在Info.plist里面添加 Required background modes, 展开后选择App plays audio or streams audio/video using AirPlay

//设置音乐后台播放的会话类型
AVAudioSession *session = [AVAudioSession sharedInstance];
NSError *error = nil;
[session setCategory:AVAudioSessionCategoryPlayback error:&error];
if (error) {
    NSLog(@"%s %@", __func__, error);
}
[session setActive:YES error:nil];
//开启远程事件(锁屏时使用)
[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

#pragma mark 接收远程事件
-(void)remoteControlReceivedWithEvent:(UIEvent *)event{
    //判断是否为远程事件
    if (event.type == UIEventTypeRemoteControl) {
        //调用
        [self myRemoteEventBlock:event];
     }
}

- (void)myRemoteEventBlock:(UIEvent*)event{
    switch (event.subtype) {
        case UIEventSubtypeRemoteControlPlay:
            [self.avAudioPlayer play];
            break;
        case UIEventSubtypeRemoteControlPause:
            [self.avAudioPlayer pause];
            break;
        case UIEventSubtypeRemoteControlPreviousTrack:
            [self last];
            break;
        case UIEventSubtypeRemoteControlNextTrack:
            [self next];
            break;
        
        default:
            break;
    }
};

-(void)next{
    if (self.flag < self.array.count - 1) {
        self.flag++;
    }else{
        self.flag = 0;
    }
    [self setupUI:self.flag];
}

-(void)last{
    if (self.flag <= 0) {
        self.flag = self.array.count - 1;
    }else{
        self.flag --;
    }
    [self setupUI:self.flag];
}



//锁屏界面
NSMutableDictionary *info = [NSMutableDictionary dictionary];
//设置专辑名称
info[MPMediaItemPropertyAlbumTitle] = @"网络热曲";
//设置歌曲名
info[MPMediaItemPropertyTitle] = self.array[index];
//设置歌手
info[MPMediaItemPropertyArtist] = self.array[index];
//设置专辑图片, 这里图片加载不出来的时候, 会崩溃
UIImage *image = [UIImage imageNamed:@"01"];
MPMediaItemArtwork *artwork = [[MPMediaItemArtwork alloc] initWithImage:image];
info[MPMediaItemPropertyArtwork] = artwork;
//设置歌曲时间
info[MPMediaItemPropertyPlaybackDuration] = @(self.avAudioPlayer.duration);
[MPNowPlayingInfoCenter defaultCenter].nowPlayingInfo = info;