MPMediaPickerController didPickMediaItems返回MPModelObjectMediaItem

Question

我有个超级奇怪的问题。我正在使用iOS13 MPMediaPickerController从用户那里获取一些苹果音乐库的歌曲，以便通过[MPMusicPlayerController applicationMusicPlayer]播放。

现在，我从一些播放列表中下载了一些未下载的歌曲，并将委托函数添加到我的库中。

- (void)mediaPicker:(MPMediaPickerController *)mediaPicker didPickMediaItems:(MPMediaItemCollection *)mediaItemCollection

报税

mediaItemCollection.items.firstObject

不能由播放机播放的MPModelObjectMediaItem类型的对象。(我也不能投到那种类型，因为它是未知的。此外，也没有这种类型的文档。它似乎是mediaplayer框架中的一个私有类。)

我期待的是MPConcreteMediaItem类型，它是为所有下载的(以及所有不在播放列表中的其他云项目)传入的。

选择器配置如下

musicPicker = [[MPMediaPickerController alloc] initWithMediaTypes:MPMediaTypeMusic];
musicPicker.showsCloudItems               = true;
musicPicker.showsItemsWithProtectedAssets = true;
musicPicker.delegate                      = self;
musicPicker.allowsPickingMultipleItems    = false;

有什么建议吗？

Answer 1

如果您没有将它们添加到您的音乐库中，那么加载到您自己的应用程序中的项目似乎就无法正确加载。(OS13.3)

我正在使用这个解决方法：

- (void)mediaPicker:(MPMediaPickerController *)mediaPicker didPickMediaItems:(MPMediaItemCollection *)mediaItemCollection
{
    assert(mediaItemCollection.count == 1);
    // this check is done because it seems that in the following scenario you dont get a
    // MPConcreteMediaItem which can be played. Instead you get a MPModelObjectMediaItem
    // this happens when an item was selected that is inside a playlist, but does not belong
    // to your library (nor is it downloaded to your device)
    if(mediaItemCollection.items.firstObject.persistentID <= 0)
    {
        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Song Not Added")
                                                                message:@"This song must be added to your Apple Music library. Please add the song to your library from the Music App."
                                                                preferredStyle:UIAlertControllerStyleAlert];
        [alertController addAction:[UIAlertAction actionWithTitle:@"Dismiss"
                                                  style:UIAlertActionStyleDefault
                                                  handler:nil]];
        [alertController addAction:[UIAlertAction actionWithTitle:@"Open Music App"
                                                  style:UIAlertActionStyleCancel
                                                  handler:^(UIAlertAction *alertAction)
                                                  {
                                                      [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"music://"]
                                                                      options:nil
                                                                      completionHandler:nil];
                                                  }]];
        [self presentViewController:alertController animated:true completion:nil];
        return;
    }
    // good to go? then load it
    [musicPlayer setQueueWithItemCollection:mediaItemCollection];
    ...
}