判断avplayer 播放状态

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

        ////监听 timeControlStatus 播放状态，播放中允许旋转屏幕
- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary<NSKeyValueChangeKey,id> *)change
                       context:(void *)context
{

    if (object == self.player && [keyPath isEqualToString:@"timeControlStatus"]) {
        
        if (@available(iOS 10.0, *)) {
            AVPlayerTimeControlStatus status = [[change objectForKey:NSKeyValueChangeNewKey]integerValue];
            if (status == AVPlayerTimeControlStatusWaitingToPlayAtSpecifiedRate) {
                // do something
            }
        } else {
            // Fallback on earlier versions
            // ios10.0之后才能够监听到暂停后继续播放的状态，ios10.0之前监测不到这个状态
            //但是可以监听到开始播放的状态 AVPlayerStatus  status监听这个属性。
        }
    }
}

//删除监听器
    if (self.player) {
         [self.player removeObserver:self forKeyPath:@"timeControlStatus"];
    }