main size.
		 * If this value is set, the length specified from layout_width
		 * (or layout_height) is overridden by the calculated value from this attribute.
		 * This attribute is only effective when the parent's MeasureSpec mode is
		 * MeasureSpec.EXACTLY. The default value is {@link #FLEX_BASIS_PERCENT_DEFAULT}, which
		 * means not set.
		 */
		public float flexBasisPercent = FLEX_BASIS_PERCENT_DEFAULT;

		/**
		 * This attribute determines the minimum width the child can shrink to.
		 */
		public int minWidth;

		/**
		 * This attribute determines the minimum height the child can shrink to.
		 */
		public int minHeight;

		/**
		 * This attribute determines the maximum width the child can expand to.
		 */
		public int maxWidth = MAX_SIZE;

		/**
		 * This attribute determines the maximum height the child can expand to.
		 */
		public int maxHeight = MAX_SIZE;

		/**
		 * This attribute forces a flex line wrapping. i.e. if this is set to {@code true} for a
		 * flex item, the item will become the first item of the new flex line. (A wrapping happens
		 * regardless of the flex items being processed in the the previous flex line)
		 * This attribute is ignored if the flex_wrap attribute is set as nowrap.
		 * The equivalent attribute isn't defined in the original CSS Flexible Box Module
		 * specification, but having this attribute is useful for Android developers to flatten
		 * the layouts when building a grid like layout or for a situation where developers want
		 * to put a new flex line to make a semantic difference from the previous one, etc.
		 */
		public boolean wrapBefore;

		public LayoutParams() {
			super();
		}

		public LayoutParams(ViewGroup.LayoutParams source) {
			super(source);
		}

		public LayoutParams(ViewGroup.MarginLayoutParams source) {
			super(source);
		}

		public LayoutParams(FrameLayout.LayoutParams source) {
			super(source);
		}

		public LayoutParams(CommonLayoutParams source) {
			super(source);
		}

		public LayoutParams(LayoutParams source) {
			super(source);

			this.order = source.order;
			this.flexGrow = source.flexGrow;
			this.flexShrink = source.flexShrink;
			this.wrapBefore = source.wrapBefore;
			this.alignSelf = source.alignSelf;
		}
	}

	/**
	 * A class that is used for calculating the view order which view's indices and order
	 * properties from Flexbox are taken into account.
	 */
	private static class Order implements Comparable<Order> {

		/**
		 * {@link View}'s index
		 */
		int index;

		/**
		 * order property in the Flexbox
		 */
		int order;

		@Override
		public int compareTo(@NonNull Order another) {
			if (order != another.order) {
				return order - another.order;
			}
			return index - another.index;
		}

		@NonNull
		@Override
		public String toString() {
			return "Order{" +
				"order=" + order +
				", index=" + index +
				'}';
		}
	}
}