android - 如何保持轮询绑定(bind)服务？

Question

我在互联网上查找，但找不到涵盖我的场景的示例。我想做的是:

1) To start and bind to a service as soon as my activity starts (done)

2) The service then binds itself to another service looking for a user input from a connected device, and saves a string a string to a variable (done)

3) I would like to send back this string to the activity, so I can check what it is and based on it to make a network call.

现在第 3 个)是我的挑战。我设法用一个运行一秒钟的计时器来做到这一点，然后检查服务中写入的值，但不知何故这似乎不是正确的方法，我认为可能有更成熟的解决方案。但是，我似乎无法弄清楚。

我从文档中获取了代码，只添加了计时器。在这个例子中，只有一个服务只生成一个随机数(这通常会被我的第二个服务取代)。这是服务的代码:

public class LocalService extends Service {

    private final IBinder mBinder = new LocalBinder();

    private final Random mGenerator = new Random();

    public class LocalBinder extends Binder {
        LocalService getService() {
            return LocalService.this;
        }
    }

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

    public int getRandomNumber() {
        return mGenerator.nextInt(100);
    }
}

这是我 Activity 中的代码:

public class MainActivity extends AppCompatActivity {

    LocalService mService;
    boolean mBound = false;
    Timer timer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        timer = new Timer();
    }

    @Override
    protected void onStart() {
        super.onStart();
        Intent intent = new Intent(this, LocalService.class);
        bindService(intent, mConnection, Context.BIND_AUTO_CREATE);

        timer.schedule(new MyTimerTask(new Handler(), this), 1000, 1000); // run on every second
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (mBound) {
            unbindService(mConnection);
            mBound = false;
        }

        timer.cancel();
        timer.purge();
    }

    private class MyTimerTask extends TimerTask {
        Handler handler;
        MainActivity ref;

        public MyTimerTask(Handler handler, MainActivity ref) {
            super();
            this.handler = handler;
            this.ref = ref;
        }

        @Override
        public void run() {
            handler.post(new Runnable() {
                @Override
                public void run() {
                    if (mBound) {
                        int num = ref.mService.getRandomNumber();
                        // just as an example, raise a toast to see if it works
                        // but otherwise the value will be handled
                        Toast.makeText(ref, "number: " + num, Toast.LENGTH_SHORT).show();
                    }
                }
            });
        }
    }

    private ServiceConnection mConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName className,
                                       IBinder service) {
            LocalService.LocalBinder binder = (LocalService.LocalBinder) service;
            mService = binder.getService();
            mBound = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            mBound = false;
        }
    };
}

我的问题是:这是一种好方法(有效)还是不好，有什么替代方法？

Answer 1

您可以使用 LocalBroadcastManager 将广播从您的 Service 发送到您的 Activity。例如，在您的 Service 中声明:

public static final String BROADCAST_INTENT = "broadcast_intent";
public static final String BROADCAST_VALUE = "broadcast_value";

private LocalBroadcastManager broadcastManager;

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

    broadcastManager = LocalBroadcastManager.getInstance(this);
}

现在，无论何时你想发送一个 String 到你的 Activity，你都可以这样做:

private void sendBroadcast(String value) {

    Intent intent = new Intent(BROADCAST_INTENT);
    intent.putExtra(BROADCAST_VALUE, value);
    broadcastManager.sendBroadcast(intent);
}

在您的Activity 中声明一个BroadcastReceiver:

private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {

        handleIntent(intent);
    }
};

当您绑定(bind)到您的服务时注册接收器:

IntentFilter broadcastIntentFilter = new IntentFilter();
broadcastIntentFilter.addAction(StreamService.BROADCAST_INTENT);
LocalBroadcastManager.getInstance(context).registerReceiver((broadcastReceiver), broadcastIntentFilter);

并在您解除服务绑定(bind)的地方取消注册:

LocalBroadcastManager.getInstance(context).unregisterReceiver(broadcastReceiver);

现在，当您的服务发送广播时，您可以在 Activity 中处理它:

private void handleIntent(Intent intent) {

    if (intent.getAction().equals(StreamService.BROADCAST_INTENT)) {
        String value = intent.getStringExtra(StreamService.BROADCAST_VALUE, "default");
    }
}