android - 我如何(应该)将处理程序添加到服务中的线程

Question

我仍在研究 Pro Android 2 的简短服务示例(第 304 页)同样，服务示例由两个类组成:如下所示的 BackgroundService.java 和如下所示的 MainActivity.java。现在我想扩展此代码以将数据传递到我的应用程序中的另一个 Activity 。根据我所学到的，我在下面的代码中添加了一个处理程序的开头:

    public class MainActivity extends Activity {
        private static final String TAG = "MainActivity";

        @Override
        public void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            Log.d(TAG, "starting service");

            Button bindBtn = (Button)findViewById(R.id.bindBtn);
            bindBtn.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {
                    Intent backgroundService = new Intent(MainActivity.this, com.marie.mainactivity.BackgroundService.class);
                    startService(backgroundService);
                }
            });

            Button unbindBtn = (Button)findViewById(R.id.unbindBtn);
            unbindBtn.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View arg0) {
                    stopService(new Intent(MainActivity.this, BackgroundService.class));
                }
            });
        }
    }

    // The handler code I added
    // I'm not sure what fills out the msg.what field for the switch
    private Handler messageHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {  
            switch(msg.what) {
                //handle update
                //possibly update another activity???
            }
        }

    };

    public class BackgroundService extends Service {
        private NotificationManager notificationMgr;

        @Override
        public void onCreate() {
            super.onCreate();

            notificationMgr = NotificationManager)getSystemService(NOTIFICATION_SERVICE);

            displayNotificationMessage("starting Background Service");

            Thread thr = new Thread(null, new ServiceWorker(), "BackgroundService");
            thr.start();
        }   

        class ServiceWorker implements Runnable
        {
            public void run() {
                mResult = doSomethingTimeConsuming();

                //Use the handler to send update to the main thread or another activity???
                messageHandler.sendMessage(Message.obtain(messageHandler, mResults));

                BackgroundService.this.stopSelf();
            }
        }

        @Override
        public void onDestroy()
        {
            displayNotificationMessage("stopping Background Service");
            super.onDestroy();
        }

        @Override
        public void onStart(Intent intent, int startId) {
            super.onStart(intent, startId);
        }

        @Override
        public IBinder onBind(Intent intent) {
            return null;
        }

        private void displayNotificationMessage(String message)
        {
            Notification notification = new Notification(R.drawable.note, message, System.currentTimeMillis());

            PendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, MainActivity.class), 0);

            notification.setLatestEventInfo(this, "Background Service", message, contentIntent);

            notificationMgr.notify(R.id.app_notification_id, notification);
        }
    }

我了解到，当我获得服务实例时，我可以将其传递给处理程序。但我不知道该怎么做。

Answer 1

如果要从服务向 Activity 发送信息，请使用广播接收器。在您的 Activity 中创建一个广播接收器内部类，这样它就可以访问 Activity 的数据。然后注册广播:

IntentFilter filter = new IntentFilter("com.damluar.intent.action.NEWTWEETS");
broadcastReceiver = new NewTweetsReceiver();
registerReceiver(broadcastReceiver, filter);

然后从服务中，您可以通过 Intent 将数据发送到广播(和外部 Activity ):

sendBroadcast(new Intent("com.damluar.intent.action.NEWTWEETS"));