Why does playbackState always return 0 (iOs+html5+phonegap)?

Question

Objective-C

I am writing on phonegap (implemented through a plugin), I need to implement a poll for audio playback buttons for iOs in a locked mode.
I'm trying to get the statuses of MPMusicPlayerController:

MPMusicPlaybackState playbackState = [[MPMusicPlayerController applicationMusicPlayer] playbackState];

if (playbackState == MPMusicPlaybackStateStopped || playbackState == MPMusicPlaybackStatePaused) {
    // код если остановлен
} else if (playbackState == MPMusicPlaybackStatePlaying) {
    // код если играет
}

The problem is that the playbackState doesn't change, it's always 0;
It turns out to control the volume through MPMusicPlayerController, according to @mezhevikin's hint , everything works fine. Any way to recognize playback stop is suitable for me, if there are any, tell me, I tried AVAudioSession, but I did not find the parameters there by which it could be tracked.