iOS- 关于AVAudioSession的使用——后台播放音乐

+ (UIBackgroundTaskIdentifier)backgroundPlayerID:(UIBackgroundTaskIdentifier)backTaskId
{
    // 1. 设置并激活音频会话类别
       AVAudioSession *session = [AVAudioSession sharedInstance];
    [session AVAudioSessionCategoryPlayback error:nil];
    [session setActive:YES error:nil];
    // 2. 允许应用程序接收远程控制
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
    // 3. 设置后台任务ID
      UIBackgroundTaskIdentifier newTaskId = UIBackgroundTaskInvalid;
    newTaskId = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:nil];
    if (newTaskId != UIBackgroundTaskInvalid && backTaskId != UIBackgroundTaskInvalid) {
        [[UIApplication sharedApplication] endBackgroundTask:backTaskId];
    }
    return newTaskId;
}

//后台播放音频设置  
AVAudioSession *session = [AVAudioSession sharedInstance];    
[session setActive:YES error:nil];    
[session setCategory:AVAudioSessionCategoryPlayback error:nil];   
  
//让app支持接受远程控制事件  
[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];  

// 后台播放任务Id
UIBackgroundTaskIdentifier  _bgTaskId;

// 设置音频会话，允许后台播放
_bgTaskId = [SoundTool backgroundPlayerID:_bgTaskId];