Click on the notification and start the app in android

Question

I am currently working on the GCM (google cloud messaging), I would like the user start the app when they click on the notification received, the problem is it can not precisely check whether the app has started, so it always start the new activity even the app is already running. Thanks

The receiver

public class GcmBroadcastReceiver extends WakefulBroadcastReceiver{

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO Auto-generated method stub

        // Explicitly specify that GcmIntentService will handle the intent.
        ComponentName comp = new ComponentName(context.getPackageName(),
                GcmIntentService.class.getName());
        // Start the service, keeping the device awake while it is launching.
        startWakefulService(context, (intent.setComponent(comp)));
        setResultCode(Activity.RESULT_OK);

    }

}

The intent handler

public class GcmIntentService extends IntentService{
    Context context;
    public static final int NOTIFICATION_ID = 1;
    private NotificationManager mNotificationManager;
    NotificationCompat.Builder builder;
    public static final String TAG = "GCM";

    public GcmIntentService() {
        super("GcmIntentService");
        // TODO Auto-generated constructor stub
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        // TODO Auto-generated method stub
        Bundle extras = intent.getExtras();
        String msg = null;
        msg = intent.getStringExtra("message");
        GoogleCloudMessaging gcm = GoogleCloudMessaging.getInstance(this);
        String messageType = gcm.getMessageType(intent);

         if (!extras.isEmpty()) {

             if (GoogleCloudMessaging.
                        MESSAGE_TYPE_SEND_ERROR.equals(messageType)) {
                    sendNotification("Send error: " + extras.toString());
                } else if (GoogleCloudMessaging.
                        MESSAGE_TYPE_DELETED.equals(messageType)) {
                    sendNotification("Deleted messages on server: " +
                            extras.toString());
                // If it's a regular GCM message, do some work.
                } else if (GoogleCloudMessaging.
                        MESSAGE_TYPE_MESSAGE.equals(messageType)) {
                    // This loop represents the service doing some work.
                    for (int i=0; i<5; i++) {
                        Log.i(TAG, "Working... " + (i+1)
                                + "/5 @ " + SystemClock.elapsedRealtime());
                        try {
                            Thread.sleep(500);
                        } catch (InterruptedException e) {
                        }
                    }
                    Log.i(TAG, "Completed work @ " + SystemClock.elapsedRealtime());
                    // Post notification of received message.
                    //sendNotification("Received: " + extras.toString());
                    sendNotification(msg);
                    Log.i(TAG, "Received: " + extras.toString());
                }
            }
         GcmBroadcastReceiver.completeWakefulIntent(intent);
    }

    private void sendNotification(String msg) {
        mNotificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
        String notifyMsg = "";
        JSONTokener tokener = new JSONTokener(msg);

        if (tokener != null) {
            try {
                notifyMsg = new JSONObject(tokener).getString("msg");
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        Intent myintent = new Intent(this, MainActivity.class);
        myintent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        PendingIntent contentIntent = PendingIntent.getActivity(this, 0, myintent, PendingIntent.FLAG_UPDATE_CURRENT);

        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
        .setSmallIcon(R.drawable.ic_launcher)
        .setContentTitle(getResources().getString(R.string.notification_title))
        .setStyle(new NotificationCompat.BigTextStyle()
        .bigText(notifyMsg))
        .setContentText(notifyMsg)
        .setContentIntent(contentIntent);

        mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
    }   
}

Answer 1

Actually you are always starting new Activity task so it's happening instead of this you need to resume or clear top activity which is already running.

Your code

private void sendNotification(String msg) {
    mNotificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
    String notifyMsg = "";
    JSONTokener tokener = new JSONTokener(msg);

    if (tokener != null) {
        try {
            notifyMsg = new JSONObject(tokener).getString("msg");
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    Intent myintent = new Intent(this, MainActivity.class);
    myintent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0, myintent, PendingIntent.FLAG_UPDATE_CURRENT);

    NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
    .setSmallIcon(R.drawable.ic_launcher)
    .setContentTitle(getResources().getString(R.string.notification_title))
    .setStyle(new NotificationCompat.BigTextStyle()
    .bigText(notifyMsg))
    .setContentText(notifyMsg)
    .setContentIntent(contentIntent);

    mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
}   

edited Code:

private void sendNotification(String msg) {
    mNotificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
    String notifyMsg = "";
    JSONTokener tokener = new JSONTokener(msg);

    if (tokener != null) {
        try {
            notifyMsg = new JSONObject(tokener).getString("msg");
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    Intent myintent = new Intent(this, MainActivity.class);
    myintent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);//changes 
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0, myintent, PendingIntent.FLAG_UPDATE_CURRENT);

    NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
    .setSmallIcon(R.drawable.ic_launcher)
    .setContentTitle(getResources().getString(R.string.notification_title))
    .setStyle(new NotificationCompat.BigTextStyle()
    .bigText(notifyMsg))
    .setContentText(notifyMsg)
    .setContentIntent(contentIntent);

    mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
}   

Hope this will help you.

Answer 2

As per android docs, you need to use singleTop launch mode for your activity.

The "standard" and "singleTop" modes differ from each other in just one respect: Every
time there's new intent for a "standard" activity, a new instance of the class is created
to respond to that intent. Each instance handles a single intent. Similarly, a new 
instance of a "singleTop" activity may also be created to handle a new intent. However, if
the target task already has an existing instance of the activity at the top of its stack,
that instance will receive the new intent (in an onNewIntent() call); a new instance is   
not created. In other circumstances — for example, if an existing instance of the
"singleTop" activity is in the target task, but not at the top of the stack, or if it's at
the top of a stack, but not in the target task — a new instance would be created and 
pushed on the stack.