Android: How to create fade-in/fade-out sound effects for any music file that my app plays?

Question

The application that I am working on plays music files. If a timer expires I want the music to fade out. How do I do that. I am using MediaPlayer to play music and music files are present in raw folder of my application.

Answer 1

This is my entire handler class for Android MediaPlayer. Look at the play() and pause() functions. Both contain the ability to either fade or not. The updateVolume() function was the key to let the sound increase/decrease linearly.

package com.stackoverflow.utilities;  import java.io.File; import java.util.Timer; import java.util.TimerTask;  import android.content.Context; import android.media.MediaPlayer; import android.net.Uri;  public class MusicHandler {     private MediaPlayer mediaPlayer;     private Context context;     private int iVolume;      private final static int INT_VOLUME_MAX = 100;     private final static int INT_VOLUME_MIN = 0;     private final static float FLOAT_VOLUME_MAX = 1;     private final static float FLOAT_VOLUME_MIN = 0;      public MusicHandler(Context context) {         this.context = context;     }      public void load(String path, boolean looping) {         mediaPlayer = MediaPlayer.create(context, Uri.fromFile(new File(path)));         mediaPlayer.setLooping(looping);     }      public void load(int address, boolean looping) {         mediaPlayer = MediaPlayer.create(context, address);         mediaPlayer.setLooping(looping);     }      public void play(int fadeDuration) {         // Set current volume, depending on fade or not         if (fadeDuration > 0)             iVolume = INT_VOLUME_MIN;         else             iVolume = INT_VOLUME_MAX;          updateVolume(0);          // Play music         if (!mediaPlayer.isPlaying())             mediaPlayer.start();          // Start increasing volume in increments         if (fadeDuration > 0) {             final Timer timer = new Timer(true);             TimerTask timerTask = new TimerTask() {                 @Override                 public void run() {                     updateVolume(1);                     if (iVolume == INT_VOLUME_MAX) {                         timer.cancel();                         timer.purge();                     }                 }             };              // calculate delay, cannot be zero, set to 1 if zero             int delay = fadeDuration / INT_VOLUME_MAX;             if (delay == 0)                 delay = 1;              timer.schedule(timerTask, delay, delay);         }     }      public void pause(int fadeDuration) {         // Set current volume, depending on fade or not         if (fadeDuration > 0)             iVolume = INT_VOLUME_MAX;         else             iVolume = INT_VOLUME_MIN;          updateVolume(0);          // Start increasing volume in increments         if (fadeDuration > 0) {             final Timer timer = new Timer(true);             TimerTask timerTask = new TimerTask() {                 @Override                 public void run() {                     updateVolume(-1);                     if (iVolume == INT_VOLUME_MIN) {                         // Pause music                         if (mediaPlayer.isPlaying())                             mediaPlayer.pause();                         timer.cancel();                         timer.purge();                     }                 }             };              // calculate delay, cannot be zero, set to 1 if zero             int delay = fadeDuration / INT_VOLUME_MAX;             if (delay == 0)                 delay = 1;              timer.schedule(timerTask, delay, delay);         }     }      private void updateVolume(int change) {         // increment or decrement depending on type of fade         iVolume = iVolume + change;          // ensure iVolume within boundaries         if (iVolume < INT_VOLUME_MIN)             iVolume = INT_VOLUME_MIN;         else if (iVolume > INT_VOLUME_MAX)             iVolume = INT_VOLUME_MAX;          // convert to float value         float fVolume = 1 - ((float) Math.log(INT_VOLUME_MAX - iVolume) / (float) Math.log(INT_VOLUME_MAX));          // ensure fVolume within boundaries         if (fVolume < FLOAT_VOLUME_MIN)             fVolume = FLOAT_VOLUME_MIN;         else if (fVolume > FLOAT_VOLUME_MAX)             fVolume = FLOAT_VOLUME_MAX;          mediaPlayer.setVolume(fVolume, fVolume);     } }