com.google.gwt.event.dom.client.TouchEvent.java Source code

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Here is the source code for com.google.gwt.event.dom.client.TouchEvent.java

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/*
 * Copyright 2010 Google Inc.
 *
 * 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 com.google.gwt.event.dom.client;

import com.google.gwt.core.client.GWT;
import com.google.gwt.core.client.JsArray;
import com.google.gwt.dom.client.Touch;
import com.google.gwt.event.shared.EventHandler;

/**
 * Abstract class representing touch events.
 *
 * See {@link <a href="http://developer.apple.com/library/safari/documentation/UserExperience/Reference/TouchEventClassReference/TouchEvent/TouchEvent.html">Safari Touch Event Documentation</a>}
 * @param <H> handler type
 */
public abstract class TouchEvent<H extends EventHandler> extends HumanInputEvent<H> {

    /**
     * Dectector for browser support for touch events.
     */
    private static class TouchSupportDetector {

        private final boolean isSupported = detectTouchSupport();

        public boolean isSupported() {
            return isSupported;
        }

        private native boolean detectTouchSupport() /*-{
                                                    var elem = document.createElement('div');
                                                    elem.setAttribute('ontouchstart', 'return;');
                                                    return (typeof elem.ontouchstart) == "function";
                                                    }-*/;
    }

    /**
     * Detector for browsers that do not support touch events.
     */
    @SuppressWarnings("unused")
    private static class TouchSupportDetectorNo extends TouchSupportDetector {
        @Override
        public boolean isSupported() {
            return false;
        }
    }

    /**
     * The implementation singleton.
     */
    private static TouchSupportDetector impl;

    /**
     * Runtime check for whether touch scrolling is supported in this browser. Returns true if touch
     * events are supported but touch based scrolling is not natively supported.
     * 
     * @return true if touch events are supported, false if not
     */
    public static boolean isSupported() {
        if (impl == null) {
            impl = GWT.create(TouchSupportDetector.class);
        }
        return impl.isSupported();
    }

    /**
     * Get an array of {@link Touch touches} which have changed since the last
     * touch event fired. Note, that for {@link TouchEndEvent touch end events},
     * the touch which has just ended will not be present in the array. Moreover,
     * if the touch which just ended was the last remaining touch, then a zero
     * length array will be returned.
     *
     * @return an array of touches
     */
    public JsArray<Touch> getChangedTouches() {
        return getNativeEvent().getChangedTouches();
    }

    /**
     * Get an array of {@link Touch touches} all touch which originated at the
     * same target as the current touch event. Note, that for {@link TouchEndEvent
     * touch end events}, the touch which has just ended will not be present in
     * the array. Moreover, if the touch which just ended was the last remaining
     * touch, then a zero length array will be returned.
     *
     * @return an array of touches
     */
    public JsArray<Touch> getTargetTouches() {
        return getNativeEvent().getTargetTouches();
    }

    /**
     * Get an array of all current {@link Touch touches}. Note, that for
     * {@link TouchEndEvent touch end events}, the touch which has just ended will
     * not be present in the array. Moreover, if the touch which just ended was
     * the last remaining touch, then a zero length array will be returned.
     *
     * @return an array of touches
     */
    public JsArray<Touch> getTouches() {
        return getNativeEvent().getTouches();
    }
}