MyWebView.java

/*
 * Copyright (c) 2015, Nils Braden
 *
 * This file is part of ttrss-reader-fork. This program is free software; you
 * can redistribute it and/or modify it under the terms of the GNU
 * General Public License as published by the Free Software Foundation;
 * either version 3 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details. You should have received a
 * copy of the GNU General Public License along with this program; If
 * not, see http://www.gnu.org/licenses/.
 */

package org.ttrssreader.gui.view;

import android.content.Context;
import android.view.View;
import android.webkit.WebView;

public class MyWebView extends WebView {

	@SuppressWarnings("unused")
	private static final String TAG = MyWebView.class.getSimpleName();

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

	private OnEdgeReachedListener mOnTopReachedListener = null;
	private OnEdgeReachedListener mOnBottomReachedListener = null;

	@SuppressWarnings("FieldCanBeLocal")
	private int mMinTopDistance = 0;
	@SuppressWarnings("FieldCanBeLocal")
	private int mMinBottomDistance = 0;

	/**
	 * Set the listener which will be called when the WebView is scrolled to within some
	 * margin of the top or bottom.
	 *
	 * @param bottomReachedListener
	 * @param allowedDifference
	 */
	// public void setOnTopReachedListener(OnEdgeReachedListener topReachedListener, int allowedDifference) {
	// mOnTopReachedListener = topReachedListener;
	// mMinTopDistance = allowedDifference;
	// }
	// public void setOnBottomReachedListener(OnEdgeReachedListener bottomReachedListener, int allowedDifference) {
	// mOnBottomReachedListener = bottomReachedListener;
	// mMinBottomDistance = allowedDifference;
	// }

	/**
	 * Implement this interface if you want to be notified when the WebView has scrolled to the top or bottom.
	 */
	private interface OnEdgeReachedListener {
		void onTopReached(View v, boolean reached);

		void onBottomReached(View v, boolean reached);
	}

	private boolean topReached = true;
	private boolean bottomReached = false;

	@Override
	protected void onScrollChanged(int left, int top, int oldLeft, int oldTop) {
		if (mOnTopReachedListener != null) handleTopReached(top);

		if (mOnBottomReachedListener != null) handleBottomReached(top);

		super.onScrollChanged(left, top, oldLeft, oldTop);
	}

	private void handleTopReached(int top) {
		boolean reached;
		if (top <= mMinTopDistance) reached = true;
		else if (top > (mMinTopDistance * 1.5)) reached = false;
		else return;

		if (!reached && !topReached) return;
		if (reached && topReached) return;

		topReached = reached;

		mOnTopReachedListener.onTopReached(this, reached);
	}

	private void handleBottomReached(int top) {
		boolean reached;
		if ((getContentHeight() - (top + getHeight())) <= mMinBottomDistance) reached = true;
		else if ((getContentHeight() - (top + getHeight())) > (mMinBottomDistance * 1.5)) reached = false;
		else return;

		if (!reached && !bottomReached) return;
		if (reached && bottomReached) return;

		bottomReached = reached;

		mOnBottomReachedListener.onBottomReached(this, reached);
	}

}