项目上线音频播放后，仍然满足不了广大学员的需求，学员想要的是音频能够在锁屏状态下也能够播放。于是和公司领导讨论完成音频的后台播放功能，现在就将我所实现音频锁屏播放的过程和遇到的坑和大家分享一下。

1、首先是集成音频播放器：（我把这个播放器放在了一个单利里面）

实现的代码如下：

#pragma mark --添加在线播放器

- (void)addOnLinePlayer {

    WS(weakSelf)

    [[SKAVPlayerManager PlayerManager] replaceItemWithUrlString:self.onLinePlayerUrl type:@"zaixian"];

    __weak typeof(SKAVPlayerManager *) manager = [SKAVPlayerManager PlayerManager];

    [SKAVPlayerManager PlayerManager].statusBlock = ^(BOOL success) {

        if (success) {

            // 如果是暂停状态则不进行播放

            if (weakSelf.playerButton.selected != YES) {

                [manager playerPlay];

                [SKAVPlayerManager PlayerManager].player.rate = weakSelf.playerRate;

            }

        } else {

        }

    };

    // 添加时间监听

    self.myTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerAction) userInfo:nil repeats:YES];

}

// 播放一段音频

- (void)replaceItemWithUrlString:(NSString *)urlString type:(NSString *)readType {

    self.ccid = urlString;

    [_playerItem removeObserver:self forKeyPath:@"status"];

    _playerItem = nil;

    if ([readType isEqualToString:@"zaixian"]) {

        _playerItem = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:urlString]];

    } else if ([readType isEqualToString:@"bendi"]){

        NSURL *audioURL = [NSURL fileURLWithPath:urlString];

        _playerItem = [[AVPlayerItem alloc] initWithURL:audioURL];

    }

    [_playerItem addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:nil];

    [self.player replaceCurrentItemWithPlayerItem:_playerItem];

}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

    if ([keyPath isEqualToString:@"status"]) {

        self.isNotify = YES;

        switch (self.player.status) {

            case AVPlayerStatusUnknown:

                // KVO：未知状态，此时不能播放

                if (self.statusBlock) {

                    self.statusBlock(NO);

                }

                break;

            case AVPlayerStatusReadyToPlay:

                //KVO：准备完毕，可以播放

                if (self.statusBlock) {

                    self.statusBlock(YES);

                }

//                [self playerPlay];

//                [[NSNotificationCenter defaultCenter] postNotificationName:PlayerStatusNormal object:nil];

                break;

            case AVPlayerStatusFailed:

                // KVO：加载失败，网络或者服务器出现问题

                if (self.statusBlock) {

                    self.statusBlock(NO);

                }

                break;

            default:

                break;

        }

    }

}

2、时间进度的控制如下以及进度条的更新：

- (void)timerAction {

    if ([SKAVPlayerManager PlayerManager].player.currentTime.timescale == 0 || [SKAVPlayerManager PlayerManager].player.currentItem.duration.timescale == 0) {

        return;

    }

    // 获得音乐总时长

    long long int totalTime = [SKAVPlayerManager PlayerManager].player.currentItem.duration.value / [SKAVPlayerManager PlayerManager].player.currentItem.duration.timescale;

    // 获得当前时间

    long long int currentTime = [SKAVPlayerManager PlayerManager].player.currentTime.value / [SKAVPlayerManager PlayerManager].player.currentTime.timescale;

    currentTimeLable.text = [NSString stringWithFormat:@"%02lld:%02lld", currentTime / 60, currentTime % 60];

    orignalTimeLable.text = [NSString stringWithFormat:@"%02lld:%02lld", totalTime / 60, totalTime % 60];

    audioSlider.maximumValue = totalTime;

    audioSlider.minimumValue = 0;

    audioSlider.value = currentTime;

    if (currentTime == totalTime) {

        // 进行下一曲播放

        [self nextButtonAction:[UIButton new]];

    }

    if (@available(iOS 11.0, *)) {

    } else {

        if ([UIApplication sharedApplication].applicationState == UIApplicationStateBackground) {

            [self onLineRemoteControl];

        }

    }

}

3、这个时候音频就能正常播放了，在保证音频能正常播放的对工程进行设置：

先要注册后台播放：

然后在info.plist文件里面进行设置：

App plays audio or streams audio/video using AirPlay

4、当程序进入后台和前台的时候通过通知监听所处的状态：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didEnterBackground) name:UIApplicationWillResignActiveNotification object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didBecomeActive) name:UIApplicationDidBecomeActiveNotification object:nil];

- (void)didEnterBackground {

        [self onLineRemoteControl];

}

// 在线后台播放

- (void)onLineRemoteControl {

        MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];

        UIImage *lockImage = [UIImage imageNamed:@"photo1.png"];

        MPMediaItemArtwork *artwork =

        [[MPMediaItemArtwork alloc] initWithImage:lockImage];

        NSDictionary *mediaDict =

        @{

          MPMediaItemPropertyTitle: self.model.title,

          MPMediaItemPropertyMediaType: @(MPMediaTypeAnyAudio),

          MPMediaItemPropertyPlaybackDuration:

              @([SKAVPlayerManager PlayerManager].player.currentItem.duration.value / [SKAVPlayerManager PlayerManager].player.currentItem.duration.timescale),

          MPNowPlayingInfoPropertyPlaybackRate: @(1.0),

          MPNowPlayingInfoPropertyElapsedPlaybackTime:

              @([SKAVPlayerManager PlayerManager].player.currentTime.value / [SKAVPlayerManager PlayerManager].player.currentTime.timescale),

          MPMediaItemPropertyAlbumArtist:self.subscribeModel.title,

          MPMediaItemPropertyArtist:self.subscribeModel.title,

          MPMediaItemPropertyArtwork: artwork};

        [center setNowPlayingInfo:mediaDict];

        //让app支持接受远程控制事件

        [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

}

- (void) didBecomeActive {

//让app结束接受远程控制事件

    [[UIApplication sharedApplication] endReceivingRemoteControlEvents];

}

5、这个时候发现是可以进行后台播放的，但是进度条无法调整，为了能够调整进度条需要添加远程控制命令中心：

#pragma mark --锁屏界面开启和监控远程控制事件

- (void)createRemoteCommandCenter{

    //远程控制命令中心 iOS 7.1 之后  详情看官方文档：https://developer.apple.com/documentation/mediaplayer/mpremotecommandcenter

    MPRemoteCommandCenter *commandCenter = [MPRemoteCommandCenter sharedCommandCenter];

    //    commandCenter.togglePlayPauseCommand 耳机线控的暂停/播放

    [commandCenter.pauseCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {

        return MPRemoteCommandHandlerStatusSuccess;

    }];

    [commandCenter.playCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {

        return MPRemoteCommandHandlerStatusSuccess;

    }];

    [commandCenter.previousTrackCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {

        NSLog(@"上一首");

        return MPRemoteCommandHandlerStatusSuccess;

    }];

    [commandCenter.nextTrackCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {

        NSLog(@"下一首");

        return MPRemoteCommandHandlerStatusSuccess;

    }];

    //在控制台拖动进度条调节进度（仿QQ音乐的效果）

    [commandCenter.changePlaybackPositionCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {

            CMTime totlaTime = [SKAVPlayerManager PlayerManager].player.currentItem.duration;

            MPChangePlaybackPositionCommandEvent * playbackPositionEvent = (MPChangePlaybackPositionCommandEvent *)event;

            [[SKAVPlayerManager PlayerManager].player seekToTime:CMTimeMake(totlaTime.value*playbackPositionEvent.positionTime/CMTimeGetSeconds(totlaTime), totlaTime.timescale) completionHandler:^(BOOL finished) {

            }];

        return MPRemoteCommandHandlerStatusSuccess;

    }];

}

这个时候就都实现了所有的功能了我们所做的有如下截图：

最后说下需要注意的几点：

1、使用changePlaybackPositionCommand进行seekTime时候，控制中心的播放进度条停止了下来 使用带handler的回调，在回调处再次对info进行进度条的更新

2、一定要注意block的循环引用问题，不然会引起内存暴涨。