Unable to update UI from IntentService

Question

A seemingly simple requirement - to update UI from an IntentService. In the shot below, when the Start Service button is clicked, I need to show a ProgressBar above the only TextView and after a delay, remove the ProgressBar.

Found a lot of answers on SO, but somehow unable to still crack it. I understand from this that LocalBroadcastManager is a good way to go. I have also tried following this, (an approach with Handlers), but it fails to show the ProgressBar too. Finally, based on this answer, here's what I have ended up with. The output I've managed so far is just the Toasts appearing in succession, after all the logging is done.

Greatly appreciate if you could point out where I am going wrong, been struggling for quite some time now. Many thanks in advance!

MainActivity updated

public class MainActivity extends AppCompatActivity
{
    private static final String TAG = "MainActivity";
    private ProgressBar pb;
    private MyBroadcastReceiver myBroadcastReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        pb = (ProgressBar) findViewById(R.id.pb);
        myBroadcastReceiver = new MyBroadcastReceiver();

        LocalBroadcastManager.getInstance(this).registerReceiver(myBroadcastReceiver, new IntentFilter("ACTION"));
    }

    private void updateUI(boolean show)
    {
        if (show)
            pb.setVisibility(View.VISIBLE);
        else
            pb.setVisibility(View.GONE);
//        Toast.makeText(this, "UI Updated...", Toast.LENGTH_LONG).show();
    }

    public void startIt(View view)
    {
        Intent intent = new Intent(this, NanisIntentService.class);
        startService(intent);
    }

    public class MyBroadcastReceiver extends BroadcastReceiver
    {
        @Override
        public void onReceive(final Context context, Intent intent)
        {
            String action = intent.getAction();
            Log.e(TAG, "In onReceive(): " + action);
            if (action.equals("ACTION"))
            {
                updateUI(true);
            } // of if (action = "ACTION")
            else if (action.equals("NOITCA"))
            {
                updateUI(false);
            } // of else of if (action = "ACTION")
        } // of onReceive()
    } // of class MyBroadcastReceiver
}

IntentService updated

public class NanisIntentService extends IntentService
{
    private static final String TAG = "NanisIntentService";

    public NanisIntentService()
    {
        super("NanisIntentService");
    }

    @Override
    protected void onHandleIntent(Intent intent)
    {
        Log.e(TAG, "In onHandleIntent(): Intent is being serviced");
        LocalBroadcastManager.getInstance(testing.com.myintentservice.NanisIntentService.this).sendBroadcast(new Intent().setAction("ACTION"));
        int i = 0;
        while (i <= 50)
        {
            try
            {
                Thread.sleep(50);
                i++;
                Log.e("", "" + i);
            } catch (InterruptedException e)
            {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void onDestroy()
    {
        super.onDestroy();
        LocalBroadcastManager.getInstance(testing.com.myintentservice.NanisIntentService.this).sendBroadcast(new Intent().setAction("NOITCA"));
        Log.e(TAG, "In onDestroy(): The service has been destroyed");
    }
}

    @Override
    public void onStart(Intent intent, int startId)
    {
        super.onStart(intent, startId);
        LocalBroadcastManager.getInstance(testing.com.myintentservice.NanisIntentService.this).sendBroadcast(new Intent().setAction("ACTION"));
    }

    @Override
    public void onDestroy()
    {
        super.onDestroy();
        LocalBroadcastManager.getInstance(testing.com.myintentservice.NanisIntentService.this).sendBroadcast(new Intent().setAction("NOITCA"));
        Log.e(TAG, "In onDestroy(): The service has been destroyed");
    }
}

    @Override
    public void onDestroy()
    {
        super.onDestroy();
        LocalBroadcastManager.getInstance(testing.com.myintentservice.NanisIntentService.this).sendBroadcast(new Intent().setAction("NOITCA"));
        Log.e(TAG, "In onDestroy(): The service has been destroyed");
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="testing.com.myintentservice.MainActivity">

    <ProgressBar
        android:id="@+id/pb"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/tv"
        android:layout_centerHorizontal="true"
        android:indeterminate="true"
        android:visibility="gone"/>

    <TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Hello IntentService!"
        android:textColor="#1298CE"
        android:textSize="32sp"/>

    <Button
        android:id="@+id/bt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Start Service"
        android:onClick="startIt"/>
</RelativeLayout>

AndroidManifest

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <service android:name="testing.com.myintentservice.NanisIntentService"/>
    </application>

Answer 1

First, you are tying up the main application thread for ~2.5 seconds. This will freeze your UI during this period of time. Do not do this.

Second, you are calling updateUI() once before the ~2.5 seconds, and once after. Since you are tying up the main application thread during that time, this will have the same visual effect as calling updateUI() twice in succession after the delay. updateUI() toggles the ProgressBar visibility, so two calls will cancel each other out, leaving you in the same state as you started.

I need to show a ProgressBar above the only TextView and after a delay, remove the ProgressBar.

Showing a ProgressBar for 2.5 seconds, irrespective of any actual work being done, is rather arbitrary.

That being said, call updateUI() once, then use pb.postDelayed() to schedule a Runnable to run 2500 milliseconds later, where the run() method in the Runnable calls updateUI() the second time. This avoids you blocking the main application thread, so it allows the first updateUI() call to take effect, while still giving you the 2.5-second duration.