How to control playback state function on MPMusicPlayer

how to control 开发者_如何学运维playback state function in MPMusicPlayer....for example i want open

ipod playlist file when the no item available at the end of next track...

how it is possible on iphone.....please help me.....

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Here's a bit of my code that does that:

    MPMediaQuery *everything = [MPMediaQuery songsQuery];

[everything setGroupingType: MPMediaGroupingPlaylist];

self.playlists = [NSMutableArray arrayWithArray:[everything collections]];

....

    NSArray *songsList = [[self.playlists objectAtIndex: currentPlayListIndex] items];

int nowIndex = [songsList indexOfObject:nowPlayingViewController.nowPlayingItem];

if(++nowIndex >= [songsList count]) 
    nowIndex = 0;

if(![self playItem: [songsList objectAtIndex:nowIndex]])