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?
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");
}
}