How to keep polling a bound service?

Question

I looked up on the internet, but couldn't find an example covering my scenario. What I am trying to do is:

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.

Now number 3) is my challenge. I managed to do it with a Timer that runs for one second and then checks the value written in the service, but somehow this doesn't seem to be the right way and I think that there might be a more mature solution. However, I can't seem to figure it out.

I've taken the code from the documentation and only added the timer. It is just one service in this example that just generates a random number (this will normally be replaced by my second service). This is the code for the service:

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);
    }
}

And this is the code in my activity:

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;
        }
    };
}

My question is: is this a good approach (it works) or is it bad and what's the alternative?

Niels Masdorp · Accepted Answer

You can use LocalBroadcastManager to send broadcasts from your Service to your Activity. For example, in your Service declare:

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);
}

Now whenever you want to send a String to your Activity you can do so like this:

private void sendBroadcast(String value) {

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

In your Activity declare a BroadcastReceiver:

private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {

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

        handleIntent(intent);
    }
};

Register the receiver when you bind to your Service:

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

And unregister where you unbind from your Service:

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

Now when your service sends the broadcast you can handle it in your Activity:

private void handleIntent(Intent intent) {

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

How to keep polling a bound service?

Answers (2)

Related Questions