WebViewEx.java

package com.cusnews.widgets;

import android.content.Context;
import android.util.AttributeSet;
import android.webkit.WebView;

/**
 * An extension of standard WebView that we can detect which direction user scrolled.
 *
 * @author Xinyue Zhao
 */
public final class WebViewEx extends WebView {
	/**
	 * A listener hooks the WebView when it scrolled.
	 */
	private OnWebViewExScrolledListener mOnWebViewExScrolledListener;

	public WebViewEx( Context context ) {
		super( context );
	}

	public WebViewEx( Context context, AttributeSet attrs ) {
		super( context, attrs );
	}

	public WebViewEx( Context context, AttributeSet attrs, int defStyle ) {
		super( context, attrs, defStyle );
	}

	@Override
	protected void onScrollChanged( int l, int t, int oldl, int oldt ) {
		if( t > 0 ) {
			if( mOnWebViewExScrolledListener != null ) {
				mOnWebViewExScrolledListener.onScrollChanged( t > oldt );
			}
		} else {
			if( t == 0 ) {
				if( mOnWebViewExScrolledListener != null ) {
					mOnWebViewExScrolledListener.onScrolledTop();
				}
			}
		}
		super.onScrollChanged( l, t, oldl, oldt );
	}

	/**
	 * Set listener hooks the WebView when it scrolled.
	 *
	 * @param onWebViewExScrolledListener
	 * 		The instance of listener.
	 */
	public void setOnWebViewExScrolledListener( OnWebViewExScrolledListener onWebViewExScrolledListener ) {
		mOnWebViewExScrolledListener = onWebViewExScrolledListener;
	}


	/**
	 * A listener hooks the WebView when it scrolled.
	 *
	 * @author Xinyue Zhao
	 */
	public interface OnWebViewExScrolledListener {
		/**
		 * Event fired when user scrolled the WebView.
		 *
		 * @param isUp
		 * 		True if user scrolled up, false then down.
		 */
		void onScrollChanged( boolean isUp );
		/**
		 * Event fired when user scrolled the WebView onto TOP.
		 */
		void onScrolledTop();
	}
}