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/*
 * Copyright 2007 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.user.client;

import com.google.gwt.event.logical.shared.CloseEvent;
import com.google.gwt.event.logical.shared.CloseHandler;

import java.util.ArrayList;

/**
 * A simplified, browser-safe timer class. This class serves the same purpose as
 * java.util.Timer, but is simplified because of the single-threaded
 * environment.
 * 
 * 

* To schedule a timer, simply create a subclass of it (overriding {@link #run}) * and call {@link #schedule} or {@link #scheduleRepeating}. *

* *

* NOTE: If you are using a timer to schedule a UI animation, use * {@link com.google.gwt.animation.client.AnimationScheduler} instead. The * browser can optimize your animation for maximum performance. *

* *

*

Example

* {@example com.google.gwt.examples.TimerExample} *

*/ public abstract class Timer { private static ArrayList timers = new ArrayList(); static { hookWindowClosing(); } private static native void clearInterval(int id) /*-{ $wnd.clearInterval(id); }-*/; private static native void clearTimeout(int id) /*-{ $wnd.clearTimeout(id); }-*/; private static native int createInterval(Timer timer, int period) /*-{ return $wnd.setInterval( $entry(function() { [email protected]::fire()(); }), period); }-*/; private static native int createTimeout(Timer timer, int delay) /*-{ return $wnd.setTimeout( $entry(function() { [email protected]::fire()(); }), delay); }-*/; private static void hookWindowClosing() { // Catch the window closing event. Window.addCloseHandler(new CloseHandler() { public void onClose(CloseEvent event) { while (timers.size() > 0) { timers.get(0).cancel(); } } }); } private boolean isRepeating; private int timerId; /** * Cancels this timer. */ public void cancel() { if (isRepeating) { clearInterval(timerId); } else { clearTimeout(timerId); } timers.remove(this); } /** * This method will be called when a timer fires. Override it to implement the * timer's logic. */ public abstract void run(); /** * Schedules a timer to elapse in the future. * * @param delayMillis how long to wait before the timer elapses, in * milliseconds */ public void schedule(int delayMillis) { if (delayMillis <= 0) { throw new IllegalArgumentException("must be positive"); } cancel(); isRepeating = false; timerId = createTimeout(this, delayMillis); timers.add(this); } /** * Schedules a timer that elapses repeatedly. * * @param periodMillis how long to wait before the timer elapses, in * milliseconds, between each repetition */ public void scheduleRepeating(int periodMillis) { if (periodMillis <= 0) { throw new IllegalArgumentException("must be positive"); } cancel(); isRepeating = true; timerId = createInterval(this, periodMillis); timers.add(this); } /* * Called by native code when this timer fires. */ final void fire() { // If this is a one-shot timer, remove it from the timer list. This will // allow it to be garbage collected. if (!isRepeating) { timers.remove(this); } // Run the timer's code. run(); } }




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