Live Audio Recording and Playing in Android and Thread & callback handling

If your requirement is while it is recording it should play(means looping back audio), In your while loop thread, you are storing the recorded data (audioData bufer), there itself you can copy it to player object with in the while loop (player.write(audioData, 0, numShortsRead);). You said like your UI thread is stuck, it might be because of you are giving more priority to Audio record thread.

Check the below the code which I used for above loop back requirement

boolean m_isRun=true;
public void loopback() {
        // Prepare the AudioRecord & AudioTrack
        try {
            buffersize = AudioRecord.getMinBufferSize(SAMPLE_RATE,
                    AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT);

            if (buffersize <= BUF_SIZE) {
                buffersize = BUF_SIZE;
            }
            Log.i(LOG_TAG,"Initializing Audio Record and Audio Playing objects");

            m_record = new AudioRecord(MediaRecorder.AudioSource.MIC,
                    SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT, buffersize * 1);

            m_track = new AudioTrack(AudioManager.STREAM_ALARM,
                    SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT, buffersize * 1,
                    AudioTrack.MODE_STREAM);

            m_track.setPlaybackRate(SAMPLE_RATE);
        } catch (Throwable t) {
            Log.e("Error", "Initializing Audio Record and Play objects Failed "+t.getLocalizedMessage());
        }

        m_record.startRecording();
        Log.i(LOG_TAG,"Audio Recording started");
        m_track.play();
        Log.i(LOG_TAG,"Audio Playing started");

        while (m_isRun) {
            m_record.read(buffer, 0, BUF_SIZE);
            m_track.write(buffer, 0, buffer.length);
        }

        Log.i(LOG_TAG, "loopback exit");
    }

    private void do_loopback() {
        m_thread = new Thread(new Runnable() {
            public void run() {
                loopback();
            }
        });

One more thing, If your requirement is record for few seconds and then play, while it is playing your record should start again, you can do that with a delay handler thread with a time out, In that thread you can stop recording copy the buffer, then start recording.