MPMediaLibraryDidChangeNotification 调用了两次? [英] MPMediaLibraryDidChangeNotification called twice?

问题描述

我的应用程序使用 iPodMusicPlayer，当暂停时，用户可能会外出并在 Apple 的音乐应用程序中进行更改，例如创建或修改播放列表，然后返回到我的应用程序.

My app uses the iPodMusicPlayer and, when suspended, the user might go out and make changes in Apple's Music App, for example creating or modifying a Playlist, then return to my App.

我收到了预期的 MPMediaLibraryDidChangeNotification，这很好，我会更新我的参考资料等，但我在大约 2 分钟后收到第二个 MPMediaLibraryDidChangeNotification，我真的不需要.

I receive the expected MPMediaLibraryDidChangeNotification, which is fine and I deal with it updating my references etc., but I receive a second MPMediaLibraryDidChangeNotification about 2 minutes later which I really don't need.

关于避免第二次通知有什么想法吗?

Any ideas on avoiding this second notification?

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(notification_iPodLibraryDidChange:) name: MPMediaLibraryDidChangeNotification object:nil];

[[MPMediaLibrary defaultMediaLibrary] beginGeneratingLibraryChangeNotifications];

推荐答案

if( !self.lastModifiedDate )        self.lastModifiedDate = [[NSDate alloc] init];
if( [self.lastModifiedDate compare:[[MPMediaLibrary defaultMediaLibrary] lastModifiedDate]] == NSOrderedSame )  return;
self.lastModifiedDate = [[MPMediaLibrary defaultMediaLibrary] lastModifiedDate];

我的通知处理程序方法中的以上几行处理了额外的调用.仍然不知道为什么我会得到它.

The above lines in my notification handler method deal with the extra call. Still no idea why I'm getting it.

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