一.设置后台播放

• 首先允许程序后台播放
• 代码实现

   - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  
       // 设置后台播放的代码,步骤
  
       // 1.获取音频的会话
  
       AVAudioSession *session = [AVAudioSession sharedInstance];
  
       // 2.设置后台播放类型
  
       [session setCategory:AVAudioSessionCategoryPlayback error:nil];
  
       // 3.激活会话
  
       [session setActive:YES error:nil];
  
       return YES;
  
   }

二.锁屏界面

• 适当的时机调用这个方法                                                                              

  #pragma mark - 设置锁屏界面的信息
  
  - (void)setupLockScreenInfo
  
  {
  
      // 1.获取当前正在播放的歌曲
  
      ChaosMusic *playingMusic = [ChaosMusicTool playingMusic];
  
      // 2.获取锁屏界面中心
  
      MPNowPlayingInfoCenter *playingCenter = [MPNowPlayingInfoCenter defaultCenter];
  
      // 3.设置展示的信息
  
      NSMutableDictionary *playingInfo = [NSMutableDictionary dictionary];
  
      playingInfo[MPMediaItemPropertyAlbumTitle] = playingMusic.name;
  
      playingInfo[MPMediaItemPropertyArtist] = playingMusic.singer;
  
      MPMediaItemArtwork *artwork = [[MPMediaItemArtwork alloc] initWithImage:[UIImage imageNamed:playingMusic.icon]];
  
      playingInfo[MPMediaItemPropertyArtwork] = artwork;
  
      playingInfo[MPMediaItemPropertyArtist] = @(self.player.currentTime);
  
      playingCenter.nowPlayingInfo = playingInfo;
  
      // 4.让应用程序可以接受远程事件
  
      [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
  
  }

• 实现了锁屏界面,没有实现监听远程事件的话,锁屏界面的下一首之类的按钮没有反应.实现下面的方法

   // 监听远程事件
  
   - (void)remoteControlReceivedWithEvent:(UIEvent *)event
  
   {
  
       switch (event.subtype) {
  
           case UIEventSubtypeRemoteControlPlay:
  
           case UIEventSubtypeRemoteControlPause:
  
               [self startOrPause:nil];
  
               break;
  
           case UIEventSubtypeRemoteControlNextTrack:
  
               [self nextMusic:nil];
  
               break;
  
           case UIEventSubtypeRemoteControlPreviousTrack:
  
               [self previousMusic:nil];
  
               break;
  
           default:
  
               break;
  
       }
  
   }