Question

i’ve got problem on implementing this functionality in Android…
i need only to output the decibel redorded from the microphone, and it’s a thing that i can’t understand:

public class Noise extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    MediaRecorder recorder=new MediaRecorder();
    recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    Timer timer=new Timer();
    timer.scheduleAtFixedRate(new RecorderTask(recorder), 0, 500);
}
private class RecorderTask extends TimerTask{
    TextView risultato=(TextView) findViewById(R.id.risultato_recorder);
    private MediaRecorder recorder;
    public RecorderTask(MediaRecorder recorder){
        this.recorder = recorder;
    }
    public void run(){
        risultato.setText(""+recorder.getMaxAmplitude());
    }
}
}

In the textview, the result is printed the first time only, and it’s 0, and then the app crash with:
11-29 14:43:27.133: E/AndroidRuntime(25785): android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

I’ve searched around, but i can’t find a comprehensive example… only examples with a lot of things and class that i don’t need.
can i fix this problem?

Answer 1

UI components can only be modified from the UI thread.

Your task is running in a background thread, so you need to force the TextView update to be done in the UI thread. You can achieve it with the Activity.runOnUiThread method.

Try this:

public void run(){
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            risultato.setText("" + recorder.getMaxAmplitude());
        }
    });
}

instead of

public void run(){
    risultato.setText(""+recorder.getMaxAmplitude());
}