Timer.java

/*******************************************************************************
 * Copyright (c) 2004, 2008 John Krasnay and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     John Krasnay - initial API and implementation
 *******************************************************************************/
package net.sf.vex.swt;

import org.eclipse.swt.widgets.Display;

/**
 * Periodic timer, built using the Display.timerExec method.
 */
public class Timer {

    /**
     * Class constructor. The timer must be explicitly started using the
     * start() method.
     * @param periodMs Milliseconds between each invocation.
     * @param runnable Runnable to execute when the period expires.
     */
    public Timer(int periodMs, Runnable runnable) {
        this.periodMs = periodMs;
        this.runnable = runnable;
    }

    /**
     * Reset the timer so that it waits another period before firing.
     */
    public void reset() {
        if (this.started) {
            this.stop();
            this.start();
        }
    }

    /**
     * Start the timer. 
     */
    public void start() {
        if (!this.started) {
            this.innerRunnable = new InnerRunnable();
            Display.getCurrent().timerExec(this.periodMs, this.innerRunnable);
            this.started = true;
        }
    }

    /**
     * Stop the timer.
     */
    public void stop() {
        if (this.started) {
            this.innerRunnable.discarded = true;
            this.innerRunnable = null;
            this.started = false;
        }
    }
    
    //==================================================== PRIVATE
    
    private Runnable runnable;
    private int periodMs;
    private boolean started = false;
    private InnerRunnable innerRunnable;
    
    private class InnerRunnable implements Runnable {
        public boolean discarded = false;
        public void run() {
            if (!discarded) {
                runnable.run();
                //Display display = Display.getCurrent();
                Display.getCurrent().timerExec(periodMs, this);
            }
        }
    }
}