.NET MAUI Windows平台网络图片无法加载问题求助

问题现象 #

• 应用基于Visual Studio 2022的MAUI项目模板生成
• 仅新增一个Image控件，其Source属性设置为https://picsum.photos/seed/picsum/200
• 图片无法加载，仅显示设置的灰色背景

原因分析 #

Windows平台的MAUI应用默认未授予网络访问权限，导致无法加载外部网络资源。

解决步骤 #

在Package.appmanifest的<Capabilities>节点中添加网络访问权限声明：

<uap:Capability Name="internetClient" />

修改后的Package.appmanifest代码 #

<?xml version="1.0" encoding="utf-8"?>
<Package xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10" 
         xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10" 
         xmlns:mp="http://schemas.microsoft.com/appx/2014/phone/manifest" 
         xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities" 
         IgnorableNamespaces="uap rescap">
    <Identity Name="maui-package-name-placeholder" Publisher="CN=User Name" Version="0.0.0.0" />
    <mp:PhoneIdentity PhoneProductId="####hiddenbyme####" PhonePublisherId="####hiddenbyme####"/>
    <Properties>
        <DisplayName>$placeholder$</DisplayName>
        <PublisherDisplayName>User Name</PublisherDisplayName>
        <Logo>$placeholder$.png</Logo>
    </Properties>
    <Dependencies>
        <TargetDeviceFamily Name="Windows.Universal" MinVersion="10.0.17763.0" MaxVersionTested="10.0.19041.0" />
        <TargetDeviceFamily Name="Windows.Desktop" MinVersion="10.0.17763.0" MaxVersionTested="10.0.19041.0" />
    </Dependencies>
    <Resources>
        <Resource Language="x-generate" />
    </Resources>
    <Applications>
        <Application Id="App" Executable="$targetnametoken$.exe" EntryPoint="$targetentrypoint$">
            <uap:VisualElements DisplayName="$placeholder$" Description="$placeholder$" Square150x150Logo="$placeholder$.png" Square44x44Logo="$placeholder$.png" BackgroundColor="transparent">
                <uap:DefaultTile Square71x71Logo="$placeholder$.png" Wide310x150Logo="$placeholder$.png" Square310x310Logo="$placeholder$.png" />
                <uap:SplashScreen Image="$placeholder$.png" />
            </uap:VisualElements>
        </Application>
    </Applications>
    <Capabilities>
        <rescap:Capability Name="runFullTrust" />
        <!-- 添加网络访问权限 -->
        <uap:Capability Name="internetClient" />
    </Capabilities>
</Package>

其他相关代码参考 #

MainPage.xaml

<?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="TryingMauiNative.MainPage">
    <ScrollView>
        <VerticalStackLayout Spacing="25" Padding="30,0" VerticalOptions="Center">
            <Image Source="dotnet_bot.png" 
                   SemanticProperties.Description="Cute dot net bot waving hi to you!" 
                   HeightRequest="200" 
                   HorizontalOptions="Center" />
            <Label Text="Hello, World!" 
                   SemanticProperties.HeadingLevel="Level1" 
                   FontSize="32" 
                   HorizontalOptions="Center" />
            <Label Text="Welcome to .NET Multi-platform App UI" 
                   SemanticProperties.HeadingLevel="Level2" 
                   SemanticProperties.Description="Welcome to dot net Multi platform App U I" 
                   FontSize="18" 
                   HorizontalOptions="Center" />
            <Button x:Name="CounterBtn" 
                    Text="Click me" 
                    SemanticProperties.Hint="Counts the number of times you click" 
                    Clicked="OnCounterClicked" 
                    HorizontalOptions="Center" />
            <Image Source="https://picsum.photos/seed/picsum/200" 
                   BackgroundColor="#535353" 
                   HeightRequest="200" 
                   WidthRequest="200" />
        </VerticalStackLayout>
    </ScrollView>
</ContentPage>

app.manifest

<?xml version="1.0" encoding="utf-8"?>
<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
    <assemblyIdentity version="1.0.0.0" name="TryingMauiNative.WinUI.app"/>
    <application xmlns="urn:schemas-microsoft-com:asm.v3">
        <windowsSettings>
            <!-- 以下两个标签组合效果：1) Windows 10周年更新及以上版本支持每显示器DPI感知 2) Windows 10周年更新以下版本使用系统DPI感知 -->
            <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true/PM</dpiAware>
            <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2, PerMonitor</dpiAwareness>
        </windowsSettings>
    </application>
</assembly>

App.xaml

<maui:MauiWinUIApplication x:Class="TryingMauiNative.WinUI.App" 
                            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
                            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
                            xmlns:maui="using:Microsoft.Maui" 
                            xmlns:local="using:TryingMauiNative.WinUI">
</maui:MauiWinUIApplication>

内容的提问来源于stack exchange，提问作者amitdigga