总结系列-Android画中画模式-看这篇就够啦

た入场券 2023-07-12 03:38 284阅读 0赞

最近做做播放器,有个浮窗播放的需求,两种实现方式,一种是申请浮窗权限,创建浮窗参考 [flowWindow][],一种是采用画中画模式(8.0以上)

## **关于画中画** ##

Android 8.0 Oreo（API Level 26）允许活动启动画中画 Picture-in-picture（PIP）模式。PIP 是一种特殊类型的多窗口模式，主要用于视频播放。PIP 模式已经可用于 Android TV，而 Android 8.0 则让该功能可进一步用于其他 Android 设备。

画中画利用 Android 7.0 中的多窗口模式 API 来提供固定的视频叠加窗口。要将画中画添加到您的应用中，您需要注册支持画中画的 Activity、根据需要将 Activity 切换为画中画模式，并确保当 Activity 处于画中画模式时，界面元素处于隐藏状态且视频能够继续播放。

![20200306180611883.png][]

# **如何使用** #

### **声明对画中画的支持** ###

默认情况下，系统不会自动为应用提供画中画支持。要想在应用中支持画中画，您可以通过将  android:supportsPictureInPicture  和  android:resizeableActivity  设置为  true ，在清单中注册视频 Activity。此外，指定您的 Activity 会处理布局配置更改，这样一来，在画中画模式转换期间发生布局更改时，您的 Activity 不会重新启动。

<activity android:name="VideoActivity"
            android:resizeableActivity="true"
            android:supportsPictureInPicture="true"
            android:configChanges=
                "screenSize|smallestScreenSize|screenLayout|orientation"
            ...

低内存设备可能无法使用画中画模式。在应用使用画中画之前，请务必通过调用 **hasSystemFeature**(PackageManager. **FEATURE\_PICTURE\_IN\_PICTURE**) 进行检查以确保可以使用画中画。

isSupportPipMode = getPackageManager().hasSystemFeature(PackageManager.FEATURE_PICTURE_IN_PICTURE) && Build.VERSION.SDK_INT >= Build.VERSION_CODES.N;
    if(videoPlayer!= null) {
        videoPlayer.setSupportPipMode(isSupportPipMode);
    }

### **对单个播放 Activity 使用画中画模式** ###

要确保将单个 Activity 用于视频播放请求并根据需要进入或退出画中画模式，请在清单中将 Activity 的 **android:launchMode** 设置为 **singleTask**：

<activity android:name="VideoActivity"
            ...
            android:supportsPictureInPicture="true"
            android:launchMode="singleTask"
            ...

在您的 Activity 中，替换 onNewIntent() 并处理新的视频，从而根据需要停止任何现有的视频播放。

### **将您的 Activity 切换到画中画模式** ###

要进入画中画模式，Activity 必须调用 **enterPictureInPictureMode()**。例如，以下代码会在用户点击应用界面中的专用按钮时，将 Activity 切换到画中画模式：

/**
    * 进入画中画模式
    */
    private PictureInPictureParams.Builder mPictureInPictureParamsBuilder;
    private void enterPiPMode() {
        if (videoPlayer == null) {
            return;
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            videoPlayer.setIsInPictureInPictureMode(true);
            if (mPictureInPictureParamsBuilder == null) {
                mPictureInPictureParamsBuilder = new PictureInPictureParams.Builder();
            }
            // Calculate the aspect ratio of the PiP screen. 计算video的纵横比
            mVideoWith = videoPlayer.getCurrentVideoWidth();
            mVideoHeight = videoPlayer.getCurrentVideoHeight();
            if (mVideoWith != 0 && mVideoHeight != 0) {
                //设置param宽高比,根据宽高比例调整初始参数
                Rational aspectRatio = new Rational(mVideoWith, mVideoHeight);
                mPictureInPictureParamsBuilder.setAspectRatio(aspectRatio);
            }
            //进入pip模式
            enterPictureInPictureMode(mPictureInPictureParamsBuilder.build());
        }
    }

### **进入 PIP 模式的最常见流程如下：** ###

1. 从按钮触发

\* onClicked (View)，onOptionsItemSelected (MenuItem) 等等。

2. 有意的离开您的应用程序触发

\* onUserLeaveHint ( )

3. 从返回触发

\* onBackPressed ( )

### **在画中画期间处理界面** ###

当 Activity 进入或退出画中画模式时，系统会调用 Activity. **onPictureInPictureModeChanged**() 或 Fragment. **onPictureInPictureModeChanged**()。

您应替换这些回调以重新绘制 Activity 的界面元素。请注意，在画中画模式下，您的 Activity 会在一个小窗口中显示。在画中画模式下，用户可能看不清小界面元素的详细信息，因此不会与这些界面元素互动。界面极简的视频播放 Activity 可提供出色的用户体验。Activity 应仅显示视频播放控件。在 Activity 进入画中画模式之前移除其他界面元素，并在 Activity 再次变为全屏时恢复这些元素：

@Override
        public void onPictureInPictureModeChanged (boolean isInPictureInPictureMode, Configuration newConfig) {
            if (isInPictureInPictureMode) {
                // Hide the full-screen UI (controls, etc.) while in picture-in-picture mode.
            } else {
                // Restore the full-screen UI.
                ...
            }
        }

### **在画中画模式下继续播放视频** ###

当您的 Activity 切换到画中画模式时，系统会将该 Activity 置于暂停状态并调用 Activity 的 **onPause**() 方法。如果该 Activity 在画中画模式下暂停，则视频播放不得暂停，而应继续播放。

在 Android 7.0 及更高版本中，当系统调用 Activity 的 **onStop**() 时，您应暂停视频播放；当系统调用 Activity 的 **onStart**() 时，您应恢复视频播放。这样一来，您就无需在 onPause() 中检查应用是否处于画中画模式，只需继续播放视频即可。如果您必须在 **onPause**() 实现中暂停播放，请通过调用 isInPictureInPictureMode() 检查画中画模式并相应地处理播放情况，例如：

@Override
        public void onPause() {
            // If called while in PIP mode, do not pause playback
            if (isInPictureInPictureMode()) {
                // Continue playback
                ...
            } else {
                // Use existing playback logic for paused Activity behavior.
                ...
            }
        }

### **切换视频/播放下一个时动态调画中画整宽高比例** ###

/**
    * 视频尺寸变化(上一个下一个时),动态调整PIP 宽高比
    *
    * @param with video宽度(非界面宽度)
    * @param height video高度(非界面高度)
    */
    private void videoSizeChange(int with, int height) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O && (height != mVideoHeight || mVideoWith != with)) {
            mVideoWith = with;
            mVideoHeight = height;
            if (mPictureInPictureParamsBuilder != null && mVideoWith != 0 && mVideoHeight != 0) {
                //设置param宽高比,根据快高比例调整初始参数
                Rational aspectRatio = new Rational(mVideoWith, mVideoHeight);
                mPictureInPictureParamsBuilder.setAspectRatio(aspectRatio);
    
                //设置更新PictureInPictureParams
                setPictureInPictureParams(mPictureInPictureParamsBuilder.build());
            }
        }
    }

# **进阶使用** #

## **添加自定义按钮:** ##

### **方式一: 通过[MediaSession][]达到如下图效果** ###

(此处有关videoPlayer相关代码根据自己播放器灵活代入,仅供参考)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEyMDA2MDQ_size_16_color_FFFFFF_t_70][]

当 Activity 进入画中画模式后，它默认没有获得输入焦点。要在画中画模式下接收输入事件，请使用 [MediaSession.setCallback()][MediaSession] 。如需详细了解如何使用 setCallback()，请参阅显示“ [正在播放][Link 1] ”卡片。

**首先在进入小窗前初始化MediaSessionCompat**

private MediaSessionCompat mSession;
    public static final long MEDIA_ACTIONS_PLAY_PAUSE = PlaybackStateCompat.ACTION_PLAY | PlaybackStateCompat.ACTION_PAUSE | PlaybackStateCompat.ACTION_PLAY_PAUSE;
    public static final long MEDIA_ACTIONS_ALL = MEDIA_ACTIONS_PLAY_PAUSE | PlaybackStateCompat.ACTION_SKIP_TO_NEXT | PlaybackStateCompat.ACTION_SKIP_TO_PREVIOUS;
    
    private void initializeMediaSession() {
        mSession = new MediaSessionCompat(this, TAG);
        mSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS | MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
        mSession.setActive(true);
        MediaControllerCompat.setMediaController(this, mSession.getController());
    
        MediaMetadataCompat metadata = new MediaMetadataCompat.Builder().build();
        mSession.setMetadata(metadata);
    
        MediaSessionCallback mMediaSessionCallback = new MediaSessionCallback(videoPlayer);
        mSession.setCallback(mMediaSessionCallback);
    
        int state = videoPlayer.getCurrentState() == GSYVideoView.CURRENT_STATE_PLAYING ? PlaybackStateCompat.STATE_PLAYING : PlaybackStateCompat.STATE_PAUSED;
        updatePlaybackState(state, MEDIA_ACTIONS_ALL, 0, 0);
    }

**在MediaSessionCompat.Callback中设置自己的播放器逻辑响应**

private class MediaSessionCallback extends MediaSessionCompat.Callback {
    
        private LocalListVideoPlayer movieView;
        private int indexInPlaylist;
    
    
        public MediaSessionCallback(LocalListVideoPlayer movieView) {
            this.movieView = movieView;
            indexInPlaylist = 1;
        }
    
        @Override
        public void onPlay() {
            super.onPlay();
            movieView.getGSYVideoManager().start();
            movieView.setIsInPictureInPictureMode(true);
            movieView.setCurrentState(GSYVideoView.CURRENT_STATE_PLAYING);
            updatePlaybackState(PlaybackStateCompat.STATE_PLAYING, 0, 0);
        }
    
        @Override
        public void onPause() {
            super.onPause();
            movieView.getGSYVideoManager().pause();
            movieView.setIsInPictureInPictureMode(true);
            movieView.setCurrentState(GSYVideoView.CURRENT_STATE_PAUSE);
            updatePlaybackState(PlaybackStateCompat.STATE_PAUSED, 0, 0);
        }
    
        @Override
        public void onSkipToNext() {
            super.onSkipToNext();
            movieView.playNext();
        }
    
        @Override
        public void onSkipToPrevious() {
            super.onSkipToPrevious();
            movieView.playLast();
        }
    }
    
    //更新按钮操作
    private void updatePlaybackState(@PlaybackStateCompat.State int state, int position, int mediaId) {
        if (mSession.getController().getPlaybackState() != null) {
            long actions = mSession.getController().getPlaybackState().getActions();
            updatePlaybackState(state, actions, position, mediaId);
        }
    }
    
    //初始化setPlaybackState
    private void updatePlaybackState(@PlaybackStateCompat.State int state, long playbackActions, int position, int mediaId) {
        if (mSession != null) {
            PlaybackStateCompat.Builder builder = new PlaybackStateCompat.Builder()
                    .setActions(playbackActions)
                    .setActiveQueueItemId(mediaId)
                    .setState(state, position, 1.0f);
            mSession.setPlaybackState(builder.build());
        }
    }

**在自己播放器状态更新时更新界面元素**

@Override
    public void onVideoStart() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            if(isInPictureInPictureMode()) {
                updatePlaybackState(PlaybackStateCompat.STATE_PLAYING, 0, 0);
            }
        }
    }
    
    @Override
    public void onVideoPause() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            if(isInPictureInPictureMode()) {
                updatePlaybackState(PlaybackStateCompat.STATE_PAUSED, 0, 0);
            }
        }
    }

### **方式2: 自定义按钮 (推荐)** ###

(注意,按钮不超过三个,位置不可调节)

您还可以通过在进入画中画模式之前构建 **[PictureInPictureParams][]**（使用 PictureInPictureParams.Builder. **[setActions][]**()）来明确指定自定义操作，并使用 enterPictureInPictureMode(android.app.PictureInPictureParams) 或 setPictureInPictureParams(android.app.PictureInPictureParams) 在进入画中画模式时传递这些参数。

首先自定义按钮初始化或刷新
    private BroadcastReceiver mReceiver;
    private static final String ACTION_MEDIA_CONTROL = "media_control";
    private static final String EXTRA_CONTROL_TYPE = "control_type";
    private static final int CONTROL_TYPE_PLAY = 1;
    private static final int CONTROL_TYPE_PAUSE = 2;
    private static final int CONTROL_TYPE_LAST = 3;
    private static final int CONTROL_TYPE_NEXT = 4;
    private static final int REQUEST_TYPE_PLAY = 1;
    private static final int REQUEST_TYPE_PAUSE = 2;
    private static final int REQUEST_TYPE_LAST = 3;
    private static final int REQUEST_TYPE_NEXT = 4;
    
    //进入画中画前判断状态,调用initPictureInPictureActions
        private void initPictureInPictureActions() {
            //int state = videoPlayer.getCurrentState() == GSYVideoView.CURRENT_STATE_PLAYING ? PlaybackStateCompat.STATE_PLAYING : PlaybackStateCompat.STATE_PAUSED;
            //STATE_PLAYING = 3  ; STATE_PAUSED = 2
            if (videoPlayer.getCurrentState() == GSYVideoView.CURRENT_STATE_PLAYING) {
                updatePictureInPictureActions(R.drawable.gsy_play_video_icon_pause, "", CONTROL_TYPE_PLAY, REQUEST_TYPE_PLAY);
            } else {
                updatePictureInPictureActions(R.drawable.gsy_play_video_icon_play, "", CONTROL_TYPE_PAUSE, REQUEST_TYPE_PAUSE);
            }
        }
    /**
    * 刷新自定义按钮 (若是初始化,注意区分进入画中画前onpause状态)
    *
    * @param iconId
    * @param title
    * @param controlType
    * @param requestCode 注意!! 每个intent的requestCode必须不一样
    */
    void updatePictureInPictureActions(@DrawableRes int iconId, String title, int controlType, int requestCode) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            if (mPictureInPictureParamsBuilder == null) {
                mPictureInPictureParamsBuilder = new PictureInPictureParams.Builder();
            }
            final ArrayList<RemoteAction> actions = new ArrayList<>();
            // This is the PendingIntent that is invoked when a user clicks on the action item.  You need to use distinct request codes for play and pause, or the PendingIntent won't be  updated.
    
    
            //上一个
            final PendingIntent intentLast = PendingIntent.getBroadcast(this, REQUEST_TYPE_NEXT, new Intent(ACTION_MEDIA_CONTROL).putExtra(EXTRA_CONTROL_TYPE, CONTROL_TYPE_LAST), 0);
            actions.add(new RemoteAction(Icon.createWithResource(this, R.drawable.gsy_play_video_icon_last), "", "", intentLast));
            //暂停/播放
            final PendingIntent intentPause = PendingIntent.getBroadcast(this, requestCode, new Intent(ACTION_MEDIA_CONTROL).putExtra(EXTRA_CONTROL_TYPE, controlType), 0);
            actions.add(new RemoteAction(Icon.createWithResource(this, iconId), title, title, intentPause));
            //下一个
            final PendingIntent intentNext = PendingIntent.getBroadcast(this, REQUEST_TYPE_LAST, new Intent(ACTION_MEDIA_CONTROL).putExtra(EXTRA_CONTROL_TYPE, CONTROL_TYPE_NEXT), 0);
            actions.add(new RemoteAction(Icon.createWithResource(this, R.drawable.gsy_play_video_icon_next), "", "", intentNext));
    
            mPictureInPictureParamsBuilder.setActions(actions);
    
            // This is how you can update action items (or aspect ratio) for Picture-in-Picture mode. Note this call can happen even when the app is not in PiP mode.
            setPictureInPictureParams(mPictureInPictureParamsBuilder.build());
        }
    }

**响应按钮发出的intent**

@Override
    public void onPictureInPictureModeChanged(boolean isInPictureInPictureMode, Configuration newConfig) {
        super.onPictureInPictureModeChanged(isInPictureInPictureMode, newConfig);
        if (videoPlayer != null) {
            isInPIPMode = isInPictureInPictureMode;
            videoPlayer.setIsInPictureInPictureMode(isInPIPMode);
        }
        //自定义action形式
        if (isInPictureInPictureMode) {
            // Starts receiving events from action items in PiP mode.
            mReceiver = new BroadcastReceiver() {
                @Override
                public void onReceive(Context context, Intent intent) {
                    if (intent == null || !ACTION_MEDIA_CONTROL.equals(intent.getAction())) {
                        return;
                    }
                    // This is where we are called back from Picture-in-Picture action
                    final int controlType = intent.getIntExtra(EXTRA_CONTROL_TYPE, 0);
                    try {
                        switch (controlType) {
                            case CONTROL_TYPE_PLAY:
                                videoPlayer.getGSYVideoManager().start();
                                videoPlayer.setIsInPictureInPictureMode(true);
                                videoPlayer.setCurrentState(GSYVideoView.CURRENT_STATE_PLAYING);
                                break;
                            case CONTROL_TYPE_PAUSE:
                                videoPlayer.getGSYVideoManager().pause();
                                videoPlayer.setIsInPictureInPictureMode(true);
                                videoPlayer.setCurrentState(GSYVideoView.CURRENT_STATE_PAUSE);
                                break;
                            case CONTROL_TYPE_LAST:
                                videoPlayer.playLast();
                                break;
                            case CONTROL_TYPE_NEXT:
                                videoPlayer.playNext();
                                break;
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            };
            registerReceiver(mReceiver, new IntentFilter(ACTION_MEDIA_CONTROL));
        } else {
            // We are out of PiP mode. We can stop receiving events from it.
            unregisterReceiver(mReceiver);
            mReceiver = null;
        }
    }

**当播放状态改变时更新按钮功能**

videoPlayer.setLocalPlayerCallback(new LocalListVideoPlayer.LocalPlayerCallback() {
        @Override
        public void clickPIPMode() {
            enterPiPMode();
        }
        @Override
        public void OnPrepareVideoSizeChanged(int with, int height) {
            videoSizeChange(with, height);
        }
        @Override
        public void surfaceDestroyed() {
            handleSurfaceDestroyed();
        }
        @Override
        public void onVideoStart() {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
              //自定义action刷新-开始播放-按钮替换为暂停
              updatePictureInPictureActions(R.drawable.gsy_play_video_icon_pause, "", CONTROL_TYPE_PLAY, REQUEST_TYPE_PLAY);
            }
        }
        @Override
        public void onVideoPause() {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            //自定义action刷新-暂停播放,按钮替换为开始
            updatePictureInPictureActions(R.drawable.gsy_play_video_icon_play, "", CONTROL_TYPE_PAUSE, REQUEST_TYPE_PAUSE);
            }

## **关于浮窗关闭后仍有声音,无法获取浮窗关闭通知** ##

### 方式一:监听**SurfaceView-**surfaceDestroyed() ###

在官方demo中,采用mediaSession方式, 以surfaceview的 **surfaceDestroyed()回调关闭播放器**

我采用的gsy播放器(同bilibili播放器),无法监听画中画浮窗关闭,采用如下的方法

在播放界面底层创建一个空的emptySurfaceView,通过callback获知浮窗被手动关闭 (此方法有个缺陷:在锁屏时也会回调此方法)

private SurfaceView emptySurfaceView;
    ....
    emptySurfaceView = findViewById(R.id.emtpy_surface);
    emptySurfaceView
            .getHolder()
            .addCallback(
                    new SurfaceHolder.Callback() {
                        @Override
                        public void surfaceCreated(SurfaceHolder holder) {
                        }
                        @Override
                        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
                        }
                        @Override
                        public void surfaceDestroyed(SurfaceHolder holder) {
                            if(mLocalPlayerCallback != null) {
                                mLocalPlayerCallback.surfaceDestroyed();
                            }
                        }
                    });

### **方式2:通过进入/退出/关闭画中画VideoActivity的生命周期判断(推荐)** ###

**操作画中画时VideoActivity相关生命周期梳理: **

进入画中画--onPause

画中画返回全屏--OnResume

关闭画中画--onStop

全屏播放状态下下锁屏/解锁 onPause ,onStop /  onStart,onResume

画中画状态下下锁屏/解锁 onStop /  onStart

//是否支持pip画中画小窗模式(自行判断赋值时机)
    protected boolean isSupportPipMode = false;
    //是否已经在画中画模式(自行判断赋值时机)
    public boolean isInPIPMode = false;
    //是否点击进入过画中画模式--用于判断程序在后台时,由画中画返回全屏后退出,是否启动首页activity,以及onstop配合判断是否点击进入过画中画且在画中画模式
    public boolean isEnteredPIPMode = false;
    
    @Override
    protected void onResume() {
        super.onResume();
        //画中画返回全屏会执行onresume
        isEnteredPIPMode = false;
    }
    
    @Override
    protected void onStop() {
        super.onStop();
        //备注: 在画中画模式下,onStop执行时, 若是关闭画中画,isInPictureInPictureMode()=false ; 若是锁屏,isInPictureInPictureMode()=true ; 判断锁屏isLockPage()一直为false
        boolean inPictureInPictureMode = false;
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.N) {
            inPictureInPictureMode = isInPictureInPictureMode();
        }
        if (BuildConfig.DEBUG) {
            Log.i(TAG, "onStop -- inPictureInPictureMode=" + inPictureInPictureMode + " ,isEnteredPIPMode=" + isEnteredPIPMode + " ,isInPIPMode=" + isInPIPMode);
        }
        if (!inPictureInPictureMode && isInPIPMode && isEnteredPIPMode) {
            //满足此条件下认为是关闭了画中画界面
            if (BuildConfig.DEBUG) {
                Log.w(TAG, "onStop -- 判断为PIP下关闭画中画");
            }
            handleSurfaceDestroyed();
            return;
        }
        if (inPictureInPictureMode && isInPIPMode && isEnteredPIPMode && videoPlayer != null) {
            //满足此条件下认为是画中画模式下锁屏
            videoPlayer.onVideoPause();
            isPause = true;
            if (BuildConfig.DEBUG) {
                Log.w(TAG, "onStop -- 判断为PIP下锁屏");
            }
        }
    }

### 关于开启浮窗关闭后显示在最近任务列表 ###

manifest添加 **android:excludeFromRecents="true"**

参考:[关于Android TaskAffinity的那些事儿][Android TaskAffinity]

[From Picture-in-Picture activity to Back-Stack activity not working in android?][From Picture-in-Picture activity to Back-Stack activity not working in android]

### **关于APP进入后台,播放完成后吊起主页activity,主页activity也进入浮窗模式(部分机型偶现)**  ###

**主页设置 android:supportsPictureInPicture="false"无效**

方案:采用遍历tasks,task.moveToFront() - task.moveToFront(); 避免采用startActivity方法使应用回到前台

参考:[Launching Intent from notification opening in picture-in-picture window][]

public static void moveLauncherTaskToFront(Context context) {
    
        ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        assert activityManager != null;
        final List<ActivityManager.AppTask> appTasks = activityManager.getAppTasks();
        for (ActivityManager.AppTask task : appTasks) {
            final Intent baseIntent = task.getTaskInfo().baseIntent;
            final Set<String> categories = baseIntent.getCategories();
            if (categories != null && categories.contains(Intent.CATEGORY_LAUNCHER)) {
                task.moveToFront();
                return;
            }
        }
    }

**判断获取用户是否关闭了应用画中画模式**

当您的应用处于画中画模式时，画中画窗口中的视频播放可能会对其他应用（例如，音乐播放器应用或语音搜索应用）造成音频干扰。为避免出现此问题，请在开始播放视频时请求音频焦点，并处理音频焦点更改通知，如管[理音频焦点][Link 2]中所述。如果您在处于画中画模式时收到音频焦点丢失通知，请暂停或停止视频播放。

//音频焦点的监听
    protected AudioManager mAudioManager;
    mAudioManager = (AudioManager) getActivityContext().getApplicationContext().getSystemService(Context.AUDIO_SERVICE);
    
    /**
    * 监听是否有外部其他多媒体开始播放
    */
    protected AudioManager.OnAudioFocusChangeListener onAudioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener() {
        @Override
        public void onAudioFocusChange(int focusChange) {
            switch (focusChange) {
                case AudioManager.AUDIOFOCUS_GAIN:
                    //获得了Audio Focus
                    onGankAudio();
                    break;
                case AudioManager.AUDIOFOCUS_LOSS:
                    //失去了Audio Focus，并将会持续很长的时间-暂停音频
                    onLossAudio();
                    break;
                case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
                    //暂时失去Audio Focus，并会很快再次获得
                    onLossTransientAudio();
                    break;
                case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
                    //暂时失去AudioFocus，但是可以继续播放，不过要在降低音量
                    onLossTransientCanDuck();
                    break;
            }
        }
    };

问题处理记录:  
页面切换进入/退出小窗播放状态处理  
小窗关闭监听  
10s退出  
权限支持判断  
自定义按钮状态  
吊起主页页面状态错误  
创建多个后台

### **参考:** ###

app: MXplayer:  (顶层activity: pipmenuActivity)

[创造 “魔术时刻” —— Android 8.0 画中画][_ _ Android 8.0]

[Google文档画中画][Google]  / [多窗口支持][Link 3]  /[ pipmenuActivity][pipmenuActivity]

[Android 8.0 PictureInPicture 画中画模式分析与使用][Android 8.0 PictureInPicture]

[Android开发笔记（一百六十七）Android8.0的画中画模式][Android_Android8.0]

[画中画权限判断][Link 4]  / [用户关闭画中画模式][Link 5]

[画中画github示例][github]

[Android 8.0 Oreo 画中画模式][Android 8.0 Oreo]

[关于Android TaskAffinity的那些事儿][Android TaskAffinity]

[From Picture-in-Picture activity to Back-Stack activity not working in android?][From Picture-in-Picture activity to Back-Stack activity not working in android]

[Launching Intent from notification opening in picture-in-picture window][]

[How Do We Leave Picture-In-Picture Mode?][How Do We Leave Picture-In-Picture Mode]

[Android Picture in picture mode and backstack management for multiple activities][]

[flowWindow]: https://github.com/yhaolpz/FloatWindow
[20200306180611883.png]: https://img-blog.csdnimg.cn/20200306180611883.png
[MediaSession]: https://developer.android.google.cn/reference/android/media/session/MediaSession#setCallback%28android.media.session.MediaSession.Callback%29
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEyMDA2MDQ_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200306180611919.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEyMDA2MDQ=,size_16,color_FFFFFF,t_70
[Link 1]: https://developer.android.google.cn/training/tv/playback/now-playing
[PictureInPictureParams]: https://developer.android.google.cn/reference/android/app/PictureInPictureParams.Builder#setActions%28java.util.List%3Candroid.app.RemoteAction%3E%29
[setActions]: https://developer.android.google.cn/reference/android/app/RemoteAction
[Android TaskAffinity]: https://www.cnblogs.com/ldq2016/p/6953106.html
[From Picture-in-Picture activity to Back-Stack activity not working in android]: https://stackoverflow.com/questions/57767263/from-picture-in-picture-activity-to-back-stack-activity-not-working-in-android
[Launching Intent from notification opening in picture-in-picture window]: https://stackoverflow.com/questions/54028535/launching-intent-from-notification-opening-in-picture-in-picture-window/60635501#60635501
[Link 2]: https://developer.android.google.cn/guide/topics/media-apps/audio-focus
[_ _ Android 8.0]: https://mp.weixin.qq.com/s?__biz=MzAwODY4OTk2Mg==&mid=2652045201&idx=1&sn=214b0ac8ee64cc93c7ecfbaef22007c8&chksm=808d5fd4b7fad6c299349ceb60e09965884802589db346c348dfa7eba4928aeb0bec2d7c9740&scene=38#wechat_redirect
[Google]: https://developer.android.google.cn/guide/topics/ui/picture-in-picture.html#java
[Link 3]: https://developer.android.google.cn/guide/topics/ui/multi-window
[pipmenuActivity]: https://source.android.google.cn/devices/tech/display/pip?hl=zh-tw
[Android 8.0 PictureInPicture]: https://blog.csdn.net/panghaha12138/article/details/87906438
[Android_Android8.0]: https://blog.csdn.net/aqi00/article/details/79693728
[Link 4]: https://stackoverflow.com/questions/53937688/enable-picture-in-picture-mode-programmatically
[Link 5]: https://stackoverflow.com/questions/52594181/how-to-know-if-user-has-disabled-picture-in-picture-feature-permission
[github]: https://github.com/android/media-samples/tree/master/PictureInPicture/#readme
[Android 8.0 Oreo]: https://www.jianshu.com/p/d76105b8ec30
[How Do We Leave Picture-In-Picture Mode]: https://stackoverflow.com/questions/43174507/how-do-we-leave-picture-in-picture-mode
[Android Picture in picture mode and backstack management for multiple activities]: https://medium.com/mindorks/android-picture-in-picture-mode-and-backstack-management-for-multiple-activities-8427fe3f8102