Can't make Audiorecord and Audiotrack work togehter

Question

public class MainActivity extends AppCompatActivity {

static  int SAMPLE_RATE_44100 = 44100;
AudioRecord audioRecord;
AudioTrack audioTrack;
CountDownTimer countdownTimer;
TextView textView_coundown_timer_display;
int bufferSize = 882000; // 44100*16*1/8*10
byte [] mediabuffer;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    textView_coundown_timer_display = (TextView) findViewById.id.textView_coundown_timer_display);
    mediabuffer = new byte[bufferSize];
    createAudioRecord();
    Log.d("audiorec", "state " + audioRecord.getState());//0 - STATE_UNINITIALIZED, 1 - STATE_INITIALIZED, 2 - STATE_NO_STATIC_DATA
    createAudiotrack();
    Log.d("audiotrack", "state " + audioTrack.getState()); //0 - STATE_UNINITIALIZED, 1 - STATE_INITIALIZED, 2 - STATE_NO_STATIC_DATA

}

void createAudioRecord () {
    audioRecord = new AudioRecord(
            MediaRecorder.AudioSource.MIC,
            SAMPLE_RATE_44100,
            AudioFormat.CHANNEL_IN_MONO,
            AudioFormat.ENCODING_PCM_16BIT,
            AudioRecord.getMinBufferSize(
                    SAMPLE_RATE_44100,
                    AudioFormat.CHANNEL_IN_MONO,
                    AudioFormat.ENCODING_PCM_16BIT)*10);


  }



public void createAudiotrack () {
 audioTrack = new AudioTrack(
         AudioManager.STREAM_MUSIC,
         SAMPLE_RATE_44100,
         AudioFormat.CHANNEL_OUT_MONO,
         AudioFormat.ENCODING_PCM_16BIT,
         bufferSize,
         AudioTrack.MODE_STREAM);
 audioTrack.setPlaybackRate(SAMPLE_RATE_44100);}

}
public void startRead(){
    new Thread(new Runnable() {
        @Override
        public void run() {
            audioRecord.read(mediabuffer, 1, bufferSize);
            Toast.makeText(getApplicationContext(), "reading" + audioRecord.getState(), Toast.LENGTH_SHORT ).show();
        }
    }).run();
}



  public void audiotrackWriteAndPlay (View view) {
                audioTrack.write(mediabuffer, 1, bufferSize);
            Toast.makeText(getApplicationContext(), "writing" , Toast.LENGTH_SHORT ).show();
    audioTrack.play();
}
public void stopRecord (){
    audioRecord.stop();
    Toast.makeText(getApplicationContext(), "mediabuffer lenght"+mediabuffer.length, Toast.LENGTH_SHORT).show();

}
void recordTimer(){
    countdownTimer = new CountDownTimer(10000, 1000) {
        @Override
        public void onTick(long millisUntilFinished) {
            textView_coundown_timer_display.setText(millisUntilFinished/1000+"");
        }

        @Override
        public void onFinish() {
            textView_coundown_timer_display.setText("0");
            stopRecord();
            startRead();
        }
    }.start();
}
}

I call AudioRecord and AudioTrack inside - onCreate. When button "Rec" pushed it call: startRecord and inside this method CoundownTimer is created. CoundownTimer stops this record after 10 sec. I write this record into the inner buffer. Then I'm trying to play this record by rewriting and playing it. What is wrong with this code? I can't understand why "Play" is not working.