IOS7 AVAudioRecorder 不能录音的解决方法

AVAudioSession * session = [AVAudioSession sharedInstance];
    NSError * sessionError;
    [session setCategory:AVAudioSessionCategoryPlayAndRecord error:&sessionError];
    if(session == nil)
        NSLog(@"Error creating session: %@", [sessionError description]);
    else
        [session setActive:YES error:nil];