Android example source code file (ResettableTimeout.java)

This example Android source code file (ResettableTimeout.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, conditionvariable, interruptedexception, os, resettabletimeout, t, thread

The ResettableTimeout.java Android example source code

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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.android.server;

import android.os.SystemClock;

import android.os.ConditionVariable;

/**
 * Utility class that you can call on with a timeout, and get called back
 * after a given time, dealing correctly with restarting the timeout.
 *
 * <p>For example, this class is used by the android.os.Vibrator class.
 */
abstract class ResettableTimeout
{
    /**
     * Override this do what you need to do when it's starting
     * This is called with the monitor on this method held, so be careful.
     *
     * @param alreadyOn is true if it's currently running
     */
    public abstract void on(boolean alreadyOn);

    /**
     * Override this to do what you need to do when it's stopping.
     * This is called with the monitor on this method held, so be careful.
     */
    public abstract void off();

    /**
     * Does the following steps.
     * <p>1. Call on()

     * <p>2. Start the timer.

     * <p>3. At the timeout, calls off()

     * <p>If you call this again, the timeout is reset to the new one
     */
    public void go(long milliseconds)
    {
        synchronized (this) {
            mOffAt = SystemClock.uptimeMillis() + milliseconds;

            boolean alreadyOn;

            // By starting the thread first and waiting, we ensure that if the
            // thread to stop it can't start, we don't turn the vibrator on
            // forever.  This still isn't really sufficient, because we don't
            // have another processor watching us.  We really should have a
            // service for this in case our process crashes.
            if (mThread == null) {
                alreadyOn = false;
                mLock.close();
                mThread = new T();
                mThread.start();
                mLock.block();
                mOffCalled = false;
            } else {
                alreadyOn = true;
                // poke the thread so it gets the new timeout.
                mThread.interrupt();
            }
            on(alreadyOn);
        }
    }

    /**
     * Cancel the timeout and call off now.
     */
    public void cancel()
    {
        synchronized (this) {
            mOffAt = 0;
            if (mThread != null) {
                mThread.interrupt();
                mThread = null;
            }
            if (!mOffCalled) {
                mOffCalled = true;
                off();
            }
        }
    }

    private class T extends Thread
    {
        public void run()
        {
            mLock.open();
            while (true) {
                long diff;
                synchronized (this) {
                    diff = mOffAt - SystemClock.uptimeMillis();
                    if (diff <= 0) {
                        mOffCalled = true;
                        off();
                        mThread = null;
                        break;
                    }
                }
                try {
                    sleep(diff);
                }
                catch (InterruptedException e) {
                }
            }
        }
    }

    private ConditionVariable mLock = new ConditionVariable();

    // turn it off at this time.
    private volatile long mOffAt;
    private volatile boolean mOffCalled;

    private Thread mThread;

}