Request audio focus when playing; Pause audio when audio focus is lost; resume playing when audio focus is granted again.

This closes #88

Author: fafaman

src/android/AudioHandler.java

@@ -27,6 +27,7 @@ Licensed to the Apache Software Foundation (ASF) under one
 import android.content.Context;
 import android.content.pm.PackageManager;
 import android.media.AudioManager;
+import android.media.AudioManager.OnAudioFocusChangeListener;
 import android.net.Uri;
 import android.os.Build;
 import android.util.Log;
@@ -55,8 +56,9 @@ Licensed to the Apache Software Foundation (ASF) under one
 public class AudioHandler extends CordovaPlugin {
 
     public static String TAG = "AudioHandler";
-    HashMap<String, AudioPlayer> players;	// Audio player object
-    ArrayList<AudioPlayer> pausedForPhone;     // Audio players that were paused when phone call came in
+    HashMap<String, AudioPlayer> players;  // Audio player object
+    ArrayList<AudioPlayer> pausedForPhone; // Audio players that were paused when phone call came in
+    ArrayList<AudioPlayer> pausedForFocus; // Audio players that were paused when focus was lost
     private int origVolumeStream = -1;
     private CallbackContext messageChannel;
 
@@ -76,6 +78,7 @@ public class AudioHandler extends CordovaPlugin {
     public AudioHandler() {
         this.players = new HashMap<String, AudioPlayer>();
         this.pausedForPhone = new ArrayList<AudioPlayer>();
+        this.pausedForFocus = new ArrayList<AudioPlayer>();
     }
 
 
@@ -297,6 +300,7 @@ public void stopRecordingAudio(String id) {
     public void startPlayingAudio(String id, String file) {
         AudioPlayer audio = getOrCreatePlayer(id, file);
         audio.startPlaying(file);
+        getAudioFocus();
     }
 
     /**
@@ -376,6 +380,55 @@ else if (output == 1) {
         }
     }
 
+    public void pauseAllLostFocus() {
+        for (AudioPlayer audio : this.players.values()) {
+            if (audio.getState() == AudioPlayer.STATE.MEDIA_RUNNING.ordinal()) {
+                this.pausedForFocus.add(audio);
+                audio.pausePlaying();
+            }
+        }
+    }
+
+    public void resumeAllGainedFocus() {
+        for (AudioPlayer audio : this.pausedForFocus) {
+            audio.startPlaying(null);
+        }
+        this.pausedForFocus.clear();
+    }
+
+    /**
+     * Get the the audio focus
+     */
+    private OnAudioFocusChangeListener focusChangeListener = new OnAudioFocusChangeListener() {
+            public void onAudioFocusChange(int focusChange) {
+                switch (focusChange) {
+                case (AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK) :
+                case (AudioManager.AUDIOFOCUS_LOSS_TRANSIENT) :
+                case (AudioManager.AUDIOFOCUS_LOSS) :
+                    pauseAllLostFocus();
+                    break;
+                case (AudioManager.AUDIOFOCUS_GAIN):
+                    resumeAllGainedFocus();
+                    break;
+                default:
+                    break;
+                }
+            }
+        };
+
+    public void getAudioFocus() {
+        AudioManager am = (AudioManager) this.cordova.getActivity().getSystemService(Context.AUDIO_SERVICE);
+        int result = am.requestAudioFocus(focusChangeListener,
+                                          AudioManager.STREAM_MUSIC,
+                                          AudioManager.AUDIOFOCUS_GAIN);
+
+        if (result != AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
+            System.out.println("AudioHandler.getAudioFocus() Error: Got " + result + " instead of " + AudioManager.AUDIOFOCUS_REQUEST_GRANTED);
+        }
+
+    }
+
+
     /**
      * Get the audio device to be used for playback.
      *