iOS 扬声器和听筒切换

  if ([[[AVAudioSession sharedInstance] category] isEqualToString:AVAudioSessionCategoryPlayback])
    {
        //切换为听筒播放
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
    }
    else
    {
        //切换为扬声器播放
        [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
    }