com.google.gwt.media.client.Audio.java Source code

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Here is the source code for com.google.gwt.media.client.Audio.java

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/*
 * Copyright 2011 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.media.client;

import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.AudioElement;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.PartialSupport;

/**
 * <p>
 * A widget representing an &lt;audio&gt; element.
 *
 * <p>
 * <span style="color:red">Experimental API: This API is still under development
 * and is subject to change. </span>
 * </p>
 *
 * This widget may not be supported on all browsers.
 */
@PartialSupport
public class Audio extends MediaBase {
    /**
     * Detector for permutations that might support {@link AudioElement}.
     */
    @SuppressWarnings("unused")
    private static class AudioElementSupportDetectedMaybe extends AudioElementSupportDetector {
        /**
         * Using a compile-time check, return true if {@link AudioElement} might be
         * supported.
         *
         * @return true if might be supported, false otherwise.
         */
        @Override
        boolean isSupportedCompileTime() {
            return true;
        }
    }

    /**
     * Detector for permutations that do not support {@link AudioElement}.
     */
    @SuppressWarnings("unused")
    private static class AudioElementSupportDetectedNo extends AudioElementSupportDetector {
        /**
         * Using a compile-time check, return true if {@link AudioElement} might be
         * supported.
         *
         * @return true if might be supported, false otherwise.
         */
        @Override
        boolean isSupportedCompileTime() {
            return false;
        }
    }

    /**
     * Detector for browser support of {@link AudioElement}.
     */
    private static class AudioElementSupportDetector {
        /**
         * Using a run-time check, return true if the {@link AudioElement} is
         * supported.
         *
         * @return true if supported, false otherwise.
         */
        static native boolean isSupportedRunTime(AudioElement element) /*-{
                                                                       return !!element.canPlayType;
                                                                       }-*/;

        /**
         * Using a compile-time check, return true if {@link AudioElement} might be
         * supported.
         *
         * @return true if might be supported, false otherwise.
         */
        boolean isSupportedCompileTime() {
            // will be true in AudioElementSupportDetectedMaybe
            // will be false in AudioElementSupportDetectedNo
            return false;
        }
    }

    private static AudioElementSupportDetector detector;

    /**
     * Return a new {@link Audio} if supported, and null otherwise.
     *
     * @return a new {@link Audio} if supported, and null otherwise
     */
    public static Audio createIfSupported() {
        if (detector == null) {
            detector = GWT.create(AudioElementSupportDetector.class);
        }
        if (!detector.isSupportedCompileTime()) {
            return null;
        }
        AudioElement element = Document.get().createAudioElement();
        if (!detector.isSupportedRunTime(element)) {
            return null;
        }
        return new Audio(element);
    }

    /**
     * Runtime check for whether the audio element is supported in this browser.
     *
     * @return whether the audio element is supported
     */
    public static boolean isSupported() {
        if (detector == null) {
            detector = GWT.create(AudioElementSupportDetector.class);
        }
        if (!detector.isSupportedCompileTime()) {
            return false;
        }
        AudioElement element = Document.get().createAudioElement();
        if (!detector.isSupportedRunTime(element)) {
            return false;
        }
        return true;
    }

    /**
     * Protected constructor. Use {@link #createIfSupported()} to create an Audio.
     */
    protected Audio(AudioElement element) {
        super(element);
    }

    /**
     * Returns the attached AudioElement.
     *
     * @return the AudioElement
     */
    public AudioElement getAudioElement() {
        return getMediaElement().cast();
    }
}