Question

I am trying to schedule a task to update a TextView once a second. As long as I have the line, with the comment after it, commented out, everything works fine. Logcat shows someting like:

Task
IN
OUT
Task
IN
OUT
...

But if I uncomment the statusLabel.setText(), this is what I see:

Task
IN
OUT
TASK
IN 

Those five rows are all I get. For some reason it seems to stop, when it tries to set the text again the second time.

My Code:

public class MyActivity extends Activity {

    TextView statusLabel;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.control);
        statusLabel = (TextView) findViewById(R.id.statusLabel);

        ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
        scheduler.scheduleAtFixedRate(
                new Runnable() {
                    public void run() {
                        Log.d("Datalogger","Task");
                        updateStatus();
                    }
                }, 0, 1, TimeUnit.SECONDS);
    }

    private void updateStatus() {
        Log.d("Datalogger","IN");
        statusLabel.setText("X");  // !! If I comment out this line, 
        Log.d("Datalogger","OUT"); //    everything works
    }
}

Answer 1

The problem is that you are attempting to update UI from a thread other than the UI(main) thread. In the runnable use runOnUiThread(Runnable action) with a new runnable to call updateStatus().