AVPlayer工具栏以及画中画的自定义实现

AVPlayerViewController使用方便但不够灵活。
搜索引擎了半天并没有找到自定义工具栏的方法。于是老老实实自己实现。

工具栏的自定义

基于AVplayer，自定义UIView，用于Player以及工具栏的显示

@interface WKPlayerView : UIView

@property(nonatomic, strong)AVPlayer *player;
@property(nonatomic, strong)AVPlayerLayer *playerLayer;
@property(nonatomic, strong)UIControl *contentView;//用于自定义工具栏，手势事件等。

@end

在这里，我删除了具体的界面布局代码。用户期望的自定义界面或事件都在contentView上实现即可。
实现方式：

_contentView = [UIControl new];
[self addSubview:_contentView];
[_contentView mas_makeConstraints:^(MASConstraintMaker *make){
    make.size.equalTo(self);
    make.center.equalTo(self);
}];

_player = [AVPlayer playerWithURL:[NSURL URLWithString:URLString]];
_playerLayer = [AVPlayerLayer playerLayerWithPlayer:_player];
[_playerLayer setVideoGravity:AVLayerVideoGravityResizeAspect];
//将playerLayer添加到contentView下，以免contentView的事件被挡住。
[self.layer insertSublayer:_playerLayer below:_contentView.layer];
[_player play];

界面部分就完成了。

播放的自定义

播放过程中，我们可能会有播放、暂停、跳转、获取进度、缓冲等等事件。AVPlayer提供了
- (void)play;
- (void)pause;
- (void)seekToTime:(CMTime)time;(还有更多实现)
- (CMTime)currentTime;
等api，可以灵活的根据需求自定义实现。

在这里记录一下观察播放进度和缓冲进度的方法：
播放进度:- addPeriodicTimeObserverForInterval:queue:usingBlock:

- (void)addPeriodicTimeObserver {
    // Invoke callback every half second
    CMTime interval = CMTimeMakeWithSeconds(0.5, NSEC_PER_SEC);
    // Queue on which to invoke the callback
    dispatch_queue_t mainQueue = dispatch_get_main_queue();
    // Add time observer
    self.timeObserverToken =
        [self.player addPeriodicTimeObserverForInterval:interval
                                                  queue:mainQueue
                                             usingBlock:^(CMTime time) {
                                                 // Use weak reference to self
                                                 // Update player transport UI
                                             }];
}

注意：添加了timeObserver后，不使用的时候记得调用- removeTimeObserver:，否则会占用大量内存。

缓冲进度：
当网络出现问题时，AVPlayer将会自动暂停，所以当缓冲好了之后，我们必须手动调用- (void)play;
AVPlayerItem是使用KVO模式观察状态，所以我们可以通过观察 loadedTimeRanges 获取缓冲进度：

[self.player.currentItem addObserver:self forKeyPath:@"loadedTimeRanges" options:NSKeyValueObservingOptionNew context:nil];// 监听loadedTimeRanges属性

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if ([keyPath isEqualToString:@"loadedTimeRanges"]){
        NSTimeInterval timeInterval = [self availableDuration];// 缓冲进度
        //todo:刷新缓冲进度条、播放等逻辑 
    }
}

更多的功能请参考API

画中画的实现

在使用AVPlayerViewController时，只需要简单设置allowsPictureInPicturePlayback，即可实现画中画功能。
那我们的自定义播放器呢？
实现方式我参考了https://stackoverflow.com/questions/32667090/how-to-display-avpictureinpicturecontroller
翻译一下：
1、首先我们在Capabilities里的Background Modes设置Audio, AirPlay and Picture in Picture，如图

设置背景模块

2、在Appdelegate里设置

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
[[AVAudioSession sharedInstance] setActive: YES error: nil];

3、在AVPlayer初始化完成后添加如下代码

-(void)play:(NSString *)URLString {
    self.player = [AVPlayer playerWithURL:[NSURL URLWithString:URLString]];
    self.playerLayer = [AVPlayerLayer playerLayerWithPlayer:_player];
    [self.playerLayer setVideoGravity:AVLayerVideoGravityResizeAspect];
    [self.layer insertSublayer:self.playerLayer below:_contentView.layer];
    [_player play];
    //添加画中画相关代码
    [self setupSuport];
}

-(void)setupSuport {
    if([AVPictureInPictureController isPictureInPictureSupported]) {
        //属性变量@property(nonatomic, strong)AVPictureInPictureController *AVPictureInPictureController;
        _AVPictureInPictureController =  [[AVPictureInPictureController alloc] initWithPlayerLayer:self.playerLayer];
        _AVPictureInPictureController.delegate = self;
    } else {
        // not supported PIP start button desable here
    }
}

4、自定义启动画中画按钮事件

if (_AVPictureInPictureController.pictureInPictureActive) {
    [_AVPictureInPictureController stopPictureInPicture];
} else {
    [_AVPictureInPictureController startPictureInPicture];
}

到这就完成了。
你还可以实现delegate，以自定义更多功能。

- (void)pictureInPictureController:(AVPictureInPictureController *)pictureInPictureController restoreUserInterfaceForPictureInPictureStopWithCompletionHandler:(void (^)(BOOL restored))completionHandler;
- (void)pictureInPictureControllerDidStopPictureInPicture:(AVPictureInPictureController *)pictureInPictureController;
- (void)pictureInPictureControllerDidStartPictureInPicture:(AVPictureInPictureController *)pictureInPictureController;
- (void)pictureInPictureControllerWillStopPictureInPicture:(AVPictureInPictureController *)pictureInPictureController;
- (void)pictureInPictureController:(AVPictureInPictureController *)pictureInPictureController failedToStartPictureInPictureWithError:(NSError *)error;
- (void)pictureInPictureControllerWillStartPictureInPicture:(AVPictureInPictureController *)pictureInPictureController;

到这里，一个自定义播放器就基本上完成了。