MPNowPlayingInfoCenter消失了所有价值

Question

如果正在播放歌曲并且用户锁定了他的iPhone，我想在锁定屏幕上显示播放（搜索栏，下一个按钮和前置按钮）和歌曲名称，艺术家姓名，图像等。但我有一个问题。问题是MPNowPlayingInfoCenter信息值显示1-2秒，之后所有值将自动消失，之后显示默认值。

这下面的截图1是完美的但是在1-2之后这个所有值都消失了，看到截图2所有值都消失了

-(void)SetLockScreenView :(NSString *)SongName ArtistName:(NSString *)ArtistName AlbumTitle:(NSString *)AlbumTitle DisplayImg:(NSString *)displayImg
{
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
    [[AVAudioSession sharedInstance] setActive: YES error: nil];
    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];



    Class playingInfoCenter = NSClassFromString(@"MPNowPlayingInfoCenter");

    if (playingInfoCenter) {
      if(displayImg.length>0 && displayImg!=nil)
        {

            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:displayImg]];

                dispatch_async(dispatch_get_main_queue(), ^{

                    if(data!=nil)
                    {
                        UIImage *image = [UIImage imageWithData:data];
                        MPMediaItemArtwork *albumArt = [[MPMediaItemArtwork alloc] initWithImage: image];

                        [songInfo setObject:albumArt forKey:MPMediaItemPropertyArtwork];
                    }
                    else
                    {
                        MPMediaItemArtwork *albumArt = [[MPMediaItemArtwork alloc] initWithImage: [UIImage imageNamed:@"artistDefaultImg"]];
                        [songInfo setObject:albumArt forKey:MPMediaItemPropertyArtwork];

                    }

                    [songInfo setObject:SongName forKey:MPMediaItemPropertyTitle];
                    [songInfo setObject:ArtistName forKey:MPMediaItemPropertyArtist];
                    [songInfo setObject:AlbumTitle forKey:MPMediaItemPropertyAlbumTitle];

                    [songInfo setObject:[NSNumber numberWithFloat:self.manager.currentItem.duration] forKey:MPMediaItemPropertyPlaybackDuration];
                    [songInfo setObject:[NSNumber numberWithInt:0] forKey:MPNowPlayingInfoPropertyPlaybackRate];

                    [[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:songInfo];

                    NSLog(@"songInfo :%@",songInfo);

                });
            });


        }
    }

}
#pragma mark - Remote Control
- (void)remoteControlReceivedWithEvent:(UIEvent *)receivedEvent {


    if (receivedEvent.type == UIEventTypeRemoteControl) {

        switch (receivedEvent.subtype) {

            case UIEventSubtypeRemoteControlPlay:
                [self.manager.player play];
                break;

            case UIEventSubtypeRemoteControlPause:

                [self.manager.player pause];
                break;

            case UIEventSubtypeRemoteControlTogglePlayPause:

                if ([self.manager.player isPlaying]) {
                    [self.manager.player pause];
                }

                else {
                    [self.manager.player play];
                }
                break;
            case UIEventSubtypeRemoteControlNextTrack:
                [self Onclick_next:self];
                NSLog(@"Next song play");
                break;
            case UIEventSubtypeRemoteControlPreviousTrack:
                [self Onclick_prev:self];
                NSLog(@"Prev song play");
                break;

            default:
                break;
        }
    }
}
- (BOOL)canBecomeFirstResponder {

    return YES;

}

- (void)viewDidAppear:(BOOL)animated {

    [super viewDidAppear:animated];

    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

    [self becomeFirstResponder];

}

- (void)viewWillDisappear:(BOOL)animated {

    [[UIApplication sharedApplication] endReceivingRemoteControlEvents];

    [self resignFirstResponder];

    [super viewWillDisappear:animated];

}