Measured focus acquisition and return of Android audio

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foreword

Recently, the boss wants to pause the music player in the mobile phone when the short video in the product is played live, and the music player in the mobile phone can continue to play the previous music after exiting the video playback.

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Android official website: manage audio focus

Official site management audio focus guidelines:

Called just before playback starts requestAudioFocus(), and verifies that the call returns AUDIOFOCUS_REQUEST_GRANTED. If you design your app as described in this guide, it should be called in the media session's onPlay()callback requestAudioFocus().
Stop or pause playback, or lower the volume while another app has audio focus.
After playback stops, relinquishes audio focus.

Different versions of audio focus are handled differently:

Beginning with Android 2.2 (API level 8), requestAudioFocus()apps abandonAudioFocus()manage audio focus by calling and . Apps must also register for these two calls AudioManager.OnAudioFocusChangeListenerin order to receive callbacks and manage their own volume.
For apps targeting Android 5.0 (API level 21) and higher, audio apps should use AudioAttributesto describe the type of audio the app is playing. For example, an application that plays speech should specify CONTENT_TYPE_SPEECH.
Apps targeting Android 8.0 (API level 26) or higher should use requestAudioFocus()the method , which accepts AudioFocusRequesta parameter. AudioFocusRequestContains information about the app's audio context and capabilities. The system uses this information to automatically manage the gaining and losing of audio focus.

API introduction

Audio focus is handled through the AudioManager class, as follows to obtain an instance of this class:
AudioManager am = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);

requestAudioFocus()//Used to apply for audio focus
abandonAudioFocus()//Used to release the audio focus
AudioManager.OnAudioFocusChangeListenerinterface, which provides onAudioFocusChange()methods to monitor audio focus changes

requestAudioFocus(OnAudioFocusChangeListener l, int streamType, int durationHint)parameter:

AudioManager.OnAudioFocusChangeListener l:
Used to monitor audio focus changes, so that appropriate operations can be performed, such as pausing playback, etc.

streamType:
The type of audio that applies for audio focus processing, for example, it can be passed in when playing music STREAM_MUSIC; it can be passed in when playing a ringtone STREAM_RING. Some optional values are listed in the table:

type	meaning	value
STREAM_VOICE_CALL	call	0
STREAM_SYSTEM	system	1
STREAM_RING	ring	2
STREAM_MUSIC	music	3
STREAM_ALARM	alarm clock	4
STREAM_NOTIFICATION	system notification	5
…	…	…

durationHint(PS: important parameters):
There are five optional values:
(1) AUDIOFOCUS_GAIN: This parameter indicates that you want to apply for a permanent audio focus, and you want the last app that holds the audio focus to stop playing; for example, when you need to play music.
(2) AUDIOFOCUS_GAIN_TRANSIENT: It means to apply for a short-term audio focus, and it will be released immediately. At this time, it is hoped that the previous app that holds the audio focus will pause playback. For example, play an alert sound.
(3) AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK: The effect is the same AUDIOFOCUS_GAIN_TRANSIENT, except that the last App that holds the focus reduces its playing sound (but it can still be played), and it will play with mixed audio at this time. For example, navigation broadcast.
(4) AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE: Indicates that a short audio focus is applied, and the system will not play any sudden sounds (such as notifications, reminders, etc.), such as the user is recording.
Return value:
AUDIOFOCUS_REQUEST_GRANTEDor AUDIOFOCUS_REQUEST_FAILED.

abandonAudioFocus(OnAudioFocusChangeListener l)Parameters pass on AudioManager.OnAudioFocusChangeListener.
AudioManager.OnAudioFocusChangeListener: Callback of onAudioFocusChange(int focusChange)the method ;

new AudioManager.OnAudioFocusChangeListener() {
    
    
  @Override
  public void onAudioFocusChange(int focusChange) {
    
    
    switch (focusChange) {
    
    
      case AudioManager.AUDIOFOCUS_GAIN:
        // TBD 继续播放
        break;
      case AudioManager.AUDIOFOCUS_LOSS:
        // TBD 停止播放
        break;
      case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
        // TBD 暂停播放
        break;
      case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
        // TBD 混音播放 
        break;
      default:
        break;
    }
  }
};

Tested code:

The core is to AudioManager.AUDIOFOCUS_GAINchangeAudioManager.AUDIOFOCUS_GAIN_TRANSIENT

public class MainActivity extends Activity {
    
    

    private AudioManager mAudioManager;
    private AudioFocusRequest mFocusRequest;
    private AudioManager.OnAudioFocusChangeListener mListener;
    private AudioAttributes mAttribute;
    @SuppressLint("HandlerLeak")
    private Handler mHandler = new Handler() {
    
    
        @Override
        public void handleMessage(@NonNull Message msg) {
    
    
            super.handleMessage(msg);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
        mListener = new AudioManager.OnAudioFocusChangeListener() {
    
    
            @Override
            public void onAudioFocusChange(int focusChange) {
    
    
                switch (focusChange) {
    
    
                    case AudioManager.AUDIOFOCUS_GAIN:
                       // TBD 继续播放
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS:
                       // TBD 停止播放
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
                        // TBD 暂停播放
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
                        // TBD 混音播放 
                        break;
                    default:
                        break;
                }

            }
        };
        //android 版本 5.0
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    
    
            mAttribute = new AudioAttributes.Builder()
                    .setUsage(AudioAttributes.USAGE_MEDIA)
                    .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                    .build();
        }
        //android 版本 8.0
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
    
    
            mFocusRequest = new AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN_TRANSIENT)
                    .setWillPauseWhenDucked(true)
                    .setAcceptsDelayedFocusGain(true)
                    .setOnAudioFocusChangeListener(mListener, mHandler)
                    .setAudioAttributes(mAttribute)
                    .build();
        }
    }
    private void requestAudioFocus() {
    
    
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    
    
					mAudioManager.requestAudioFocus(mFocusRequest);
        } else {
    
    
          mAudioManager.requestAudioFocus(mListener, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
        }
    }
    private void abandonAudioFocus() {
    
    
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    
    
            mAudioManager.abandonAudioFocusRequest(mFocusRequest);
        } else {
    
    
          mAudioManager.abandonAudioFocus(mListener);
        }

    }
}

reference:

https://segmentfault.com/a/1190000022234509

https://www.jianshu.com/p/26ea60c499a7

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