Create audio Visualizer for MediaPlayer

This example create audio Visualizer for MediaPlayer, reference Android demo example: ApiDemos > Media > AudioTx. Permission android.permission.RECORD_AUDIO is needed,  to use visualizer.

remark@2016-10-18:
I found that the example code removed from Android Studio examples list, may be it is  NOT work now.



Create custom VisualizerView extends View, VisualizerView.java

package com.example.androidaudiovisualizer;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.View;

public class VisualizerView extends View {

 private byte[] mBytes;
 private float[] mPoints;
 private Rect mRect = new Rect();
 private Paint mForePaint = new Paint();

 public VisualizerView(Context context) {
  super(context);
  init();
 }

 public VisualizerView(Context context, AttributeSet attrs) {
  super(context, attrs);
  init();
 }

 public VisualizerView(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  init();
 }

 private void init() {
  mBytes = null;
  mForePaint.setStrokeWidth(1f);
  mForePaint.setAntiAlias(true);
  mForePaint.setColor(Color.rgb(0, 128, 255));
 }

 public void updateVisualizer(byte[] bytes) {
  mBytes = bytes;
  invalidate();
 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  if (mBytes == null) {
   return;
  }
  if (mPoints == null || mPoints.length < mBytes.length * 4) {
   mPoints = new float[mBytes.length * 4];
  }
  mRect.set(0, 0, getWidth(), getHeight());
  for (int i = 0; i < mBytes.length - 1; i++) {
   mPoints[i * 4] = mRect.width() * i / (mBytes.length - 1);
   mPoints[i * 4 + 1] = mRect.height() / 2
     + ((byte) (mBytes[i] + 128)) * (mRect.height() / 2) / 128;
   mPoints[i * 4 + 2] = mRect.width() * (i + 1) / (mBytes.length - 1);
   mPoints[i * 4 + 3] = mRect.height() / 2
     + ((byte) (mBytes[i + 1] + 128)) * (mRect.height() / 2)
     / 128;
  }
  canvas.drawLines(mPoints, mForePaint);
 }

}

Add <com.example.androidaudiovisualizer.VisualizerView> to layout file, activity_main.xml.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.androidaudiovisualizer.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />
    
    <com.example.androidaudiovisualizer.VisualizerView
        android:id="@+id/myvisualizerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

MainActivity.java

package com.example.androidaudiovisualizer;

import android.support.v7.app.ActionBarActivity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.audiofx.Visualizer;
import android.os.Bundle;

/*
 * Copy test.mp3 to /res/raw/ folder
 * 
 * needed in AndroidManifest.xml
 * android:minSdkVersion="9"
 * uses-permission of "android.permission.RECORD_AUDIO"
 * 
 * reference: Android demo example -
 * ApiDemos > Media > AudioTx
 */

public class MainActivity extends ActionBarActivity {

 VisualizerView mVisualizerView;

 private MediaPlayer mMediaPlayer;
 private Visualizer mVisualizer;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  mVisualizerView = (VisualizerView) findViewById(R.id.myvisualizerview);

  initAudio();
 }

 @Override
 protected void onPause() {
  super.onPause();
  if (isFinishing() && mMediaPlayer != null) {
   mVisualizer.release();
   mMediaPlayer.release();
   mMediaPlayer = null;
  }
 }

 private void initAudio() {
  setVolumeControlStream(AudioManager.STREAM_MUSIC);
  mMediaPlayer = MediaPlayer.create(this, R.raw.test);

  setupVisualizerFxAndUI();
  // Make sure the visualizer is enabled only when you actually want to
  // receive data, and
  // when it makes sense to receive data.
  mVisualizer.setEnabled(true);
  // When the stream ends, we don't need to collect any more data. We
  // don't do this in
  // setupVisualizerFxAndUI because we likely want to have more,
  // non-Visualizer related code
  // in this callback.
  mMediaPlayer
    .setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
     public void onCompletion(MediaPlayer mediaPlayer) {
      mVisualizer.setEnabled(false);
     }
    });
  mMediaPlayer.start();

 }

 private void setupVisualizerFxAndUI() {

  // Create the Visualizer object and attach it to our media player.
  mVisualizer = new Visualizer(mMediaPlayer.getAudioSessionId());
  mVisualizer.setCaptureSize(Visualizer.getCaptureSizeRange()[1]);
  mVisualizer.setDataCaptureListener(
    new Visualizer.OnDataCaptureListener() {
     public void onWaveFormDataCapture(Visualizer visualizer,
       byte[] bytes, int samplingRate) {
      mVisualizerView.updateVisualizer(bytes);
     }

     public void onFftDataCapture(Visualizer visualizer,
       byte[] bytes, int samplingRate) {
     }
    }, Visualizer.getMaxCaptureRate() / 2, true, false);
 }

}

Next example:
- Visible DTMF Piano: Visualizer + ToneGenerator