0. 现完成功能：

• 悬浮窗区分横屏竖屏两种尺寸
• 悬浮窗可以在页面上随意拖动
• 在播放视频时按返回键/Home键/离开当前页时触发开启
• 悬浮窗显示在退到后台/在应用内/桌面
• 带播放进度开启悬浮窗，带播放进度回到应用内页面
• 权限：每次开启前判断有无权限，没权限并且请求过就不开悬浮窗

已通过现有机型测试：三星、华为、vivo

1.引入依赖

//完整版引入
implementation 'com.shuyu:GSYVideoPlayer:8.1.2'

github：https://github.com/CarGuo/GSYVideoPlayer（强烈建议下载Demo源码，每个方法注释写的很清晰）

踩坑1：部分依赖时 打包apk一播放视频就崩溃，连接真机正常播放。报错是aliplay原因，注释掉换一个播放器内核：

implementation 'com.github.CarGuo.GSYVideoPlayer:gsyVideoPlayer-java:v8.3.4-release-jitpack'
//implementation 'com.github.CarGuo.GSYVideoPlayer:GSYVideoPlayer-aliplay:8.3.4-release-jitpack'

PlayerFactory.setPlayManager(SystemPlayerManager.class); // 换个系统内核

2.清单文件声明悬浮窗权限

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

3.从Demo源码导出需要的15个文件加入自己项目，并进行部分修改

1）修改悬浮窗布局 layout_floating_video，加上删除和回到应用的icon，点击播放/暂停的区域

layout_floating_video.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/surface_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center">

    </FrameLayout>

    <LinearLayout
        android:id="@+id/ll_center"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:gravity="center">

        <moe.codeest.enviews.ENPlayView
            android:id="@+id/start"
            android:layout_width="35dp"
            android:layout_height="35dp" />

    </LinearLayout>

    <ImageView
        android:id="@+id/iv_delete"
        android:layout_width="38dp"
        android:layout_height="38dp"
        android:layout_alignParentLeft="true"
        android:padding="9dp"
        android:src="@drawable/video_small_close" />

    <ImageView
        android:id="@+id/iv_detail"
        android:layout_width="38dp"
        android:layout_height="38dp"
        android:layout_alignParentRight="true"
        android:padding="12dp"
        android:src="@drawable/video_enlarge" />

</RelativeLayout>

FloatingVideo.java

public class FloatingVideo extends StandardGSYVideoPlayer {
	//... 以下新添
	//用于跳转回对应页面
	public int newsId;
	private NewsDetailActivity activity;
	public FloatingVideo(Context context, int newsId, LaunchActivity activity){
        super(context);
        this.newsId = newsId;
        this.activity = activity;
    }
    @Override
    protected void init(Context context) {
    	//...
    	//mStartButton.setOnClickListener(new OnClickListener() {
        //    @Override
        //    public void onClick(View v) {
        //        clickStartIcon();
        //    }
        //});
        
        //播放/暂停
        LinearLayout llCenter = findViewById(R.id.ll_center);
        llCenter.setOnClickListener(v -> clickStartIcon());
        //关闭
        ImageView ivDelete = findViewById(R.id.iv_delete);
        ivDelete.setOnClickListener(view -> {
            GSYVideoManager.instance().releaseMediaPlayer();
            FloatWindow.destroy();
        });
        //去详情
        ImageView ivDetail = findViewById(R.id.iv_detail);
        ivDetail.setOnClickListener(view -> {
            if(mContext!=null && newsId!=0){
                Long progress = getGSYVideoManager().getCurrentPosition();
                Bundle bundle = new Bundle();
                bundle.putInt("news_id", newsId);
                if(activity != null){
                	activity.startActivity(new NewsDetailActivity(bundle))
                    setTopApp(context);
                }
                GSYVideoManager.instance().releaseMediaPlayer();
                FloatWindow.destroy();
            }
        });
	}
	
	//当本应用位于后台时，则将它切换到最前端
    public static void setTopApp(Context context) {
        if (isRunningForeground(context)) {
            return;
        }
        //获取ActivityManager
        ActivityManager activityManager = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);

        //获得当前运行的task(任务)
        List<ActivityManager.RunningTaskInfo> taskInfoList = activityManager.getRunningTasks(100);
        for (ActivityManager.RunningTaskInfo taskInfo : taskInfoList) {
            //找到本应用的 task，并将它切换到前台
            if (taskInfo.topActivity.getPackageName().equals(context.getPackageName())) {
                activityManager.moveTaskToFront(taskInfo.id, 0);
                break;
            }
        }
    }

    //判断本应用是否已经位于最前端：已经位于最前端时，返回 true；否则返回 false
    public static boolean isRunningForeground(Context context) {
        ActivityManager activityManager = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> appProcessInfoList = activityManager.getRunningAppProcesses();

        for (ActivityManager.RunningAppProcessInfo appProcessInfo : appProcessInfoList) {
            if (appProcessInfo.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND
                    && appProcessInfo.processName.equals(context.getApplicationInfo().processName)) {
                return true;
            }
        }
        return false;
    }
	
}

2）悬浮窗接收参数：播放进度和数据源

FloatPlayerViewjava

public class FloatPlayerView extends FrameLayout {
//... 以下新添
	public FloatPlayerView(Context context, Bundle bundle, LaunchActivity activity) {
        super(context);
        init(bundle,activity);
    }
    private void init(Bundle bundle, LaunchActivity activity) {
		if(bundle == null) return;
        videoPlayer = new FloatingVideo(getContext(), (int) bundle.get("vNewsId"),activity);
        LayoutParams layoutParams = new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
        layoutParams.gravity = Gravity.CENTER;

        addView(videoPlayer, layoutParams);
        //设置播放源
        videoPlayer.setUp((String) bundle.get("vSource"), true, "");
        //设置播放进度
        videoPlayer.setSeekOnStart((Long) bundle.get("vPosition"));
        //是否可以滑动调整
        videoPlayer.setIsTouchWiget(false);
        //开始播放
        videoPlayer.startPlayLogic();
	}

3）解决bug：拒绝权限还存在视频声音

FloatPhone.java

class FloatPhone extends FloatView {
	//...
	@RequiresApi(api = Build.VERSION_CODES.M)
    @Override
    public void init() {
        if (Util.hasPermission(mContext)) {//...
        } else {
            FloatVideoActivity.request(mContext, new PermissionListener() {//...
                @Override
                public void onFail() {
                	//就这行
                    GSYVideoManager.instance().releaseMediaPlayer();
                }
            });
        }
    }
    @Override
    public void dismiss() {
    	//捕获异常
        try{
            mWindowManager.removeView(mView);
        }catch (Exception e){
            Log.e("FloatWindow",e.getMessage());
        }
    }
}

4. 播放视频&开启悬浮窗

XxxActivity.java 自己的页面

	//视频
    private OrientationUtils orientationUtils;
    private long floatProgress;
    private FloatPlayerView floatPlayerView;
    
	//准备视频播放器：请求完数据后调用
	private synchronized void prepareVideo() {
        //关掉悬浮窗
        if (FloatWindow.get() != null) {
           FloatWindow.destroy();
        }
        videoPlayer.setVisibility(View.VISIBLE);
        //设置内核
        PlayerFactory.setPlayManager(SystemPlayerManager.class);
        //设置代理缓存模式
        CacheFactory.setCacheManager(ProxyCacheManager.class);
        //封面
        ImageView imageView = new ImageView(getContext());
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        Glide.with(getContext()).load(newsBean.getVideo()).dontAnimate().into(imageView);
        videoPlayer.setThumbImageView(imageView);
        //隐藏返回键和标题
        videoPlayer.getTitleTextView().setVisibility(View.GONE);
        videoPlayer.getBackButton().setVisibility(View.GONE);
        videoPlayer.setUp(newsBean.getVideo(), true, "");
        //旋转
        orientationUtils = new OrientationUtils(getParentActivity(), videoPlayer);
        //全屏按键功能,这是使用的是选择屏幕，而不是全屏
        videoPlayer.getFullscreenButton().setOnClickListener(v -> {
            //旋转屏幕
            orientationUtils.resolveByClick();
            videoPlayer.startWindowFullscreen(getContext(), false, true);
        });
        //是否可以滑动调整
        videoPlayer.setIsTouchWiget(true);
        videoPlayer.setNeedLockFull(true);
        videoPlayer.setAutoFullWithSize(true);
        //拖到已有进度播放
        if (floatProgress > 0) 
            videoPlayer.setSeekOnStart(floatProgress);
        }
    }
    
    //init ：onCreate调用
	private void initDataNewsDetail() {
		//和小窗同一条新闻 -> 读取进度 不同新闻 -> 关小窗
        if (FloatWindow.get() != null && FloatWindow.newsId == newsId) { 
            if (FloatWindow.get().getView() != null) {
                floatProgress = ((FloatPlayerView) FloatWindow.get().getView()).getVideoPlayer().getGSYVideoManager().getCurrentPosition();
            }
            FloatWindow.destroy();
        }
        presenter.getDetail(newsId);
    }
    
    //开启悬浮窗
    private void openFloatVideo() {
        if (orientationUtils != null) {
            orientationUtils.backToProtVideo();
        }
        //记录有没有请求过
        boolean isFirstRePermission = SPUtils.getInstance().get("is_first_request_window",true);
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
        	//没权限并且请求过 就pass不开悬浮窗
            if(!Util.hasPermission(getContext()) && !isFirstRePermission){
                getCurPlay().onVideoPause();
                return;
            }
        }

        if(isFirstRePermission){
            SPUtils.getInstance().save("is_first_request_window",false);
        }

        if (!GSYVideoManager.backFromWindowFull(getContext())) {
            if (FloatWindow.get() == null && videoPlayer.getCurrentPlayer().getCurrentState() == CURRENT_STATE_PLAYING && !TextUtils.isEmpty(newsBean.getVideo())) {
                videoPlayer.onVideoPause();
                FloatWindow.newsId = newsId;
                long position = videoPlayer.getGSYVideoManager().getCurrentPosition();
                Bundle bundle = new Bundle();
                //传参给悬浮窗
                bundle.putString("vSource", newsBean.getVideo());
                bundle.putLong("vPosition", position);
                bundle.putInt("vNewsId", newsBean.getId());
                floatPlayerView = new FloatPlayerView(getParentActivity().getApplicationContext(), bundle, (LaunchActivity) getParentActivity());
                //悬浮窗比例
                float ratio = 0.55f;//横屏
                FloatingVideo floatingVideo = floatPlayerView.getVideoPlayer();
                floatingVideo.setAutoFullWithSize(true);
                if(floatingVideo.isVerticalFullByVideoSize()){
                    ratio = 0.3f;//竖屏
                }
                FloatWindow
                        .with(getParentActivity().getApplicationContext())
                        .setView(floatPlayerView)
                        .setWidth(Screen.width, ratio)
                        .setHeight(Screen.width, (float)floatingVideo.getCurrentVideoHeight()/(float)floatingVideo.getCurrentVideoWidth() * ratio)
                        .setX(Screen.width, 0.8f)
                        .setY(Screen.height, 0.3f)
                        .setMoveType(MoveType.slide)
                        .setFilter(false)
                        .setMoveStyle(500, new BounceInterpolator())
                        .build();
                FloatWindow.get().show();
            }
        }
    }

---

若出现未考虑的情况或其他bug，欢迎评论补充。