ID #58361


ConditionVariable类位于Android.os.ConditionVariable,它可以帮助Android线程同步。在SDK上的介绍ConditionVariable不同于标准Java位于java.lang.Object wait() 和 notify() ,这个类可以等待自己,这就意味着 open(), close() 和 block() 可能会假死 ,如果使用ConditionVariable类的open()在调用 block() 之前, block() 将不会阻塞,相反将会返回立即。


boolean  block(long timeout)
阻止当前线程知道条件是open,或直到超时,这里参数long timeout为超时设置,Android123提示大家如果你们从事过Win32开发,这个方法类似DWORD WaitForSingleObject(HANDLE hHandle,DWORD dwMilliseconds); 函数。

void  block()
阻止当前线程知道条件 open ,是上面的无超时等待重载版本。

void  close()
重置条件为 close状态。

void  open()

ConditionVariable 在创建时还有一种构造方法是 public ConditionVariable (boolean state) ,如果为true,默认时为opened,如果为false则是closed. ,默认public ConditionVariable()为closed.

 * 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 
 * 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. 
// Need the following import to get access to the app resources, since this  
// class is in a sub-package.  
import android.content.Intent;  
import android.os.Binder;  
import android.os.ConditionVariable;  
import android.os.IBinder;  
import android.os.Parcel;  
import android.os.RemoteException;  
import android.widget.RemoteViews;  
 * This is an example of service that will update its status bar balloon  
 * every 5 seconds for a minute. 
public class NotifyingService extends Service {  
    // Use a layout id for a unique identifier  
    private static int MOOD_NOTIFICATIONS = R.layout.status_bar_notifications;  
    // variable which controls the notification thread   
    private ConditionVariable mCondition;  
    public void onCreate() {  
        mNM = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);  
        // Start up the thread running the service.  Note that we create a  
        // separate thread because the service normally runs in the process's  
        // main thread, which we don't want to block.  
        Thread notifyingThread = new Thread(null, mTask, "NotifyingService");  
        mCondition = new ConditionVariable(false);  
    public void onDestroy() {  
        // Cancel the persistent notification.  
        // Stop the thread from generating further notifications ;  
    private Runnable mTask = new Runnable() {  
        public void run() {  
            for (int i = 0; i < 4; ++i) {  
                if (mCondition.block(5 * 1000))   
                if (mCondition.block(5 * 1000))   
                if (mCondition.block(5 * 1000))   
            // Done with our work...  stop the service!  
    public IBinder onBind(Intent intent) {  
        return mBinder;  
    private void showNotification(int moodId, int textId) {  
        // In this sample, we'll use the same text for the ticker and the expanded notification  
        CharSequence text = getText(textId);  
        // Set the icon, scrolling text and timestamp.  
        // Note that in this example, we pass null for tickerText.  We update the icon enough that  
        // it is distracting to show the ticker text every time it changes.  We strongly suggest  
        // that you do this as well.  (Think of of the "New hardware found" or "Network connection  
        // changed" messages that always pop up)  
        Notification notification = new Notification(moodId, null, System.currentTimeMillis());  
        // The PendingIntent to launch our activity if the user selects this notification  
        PendingIntent contentIntent = PendingIntent.getActivity(this, 0,  
                new Intent(this, NotifyingController.class), 0);  
        // Set the info for the views that show in the notification panel.  
        notification.setLatestEventInfo(this, getText(R.string.status_bar_notifications_mood_title),  
                       text, contentIntent);  
        // Send the notification.  
        // We use a layout id because it is a unique number.  We use it later to cancel.  
        mNM.notify(MOOD_NOTIFICATIONS, notification);  
    // This is the object that receives interactions from clients.  See  
    // RemoteService for a more complete example.  
    private final IBinder mBinder = new Binder() {  
        protected boolean onTransact(int code, Parcel data, Parcel reply,  
                int flags) throws RemoteException {  
            return super.onTransact(code, data, reply, flags);  
    private NotificationManager mNM;