没有AVPlayer代表？歌曲播放完毕后如何追踪？Objective C iPhone开发

Question

我环顾四周,但我找不到代表协议AVPlayer class.是什么赋予了？

我正在使用它的子类,AVQueuePlayer来播放一个数组AVPlayerItems,每个数组都从一个URL加载.有什么方法可以在歌曲播放完毕后调用方法吗？特别是在队列的最后？

如果那是不可能的,那么在缓冲之后,当歌曲STARTS播放时,我有什么方法可以调用方法吗？我正试图在那里获得一个加载图标,但它会在音乐实际开始之前关闭图标,即使它是在[audioPlayer play]动作之后.

Answer 1

是的,AVPlayer类没有像AVAudioPlayer那样的委托协议.您需要订阅AVPlayerItem上的通知.您可以使用您-initWithURL:在AVPlayer上传递的相同URL创建AVPlayerItem.

-(void)startPlaybackForItemWithURL:(NSURL*)url {

    // First create an AVPlayerItem
    AVPlayerItem* playerItem = [AVPlayerItem playerItemWithURL:url];

    // Subscribe to the AVPlayerItem's DidPlayToEndTime notification.
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(itemDidFinishPlaying:) name:AVPlayerItemDidPlayToEndTimeNotification object:playerItem];

    // Pass the AVPlayerItem to a new player
    AVPlayer* player = [[[AVPlayer alloc] initWithPlayerItem:playerItem] autorelease];

    // Begin playback
    [player play]

} 

-(void)itemDidFinishPlaying:(NSNotification *) notification {
    // Will be called when AVPlayer finishes playing playerItem
}

Answer 2

是.将KVO观察者添加到玩家的状态或比率:

- (IBAction)go {
   self.player = .....
   self.player.actionAtItemEnd = AVPlayerActionStop;
   [self.player addObserver:self forKeyPath:@"rate" options:0 context:0]; 
}

- (void)stopped {
    ...
    [self.player removeObserver:self]; //assumes we are the only observer
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if (context == 0) {
        if(player.rate==0.0) //stopped
            [self stopped];
    }
    else
        [super observeVal...];
}

所以基本上就是这样.

免责声明:我在这里写了这个,所以我没有检查代码是否良好.我之前从未使用过AVPlayer,但它应该是正确的.

Answer 3

Swift 3 - 我AVPlayerItem每次向播放器添加视频时都会添加一个观察者:

func playVideo(url: URL) {
  let playerItem = AVPlayerItem(asset: AVURLAsset(url: someVideoUrl))
  NotificationCenter.default.addObserver(self, selector: #selector(playerItemDidPlayToEndTime), name: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: playerItem)
  self.player.replaceCurrentItem(with: playerItem)
  self.player.play()
}

func playerItemDidPlayToEndTime() {
  // load next video or something
}

Answer 4

Apple 文档AVFoundation 编程指南中有很多信息（查找监控播放部分）。它似乎主要是通过 KVO 进行的，因此如果您不太熟悉，您可能希望温习一下（Key Value Observing PlanningGuide有一个指南）。