c# windows phone zXing green screen

我在做一个二维码阅读器。

当我扫描二维码时，我想在另一个名为 reader.xaml 的页面中导航，在那里我做了一些事情。

但是当我按下按钮 返回 从 reader.xaml 到初始页面时......有时出现绿屏，我必须重新启动我的 Lumia 920...

我不明白为什么?!?!

我正在使用zxing库。

有人可以帮我

    public MainPage()
    {
        InitializeComponent();
        /* CHECKING CONNECTION STATUS */
        bool isConnected = NetworkInterface.GetIsNetworkAvailable();
        if (!isConnected)
        {
            MessageBox.Show("No internet connection", MessageBoxButton.OK);
            Microsoft.Xna.Framework.Game game = new Microsoft.Xna.Framework.Game();
            game.Exit(); 
        }
        //reading value
        if (IsolatedStorageSettings.ApplicationSettings.Contains("idDevice"))
        {
            idDevice = (string)IsolatedStorageSettings.ApplicationSettings["idDevice"];
        }   
        else
        {
            //insert
            Random random = new Random();
            var duration = DateTime.Now - new DateTime(1970, 1, 1, 0, 0, 0);
            long ticks = (long)duration.TotalSeconds;
            idDevice = ticks.ToString() + "-" + random.Next(1, 2000000001).ToString();
            IsolatedStorageSettings.ApplicationSettings.Add("idDevice", idDevice);
            IsolatedStorageSettings.ApplicationSettings.Save();
        }
        _timer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(2) };
        GameTimer gameTimer = new GameTimer();
        gameTimer.UpdateInterval = TimeSpan.FromMilliseconds(33);
        // Call FrameworkDispatcher.Update to update the XNA Framework internals.
        gameTimer.Update += delegate { try { FrameworkDispatcher.Update(); } catch { } };
        // Start the GameTimer running.
        if (Microsoft.Xna.Framework.Media.MediaPlayer.State == MediaState.Playing || Microsoft.Xna.Framework.Media.MediaPlayer.State == MediaState.Paused)
        {
            if (MessageBox.Show("Media is currently playing, do you want to stop it?", "Stop Player", MessageBoxButton.OKCancel) == MessageBoxResult.OK)
            {
                try
                {
                    gameTimer.Stop();
                    Microsoft.Xna.Framework.Media.MediaPlayer.Stop();
                    AudioPlayerS.Source = new Uri("/audioProva.mp3", UriKind.Relative);
                }
                catch { }
            }
            else
            {
                Microsoft.Xna.Framework.Game game = new Microsoft.Xna.Framework.Game();
                game.Exit(); 
            }  
       }
        // Prime the pump or we'll get an exception.
        FrameworkDispatcher.Update();
    }

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        _photoCamera = new PhotoCamera();
        _photoCamera.Initialized += OnPhotoCameraInitialized;
        _previewVideo.SetSource(_photoCamera);
        //CameraButtons.ShutterKeyHalfPressed += (o, arg) => _photoCamera.Focus();
        try
        {
            if (_photoCamera.IsFocusSupported)
            {
                _timer.Tick += (o, arg) => { try { _photoCamera.FlashMode = FlashMode.Off; _photoCamera.Focus(); } catch (Exception) { } };
                _photoCamera.AutoFocusCompleted += (o, arg) => { if (arg.Succeeded) ScanPreviewBuffer(); };
            }
            else
            {
                _timer.Tick += (o, arg) => ScanPreviewBuffer();
            }
        }
        catch
        {
            _timer.Tick += (o, arg) => ScanPreviewBuffer();
        }
        base.OnNavigatedTo(e);
    }
    private void OnPhotoCameraInitialized(object sender, CameraOperationCompletedEventArgs e)
    {
        int width = Convert.ToInt32(_photoCamera.PreviewResolution.Width);
        int height = Convert.ToInt32(_photoCamera.PreviewResolution.Height);
        _luminance = new PhotoCameraLuminanceSource(width, height);
        _reader = new QRCodeReader();
        Dispatcher.BeginInvoke(() =>
        {
            _timer.Start();
            _previewTransform.Rotation = _photoCamera.Orientation; 
        });
    }

    private void ScanPreviewBuffer()
    {
        try
        {
            _photoCamera.GetPreviewBufferY(_luminance.PreviewBufferY);
            var binarizer = new HybridBinarizer(_luminance);
            var binBitmap = new BinaryBitmap(binarizer);
            var result = _reader.decode(binBitmap);
            Dispatcher.BeginInvoke(() => CheckQr(result.Text));
        }
        catch
        {
        }
    }
    private void CheckQr(string link)
    {
        if (IsValidHttpUri(link) == false)
        {
            MessageBox.Show("error", MessageBoxButton.OK);
            return;
        }
        else
        {
            _timer.Stop();
            try
            {
                _photoCamera.CancelFocus();
            }
            catch
            {
            }
            NavigationService.Navigate(new Uri("/reader.xaml?linkQr=" + link, UriKind.Relative));
        }
    }

当我从reader.xaml回来时，出现绿屏。

https://zxingnet.codeplex.com/discussions/407383