为什么zxing在.net maui中显示黑屏？

Question

我正在尝试使用来自 https://github.com/Redth/ZXing.Net.Maui 的条形码扫描 ZXing.Net.Maui

我将扫描仪添加到页面，如下所示：

    <?xml version="1.0" encoding="utf-8" ?>
    <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
                 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                 x:Class="myapp.Pages.ControleDesBillets"
                 x:DataType="viewmodel:StandardPageVM"
                 xmlns:viewmodel="clr-namespace:myapp.ViewModels"
                 xmlns:Controls="clr-namespace:myapp.Resources.Controls"             
                 xmlns:zxing="clr-namespace:ZXing.Net.Maui.Controls;assembly=ZXing.Net.MAUI">

        <Grid RowDefinitions="*" ColumnDefinitions="*">
            <zxing:CameraBarcodeReaderView x:Name="cameraBarcodeReaderView" Grid.Column="0" Grid.Row="0" HeightRequest="200" WidthRequest="200"/>
        </Grid>

    </ContentPage>

当应用程序运行时，它会提示允许相机访问，然后显示黑屏，没有其他内容。

扫描仪在应用程序启动时初始化：

    public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();

        builder.UseMauiApp<App>().UseMauiCommunityToolkit();
        builder.UseBarcodeReader();  // << here
        return builder.Build();
    }       

我正在使用物理设备进行测试。这是我的输出：

    Loaded assembly: /data/data/com.companyname.myapp/files/.__override__/Xamarin.Google.Guava.ListenableFuture.dll [External]
    [CameraManagerGlobal] Connecting to camera service
    [CameraManagerGlobal] [soar.cts] ignore the status update of camera: 2
    [CameraManagerGlobal] [soar.cts] ignore the status update of camera: 3
    [CameraManagerGlobal] [soar.cts] ignore the status update of camera: 4
    [CameraManagerGlobal] [soar.cts] ignore the status update of camera: 5
    [CameraManagerGlobal] ignore the torch status update of camera: 3
    [CameraManagerGlobal] ignore the torch status update of camera: 4
    [CameraMetadataJV] setAppNameAndSensorId all [com.antutu:0,ssize,12032x9024,0,false]
    [CameraMetadataJV] setAppNameAndSensorId all [com.antutu:1,ssize,5184x3880,0,false]
    [CameraRepository] Added camera: 0
    [Camera2CameraInfo] Device Level: INFO_SUPPORTED_HARDWARE_LEVEL_3
    [CameraRepository] Added camera: 1
    [Camera2CameraInfo] Device Level: INFO_SUPPORTED_HARDWARE_LEVEL_3
    [CameraValidator] Verifying camera lens facing on rain, lensFacingInteger: null
    Thread finished: <Thread Pool> #2
    Thread finished: <Thread Pool> #4
    Le thread 0x2 s'est arrêté avec le code 0 (0x0).
    Le thread 0x4 s'est arrêté avec le code 0 (0x0).
    [CompatibilityChangeReporter] Compat change id reported: 150939131; UID 10378; state: ENABLED

我做错了什么？

Answer 1

这是一个已知问题：https://github.com/Redth/ZXing.Net.Maui/issues/7

Zxing无论是XF还是MAUI一直都是垃圾。它要么速度慢、性能低，要么存在随机问题并且几乎没有好的功能。

还有另一个基于 MLKit 的 BarcodeScanner，它与我上面提到的相反。

安装步骤在这里：https://github.com/JimmyPun610/BarcodeScanner.Mobile/wiki/3.-Installation-for-Maui

安装完毕并准备好基本设置后，您所要做的就是如下所示：

 <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="SampleApp.Maui.Page1"
             xmlns:gv="clr-namespace:BarcodeScanner.Mobile.Maui;assembly=BarcodeScanner.Mobile.Maui"
             Title="Page1">
   <ContentPage.Content>
     <!--VirbationOnDetected: Indicate the device will vibrate or not when detected barcode, default is True
         TorchOn: Indicate the torch will on or not when the view appear, default is False
         IsScanning : Indicate whether the device will start scanning after it is opened, default is True
         RequestedFPS: Affect Android only, remove it if you want a default value (https://developers.google.com/android/reference/com/google/android/gms/vision/CameraSource.Builder.html#public-camerasource.builder-setrequestedfps-float-fps)
         ScanInterval: Scan interval for iOS, default is 500ms and the minimum is 100ms, please be reminded that double scanning may be occurred if it is too small
         -->
          <gv:CameraView HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" OnDetected="CameraView_OnDetected" Grid.Row="1"
                           TorchOn="False" VibrationOnDetected="False" ScanInterval="50" x:Name="Camera"/>

   </ContentPage.Content>
</ContentPage>

你就完成了。

Answer 2

当我推送带有摄像头视图的页面（包裹在 NavigationPage 中）时，它会冻结。

await Shell.Current.Navigation.PushModalAsync(new NavigaionPage(new ScannerPage), false);

但是推送页面本身就可以正常工作，没有问题

await Shell.Current.Navigation.PushModalAsync(new ScannerPage(), false);

Answer 3

正如 FreakyAli 提到的，这个问题已被报告。

现在，如果您想坚持使用 ZXing，有一个解决方法（在链接的问题中提到）：

 protected override void OnNavigatedTo(NavigatedToEventArgs args)
    {
        RecreateCameraView();
    }
    private void RecreateCameraView()
    {
        // Create a new instance for CameraBarcodeReaderView
        var newCameraView = new CameraBarcodeReaderView()
        {
            Options = CameraView.Options,
            CameraLocation = CameraLocation.Rear
        };

        newCameraView.BarcodesDetected += cameraView_BarCodeDetected;
        
        var index = CameraGrid.Children.IndexOf(CameraView);
        CameraGrid.Children.Remove(CameraView);
        `CameraGrid.Children.Insert(index,newCameraView);`

        // Assign your new instance to CameraView.
        CameraView = newCameraView;
    }

在本例中，

CameraGrid

是父容器。

CameraView

，嗯，是你的相机视图。

希望有帮助！ 😉