Android: runOnUiThread does not always choose the right thread?

Question

I've got an activity that keeps reading words to the user, and using onUtteranceCompleted with textTospeech to display something when the code is completed.

Inside onUtteranceCompleted I have this code to delay a function with a second:

Runnable task = new Runnable() {
    public void run() {
        //runs on ui
        runOnUiThread(new Runnable() {
            public void run() {
                readWord();
            }
        });
    }
};
worker.schedule(task, 1, TimeUnit.SECONDS);

This seems like it works well, but I think it is causing a problem. When I rotate the screen of my phone (I guess this starts a new activity). I hear some words being read in the background. I guess this is because of runOnUiThread() which makes the activity continue in the background.

How could I avoid 2 activities running ? I would prefer if I don't have to stop the screen from rotating on doing some weird patch!

Thank you

EDIT:

public void readWord() {
    if (this.readingOnPause) {
        return;
    }

    txtCurrentWord.setText(currentItem[1]);

    this.hashAudio.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID,"word");
    this.tts.setLanguage(Locale.US);
    this.tts.speak(this.currentItem[1], TextToSpeech.QUEUE_FLUSH,this.hashAudio);
}

EDIT2:

instantiation of worker:

private static final ScheduledExecutorService worker = Executors.newSingleThreadScheduledExecutor();

worked is instantiated like this: private static final ScheduledExecutorService worker = Executors .newSingleThreadScheduledExecutor(); — Andrei, Feb 25 '12 at 22:01
is it because I'm making an "invite loop" of runOnUiThread ? onUtteranceCompleted > runOnUiThread > readWord > onUtteranceCompleted > runOnUiThread > readWord etc.. — Andrei, Feb 25 '12 at 23:23
is your tts static? if its recreating the activity than it would be a new object — L7ColWinters, Feb 25 '12 at 23:30
It wasn't static, I've put it static but it didn't change anything :( — Andrei, Feb 26 '12 at 00:02

score 2 · Answer 1 · answered Feb 28 '12 at 17:32

I would use a Handler instead of runOnUiThread().

For one thing, you're using a Thread that starts another Thread - why?

Secondly, if you create a simple Handler, it should kill itself on the rotate config change. IE:

private Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        // do your background or UI stuff
    }
};

Then later use a Thread to call the handler, which will kick off whatever process you want to run on the UI thread:

new Thread() {
    @Override
    public void run() {
        long timestamp = System.currentTimeMillis();
        // thread blocks for your 1 second delay
        while (System.currentTimeMillis() - timestamp <= 1000) {
            // loop
        }

        handler.sendEmptyMessage(0);
    }
}.start();

score 0 · Accepted Answer · answered Feb 26 '12 at 00:13

Ok so this is a fix I've come up with, if someone has a better solution, I'm listening.

I've added android:configChanges="keyboardHidden|orientation" inside the activity in the androidmanifest

and then a function that is called when the screen is rotate:

@Override
public void onConfigurationChanged(Configuration newConfig)
{
  super.onConfigurationChanged(newConfig);
  setContentView(R.layout.streaming);

  initializeUI(); //contains all the findViewByID etc...
}

Android: runOnUiThread does not always choose the right thread?

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