com.clouway.gwtphonegap.client.channel.ChannelFactory.java Source code

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Here is the source code for com.clouway.gwtphonegap.client.channel.ChannelFactory.java

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package com.clouway.gwtphonegap.client.channel;/*
                                               * Copyright (C) 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.
                                               */

import com.google.gwt.appengine.channel.client.Channel;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.ScriptElement;
import com.google.gwt.user.client.Timer;

/** Manages creating {@link Channel}s to receive messages from the server. */
public class ChannelFactory {

    private static final String CHANNEL_SRC = "/_ah/channel/jsapi";
    private static Channel channel;

    /**
     * Creates a {@link Channel} with the given client ID, passing it to the given
     * {@link ChannelCreatedCallback}.
     *
     * <p>
     * If a Channel has already been created, this will immediately be passed to
     * the callback, so only one Channel will ever be created by this method.
     * </p>
     */
    public static void createChannel(final String clientId, final ChannelCreatedCallback callback) {
        ScriptElement script = Document.get().createScriptElement();
        script.setSrc(CHANNEL_SRC);
        Document.get().getElementsByTagName("head").getItem(0).appendChild(script);

        new Timer() {
            @Override
            public void run() {
                if (scriptLoaded()) {
                    channel = createChannelImpl(clientId);
                    callback.onChannelCreated(channel);
                    this.cancel();
                }
            }
        }.scheduleRepeating(100);
    }

    private static native boolean scriptLoaded() /*-{
                                                 return !!$wnd.goog && !!$wnd.goog.appengine && !!$wnd.goog.appengine.Channel;
                                                 }-*/;

    private static final native Channel createChannelImpl(String clientId) /*-{
                                                                           return new $wnd.goog.appengine.Channel(clientId);
                                                                           }-*/;

    public interface ChannelCreatedCallback {
        public void onChannelCreated(Channel channel);
    }
}