Android Activity Foreground Surveillance

In order to check if an Activity of my Android application is currently in the foreground I wrote a simple Service.

public class UEService extends Service {
    private static final String TAG = "UEService";
    private Timer timer;
    private static final int delay = 1000; // delay for 1 sec before first start
    private static final int period = 10000; // repeat check every 10 sec.

    // This is the old onStart method that will be called on the pre-2.0
    // platform. On 2.0 or later we override onStartCommand() so this
    // method will not be called.
    @Override
    public void onStart(Intent intent, int startId) {
        handleCommand(intent);
    }

    // To make this Service work in pre Level 5 APIs just remove this method
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        handleCommand(intent);
        return START_NOT_STICKY;
    }

    // handles a Start command
    private void handleCommand(Intent intent) {
        Log.d(TAG, "service is starting");

        if (timer == null) {
            timer = new Timer();
            timer.schedule(new TimerTask() {
                public void run() {
                    checkActivityForeground();
                }
            }, delay, period);
        }
    }

    protected void checkActivityForeground() {
        Log.d(TAG, "start checking for Activity in foreground");
        Intent intent = new Intent();
        intent.setAction(UESurveillanceActivity.UE_ACTION);
        sendOrderedBroadcast(intent, null, new BroadcastReceiver() {

            @Override
            public void onReceive(Context context, Intent intent) {
                int result = getResultCode();

                if (result != Activity.RESULT_CANCELED) { // Activity caught it
                    Log.d(TAG, "An activity caught the broadcast, result " + result);
                    activityInForeground();
                    return;
                }
                Log.d(TAG, "No activity did catch the broadcast.");
                noActivityInForeground();
            }
        }, null, Activity.RESULT_CANCELED, null, null);
    }

    protected void activityInForeground() {
        Log.d(TAG, "starting method which gets called when an SureveillanceActivity is in foreground");

        // TODO something you want to happen when an Activity is in the foreground
    }

    protected void noActivityInForeground() {
        Log.d(TAG, "starting method which gets called when no SureveillanceActivity is in foreground");

        // TODO something you want to happen when no Activity is in the foreground

        stopSelf(); // quit
    }

    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        timer.cancel();
        Log.d(TAG, "service is destroyed");
    }
}

The Service class sends a special Intent witch gets answered by our custom Activity in case it is currently in the foreground.

public class UESurveillanceActivity extends Activity {
    public static final String UE_ACTION = "at.mannaz.surveilance.inforeground";
    private IntentFilter mIntentFilter;

    private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (action.equals(UE_ACTION)) {
                Log.d("UESurveilanceActivity", "i'm in the foreground");
                this.setResultCode(Activity.RESULT_OK);
            }
        }
    };

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

        mIntentFilter = new IntentFilter();
        mIntentFilter.addAction(UE_ACTION);

        Intent serviceIntent = new Intent(this, UEService.class);
        startService(serviceIntent);
    }

    @Override
    protected void onResume() {
        registerReceiver(mIntentReceiver, mIntentFilter);

        super.onResume();
    }

    @Override
    protected void onPause() {
        unregisterReceiver(mIntentReceiver);

        super.onPause();
    }
}

This activity registers a BroadcastReceiver when it comes to the foreground and unregisters it when it goes to the background.

Here is how you use those two classes in your application:

public class DashboardActivity extends UESurveillanceActivity {
    ...

Thats all. All you have to do is to change the parent class of your Activity to UESurveillanceActivity and register the Service in your AndroidManifest.xml :

<service android:name=".UEService"></service>