-(AVPlayer *)player
{
  if (_player == nil) {
     // AVPlayerItem是一个包装音乐资源的类，初始化时可以传入一个音乐的url
    AVPlayerItem *item = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:@"http://xxxxxxxx"]];
    //通过AVPlayerItem初始化player
    _player = [[AVPlayer alloc] initWithPlayerItem:item];
  }

  return _player;
}

  //开始播放
  [self.player play];
   //停止播放
  [self.player pause];

//创建需要播放的AVPlayerItem
 AVPlayerItem *item = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:model.url]];
 //替换当前音乐资源 
 [self.player replaceCurrentItemWithPlayerItem:item];

 [self.player.currentItem addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:nil];

typedef NS_ENUM(NSInteger, AVPlayerItemStatus) {
  AVPlayerItemStatusUnknown,//未知状态
  AVPlayerItemStatusReadyToPlay,//准备播放
  AVPlayerItemStatusFailed//加载失败
};

//观察者回调
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
{
  //注意这里查看的是self.player.status属性
  if ([keyPath isEqualToString:@"status"]) {
    switch (self.player.status) {
      case AVPlayerStatusUnknown:
      {
        NSLog(@"未知转态");
      }
        break;
      case AVPlayerStatusReadyToPlay:
      {
        NSLog(@"准备播放");
      }
        break;
      case AVPlayerStatusFailed:
      {
        NSLog(@"加载失败");
      }
        break;
         default:
        break；
    }
  }
}

//移除观察者
 [self.player.currentItem removeObserver:self forKeyPath:@"status"];

//KVO监听音乐缓冲状态
[self.player.currentItem addObserver:self forKeyPath:@"loadedTimeRanges" options:NSKeyValueObservingOptionNew context:nil];

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
{
  if ([keyPath isEqualToString:@"loadedTimeRanges"]) {

    NSArray * timeRanges = self.player.currentItem.loadedTimeRanges;
    //本次缓冲的时间范围
    CMTimeRange timeRange = [timeRanges.firstObject CMTimeRangeValue];
    //缓冲总长度
    NSTimeInterval totalLoadTime = CMTimeGetSeconds(timeRange.start) + CMTimeGetSeconds(timeRange.duration);
    //音乐的总时间
    NSTimeInterval duration = CMTimeGetSeconds(self.player.currentItem.duration);
    //计算缓冲百分比例
    NSTimeInterval scale = totalLoadTime/duration;
    //更新缓冲进度条
    self.loadTimeProgress.progress = scale;
  }

}

typedef struct
{
  CMTime      start;    
  CMTime      duration;  
} CMTimeRange;

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

/**
 监听音乐播放进度

 @param interval 监听的时间间隔，用来设置多长时间回调一次
 @param queue  队列，一般传主队列
 @param block  回调的block，会把当前的播放时间传递过来

 @return 监听的对象
 */
- (id)addPeriodicTimeObserverForInterval:(CMTime)interval queue:(nullable dispatch_queue_t)queue usingBlock:(void (^)(CMTime time))block;

 __weak typeof(self) weakSelf = self;
  self.timeObserver = [self.player addPeriodicTimeObserverForInterval:CMTimeMake(1.0, 1.0) queue:dispatch_get_main_queue() usingBlock:^(CMTime time) {
    //当前播放的时间
    float current = CMTimeGetSeconds(time);
    //总时间
    float total = CMTimeGetSeconds(item.duration);
    if (current) {
      float progress = current / total;
      //更新播放进度条
      weakSelf.playSlider.value = progress;
      weakSelf.currentTime.text = [weakSelf timeFormatted:current];
    }
  }];

  typedef struct
   CMTimeValue  value;    
   CMTimeScale  timescale;  
   CMTimeFlags  flags;    
   CMTimeEpoch  epoch;    
  } CMTime;

Float64 CMTimeGetSeconds(CMTime time)

if (self.timeObserver) {
    [self.player removeTimeObserver:self.timeObserver];
    self.timeObserver = nil;
  }

/**
 定位播放时间

 @param time 指定的播放时间
 */
- (void)seekToTime:(CMTime)time;
具体使用如下：

//移动滑块调整播放进度
- (IBAction)playSliderValueChange:(UISlider *)sender
{
  //根据值计算时间
  float time = sender.value * CMTimeGetSeconds(self.player.currentItem.duration);
  //跳转到当前指定时间
  [self.player seekToTime:CMTimeMake(time, 1)];
}

//给AVPlayerItem添加播放完成通知
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playFinished:) name:AVPlayerItemDidPlayToEndTimeNotification object:_player.currentItem];

  //一般在方法：application: didFinishLaunchingWithOptions:设置
  //获取音频会话
  AVAudioSession *session = [AVAudioSession sharedInstance];
  //设置类型是播放。
  [session setCategory:AVAudioSessionCategoryPlayback error:nil];
  //激活音频会话。
  [session setActive:YES error:nil];

//音乐锁屏信息展示
- (void)setupLockScreenInfo
{
  // 1.获取锁屏中心
  MPNowPlayingInfoCenter *playingInfoCenter = [MPNowPlayingInfoCenter defaultCenter];

  //初始化一个存放音乐信息的字典
  NSMutableDictionary *playingInfoDict = [NSMutableDictionary dictionary];
  // 2、设置歌曲名
  if (self.currentModel.name) {
    [playingInfoDict setObject:self.currentModel.name forKey:MPMediaItemPropertyAlbumTitle];
  }
  // 设置歌手名
  if (self.currentModel.artist) {
    [playingInfoDict setObject:self.currentModel.artist forKey:MPMediaItemPropertyArtist];
  }
  // 3设置封面的图片
  UIImage *image = [self getMusicImageWithMusicId:self.currentModel];
  if (image) {
    MPMediaItemArtwork *artwork = [[MPMediaItemArtwork alloc] initWithImage:image];
    [playingInfoDict setObject:artwork forKey:MPMediaItemPropertyArtwork];
  }

  // 4设置歌曲的总时长
  [playingInfoDict setObject:self.currentModel.detailDuration forKey:MPMediaItemPropertyPlaybackDuration];

  //音乐信息赋值给获取锁屏中心的nowPlayingInfo属性
  playingInfoCenter.nowPlayingInfo = playingInfoDict;

  // 5.开启远程交互，只有开启这个才能进行远程操控
  [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
}

//监听远程交互方法
- (void)remoteControlReceivedWithEvent:(UIEvent *)event
{

  switch (event.subtype) {
    //播放
    case UIEventSubtypeRemoteControlPlay:{
      [self.player play];
          }
      break;
    //停止
    case UIEventSubtypeRemoteControlPause:{
      [self.player pause];
          }
      break;
    //下一首
    case UIEventSubtypeRemoteControlNextTrack:
      [self nextBtnAction:nil];
      break;
    //上一首
    case UIEventSubtypeRemoteControlPreviousTrack:
      [self lastBtnAction:nil];
      break;

    default:
      break;
  }
}