iOS之使用MediaPlayer框架选取音乐播放

        iOS开发中播放音乐可以使用MPMusicPlayerController类来实现，播放视频可以使用MPMoviePlayerController和MPMoviePlayerViewController类来实现，同时MPMediaPickerController 类可以用于从系统媒体库中选择媒体播放。这几个类都包含与MediaPlayer.framework框架中。

       本文讲的是从系统媒体库中选择音乐并播放。

       1.新建一个项目，并加入MediaPlayer.framework

       2.在ViewController.h 文件中 导入#import <MediaPlayer/MediaPlayer.h>,并实现<MPMediaPickerControllerDelegate>协议。

      3.设置xib，并通过InterfaceBuilder设置控件的IBAction，分别为：

    - (IBAction)pickAndPlay:(id)sender;

    - (IBAction)stopPlay:(id)sender;

     布局 如下图：

     

   下面是主要代码：

   ViewController.h 文件： 

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
- (IBAction)pickAndPlay:(id)sender;
- (IBAction)stopPlay:(id)sender;

@end

   ViewController.m文件：

#import "ViewController.h"

#import <MediaPlayer/MediaPlayer.h>
@interface ViewController () <MPMediaPickerControllerDelegate>

@property (nonatomic,strong) MPMusicPlayerController * myMusicPlayer;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)pickAndPlay:(id)sender {
    
    MPMediaPickerController * mediaPicker = [[MPMediaPickerController alloc] initWithMediaTypes:MPMediaTypeMusic];
    if(mediaPicker != nil)
    {
        NSLog(@"Successfully instantiated a media picker");
        mediaPicker.delegate = self;
        mediaPicker.allowsPickingMultipleItems = YES;
        [self presentViewController:mediaPicker animated:YES completion:nil];
    }
    else
    {
        NSLog(@"Could not instantiate a media picker");
    }
    
}

- (IBAction)stopPlay:(id)sender {
    
    if(self.myMusicPlayer != nil)
    {
        [[NSNotificationCenter defaultCenter] removeObserver:self name:MPMusicPlayerControllerPlaybackStateDidChangeNotification object:self.myMusicPlayer];
        [[NSNotificationCenter defaultCenter] removeObserver:self name:MPMusicPlayerControllerNowPlayingItemDidChangeNotification object:self.myMusicPlayer];
        [[NSNotificationCenter defaultCenter] removeObserver:self name:MPMusicPlayerControllerVolumeDidChangeNotification object:self.myMusicPlayer];
        
        [self.myMusicPlayer stop];
    }
    
}

-(void)mediaPicker:(MPMediaPickerController *)mediaPicker didPickMediaItems:(MPMediaItemCollection *)mediaItemCollection
{
    NSLog(@"Media Picker returned");
    self.myMusicPlayer = nil;
    self.myMusicPlayer = [[MPMusicPlayerController alloc] init];
    [self.myMusicPlayer beginGeneratingPlaybackNotifications];
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(musicPlayerStatedChanged:) name:MPMusicPlayerControllerPlaybackStateDidChangeNotification object:self.myMusicPlayer];
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(nowPlayingItemIsChanged:) name:MPMusicPlayerControllerNowPlayingItemDidChangeNotification object:self.myMusicPlayer];
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(volumeIsChanged:) name:MPMusicPlayerControllerVolumeDidChangeNotification object:self.myMusicPlayer];
    
    [self.myMusicPlayer setQueueWithItemCollection:mediaItemCollection];
    
    [self.myMusicPlayer play];
    
    [mediaPicker dismissViewControllerAnimated:YES completion:nil];
    
}
-(void)mediaPickerDidCancel:(MPMediaPickerController *)mediaPicker
{
    NSLog(@"Media Picker was cancelled");
    [mediaPicker dismissViewControllerAnimated:YES completion:nil];
}

-(void)musicPlayerStatedChanged:(NSNotification *)paramNotification
{
    NSLog(@"Player State Changed");
    NSNumber * stateAsObject = [paramNotification.userInfo objectForKey:@"MPMusicPlayerControllerPlaybackStateKey"];
    NSInteger state = [stateAsObject integerValue];
    switch (state) {
        case MPMusicPlaybackStateStopped:
            
            break;
        case MPMusicPlaybackStatePlaying:
            break;
            
        case MPMusicPlaybackStatePaused:
            break;
        case MPMusicPlaybackStateInterrupted:
            break;
        case MPMusicPlaybackStateSeekingForward:
            break;
        case MPMusicPlaybackStateSeekingBackward:
            break;
            
        default:
            break;
    }
}

-(void)nowPlayingItemIsChanged:(NSNotification *)paramNotification
{
    NSLog(@"Playing Item is Changed");
    NSString * persistentID = [paramNotification.userInfo objectForKey:@"MPMusicPlayerControllerNowPlayingItemPersistentIDKey"];
    NSLog(@"Persistent ID = %@",persistentID);
    
}

-(void)volumeIsChanged:(NSNotification *)paramNotification
{
    NSLog(@"Volume Is Changed");
}
@end