暂停播放时，MPNowPlayingInfoCenter无法正常反应 [英] MPNowPlayingInfoCenter not reacting properly when pausing playback

问题描述

我正在尝试让MPNowPlayingInfoCenter在暂停播放时正常工作。 （我有一个使用AVPlayer进行播放的流式音乐应用程序，我正在通过Airplay在我的Apple TV上播放。）除了暂停之外的所有内容似乎都在Apple TV UI中正确反映出来。我正在这样初始化它：

I am trying to get MPNowPlayingInfoCenter to work properly when pausing playback. (I have a streaming music app that uses AVPlayer for playback, and I am playing back in my Apple TV over Airplay.) Everything but pausing seems to be reflected correctly in the Apple TV UI. I am initializing it like this:

MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
NSDictionary *songInfo = @{
    MPMediaItemPropertyTitle: title,
    MPMediaItemPropertyArtist: artist
};
center.nowPlayingInfo = songInfo;

由于我正在播放，因此在开始播放时我没有持续时间信息。当我从流中获得就绪信号时，我会更新Apple TV上正确显示的持续时间：

Since I am streaming, I do not have duration info upon starting the playback. When I get "ready" signal from the stream, I update the duration that shows up correctly on my Apple TV:

MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
NSMutableDictionary *playingInfo = [NSMutableDictionary dictionaryWithDictionary:center.nowPlayingInfo];
[playingInfo setObject:[NSNumber numberWithFloat:length] forKey:MPMediaItemPropertyPlaybackDuration];
center.nowPlayingInfo = playingInfo;

当用户寻找音轨时，我也可以使用这种技术：

I can also seek with this technique when the user seeks the track:

[playingInfo setObject:[NSNumber numberWithFloat:length * targetProgress] forKey:MPNowPlayingInfoPropertyElapsedPlaybackTime];

我无法弄清楚的一件事是，如何暂停Apple TV上的播放头。当用户在我的UI中点击暂停时，我正在尝试执行以下操作：

The one thing I can NOT figure out is, how to pause the playhead on my Apple TV. When user taps pause in my UI, I am trying to do something like:

MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
NSMutableDictionary *playingInfo = [NSMutableDictionary dictionaryWithDictionary:center.nowPlayingInfo];        
[playingInfo setObject:[NSNumber numberWithFloat:0.0f] forKey:MPNowPlayingInfoPropertyPlaybackRate];            
center.nowPlayingInfo = playingInfo;

这不是暂停，而是将播放头恢复为零并继续推进它。

Instead of pausing, this seeks the playhead back to zero and keeps advancing it.

如何让播放头在我的Apple TV UI中正确暂停？

How do I get the playhead to pause correctly in my Apple TV UI?

推荐答案

我有解决方案！仅设置MPMediaItemPropertyPlaybackDuration

I've the solution! Set only the MPMediaItemPropertyPlaybackDuration

1 - 启动曲目时，使用曲目的总持续时间设置属性：

1 - When you start the track, set the property with the total duration of the track:

MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
NSDictionary *songInfo = @{
    MPMediaItemPropertyTitle: title,
    MPMediaItemPropertyArtist: artist
    MPMediaItemPropertyPlaybackDuration : [NSNumber numberWithFloat:length]
};
center.nowPlayingInfo = songInfo;

2 - 当您暂停音轨时......什么都不做。

2 - when you pause the track... do nothing.

3 - 播放曲目时，使用currentTrackTime设置属性：

3 - when you play the track, set the property with the currentTrackTime:

MPNowPlayingInfoCenter *center = [MPNowPlayingInfoCenter defaultCenter];
NSMutableDictionary *playingInfo = [NSMutableDictionary dictionaryWithDictionary:center.nowPlayingInfo];        
[playingInfo setObject:[NSNumber numberWithFloat:player.currentTrackTime] forKey:MPNowPlayingInfoPropertyElapsedPlaybackTime];            
center.nowPlayingInfo = playingInfo;

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