iOS后台音频播放及锁屏歌词

//后台播放音频设置,需要在Capabilities->Background Modes中勾选Audio,Airplay,and Picture in Picture
    AVAudioSession *session = [AVAudioSession sharedInstance];
    [session setActive:YES error:nil];
    [session setCategory:AVAudioSessionCategoryPlayback error:nil];

//开始接受远程控制
     [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
     //结束远程控制,需要的时候关闭
     //     [[UIApplication sharedApplication] endReceivingRemoteControlEvents];

//处理后台传递给我们的信息，用于音乐，在AppDelegate.m中重写
    - (void)remoteControlReceivedWithEvent:(UIEvent *)event{
    //处理后台传递给我们的控制信息，用于音乐
    if (event.type == UIEventTypeRemoteControl) {
     
        NSLog(@"%ld",event.subtype);
        
        [[NSNotificationCenter defaultCenter] postNotificationName:@"songControlNotification" object:self userInfo:@{@"subtype":@(event.subtype)}];
        
        /*
         
         subtype中的枚举便是点击这些控制键后传递给我们的消息，我们可以根据这些消息在app内做逻辑处理。枚举如下，其中只有100之后的在音频控制中对我们有效：
         
         typedef NS_ENUM(NSInteger, UIEventSubtype) {
         
            // available in iPhone OS 3.0
            UIEventSubtypeNone                              = 0,
            // for UIEventTypeMotion, available in iPhone OS 3.0
            UIEventSubtypeMotionShake                       = 1,
            //这之后的是我们需要关注的枚举信息
            // for UIEventTypeRemoteControl, available in iOS 4.0
            //点击播放按钮或者耳机线控中间那个按钮
            UIEventSubtypeRemoteControlPlay                 = 100,
            //点击暂停按钮
            UIEventSubtypeRemoteControlPause                = 101,
            //点击停止按钮
            UIEventSubtypeRemoteControlStop                 = 102,
            //点击播放与暂停开关按钮(iphone抽屉中使用这个)
            UIEventSubtypeRemoteControlTogglePlayPause      = 103,
            //点击下一曲按钮或者耳机中间按钮两下
            UIEventSubtypeRemoteControlNextTrack            = 104,
            //点击上一曲按钮或者耳机中间按钮三下
            UIEventSubtypeRemoteControlPreviousTrack        = 105,
            //快退开始 点击耳机中间按钮三下不放开
            UIEventSubtypeRemoteControlBeginSeekingBackward = 106,
            //快退结束 耳机快退控制松开后
            UIEventSubtypeRemoteControlEndSeekingBackward   = 107,
            //开始快进 耳机中间按钮两下不放开
            UIEventSubtypeRemoteControlBeginSeekingForward  = 108,
            //快进结束 耳机快进操作松开后
            UIEventSubtypeRemoteControlEndSeekingForward    = 109,
        };
     */
        
        }
    }


    //监听锁屏状态 lock=1则为锁屏状态
        uint64_t locked;
        __block int token = 0;
       notify_register_dispatch("com.apple.springboard.lockstate",&token,dispatch_get_main_queue(),^(int t){
        });
        notify_get_state(token, &locked);
        
        //监听屏幕点亮状态 screenLight=1则为变暗关闭状态
        uint64_t screenLight;
        __block int lightToken = 0;
    notify_register_dispatch("com.apple.springboard.hasBlankedScreen",&lightToken,dispatch_get_main_queue(),^(int t){
        });
        notify_get_state(lightToken, &screenLight);
        
       // NSLog(@"screenLight=%llu locked=%llu",screenLight,locked);
        if (screenLight == 1|| locked == 0) {
            return;
        }
        //锁屏信息
            [self showLockScreenTotaltime:totalSeconds andCurrentTime:playSeconds];




    //锁屏控制音乐播放事件的通知
    - (void)addNotification{
    
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(songPlayControl:) name:@"songControlNotification" object:nil];
    
    }
    - (void)songPlayControl:(NSNotification *)noti{  
       NSNumber* subtype = noti.userInfo[@"subtype"];
    int type = [subtype intValue];
    switch (type) {
          case UIEventSubtypeRemoteControlNextTrack:
            [self nextSongBtnClick];
            break;
          case UIEventSubtypeRemoteControlPreviousTrack:
            [self previousSongBtnClick];
            break;
          case  UIEventSubtypeRemoteControlPause:
            [self playBtnClick:_playBtn];
            break;
            case  UIEventSubtypeRemoteControlPlay:
            [self playBtnClick:_playBtn];
            break;
        default:
            break;
        }
       }






    #pragma mark --- 锁屏歌曲信息
    - (void)showLockScreenTotaltime:(float)totalTime andCurrentTime:(float)currentTime{
    
    NSMutableDictionary * songDict = [[NSMutableDictionary alloc] init];
    SongModel * songModel = self.songArray[_playIndex];
    //设置歌曲题目
    [songDict setObject:songModel.songName forKey:MPMediaItemPropertyTitle];
    //设置歌手名
    [songDict setObject:songModel.singerName forKey:MPMediaItemPropertyArtist];
    //设置专辑名
    [songDict setObject:songModel.songName forKey:MPMediaItemPropertyAlbumTitle];
    //设置歌曲时长
    [songDict setObject:[NSNumber numberWithDouble:totalTime] forKey:MPMediaItemPropertyPlaybackDuration];
    //设置已经播放时长
    [songDict setObject:[NSNumber numberWithDouble:currentTime] forKey:MPNowPlayingInfoPropertyElapsedPlaybackTime];
    
    if (!_lrcImageView) {
        _lrcImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width - 100,self.view.frame.size.width - 100 + 50)];
        
    }
    [_lrcImageView addSubview:self.lockScreenTableView];
     _lrcImageView.image = _songImage.image;
    
    //获取添加了歌词数据的背景图

    UIGraphicsBeginImageContextWithOptions(_lrcImageView.frame.size, NO, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [_lrcImageView.layer renderInContext:context];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    //设置显示的图片
    [songDict setObject:[[MPMediaItemArtwork alloc] initWithImage:img]
             forKey:MPMediaItemPropertyArtwork];
    
    //更新字典
    [[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:songDict];
    
    }