import { ElementRef, OnDestroy } from '@angular/core';
import { MDCTextFieldHelperTextFoundation } from '@material/textfield';
import { MDCComponent } from '@shraddhar/web/base';
export declare class MdcTextFieldHelperTextFoundation extends MDCComponent<MDCTextFieldHelperTextFoundation> implements OnDestroy {
    _hostElement: ElementRef<HTMLElement>;
    private _document;
    private _initialized;
    _helperLineElement?: HTMLElement;
    private _helperTextContentElement?;
    get foundation(): MDCTextFieldHelperTextFoundation;
    constructor(_hostElement: ElementRef<HTMLElement>, _document: Document);
    getDefaultFoundation(): MDCTextFieldHelperTextFoundation;
    /** Sets the persistency of the helper text. */
    setPersistent(isPersistent: boolean): void;
    /** True to make the helper text act as an error validation message. */
    setValidation(isValidation: boolean): void;
    /** Sets the validity of the helper text based on inputIsValid. */
    setValidity(inputIsValid: boolean): void;
    /** Makes the helper text visible to the screen reader. */
    showToScreenReader(): void;
    /** Sets the content of the helper text field. */
    setContent(content: string): void;
    /** Initializes the foundation. */
    init(): void;
    /** Destroys the foundation. */
    destroy(): void;
    /** Creates and appends the helper element. */
    private _createHelperElement;
    /**
     * Appends the helper element to the textfield or textarea.
     */
    private _appendHelperElement;
    ngOnDestroy(): void;
}