我的Android应用程序中有一个名为UploadManager的AsyncTask,它检查已处理的项目,并将它们上传到服务器.
为此,我使用ScheduledExecutorService.scheduleAtFixedRate每1分钟检查一次项目,并将它们上传到服务器.
但是,有时会创建多个线程池(这种情况发生在10％的时间),因此有时会向服务器发送两次相同的请求,尽管这种并发性在服务器和服务器上都得到了处理.客户端级别,但我仍然不希望这种情况发生在客户端.
下面是代码的样子.
在MainActivity(start-activity)中,我将UploadManager启动为：

public class MainActivity extends BaseActivity {

   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       .
       .
       .
       new UploadManager().execute(this);
   }
}

UploadManager的工作原理如下：

public class UploadManager extends AsyncTask<Context, Integer, Integer> {

    private ScheduledExecutorService scheduledExecutorService;
    private static final int NUM_OF_THREADS = 5;
    private static final int DELAY_IN_SECONDS = 60;
    private Context context;
    private final Logger logger = new Logger(getClass().getSimpleName());

    protected Integer doInBackground(Context... context) {
        this.context = context[0];
        scheduledExecutorService = Executors.newScheduledThreadPool(NUM_OF_THREADS);
        scheduledExecutorService.scheduleAtFixedRate(postInformation, 5, DELAY_IN_SECONDS, TimeUnit.SECONDS);
       return 0;
    }

    private Runnable postInformation = new Runnable() {
        @Override
        public void run() {
            if (NetworkManager.isInternetAvailable(context)) {
                uploadAcknowledgement();
            }
        }
    };

    private void uploadAcknowledgement() {
        List<Acknowledgement> ackList = null;
        try {
            logger.info("RUNNING TASK TO POST ACKNOWLEDGEMENT");
            .
            .
        }
    }
}

当我检查日志时,它说：

35119 [pool-2-thread-1] INFO  Upload Manager - [1363841355530] : 21/03/2013 10:19:15 : RUNNING TASK TO POST ACKNOWLEDGEMENT  
35122 [pool-3-thread-1] INFO  Upload Manager - [1363841355532] : 21/03/2013 10:19:15 : RUNNING TASK TO POST ACKNOWLEDGEMENT

这清楚地表明现在有多个线程池,因此,uploadAcknowledgement()方法被多次调用.

MainActivity在AndroidManifest.xml中声明为：

<application android:label="@string/app_name" android:icon="@drawable/icon">
    <activity android:name="MainActivity"
              android:label="@string/app_name"
              android:theme="@android:style/Theme.NoTitleBar">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
            <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
        </intent-filter>
    </activity>
    .
    .

解决方法:

我最终想出了原因,如果ScheduledExecutor的服务运行重叠,那么它会产生新的工作线程(例如,在这种情况下,postInformation()创建一个新的工作线程),最终产生一个新的池.
但是,使用newSingleThreadScheduledExecutor而不是newScheduledThreadPool(int corePoolSize)’可以避免多个worker.
因此,不要将`scheduledExecutorService’初始化为：

scheduledExecutorService = Executors.newScheduledThreadPool(NUM_OF_THREADS);  

它应该被初始化为：

scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();  

这样就可以确保没有多个工作线程在运行.