ZXing.Net背导航C#

Question

我正在使用ZXing.Net相机条形码扫描仪，xamarin表单和C#，它看起来很好。但是我有一个问题，如果我通过Navigation.PushAsync()进入下一页，然后单击Back导航按钮，ZXingScannerPage摄像机将不会重新加载.(它将只是最后一张照片的静止图像)...how是否重新加载ZXingScannerPage以便相机在按下Back导航时处于活动状态？是否要刷新附在页面上的相机视图？

Answer 1

我发现的允许使用ZXing扫描页进行回显导航的解决方案是，在将页面的新实例推送到导航堆栈之前，删除ZXing扫描页的所有实例。在您的navigation.cs中，当您准备推送页面时，请使用以下命令：

        foreach(var x in _navigation.Navigation.NavigationStack.ToList())
        {
          if((x.GetType() == typeof(/* name of your scanner page */)))
          {
            _navigation.Navigation.RemovePage(x);
          }
        }
        var page = new /* your scanner page */();
        _navigation.PushAsync( /* your scanner page */);

Answer 2

使用以下代码。扫描完成后立即停止扫描。别做手工操作。

    Entry objScanner= new Entry();
                    objScanner.Placeholder = "Barcode";
                    objScanner.Keyboard = Keyboard.Numeric;
                    objScanner.HorizontalOptions = LayoutOptions.StartAndExpand;
                    objScanner.WidthRequest = Application.Current.MainPage.Width - 40;



                    objScanner.SetBinding(Entry.TextProperty, "ElementValue", BindingMode.TwoWay);
                    objScanner.BindingContext = control;


                    layout.Children.Add(objScanner);

                    objScanner.Focused +=  async (s, e) =>
                    {
                        var scanPage = new ZXingScannerPage();
                        await Navigation.PushAsync(scanPage);

                        scanPage.OnScanResult += (result) =>
                            {
                                // Stop scanning
                                scanPage.IsScanning = false;

                                // Pop the page and show the result
                                Device.BeginInvokeOnMainThread(async () =>
                               {
                                   await Navigation.PopAsync();
                                   objScanner.Text = result.Text;
                                  // await DisplayAlert("Scanned Barcode", result.Text, "OK");
                               });
                            };
                    };

Answer 3

我找到了一个可能有用的解决办法。在内容页上，创建一个本地内容变量。如果我实例化扫描仪并将它添加到OnAppearing方法中的内容中，那么设置Content = null OnDisappearing方法。取消内容似乎会触发堆栈上必要的清理。

这是我的密码：

public class QrCodeScanPage : ZXingScannerPage
{
    View _content;
    public QrCodeScanPage()
    {
        InitScanner();
    }

    void InitScanner()
    {
        IsAnalyzing = true;
        IsScanning = true;
        DefaultOverlayTopText = "Align the barcode within the frame";
        DefaultOverlayBottomText = string.Empty;

        OnScanResult += ScanPage_OnScanResult;

        Title = "Scan Code";

        var item = new ToolbarItem
        {
            Text = "Cancel",
            Command = new Command(async () =>
            {
                IsScanning = false;
                await Navigation.PopAsync();
            })
        };
        if (Device.RuntimePlatform != Device.iOS)
            item.IconImageSource = "toolbar_close.png";

        ToolbarItems.Add(item);
    }

    void ScanPage_OnScanResult(ZXing.Result result)
    {
        Device.BeginInvokeOnMainThread(async () =>
        {
            IsScanning = false;
            IsAnalyzing = false;
            await Navigation.PushAsync(new QrCodeScanResultPage());
        });
    }

    protected override void OnAppearing()
    {
        IsScanning = true;
        IsAnalyzing = true;
        base.OnAppearing();
        if (Content != null)
        {
            _content = Content;
        }
        if (Content == null)
        {
            Content = _content;
        }
    }

    protected override void OnDisappearing()
    {
        base.OnDisappearing();
        Content = null;
    }
}