ConditionVariable控制通知栏消息变更

zxl_ong

ConditionVariable介绍：
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。

该类一共有4个方法

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()
Open条件，释放所有线程的阻塞.

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 * *      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.example.android.apis.app;// Need the following import to get access to the app resources, since this// class is in a sub-package.import com.example.android.apis.R;import android.app.Notification;import android.app.NotificationManager;import android.app.PendingIntent;import android.app.Service;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;     @Override    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);        notifyingThread.start();    }    @Override    public void onDestroy() {        // Cancel the persistent notification.        mNM.cancel(MOOD_NOTIFICATIONS);        // Stop the thread from generating further notifications        mCondition.open();    }    private Runnable mTask = new Runnable() {        public void run() {            for (int i = 0; i < 4; ++i) {                showNotification(R.drawable.stat_happy,                        R.string.status_bar_notifications_happy_message);                if (mCondition.block(5 * 1000))                     break;                showNotification(R.drawable.stat_neutral,                        R.string.status_bar_notifications_ok_message);                if (mCondition.block(5 * 1000))                     break;                showNotification(R.drawable.stat_sad,                        R.string.status_bar_notifications_sad_message);                if (mCondition.block(5 * 1000))                     break;            }            // Done with our work...  stop the service!            NotifyingService.this.stopSelf();        }    };    @Override    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() {        @Override        protected boolean onTransact(int code, Parcel data, Parcel reply,                int flags) throws RemoteException {            return super.onTransact(code, data, reply, flags);        }    };    private NotificationManager mNM;}