如何播放mpmoviePlayer中的下一首歌曲？

Question

我正在使用MPMoviePlayerController来播放音频。
我试图播放下一个音频，但它不起作用。 所以我如何使用MpMoviePlayerController播放下一个音频。

我使用这个代码...

MPMoviePlayerViewController *moviePlayerViewController = [[MPMoviePlayerViewController alloc] initWithContentURL:[NSURL fileURLWithPath:contentURL]]; 

    if (moviePlayerViewController) 
    { 
     [self presentMoviePlayerViewControllerAnimated:moviePlayerViewController]; 
     [moviePlayerViewController.moviePlayer setMovieSourceType:MPMovieSourceTypeFile]; 

     if ([moviePlayerViewController.moviePlayer respondsToSelector:@selector(setAllowsAirPlay:)]) 
     { 
      [moviePlayerViewController.moviePlayer setAllowsAirPlay:YES]; 
     } 

     [[NSNotificationCenter defaultCenter] addObserverForName:MPMoviePlayerPlaybackDidFinishNotification object:moviePlayerViewController queue:nil usingBlock:^(NSNotification *notification) 
     { 
      [[NSNotificationCenter defaultCenter] removeObserver:self]; 
      [self dismissMoviePlayerViewControllerAnimated]; 
      [moviePlayerViewController release]; 
     }]; 

     [moviePlayerViewController.moviePlayer play]; 
    } 

Answer 1

// 
// NowPlayingViewController.h 

#import <UIKit/UIKit.h> 

#import <MediaPlayer/MediaPlayer.h> 

@interface NowPlayingViewController : UIViewController 
{ 

    MPMusicPlayerController *musiPlayer; 

    IBOutlet UIImageView *artworkImageView; 

    IBOutlet UIButton *playPauseButton; 

    IBOutlet UISlider *volumeSlider; 

    IBOutlet UILabel *artistLabel; 

    IBOutlet UILabel *titleLabel; 

    IBOutlet UILabel *albumLabel; 


} 
@property (nonatomic, retain) MPMusicPlayerController *musicPlayer; 

- (IBAction)playPause:(id)sender; 

- (IBAction)nextSong:(id)sender; 

- (IBAction)previousSong:(id)sender; 

- (IBAction)volumeSliderChanged:(id)sender; 

- (void) registerMediaPlayerNotifications; 

@end 

// 
// NowPlayingViewController.m 
// Music 

#import "NowPlayingViewController.h" 

@interface NowPlayingViewController() 

@end 

@implementation NowPlayingViewController 

@synthesize musicPlayer; 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 

    if (self) { 
     // Custom initialization 
    } 

    return self; 
} 

#pragma mark - UI Setup 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    // Music player setup 

    musicPlayer = [MPMusicPlayerController iPodMusicPlayer]; 
    [self registerMediaPlayerNotifications]; 

    // Back button 

    UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(back)]; 
    self.navigationItem.leftBarButtonItem = backButton; 

    // Custom UI 

    artistLabel.textColor = [UIColor colorWithRed:0.278 green:0.278 blue:0.278 alpha:1.0]; 
    artistLabel.shadowColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0]; 
    artistLabel.shadowOffset = CGSizeMake(0, 1); 

    titleLabel.textColor = [UIColor colorWithRed:0.278 green:0.278 blue:0.278 alpha:1.0]; 
    titleLabel.shadowColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0]; 
    titleLabel.shadowOffset = CGSizeMake(0, 1); 

    albumLabel.textColor = [UIColor colorWithRed:0.278 green:0.278 blue:0.278 alpha:1.0]; 
    albumLabel.shadowColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0]; 
    albumLabel.shadowOffset = CGSizeMake(0, 1); 
} 

- (void) back 
{ 

    [self.navigationController popViewControllerAnimated:YES]; 

} 

- (void) viewWillAppear:(BOOL)animated 
{ 

    [super viewWillAppear:YES]; 

    // update control button 

    if ([musicPlayer playbackState] == MPMusicPlaybackStatePlaying) { 

      [playPauseButton setImage:[UIImage imageNamed:@"Pause-icon.png"] forState:UIControlStateNormal]; 
    } 

    else { 
      [playPauseButton setImage:[UIImage imageNamed:@"Play-icon.png"] forState:UIControlStateNormal]; 
    } 


    // Update volumelider 

    [volumeSlider setValue:[musicPlayer volume]]; 


    // Update now playing info 

    MPMediaItem *currentItem = [musicPlayer nowPlayingItem]; 

    MPMediaItemArtwork *artwork = [currentItem valueForProperty: MPMediaItemPropertyArtwork]; 
    UIImage *artworkImage = [artwork imageWithSize: CGSizeMake (320, 320)]; 

    if (!artworkImage) { 

      artworkImage = [UIImage imageNamed:@"No-artwork.png"]; 
    } 

    [artworkImageView setImage:artworkImage]; 


    NSString *titleString = [currentItem valueForProperty:MPMediaItemPropertyTitle]; 
    if (titleString) { 
      titleLabel.text = titleString; 
    } 

    else { 
      titleLabel.text = @"Unknown title"; 
    } 

    NSString *artistString = [currentItem valueForProperty:MPMediaItemPropertyArtist]; 
    if (artistString) { 
      artistLabel.text = artistString; 
    } 

    else { 
      artistLabel.text = @"Unknown artist"; 
    } 

    NSString *albumString = [currentItem valueForProperty:MPMediaItemPropertyAlbumTitle]; 
    if (albumString) { 
      albumLabel.text = albumString; 
    } 

    else { 
      albumLabel.text = @"Unknown album"; 
    } 

} 

#pragma mark - Register media player notifications 

- (void) registerMediaPlayerNotifications 
{ 
    NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter]; 

    [notificationCenter addObserver: self 
          selector: @selector (handle_NowPlayingItemChanged:) 
           name: MPMusicPlayerControllerNowPlayingItemDidChangeNotification 
          object: musicPlayer]; 

    [notificationCenter addObserver: self 
          selector: @selector (handle_PlaybackStateChanged:) 
           name: MPMusicPlayerControllerPlaybackStateDidChangeNotification 
          object: musicPlayer]; 

    [notificationCenter addObserver: self 
          selector: @selector (handle_VolumeChanged:) 
           name: MPMusicPlayerControllerVolumeDidChangeNotification 
          object: musicPlayer]; 

    [musicPlayer beginGeneratingPlaybackNotifications]; 
} 

- (void) handle_NowPlayingItemChanged: (id) notification 
{ 

    if ([musicPlayer playbackState] != MPMusicPlaybackStateStopped) { 
     MPMediaItem *currentItem = [musicPlayer nowPlayingItem]; 

     MPMediaItemArtwork *artwork = [currentItem valueForProperty: MPMediaItemPropertyArtwork]; 
     UIImage *artworkImage = [artwork imageWithSize: CGSizeMake (320, 320)]; 

     if (!artworkImage) { 
       artworkImage = [UIImage imageNamed:@"No-artwork.png"]; 
     } 

     [artworkImageView setImage:artworkImage]; 

     NSString *titleString = [currentItem valueForProperty:MPMediaItemPropertyTitle]; 
     if (titleString) { 
       titleLabel.text = titleString; 
     } 

     else { 
       titleLabel.text = @"Unknown title"; 
     } 

     NSString *artistString = [currentItem valueForProperty:MPMediaItemPropertyArtist]; 

     if (artistString) { 
       artistLabel.text = artistString; 
     } 


     else { 
       artistLabel.text = @"Unknown artist"; 
     } 

     NSString *albumString = [currentItem valueForProperty:MPMediaItemPropertyAlbumTitle]; 

     if (albumString) { 
       albumLabel.text = albumString; 
     } 

     else { 
       albumLabel.text = @"Unknown album"; 
     } 

    } 
} 


- (void) handle_PlaybackStateChanged: (id) notification 
{ 
    MPMusicPlaybackState playbackState = [musicPlayer playbackState]; 

    if (playbackState == MPMusicPlaybackStatePaused) { 
     [playPauseButton setImage:[UIImage imageNamed:@"Play-icon.png"] forState:UIControlStateNormal]; 


    } 

     else if (playbackState == MPMusicPlaybackStatePlaying) { 
     [playPauseButton setImage:[UIImage imageNamed:@"Pause-icon.png"] forState:UIControlStateNormal]; 

    } 

     else if (playbackState == MPMusicPlaybackStateStopped) { 

     [playPauseButton setImage:[UIImage imageNamed:@"Play-icon.png"] forState:UIControlStateNormal]; 

      [musicPlayer stop]; 

     [self.navigationController popViewControllerAnimated:YES]; 

    } 

} 


- (void) handle_VolumeChanged: (id) notification 
{ 
     [volumeSlider setValue:[musicPlayer volume]]; 
} 


- (void)didReceiveMemoryWarning 
{ 
     [super didReceiveMemoryWarning]; 


} 

#pragma mark - Controls 

- (IBAction)playPause:(id)sender 
{ 
    if ([musicPlayer playbackState] == MPMusicPlaybackStatePlaying) { 

     [musicPlayer pause]; 

    } 

    else { 

     [musicPlayer play]; 
    } 
} 

- (IBAction)nextSong:(id)sender 
{ 

     [musicPlayer skipToNextItem]; 
} 

- (IBAction)previousSong:(id)sender 
{ 

     [musicPlayer skipToPreviousItem]; 

} 

- (IBAction)volumeSliderChanged:(id)sender 
{ 

     [musicPlayer setVolume:volumeSlider.value]; 

} 


@end