如何在uitableview中显示从avplayer播放的ipodLibrary中选择的歌曲

Question

我正在使用 AVPlayer 播放歌曲。我也可以在后台播放它。有一个名为showPlaylist 的UIButton。当我点击它时，我需要显示我从UITableView 中的ipodLibrary 中选择的歌曲列表，并且我应该能够显示艺术品、歌曲中剩余的分钟数以及艺术家的姓名（如果它在歌曲。

我有播放和暂停按钮：当我单击暂停按钮时，歌曲会暂停，但当我再次点击播放按钮时，它会转到 ipodLibrary。点击播放按钮后如何恢复播放？

当UITableView 中有多首歌曲时，我希望它在第一首曲目完成后立即继续下一首曲目。我想知道该怎么做。

-(IBAction)playButtonPressed:(UIButton *)sender {
  // Create picker view
  MPMediaPickerController* picker = [[MPMediaPickerController alloc] init];
  picker.delegate = self;
  if (userMediaItemCollection) {
    MusicTableViewController *controller = [[MusicTableViewController alloc]
     initWithNibName: @"MusicTableView" bundle: nil];
    controller.delegate = self;
    controller.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
    [self presentModalViewController: controller animated: YES];
  } else {
    MPMediaPickerController *picker = [[MPMediaPickerController alloc]
      initWithMediaTypes: MPMediaTypeMusic];
    picker.delegate  = self;
    picker.allowsPickingMultipleItems = YES;
    picker.prompt = NSLocalizedString
      (@"Add songs to play", "Prompt in media item picker");
    [[UIApplication sharedApplication] setStatusBarStyle:
      UIStatusBarStyleDefault animated: YES];
    [self presentModalViewController: picker animated: YES];
  }
}

-(IBAction)pauseButtonPressed:(UIButton *)sender {
  [myPlayer pause];
}

-(void) mediaPickerDidCancel:(MPMediaPickerController *)mediaPicker {
  [self dismissViewControllerAnimated:YES completion:nil];
}

-(void) mediaPicker:(MPMediaPickerController *)mediaPicker didPickMediaItems:
  (MPMediaItemCollection *)mediaItemCollection {
  [self dismissViewControllerAnimated:YES completion:nil];
  NSURL* assetUrl = [mediaItemCollection.representativeItem
    valueForProperty:MPMediaItemPropertyAssetURL];
  AVURLAsset* asset = [AVURLAsset URLAssetWithURL:assetUrl options:nil];
  AVPlayerItem* playerItem = [AVPlayerItem playerItemWithAsset:asset];
  myPlayer = [AVPlayer playerWithPlayerItem:playerItem];
  [myPlayer play];
}

- (void)viewDidAppear:(BOOL)animated {
  [super viewDidAppear:animated];
  [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
  [self becomeFirstResponder];
}

- (BOOL)canBecomeFirstResponder {
  return YES;
}

- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];
  [[UIApplication sharedApplication] endReceivingRemoteControlEvents];
  [self resignFirstResponder];
}

-(void)remoteControlReceivedWithEvent:(UIEvent *)event {
  switch (event.subtype) {
    case UIEventSubtypeRemoteControlTogglePlayPause:
      if (myPlayer.rate == 0.0) {
        [myPlayer play];
      } else {
        [myPlayer pause];
      }
      break;
    case UIEventSubtypeRemoteControlPlay:
      [myPlayer play];
      break;
    case UIEventSubtypeRemoteControlPause:
      [myPlayer pause];
      break;
    default:
      break;
  }
}

Answer 1

我会查看 Apple 的示例代码 "Add Music"，它清楚地展示了如何执行您所描述的所有操作。

此示例应用程序将让您了解如何使用保存到MPMediaItemCollection 的 iPod 库中选定歌曲的可变副本的内容填充UITableView。它还展示了如何使用 MPMediaItems 和 MPMediaItemCollections 将轨道特定属性显示为单元格标题标签等。

1. 为了填充表格视图，您可以这样设置：

   MPMediaItem *mediaItem = (MPMediaItem *)[collectionMutableCopy objectAtIndex:row];

   MPMediaItemArtwork *artwork = [mediaItem valueForProperty:MPMediaItemPropertyArtwork];

   if (mediaItem) {
       cell.textLabel.text = [mediaItem valueForProperty:MPMediaItemPropertyTitle];
       cell.detailTextLabel.text = [mediaItem valueForProperty:MPMediaItemPropertyArtist];
       if (artwork != nil) {
           cell.imageView.image = [artwork imageWithSize:CGSizeMake (40, 40)];
       }else{
           cell.imageView.image = [UIImage imageNamed:@"no_artwork.png"];
       }
   }
   

2. 将链接到播放按钮的按钮重命名为“选择音乐”，并创建一个名为“播放”的新按钮，并将其操作设置为：

   - (IBAction)playMusic { [myPlayer play]; }

编辑：从MPMediaItemCollection的内容创建数组：

NSMutableArray *collectionMutableCopy = [[NSMutableArray alloc] initWithArray:myMediaItemCollection.items];

编辑 2： 取消项目中以下行的注释：

在- (void) registerForMediaPlayerNotifications

/*
 // This sample doesn't use libray change notifications; this code is here to show how
 //     it's done if you need it.
 [[NSNotificationCenter defaultCenter] removeObserver: self
 name: MPMediaLibraryDidChangeNotification
 object: musicPlayer];

 [[MPMediaLibrary defaultMediaLibrary] endGeneratingLibraryChangeNotifications];

 */

在- (void)dealloc

/*
 // This sample doesn't use libray change notifications; this code is here to show how
 //     it's done if you need it.
 [notificationCenter addObserver: self
 selector: @selector (handle_iPodLibraryChanged:)
 name: MPMediaLibraryDidChangeNotification
 object: musicPlayer];

 [[MPMediaLibrary defaultMediaLibrary] beginGeneratingLibraryChangeNotifications];
 */

替换这一行：

[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryAmbient error: nil];

有了这个

 [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: nil];

 UInt32 doSetProperty = 0;
 AudioSessionSetProperty (
 kAudioSessionProperty_OverrideCategoryMixWithOthers,
 sizeof (doSetProperty),
 &doSetProperty
 );

然后将以下内容添加到您的项目 info.plist 文件中

Answer 2

您的问题是您的播放按钮所做的不仅仅是告诉音乐播放器播放。你需要一个只打电话给[myPlayer play]；在播放按钮以外的地方进行所有设置。

让您的播放按钮同时选择歌曲并不是一个很好的编码实践（最好保持一个按钮 -> 一个功能的想法）。所以有一个按钮可以立即执行播放按钮中的操作，然后让播放按钮调用[myPlayer play]

至于你的其他问题，你应该看看这个：Play multiple audio files using AVAudioPlayer

请注意，您不应该在同一篇文章中提出多个问题。这使得提供简洁、有用的答案变得更加困难，并且会使网站更难找到内容。

我不确定您是否在询问如何显示歌曲信息，但我猜它在您的标题中。对于这个，iPhone sdk - accessing current song information through an app。