Android: Audio Recording with voice level visualization

Question

I need to create a android application which is for recording voice while showing the voice(sound) level visualization.

I already created an audio recording application

Answer 1

I like Ali's answer, but here's a simpler version that performs much better. The real speed comes from making the view class's onDraw method as fast as possible. Store the correct values in memory first by doing any computations not required for drawing outside the draw loop, and pass fully populated structures to draw routines to allow the hardware to optimize drawing many lines.

I launched my RecordingActivity and set it full screen, but you can create a layout resource or add the view anywhere.

Actvity:

public class RecordingActivity extends Activity {
    private VisualizerView visualizerView;
    private MediaRecorder recorder = new MediaRecorder();
    private Handler handler = new Handler();
    final Runnable updater = new Runnable() {
        public void run() {
            handler.postDelayed(this, 1);
            int maxAmplitude = recorder.getMaxAmplitude();
            if (maxAmplitude != 0) {
                visualizerView.addAmplitude(maxAmplitude);
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recording);
        visualizerView = (VisualizerView) findViewById(R.id.visualizer);
        try {
            recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
            recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
            recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
            recorder.setOutputFile("/dev/null");
            recorder.prepare();
            recorder.start();
        } catch (IllegalStateException | IOException ignored) {
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        handler.removeCallbacks(updater);
        recorder.stop();
        recorder.reset();
        recorder.release();
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        handler.post(updater);
    }
}

View:

public class VisualizerView extends View {
    private static final int MAX_AMPLITUDE = 32767;

    private float[] amplitudes;
    private float[] vectors;
    private int insertIdx = 0;
    private Paint pointPaint;
    private Paint linePaint;
    private int width;
    private int height;

    public VisualizerView(Context context, AttributeSet attrs) {
        super(context, attrs);
        linePaint = new Paint();
        linePaint.setColor(Color.GREEN);
        linePaint.setStrokeWidth(1);
        pointPaint = new Paint();
        pointPaint.setColor(Color.BLUE);
        pointPaint.setStrokeWidth(1);
    }

    @Override
    protected void onSizeChanged(int width, int h, int oldw, int oldh) {
        this.width = width;
        height = h;
        amplitudes = new float[this.width * 2]; // xy for each point across the width
        vectors = new float[this.width * 4]; // xxyy for each line across the width
    }

    /**
     * modifies draw arrays. cycles back to zero when amplitude samples reach max screen size
     */
    public void addAmplitude(int amplitude) {
        invalidate();
        float scaledHeight = ((float) amplitude / MAX_AMPLITUDE) * (height - 1);
        int ampIdx = insertIdx * 2;
        amplitudes[ampIdx++] = insertIdx;   // x
        amplitudes[ampIdx] = scaledHeight;  // y
        int vectorIdx = insertIdx * 4;
        vectors[vectorIdx++] = insertIdx;   // x0
        vectors[vectorIdx++] = 0;           // y0
        vectors[vectorIdx++] = insertIdx;   // x1
        vectors[vectorIdx] = scaledHeight;  // y1
        // insert index must be shorter than screen width
        insertIdx = ++insertIdx >= width ? 0 : insertIdx;
    }

    @Override
    public void onDraw(Canvas canvas) {
        canvas.drawLines(vectors, linePaint);
        canvas.drawPoints(amplitudes, pointPaint);
    }
}