应用程序激活后恢复AVPlayer视频播放

Question

我从AVPlayer编写自定义播放器进行视频播放.根据Apple docs设置的视频层:

    self.player = [IPLPlayer new];
    self.player.playerLayer = (AVPlayerLayer *)self.playerView.layer;

self.playerView是那些文档的常用类:

    @implementation PlayerView

+ (Class) layerClass {
    return [AVPlayerLayer class];
}

- (AVPlayer *)player {
    return [(AVPlayerLayer *)[self layer] player];
}

- (void)setPlayer:(AVPlayer *) player {
    [(AVPlayerLayer *) [self layer] setPlayer:player];
}

问题是:当关闭应用程序(主页按钮)或阻止屏幕时,视频播放停止,当恢复仅恢复音频播放时,屏幕上的图像仍然是块屏幕之前的图像 - 它是完全静态的并且记录更改帧.

如何在屏幕被阻止后恢复视频播放？

似乎我必须注册通知,并在应用程序变为活动后恢复视频层:

    -(void)registerNotification
{
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(willEnterBackground)
                                                 name:UIApplicationWillResignActiveNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(didEnterForeground)
                                                 name:UIApplicationDidBecomeActiveNotification object:nil];
}

-(void)unregisterNotification
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}


-(void)willEnterBackground
{
    NSLog(@"willEnterBackground");
    [self.playerView willEnterBackground];
}

-(void)didEnterForeground
{
    NSLog(@"didEnterForeground");
    [self.playerView didEnterForeground];
}

Answer 1

一种解决方案将所有这些信息绑定在一起.

也许播放器状态应该以不同的方式处理,但我喜欢递归方式.

注意:如果您不需要精确的搜索时间,可以使用[_player seekToTime:<#(CMTime)#> completionHandler:<#^(BOOL finished)completionHandler#>]它更快,但它会寻找最近的关键帧.

- (void)viewDidLoad
{
    [super viewDidLoad];

....

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(appEnteredForeground) name:UIApplicationWillEnterForegroundNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(appEnteredBackground) name:UIApplicationDidEnterBackgroundNotification object:nil];
}

-(void)viewWillDisappear:(BOOL)animated
{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationWillEnterForegroundNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidEnterBackgroundNotification object:nil];
}

....

-(void) appEnteredForeground {
    AVPlayerLayer *player = (AVPlayerLayer *)[playerView layer];
    [player setPlayer:NULL];
    [player setPlayer:_player];
    [self playAt:currentTime];
}

-(void) appEnteredBackground {
    [_player pause];
    currentTime = [_player currentTime];
}

-(void)playAt: (CMTime)time {
    if(_player.status == AVPlayerStatusReadyToPlay && _player.currentItem.status == AVPlayerItemStatusReadyToPlay) {
        [_player seekToTime:time toleranceBefore:kCMTimeZero toleranceAfter:kCMTimeZero completionHandler:^(BOOL finished) {
            [_player play];
        }];
    } else {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [self playAt:time];
        });
    }
}

Answer 2

这适用于Swift 3

在设置视图时添加某处:

NotificationCenter.default.addObserver(self, 
  selector: #selector(appWillEnterForegroundNotification),
  name: .UIApplicationWillEnterForeground, object: nil)

抓住你的玩家并强制它玩:

func appWillEnterForegroundNotification() {
  myPlayer.play()
}

不要忘记在不需要时删除观察者:

override func viewWillDisappear(_ animated: Bool) {
  super.viewWillDisappear(animated)
  NotificationCenter.default.removeObserver(self)
}