问基于iOS模式的MPVolumeView中断

EN

    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

    // Make sure the session on this thread matches.
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionMixWithOthers | AVAudioSessionCategoryOptionAllowBluetooth error:nil];

    // Here is the main connundrum: I want to set AVAudioSessionModeDefault so that the MPVolumeView will work,
    // but when I do that the mic picks up the audio from the speaker and plays it back creating an unwanted feeback loop.
    // If I set the mode to AVAudioSessionModeVoiceChat the voice processing (primarily the AEC) fixes the feeback loop,
    // but then the MPVolumeView no longers works.  (It no longer adjusts the system volume.
    //Question: How can I have BOTH the voice processing AND the MPVolumeView adjust the system volume?
    if(!appDelegate.viewController.voiceChatMode)
        [audioSession setMode:AVAudioSessionModeDefault error:nil];
    else
        [audioSession setMode:AVAudioSessionModeVoiceChat error:nil];

    [audioSession setPreferredIOBufferDuration:0.005 error:nil];
    [audioSession setActive:YES error:nil];