尽管找到了条形码，但ZXingScannerFragment.StartScan（）未返回

Question

我正在尝试使用ZXingScannerFragment类扫描Xamarin.Android中的QR码。摄像机运行正常，一切正常，ZXing甚至将“找到条形码”写入输出控制台。但是，永远不会调用处理结果的函数。我有一个预感，问题可能出在上下文和活动上，但是相机再次像我想要的那样加载得很好，但是我从来没有得到任何扫描结果。

这是我的片段代码：

    public class HomeFragment : Fragment
{
    private ZXingScannerFragment scanFragment;
    public override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);


        // Create your fragment here
    }

    public override void OnResume()
    {
        base.OnResume();
        MobileBarcodeScanner.Initialize(this.Activity.Application);
        var needsPermissionRequest = ZXing.Net.Mobile.Android.PermissionsHandler.NeedsPermissionRequest(Model.Model.MainActivityContext);
        if (needsPermissionRequest)
            ZXing.Net.Mobile.Android.PermissionsHandler.RequestPermissionsAsync(this.Activity);

        if (scanFragment == null)
        {
            scanFragment = new ZXingScannerFragment();

            FragmentManager.BeginTransaction()
                .Replace(Resource.Id.container, scanFragment)
                .Commit();
        }

        if (!needsPermissionRequest)
            Scan();

    }

    private void Scan()
    {
        var opts = new MobileBarcodeScanningOptions
        {

            PossibleFormats = new List<BarcodeFormat> {
                ZXing.BarcodeFormat.QR_CODE
            },
            CameraResolutionSelector = availableResolutions => {

                foreach (var ar in availableResolutions)
                {
                    Console.WriteLine("Resolution: " + ar.Width + "x" + ar.Height);
                }
                return null;
            }
        };

        scanFragment.StartScanning(result => {

            // This function is never called
            if (result == null || string.IsNullOrEmpty(result.Text))
            {
                Toast.MakeText(Model.Model.MainActivityContext, "Scanning Cancelled", ToastLength.Long).Show();
                return;
            }


            Activity.RunOnUiThread(() => Toast.MakeText(Model.Model.MainActivityContext, "Scanned: " + result.Text, ToastLength.Short).Show());
        }, opts);
    }

    public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        return inflater.Inflate(Resource.Layout.home_fragment, container, false);
        //return base.OnCreateView(inflater, container, savedInstanceState);
    }


}

大多数内容来自ZXing在其GitHub页面上提供的示例。

谢谢！