你需要将播放速率设置为1.0f，即使文档说它默认为1.0。

You need to setup playback rate to 1.0f even if documentation says it's 1.0 by default.

NSDictionary *mediaInfo = @{
    MPMediaItemPropertyTitle: audio.title,
    MPMediaItemPropertyArtist: audio.artist,
    MPMediaItemPropertyPlaybackDuration: audio.duration,
    MPNowPlayingInfoPropertyPlaybackRate: @(1.0)
};

[[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:mediaInfo];