de.swm.commons.mobile.client.utils.GhostClickPreventer.java Source code

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Here is the source code for de.swm.commons.mobile.client.utils.GhostClickPreventer.java

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/*
 * Copyright 2011 SWM Services GmbH.
 * 
 * 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 de.swm.commons.mobile.client.utils;

import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.Timer;
import de.swm.commons.mobile.client.event.DragControllerMobile;

import java.util.ArrayList;
import java.util.List;

/**
 * Helper class to prevent 'ghost clicks' (extra click events that occur when a touch end event is converted to a click event).
 * Used in {code}DragControllerMobile{code}.
 * 
 * See https://developers.google.com/mobile/articles/fast_buttons?hl=fi-FI
 * 
 * @see DragControllerMobile
 */
public class GhostClickPreventer {

    private static final int GHOST_CLICK_DELAY_MILLIS = 2500;
    private static final int GHOST_CLICK_RADIUS = 25;

    final List<Point> clickedPoints = new ArrayList<Point>();

    public void rememberGhostClick(Point point) {
        clickedPoints.add(point);

        Timer timer = new Timer() {

            @Override
            public void run() {
                Point removedP = clickedPoints.remove(0);
            }

        };
        timer.schedule(GHOST_CLICK_DELAY_MILLIS);
    }

    public boolean preventGhostClick(Event event, Point point) {
        for (Point clickedPoint : clickedPoints) {
            if ((Math.abs(clickedPoint.xPos() - point.xPos()) < GHOST_CLICK_RADIUS)
                    && (Math.abs(clickedPoint.yPos() - point.yPos()) < GHOST_CLICK_RADIUS)) {

                event.stopPropagation();
                event.preventDefault();

                return true;
            }
        }

        return false;
    }

}