iOS Swift我的应用程序的音量不再下降

Question

在我的应用中运行音频 按下音量调低键 降至1 1将不再下降。 我按调低音量键1 我想被静音。

我使用了Swift 4，iOS 11

在didFinishLaunchingWithOptions

中

let session: AVAudioSession = AVAudioSession.sharedInstance()

    do {
        if #available(iOS 10.0, *) {
            try session.setCategory(AVAudioSessionCategoryPlayAndRecord, mode: AVAudioSessionModeDefault, routeSharingPolicy: .longForm, options: [.defaultToSpeaker , .allowAirPlay ,.allowBluetooth ,.allowBluetoothA2DP])
            try session.overrideOutputAudioPort(AVAudioSessionPortOverride.none)
        } else {
            session.perform(NSSelectorFromString("setCategory:withOptions:error:"), with: AVAudioSessionCategoryPlayAndRecord, with:  [AVAudioSession.CategoryOptions.allowBluetooth,AVAudioSession.CategoryOptions.allowBluetoothA2DP,AVAudioSession.CategoryOptions.allowAirPlay])
        }
        try session.setActive(true)
    } catch {

    }
let commandCenter = MPRemoteCommandCenter.shared()
commandCenter.nextTrackCommand.isEnabled = false
commandCenter.previousTrackCommand.isEnabled = false
commandCenter.skipForwardCommand.isEnabled = false
commandCenter.skipBackwardCommand.isEnabled = false

当我按下降低音量键时，我希望音量完全关闭。 我的AVAudioSession是否有问题？