//设置后台播放
NSError *sessionError;
[audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&sessionError];
//判断后台有没有播放
if (audioSession == nil) {
NSLog(@"Error creating sessing:%@", [sessionError description]);
} else {
[audioSession setActive:YES error:nil];
}
UInt32 audioRoute = kAudioSessionOverrideAudioRoute_Speaker;
AudioSessionSetProperty(kAudioSessionProperty_OverrideAudioRoute, sizeof(audioRoute), &audioRoute);