iOS MediaPlayer 远程控制事件不起作用

Question

我正在尝试将远程控制事件添加到音乐播放器应用程序，但无法正常运行。

一些事实:

• 我正在使用 [MPMusicPlayerController applicationMusicPlayer];
• 我在图片背景模式中添加了音频、AirPlay和图片；
• 例子是播放音频；
• 它不接收来自锁屏和控制中心的远程通知；

我做了一个示例项目，可以在这里下载: example project 主要来源:

#import "ViewController.h"
#import <MediaPlayer/MPMediaPickerController.h>
#import <MediaPlayer/MPMediaQuery.h>
#import <MediaPlayer/MediaPlayer.h>

@interface ViewController ()

@property (strong, nonatomic) MPMusicPlayerController *MusicPlayer;
@property (strong, nonatomic) MPMediaItemCollection *MusicPlayerSongs;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    _MusicPlayerSongs = [MPMediaItemCollection alloc];
    _MusicPlayer = [MPMusicPlayerController applicationMusicPlayer];
    [_MusicPlayer setShuffleMode: MPMusicShuffleModeOff];
    [_MusicPlayer setRepeatMode: MPMusicRepeatModeNone];
    [_MusicPlayer beginGeneratingPlaybackNotifications];
}

-(void)viewDidAppear:(BOOL)animated{

    [super viewDidAppear:animated];

    NSMutableArray *selectedTracks = [NSMutableArray new];

    //Find all tracks that contains an 'a'
    MPMediaPropertyPredicate *songPredicate =
    [MPMediaPropertyPredicate predicateWithValue:@"a"
                                     forProperty:MPMediaItemPropertyTitle
                                  comparisonType:MPMediaPredicateComparisonContains];

    MPMediaQuery *mediaQuery = [[MPMediaQuery alloc] init];
    [mediaQuery addFilterPredicate:songPredicate];
    [selectedTracks addObjectsFromArray:[mediaQuery items]];

    NSLog(@"Number of tracks containing an 'a': %lu",(unsigned long)selectedTracks.count);

    self.MusicPlayerSongs = [[MPMediaItemCollection alloc]initWithItems:selectedTracks];

    [self.MusicPlayer setQueueWithItemCollection:self.MusicPlayerSongs];
    [self.MusicPlayer play];
    [self.MusicPlayer beginGeneratingPlaybackNotifications];

    [self basicSetup];
    [self updateNowPlayingCenter];
}

- (void)basicSetup {

    //Listen to remote control events
    [MPRemoteCommandCenter sharedCommandCenter].previousTrackCommand.enabled = NO;
    [MPRemoteCommandCenter sharedCommandCenter].nextTrackCommand.enabled = NO;
    [MPRemoteCommandCenter sharedCommandCenter].playCommand.enabled = YES;
    [MPRemoteCommandCenter sharedCommandCenter].pauseCommand.enabled = YES;
    [MPRemoteCommandCenter sharedCommandCenter].togglePlayPauseCommand.enabled = YES;
    [[MPRemoteCommandCenter sharedCommandCenter].nextTrackCommand addTarget:self action:@selector(remoteNext)];
    [[MPRemoteCommandCenter sharedCommandCenter].previousTrackCommand addTarget:self action:@selector(remotePrevious)];
    [[MPRemoteCommandCenter sharedCommandCenter].playCommand addTarget:self action:@selector(remotePlay)];
    [[MPRemoteCommandCenter sharedCommandCenter].pauseCommand addTarget:self action:@selector(remotePlay)];
    [[MPRemoteCommandCenter sharedCommandCenter].togglePlayPauseCommand addTarget:self action:@selector(remoteTogglePlayState)];

    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

}

-(void)remotePlay{
    NSLog(@"remotePlay");
    [self.MusicPlayer play];
}

-(void)remoteNext{
    NSLog(@"remoteNext");
    [self.MusicPlayer skipToNextItem];
    [self updateNowPlayingCenter];
}

-(void)remotePrevious{
    NSLog(@"remotePrevious");
    [self.MusicPlayer skipToPreviousItem];
    [self updateNowPlayingCenter];
}

-(void)remotePause{
    NSLog(@"remotePause");
    [self.MusicPlayer pause];
}

-(void)remoteTogglePlayState{
    NSLog(@"remoteTogglePlayState");
    if([self.MusicPlayer playbackState] == MPMusicPlaybackStatePlaying){
        [self.MusicPlayer pause];
    }else{
        [self.MusicPlayer play];
    }
}

-(void)updateNowPlayingCenter{

    MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
    NSMutableDictionary *songInfo = [NSMutableDictionary dictionaryWithDictionary:@{
                                                                                    MPMediaItemPropertyArtist: [self.MusicPlayer nowPlayingItem].artist,
                                                                                    MPMediaItemPropertyTitle: [self.MusicPlayer nowPlayingItem].title,
                                                                                    MPMediaItemPropertyAlbumTitle: [self.MusicPlayer nowPlayingItem].albumTitle,
                                                                                    }];
    center.nowPlayingInfo = songInfo;
}

我只是想不通为什么它不起作用:(

进度更新 到目前为止我发现，如果我重新启动我的 iPhone，它就可以工作。但之后每次都不会。

锁屏和控制中心都显示正确的轨道，但仍然无法控制应用。

Answer 1

不确定这是否对您有帮助，但这是我收到任何更改的方式(在 Swift 中)。

override func viewDidLoad() {
    super.viewDidLoad()

    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.getNowPlayingItem), name: MPMusicPlayerControllerNowPlayingItemDidChangeNotification, object: nil)
    player.beginGeneratingPlaybackNotifications()
}

deinit {
    player.endGeneratingPlaybackNotifications()
    NSNotificationCenter.defaultCenter().removeObserver(self)
}

有必要(addObserver 和 beginGeneratingPlaybackNotifications)，也有必要(removeObserver 和 endGeneratingPlaybackNotification)。我还不熟悉远程控制事件，但您可能也想尝试结束这些通知。希望这对您有所帮助!