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 MPMusicPlaybackState
enum {
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
- – endGeneratingPlaybackNotifications
MPMusicPlayerControllerPlaybackStateDidChangeNotification
可以通过该通知来改变播放按钮的样式
MPMusicPlayerControllerNowPlayingItemDidChangeNotification
MPMusicPlayerControllerVolumeDidChangeNotification
具体步骤
1.注册和开始发送通知
- 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];
- 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
- Listing 2-3 Creating an application music player
- MPMusicPlayerController* appMusicPlayer =
- [MPMusicPlayerController applicationMusicPlayer];
- [appMusicPlayer setShuffleMode: MPMusicShuffleModeOff];
- [appMusicPlayer setRepeatMode: MPMusicRepeatModeNone];
- 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
- <span style="font-size:18px;">- (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
- <span style="font-size:18px;">#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
- - (id) valueForProperty: (NSString *) property
NSString *const MPMediaItemPropertyTitle;
NSString *const MPMediaItemPropertyAlbumTitle;
NSString *const MPMediaItemPropertyArtist;
5.MPMediaItemCollection
collection是一组有序的item集合,可用同样的方法来获取collection的metadata
- - (id) valueForProperty: (NSString *) property
创建
- + collectionWithItems:
- – initWithItems:
属性
- items property
- representativeItem property
- count property
- mediaTypes property
6.MPMediaPlaylist
- 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 type
filter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collections
- When 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
- 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
- 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
- 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];
- Listing 4-4 Applying multiple predicates when initializing a media query
- NSSet *predicates =
- [NSSet setWithObjects: artistNamePredicate, albumNamePredicate, nil];
- MPMediaQuery *specificQuery =
- [[MPMediaQuery alloc] initWithFilterPredicates: predicates];
- 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];
- }
- 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
- 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"];
- }