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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.core.client.JavaScriptObject;

/**
 * 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 boolean isRepeating; private Integer timerId = null; /** * Workaround for broken clearTimeout in IE. Keeps track of whether cancel has been called since * schedule was called. See https://code.google.com/p/google-web-toolkit/issues/detail?id=8101 */ private int cancelCounter = 0; /** * Returns {@code true} if the timer is running. Timer is running if and only if it is scheduled * but it is not expired or cancelled. */ public final boolean isRunning() { return timerId != null; } /** * Cancels this timer. If the timer is not running, this is a no-op. */ public void cancel() { if (!isRunning()) { return; } cancelCounter++; if (isRepeating) { clearInterval(timerId); } else { clearTimeout(timerId); } timerId = null; } /** * 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. If the timer is already running then it will be * first canceled before re-scheduling. * * @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 non-negative"); } if (isRunning()) { cancel(); } isRepeating = false; timerId = setTimeout(createCallback(this, cancelCounter), delayMillis); } /** * Schedules a timer that elapses repeatedly. If the timer is already running then it will be * first canceled before re-scheduling. * * @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"); } if (isRunning()) { cancel(); } isRepeating = true; timerId = setInterval(createCallback(this, cancelCounter), periodMillis); } /* * Called by native code when this timer fires. * * Only call run() if cancelCounter has not changed since the timer was scheduled. */ final void fire(int scheduleCancelCounter) { // Workaround for broken clearTimeout in IE. if (scheduleCancelCounter != cancelCounter) { return; } if (!isRepeating) { timerId = null; } // Run the timer's code. run(); } private static native JavaScriptObject createCallback(Timer timer, int cancelCounter) /*-{ return $entry(function() { timer.@Timer::fire(I)(cancelCounter); }); }-*/; private static native int setInterval(JavaScriptObject func, int time) /*-{ return $wnd.setInterval(func, time); }-*/; private static native int setTimeout(JavaScriptObject func, int time) /*-{ return $wnd.setTimeout(func, time); }-*/; private static native void clearInterval(int timerId) /*-{ $wnd.clearInterval(timerId); }-*/; private static native void clearTimeout(int timerId) /*-{ $wnd.clearTimeout(timerId); }-*/; }




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