elemental/src/elemental/util/Timer.java

/*
 * 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 elemental.util;

import static elemental.client.Browser.getWindow;

import elemental.html.Window;
import elemental.dom.TimeoutHandler;

/**
 * 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}.
 */
public abstract class Timer {

  private boolean isRepeating;
  private int timerId;

  /**
   * Cancels this timer.
   */
  public void cancel() {
    if (isRepeating) {
      getWindow().clearInterval(timerId);
    } else {
      getWindow().clearTimeout(timerId);
    }
  }

  /**
   * 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 non-negative");
    }
    cancel();
    isRepeating = false;

    timerId = getWindow().setTimeout(new TimeoutHandler() {
      @Override
      public void onTimeoutHandler() {
        run();
      }
    }, delayMillis);
  }

  /**
   * 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 = getWindow().setInterval(new TimeoutHandler() {
      @Override
      public void onTimeoutHandler() {
        run();
      }
    }, periodMillis);
  }
}