Question

I don’t kno why but the start() method throw an error and crash the app:

public class Noise extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.noise);
    MediaRecorder recorder=new MediaRecorder();
    recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    try{
        recorder.prepare();
    }catch(IllegalStateException e){
        Log.d("Error",e.toString());
        e.printStackTrace();
    }catch(IOException e){
        Log.d("Error",e.toString());
        e.printStackTrace();
    }
    recorder.start();
    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(){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                risultato.setText("" + recorder.getMaxAmplitude());
            }
        });
    }
}
}

if i remove the prepare and the start, it work but return always 0 in the textview.
anyone can help me? this thing make me crazy

this is the logcat: https://dl.dropbox.com/u/16047047/log.txt

and in the phone, it crash.

Answer 1

It seems you miss a recorder.setOutputFile(PATH_NAME); See the documentation for MediaRecorder

At least, this is what the stack trace tells us:

11-29 16:04:08.933: W/System.err(9323): java.io.IOException: No valid output file

This is the relevant source code for MediaRecorder.prepare():

public void prepare() throws IllegalStateException, IOException
{
    if (mPath != null) {
        FileOutputStream fos = new FileOutputStream(mPath);
        try {
            _setOutputFile(fos.getFD(), 0, 0);
        } finally {
            fos.close();
        }
    } else if (mFd != null) {
        _setOutputFile(mFd, 0, 0);
    } else {
        throw new IOException("No valid output file");
    }
    _prepare();
}

(you can read it on grepcode) The exception is thrown if both the File object and the FileDescriptor are null. So I don’t think you can use MediaRecorder without supplying a file. You can try the tricky /dev/null but I don’t know if it works, and can’t test right now