LocalBroadcast not working inside worker thread despite using Looper.getMainLooper()

Question

I am trying to work on a screen(say Activity A) where there is a progress bar displayed on the screen and I need to send a broadcast to a different activity(Activity B) broadcastReceiver while the progressbar is running. And if the function in the activity B is completed it will display that back to this activity A.

Now I am running progress bar in a worker thread like this and sending localbroadcast using handler(Looper.getMainLooper()):

final Context context = Activity.this.getApplicationContext();
new Thread(new Runnable() {
  @Override
  public void run() {
     while (progressBar.getProgress() != 100) {
        try {
            progressBar.incrementProgressBy(2);
            Thread.currentThread().sleep(100);
        } catch (InterruptedException ie) {
            Log.e(LOG_TAG, "Interrupted exception in progress bar: " + ie);
        }
        if (progressBar.getProgress() == 10) {
           Handler handler = new Handler(Looper.getMainLooper());
           handler.post(new Runnable() {
               @Override
               public void run() {
                   // model is a parameter which I want to send using intents
                   Intent intent = new Intent("new_device");
                   intent.putExtra("device", model);
                           LocalBroadcastManager.getInstance(context).sendBroadcast(intent);
               }
           });
        }
     }
  }
}).start();

But it's not working. Broadcast is not received by the other activity. I know that Broadcast should be done on UI thread and it works fine if I do it in onResume() or onCreate() method. But when I'm using it in a handler inside a thread (inside onCreate()) it is not working.

Am I doing something wrong or is there any other way of doing it?

EDIT

I am receiving my intent in Activity B as follows:

private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            Model model = (Model) intent.getSerializableExtra("device");
            onConnectDevice(model.getDevice());
        }
    };

Yes I am registering my receiver in Activity B's onCreate() method: LocalBroadcastManager.getInstance(this).registerReceiver(mMessageReceiver, new IntentFilter("new_device")); — AND_SUN, Jan 26 '16 at 19:32
You could start by adding a debug flag to your intent so that you can check whats crops up in the logs. `intent.addFlags(Intent.FLAG_DEBUG_LOG_RESOLUTION)` — VallaDanger, Jan 20 '17 at 09:01

score 0 · Answer 1 · answered Jan 26 '16 at 19:19

0

Try using runonuithread method of the activity inside your thread

answered Jan 26 '16 at 19:19

Suhaib Roomy

2,501
1
16
22

you mean the activity which contains the thread? Like this : ((Activity)context).runOnUiThread(new Runnable() { @Override public void run() { // model is a parameter which I want to send using intents Intent intent = new Intent("device"); intent.putExtra("device", model); LocalBroadcastManager.getInstance(context).sendBroadcast(intent); } }); – AND_SUN Jan 26 '16 at 19:29
You can juse use Activity.this.runOnUiThread. also register your reciever in the oncreate by passing broadcast receiver and intent filter to the registerreceiver method – Suhaib Roomy Jan 26 '16 at 19:35
Actually it doesn't work. runOnUiThread also doesn't work and I have no idea why! – AND_SUN Jan 26 '16 at 19:35
Yes I have registered my receiver in Activity B's onCreate() method. See my above comment. But still it doesn't work with runOnUiThread() – AND_SUN Jan 26 '16 at 19:37

natario · Answer 2 · 2016-01-26T19:58:54.600

I believe your issue is in progressBar.incrementProgress(), because you are trying to alter a UI element from outside the UI thread. Keeping your structure, you can try something like:

final Handler handler = new Handler(Looper.getMainLooper());
final Thread thread = new Thread(new Runnable() {
  @Override
  public void run() {
     while (progressBar.getProgress() != 100) {
        try {

            handler.post(new Runnable() {
                @Override
                public void run() {
                    progressBar.incrementProgressBy(2);
                }
            });
            Thread.sleep(100);

        } catch (InterruptedException ie) {

        }
        if (progressBar.getProgress() == 10) {
           handler.post(new Runnable() {
               @Override
               public void run() {
                   Intent intent = new Intent("new_device");
                   intent.putExtra("device", model);
                   Context context = progressBar.getContext();
                   LocalBroadcastManager.getInstance(context).sendBroadcast(intent);
               }
           });
        }
     }
  }
}); 

thread.start();

Also make sure that 10 is ever reached (for example, the sequence could be 1-3-5-7-9-11 and you won’t get anything.

I also took context from the progress bar, you don’t need to fetch it first.

There are better solutions than this but I just kept your structure.

Thanks for the code! But this is also not working. BroadcastReceiver in other activity is not receiving anything. There are better solutions than this. Can you give me a an example or some hint as to how to proceed? — AND_SUN, Jan 26 '16 at 19:53
Also you have written thread.sleep(100); This should be Thread.sleep(100); right? — AND_SUN, Jan 26 '16 at 19:56
Yes. Progress bar editing is the only thing that comes to my mind. Are you getting any warning in your logcat? — natario, Jan 26 '16 at 19:58
Also, registering your receiver onCreate() is bad if your are unregistering onPause() or onStop(). — natario, Jan 26 '16 at 20:01
No I am not getting any warning in my logcat. And I am unregistering it in onDestroy() — AND_SUN, Jan 26 '16 at 20:04

LocalBroadcast not working inside worker thread despite using Looper.getMainLooper()

EDIT

2 Answers2