1.访问音乐库的两种方法，如下图（只能访问音频文件，如music，podcast，audiobook等）2.MPMusicPlayerController的使用有两种播放器可以选择，一种是application　music　player，另外一种是iPod　music　player。第一种播放器是一种内部播放器，当程序对出后停止播放；而第二种播放器则与iPod播放器内的信息相关，退出之后不会停止播放。获取方式如下： + applicationMusicPlayer+ iPodMusicPlayer 播放之前需要设置播放器的播放队列– setQueueWithQuery:– setQueueWithItemCollection:管理播放模式和播放状态的一些属性  currentPlaybackTime  property  nowPlayingItem  property  playbackState  property  repeatMode  property  shuffleMode  property  volume  property播放状态　MPMusicPlaybackStateenum {   MPMusicPlaybackStateStopped,   MPMusicPlaybackStatePlaying,   MPMusicPlaybackStatePaused,   MPMusicPlaybackStateInterrupted,   MPMusicPlaybackStateSeekingForward,   MPMusicPlaybackStateSeekingBackward};typedef NSInteger MPMusicPlaybackState;播放控制方法– play– pause– stop– beginSeekingForward– beginSeekingBackward– endSeeking– skipToNextItem– skipToBeginning– skipToPreviousItem播放状态发生变化时可以发送通知– beginGeneratingPlaybackNotifications– endGeneratingPlaybackNotificationsMPMusicPlayerControllerPlaybackStateDidChangeNotification可以通过该通知来改变播放按钮的样式MPMusicPlayerControllerNowPlayingItemDidChangeNotificationMPMusicPlayerControllerVolumeDidChangeNotification 具体步骤１.注册和开始发送通知 [plain] view plaincopyprint? Listing 2-1  Registering for and activating music player notifications  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];     [musicPlayer beginGeneratingPlaybackNotifications];    [plain] view plaincopyprint? Listing 2-2  Unregistering and deactivating music player notifications  [[NSNotificationCenter defaultCenter]      removeObserver: self      name:           MPMusicPlayerControllerNowPlayingItemDidChangeNotification      object:         musicPlayer];     [[NSNotificationCenter defaultCenter]      removeObserver: self      name:           MPMusicPlayerControllerPlaybackStateDidChangeNotification      object:         musicPlayer];     [musicPlayer endGeneratingPlaybackNotifications];  ２.创建并配置一个Music　Player  [plain] view plaincopyprint? Listing 2-3  Creating an application music player  MPMusicPlayerController* appMusicPlayer =      [MPMusicPlayerController applicationMusicPlayer];     [appMusicPlayer setShuffleMode: MPMusicShuffleModeOff];  [appMusicPlayer setRepeatMode: MPMusicRepeatModeNone];    [plain] view plaincopyprint? Listing 2-4  Creating an iPod music player  MPMusicPlayerController* iPodMusicPlayer =      [MPMusicPlayerController iPodMusicPlayer];     if ([iPodMusicPlayer nowPlayingItem]) {      // Update the UI (artwork, song name, volume indicator, etc.)      //        to reflect the iPod state  }  ３.设置播放队列  – setQueueWithQuery:– setQueueWithItemCollection:４.控制播放  3.MPMediaPickerController的使用 [plain] view plaincopyprint? <span >- (IBAction)addSongsToMusicPlayer:(id)sender  {      MPMediaPickerController *mpController = [[MPMediaPickerController alloc] initWithMediaTypes:MPMediaTypeMusic];      mpController.delegate = self;      mpController.prompt = @"Add songs to play";      mpController.allowsPickingMultipleItems = YES;            [self presentModalViewController:mpController animated:YES];      [mpController release];  }  </span>  主要是设置代理和选择多媒体类型，然后通过代理方法来获取选中的歌曲   [plain] view plaincopyprint? <span >#pragma mark - Media Picker Delegate Methods    - (void)mediaPicker:(MPMediaPickerController *)mediaPicker didPickMediaItems:(MPMediaItemCollection *)mediaItemCollection  {      [self.musicPlayer setQueueWithItemCollection:mediaItemCollection];      [self dismissModalViewControllerAnimated:YES];  }    - (void)mediaPickerDidCancel:(MPMediaPickerController *)mediaPicker  {      [self dismissModalViewControllerAnimated:YES];  }</span>   4.MPMediaItem用此方法来获取item的metadata[plain] view plaincopyprint? - (id) valueForProperty: (NSString *) property   NSString *const MPMediaItemPropertyTitle;                   NSString *const MPMediaItemPropertyAlbumTitle;              NSString *const MPMediaItemPropertyArtist;                   5.MPMediaItemCollectioncollection是一组有序的item集合，可用同样的方法来获取collection的metadata[plain] view plaincopyprint? - (id) valueForProperty: (NSString *) property   创建+ collectionWithItems:– initWithItems:属性  items  property  representativeItem  property  count  property  mediaTypes  property6.MPMediaPlaylist[plain] view plaincopyprint? MPMediaQuery *myPlaylistsQuery = [MPMediaQuery playlistsQuery];  NSArray *playlists = [myPlaylistsQuery collections];     for (MPMediaPlaylist *playlist in playlists) {      NSLog (@"%@", [playlist valueForProperty: MPMediaPlaylistPropertyName]);         NSArray *songs = [playlist items];      for (MPMediaItem *song in songs) {          NSString *songTitle =              [song valueForProperty: MPMediaItemPropertyTitle];          NSLog (@"\t\t%@", songTitle);      }  }   7.MPMediaQuery需要设置两个属性: filter  and  grouping typefilter描述查询内容，grouping type 描述返回内容的排列方式  查询可以获取items，也可以获取collectionsWhen you ask for items, the query returns a collection containing all the items that match the filter. The items are in “natural” order, meaning that they are ordered as iTunes shows them on the desktop.When you ask for collections, the media query employs not only its filter but also its grouping type. 获取全部歌曲[plain] view plaincopyprint? MPMediaQuery *everything = [[MPMediaQuery alloc] init];   NSLog(@"Logging items from a generic query...");  NSArray *itemsFromGenericQuery = [everything items];  for (MPMediaItem *song in itemsFromGenericQuery) {      NSString *songTitle = [song valueForProperty: MPMediaItemPropertyTitle];      NSLog (@"%@", songTitle);  }   获取名为“Happy the Clown”的艺术家的歌曲[plain] view plaincopyprint? MPMediaPropertyPredicate *artistNamePredicate =      [MPMediaPropertyPredicate predicateWithValue: @"Happy the Clown"                                       forProperty: MPMediaItemPropertyArtist];     MPMediaQuery *myArtistQuery = [[MPMediaQuery alloc] init];  [myArtistQuery addFilterPredicate: artistNamePredicate];     NSArray *itemsFromArtistQuery = [myArtistQuery items];  多个查找条件，查找名为"Sad the Joker"的艺术家的"Stair Tumbling"专辑[plain] view plaincopyprint? MPMediaPropertyPredicate *artistNamePredicate =      [MPMediaPropertyPredicate predicateWithValue: @"Sad the Joker"                                       forProperty: MPMediaItemPropertyArtist];     MPMediaPropertyPredicate *albumNamePredicate =      [MPMediaPropertyPredicate predicateWithValue: @"Stair Tumbling"                                       forProperty: MPMediaItemPropertyAlbumTitle];     MPMediaQuery *myComplexQuery = [[MPMediaQuery alloc] init];     [myComplexQuery addFilterPredicate: artistNamePredicate];  [myComplexQuery addFilterPredicate: albumNamePredicate];    [plain] view plaincopyprint? Listing 4-4  Applying multiple predicates when initializing a media query  NSSet *predicates =      [NSSet setWithObjects: artistNamePredicate, albumNamePredicate, nil];     MPMediaQuery *specificQuery =      [[MPMediaQuery alloc] initWithFilterPredicates: predicates];  [plain] view plaincopyprint? Listing 4-5  Testing if a property key can be used for a media property predicate  if ([MPMediaItem canFilterByProperty: MPMediaItemPropertyGenre]) {      MPMediaPropertyPredicate *rockPredicate =          [MPMediaPropertyPredicate predicateWithValue: @"Rock"                                           forProperty: MPMediaItemPropertyGenre];      [query addFilterPredicate: rockPredicate];  }    [plain] view plaincopyprint? Listing 4-6  Using grouping type to specify media item collections  MPMediaQuery *query = [[MPMediaQuery alloc] init];     [query addFilterPredicate: [MPMediaPropertyPredicate                                 predicateWithValue: @"Moribund the Squirrel"                                        forProperty: MPMediaItemPropertyArtist]];  // Sets the grouping type for the media query  [query setGroupingType: MPMediaGroupingAlbum];     NSArray *albums = [query collections];  for (MPMediaItemCollection *album in albums) {      MPMediaItem *representativeItem = [album representativeItem];      NSString *artistName =          [representativeItem valueForProperty: MPMediaItemPropertyArtist];      NSString *albumName =          [representativeItem valueForProperty: MPMediaItemPropertyAlbumTitle];      NSLog (@"%@ by %@", albumName, artistName);         NSArray *songs = [album items];      for (MPMediaItem *song in songs) {          NSString *songTitle =              [song valueForProperty: MPMediaItemPropertyTitle];          NSLog (@"\t\t%@", songTitle);      }  }    query的一些简便构造方法专辑封面的使用 [plain] view plaincopyprint? Listing 4-7  Displaying album artwork for a media item  MPMediaItemArtwork *artwork =      [mediaItem valueForProperty: MPMediaItemPropertyArtwork];  UIImage *artworkImage =      [artwork imageWithSize: albumImageView.bounds.size];  if (artworkImage) {      albumImageView.image = artworkImage;  } else {      albumImageView.image = [UIImage imageNamed: @"noArtwork.png"];  }