为何ZXing.Net.Maui条码扫描器在iOS模拟器运行时崩溃？

环境与代码 #

XAML代码 #

<ScrollView>
    <VerticalStackLayout
        Spacing="25"
        Padding="30,0"
        VerticalOptions="Center">

        <zxing:CameraBarcodeReaderView x:Name="cameraBarcodeReaderView" />
    </VerticalStackLayout>
</ScrollView>
</ContentPage>

C#代码（MainPage.cs） #

using ZXing.Net.Maui;

namespace CameraTest;

public partial class MainPage : ContentPage
{
    int count = 0;

    public MainPage()
    {
        InitializeComponent();

        cameraBarcodeReaderView.Options = new BarcodeReaderOptions
        {
            Formats = BarcodeFormats.OneDimensional,
            AutoRotate = true,
            Multiple = true
        };
    }
}

MauiProgram.cs代码 #

using ZXing.Net.Maui;
using Microsoft.Extensions.Logging;

namespace CameraTest;

public static class MauiProgram
{
    public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();
        builder
            .UseMauiApp<App>()
            .UseBarcodeReader()
            .ConfigureFonts(fonts =>
            {
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
            });

#if DEBUG
        builder.Logging.AddDebug();
#endif

        return builder.Build();
    }
}

Info.plist配置 #

<key>NSCameraUsageDescription</key>
<string>This app uses barcode scanning to...</string>

错误信息 #

{System.ArgumentNullException: Value cannot be null. (Parameter 'device')
   at ObjCRuntime.ThrowHelper.ThrowArgumentNullException(String argumentName)
   at ObjCRuntime.NativeObjectExtensions.GetNonNullHandle(INativeObject self, String argumentName)
   at AVFoundation.AVCaptureDeviceInput..ctor(AVCaptureDevice device, NSError& error)
   at ZXing.Net.Maui.CameraManager.UpdateCamera()
   at ZXing.Net.Maui.CameraManager.UpdateCameraLocation(CameraLocation cameraLocation)
   at ZXing.Net.Maui.CameraBarcodeReaderViewHandler.<>c.<.cctor>b__24_1(CameraBarcodeReaderViewHandler handler, ICameraBarcodeReaderView virtualView)
   at Microsoft.Maui.PropertyMapper`2.<>c__DisplayClass5_0[[ZXing.Net.Maui.ICameraBarcodeReaderView, ZXing.Net.Maui, Version=1.0.2.0, Culture=neutral, PublicKeyToken=null],[ZXing.Net.Maui.CameraBarcodeReaderViewHandler, ZXing.Net.Maui, Version=1.0.2.0, Culture=neutral, PublicKeyToken=null]].<Add>b__0(IElementHandler h, IElement v)
   at Microsoft.Maui.PropertyMapper.UpdatePropertyCore(String key, IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.PropertyMapper.UpdateProperties(IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.Handlers.ElementHandler.SetVirtualView(IElement view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[ZXing.Net.Maui.ICameraBarcodeReaderView, ZXing.Net.Maui, Version=1.0.2.0, Culture=neutral, PublicKeyToken=null],[UIKit.UIView, Microsoft.iOS, Version=16.4.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065]].SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[ZXing.Net.Maui.ICameraBarcodeReaderView, ZXing.Net.Maui, Version=1.0.2.0, Culture=neutral, PublicKeyToken=null],[UIKit.UIView, Microsoft.iOS, Version=16.4.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065]].SetVirtualView(IElement view)
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ElementExtensions.ToPlatform(IElement view, IMauiContext context)
   at Microsoft.Maui.Handlers.LayoutHandler.SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.ILayout, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Platform.LayoutView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].SetVirtualView(IElement view)
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ElementExtensions.ToPlatform(IElement view, IMauiContext context)
   at Microsoft.Maui.Handlers.ScrollViewHandler.UpdateContentView(IScrollView scrollView, IScrollViewHandler handler)
   at Microsoft.Maui.Handlers.ScrollViewHandler.MapContent(IScrollViewHandler handler, IScrollView scrollView)
   at Microsoft.Maui.PropertyMapper`2.<>c__DisplayClass5_0[[Microsoft.Maui.IScrollView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Handlers.IScrollViewHandler, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].<Add>b__0(IElementHandler h, IElement v)
   at Microsoft.Maui.PropertyMapper.UpdatePropertyCore(String key, IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.PropertyMapper.UpdateProperties(IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.Handlers.ElementHandler.SetVirtualView(IElement view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.IScrollView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[UIKit.UIScrollView, Microsoft.iOS, Version=16.4.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065]].SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.IScrollView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[UIKit.UIScrollView, Microsoft.iOS, Version=16.4.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065]].SetVirtualView(IElement view)
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ElementExtensions.ToPlatform(IElement view, IMauiContext context)
   at Microsoft.Maui.Handlers.ContentViewHandler.UpdateContent(IContentViewHandler handler)
   at Microsoft.Maui.Handlers.ContentViewHandler.MapContent(IContentViewHandler handler, IContentView page)
   at Microsoft.Maui.PropertyMapper`2.<>c__DisplayClass5_0[[Microsoft.Maui.IContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Handlers.IContentViewHandler, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].<Add>b__0(IElementHandler h, IElement v)
   at Microsoft.Maui.PropertyMapper.UpdatePropertyCore(String key, IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.PropertyMapper.UpdateProperties(IElementHandler viewHandler, IElement virtualView)
   at Microsoft.Maui.Handlers.ElementHandler.SetVirtualView(IElement view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.IContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Platform.ContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ContentViewHandler.SetVirtualView(IView view)
   at Microsoft.Maui.Handlers.ViewHandler`2[[Microsoft.Maui.IContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.Maui.Platform.ContentView, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].SetVirtualView(IElement view)
   at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler newHandler)
   at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IElement.set_Handler(IElementHandler value)
   at Microsoft.Maui.Platform.ElementExtensions.ToHandler(IElement view, IMauiContext context)
   at Microsoft.Maui.Platform.ViewExtensions.ToHandler(IView view, IMauiContext context)
   at Microsoft.Maui.Controls.Platform.Compatibility.ShellSectionRootRenderer.SetPageRenderer(Page page, ShellContent shellContent)
   at Microsoft.Maui.Controls.Platform.Compatibility.ShellSectionRootRenderer.LoadRenderers()
   at Microsoft.Maui.Controls.Platform.Compatibility.ShellSectionRootRenderer.ViewDidLoad()
   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName)
   at UIKit.UIApplication.Main(String[] args, Type principalClass, Type delegateClass)
   at CameraTest.Program.Main(String[] args) in D:\Maui\annex_apps\CameraTest\CameraTest\Platforms\iOS\Program.cs:line 13}

问题原因 #

这个错误的核心原因是iOS模拟器没有真实的摄像头硬件：

• ZXing.Net.Maui的CameraManager.UpdateCamera()方法会尝试获取系统中的可用摄像头设备，但iOS模拟器没有物理摄像头，导致获取到的设备对象为null。
• 当代码尝试将这个null设备传入AVCaptureDeviceInput构造函数时，直接触发了ArgumentNullException，因为该构造函数要求设备参数不能为空。

另外需要说明：你已添加的相机权限描述不是本次报错的原因——权限不足会抛出权限相关异常，而非设备null的错误。

解决办法 #

1. 使用真实iOS设备测试：只有物理iOS设备具备可用的摄像头硬件，模拟器无法模拟摄像头功能，直接在真机上运行即可正常使用ZXing的扫码功能。
2. 添加模拟器环境判断（调试用）：如果需要在模拟器中调试其他功能，可以临时隐藏扫码控件并提示用户：

public MainPage()
{
    InitializeComponent();

#if DEBUG
    // 判断当前是否为模拟器环境
    if (DeviceInfo.DeviceType == DeviceType.Virtual)
    {
        cameraBarcodeReaderView.IsVisible = false;
        // 可添加Label提示用户使用真机测试扫码功能
        var tipLabel = new Label { Text = "请使用真实iOS设备测试扫码功能" };
        ((VerticalStackLayout)cameraBarcodeReaderView.Parent).Add(tipLabel);
    }
#endif

    cameraBarcodeReaderView.Options = new BarcodeReaderOptions
    {
        Formats = BarcodeFormats.OneDimensional,
        AutoRotate = true,
        Multiple = true
    };
}

内容的提问来源于stack exchange，提问作者Thomas Carlton