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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.example.android.musicplayer;
     18 
     19 import android.content.Context;
     20 import android.media.AudioManager;
     21 
     22 /**
     23  * Convenience class to deal with audio focus. This class deals with everything related to audio
     24  * focus: it can request and abandon focus, and will intercept focus change events and deliver
     25  * them to a MusicFocusable interface (which, in our case, is implemented by {@link MusicService}).
     26  *
     27  * This class can only be used on SDK level 8 and above, since it uses API features that are not
     28  * available on previous SDK's.
     29  */
     30 public class AudioFocusHelper implements AudioManager.OnAudioFocusChangeListener {
     31     AudioManager mAM;
     32     MusicFocusable mFocusable;
     33 
     34     public AudioFocusHelper(Context ctx, MusicFocusable focusable) {
     35         mAM = (AudioManager) ctx.getSystemService(Context.AUDIO_SERVICE);
     36         mFocusable = focusable;
     37     }
     38 
     39     /** Requests audio focus. Returns whether request was successful or not. */
     40     public boolean requestFocus() {
     41         return AudioManager.AUDIOFOCUS_REQUEST_GRANTED ==
     42             mAM.requestAudioFocus(this, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);
     43     }
     44 
     45     /** Abandons audio focus. Returns whether request was successful or not. */
     46     public boolean abandonFocus() {
     47         return AudioManager.AUDIOFOCUS_REQUEST_GRANTED == mAM.abandonAudioFocus(this);
     48     }
     49 
     50     /**
     51      * Called by AudioManager on audio focus changes. We implement this by calling our
     52      * MusicFocusable appropriately to relay the message.
     53      */
     54     public void onAudioFocusChange(int focusChange) {
     55         if (mFocusable == null) return;
     56         switch (focusChange) {
     57             case AudioManager.AUDIOFOCUS_GAIN:
     58                 mFocusable.onGainedAudioFocus();
     59                 break;
     60             case AudioManager.AUDIOFOCUS_LOSS:
     61             case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
     62                 mFocusable.onLostAudioFocus(false);
     63                 break;
     64             case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
     65                 mFocusable.onLostAudioFocus(true);
     66                 break;
     67              default:
     68         }
     69     }
     70 }
     71