切换听筒/扬声器播放

场景：微信语音消息，靠近听筒切换为听筒播放

//切换为听筒播放
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];

//切换为扬声器播放
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];