.NET Maui中Navigation.PushAsync跳转页面空白问题排查

将Xamarin Forms（XF）应用迁移至.NET MAUI后，出现以下异常情况：

• 导航栏中定义的ToolbarItem点击后，跳转的EventSetupPage在Android 12模拟器中显示空白，但页面构造函数已被正常调用。
• 父页面通过MessagingCenter消息触发加载，相关代码如下：

父页面ToolbarItem定义 #

<ContentPage.ToolbarItems>
    <ToolbarItem Text="New Game" Clicked="NewGame_Clicked" x:Name="NewGame" />
</ContentPage.ToolbarItems>
<VerticalStackLayout><ListView........./></VerticalStackLayout>

点击事件代码 #

private void NewGame_Clicked(object sender, EventArgs e)
{
    Navigation.PushAsync(new EventSetupPage());
}

EventSetupPage简化代码 #

<?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="ScanAndScoringMauiApp.Pages.EventSetupPage"
             Title="EventSetupPage">
    <VerticalStackLayout>
        <Label 
            Text="Welcome to .NET MAUI!"
            VerticalOptions="Center" 
            HorizontalOptions="Center" />
    </VerticalStackLayout>
</ContentPage>

父页面加载逻辑 #

MessagingCenter.Subscribe<string>(this, "UpdateMainPage", (sender) =>
{
    MainThread.BeginInvokeOnMainThread(() =>
    {
        MainPage = new NavigationPage(new GameList());
    });
});

1. 显式在主线程执行导航操作 #

尽管PushAsync默认会处理线程切换，但在MessagingCenter触发的页面上下文中，显式包裹主线程调用可避免渲染异常：

private async void NewGame_Clicked(object sender, EventArgs e)
{
    await MainThread.InvokeOnMainThreadAsync(() => 
        Navigation.PushAsync(new EventSetupPage())
    );
}

2. 验证Navigation实例有效性 #

确保当前页面的Navigation属性不为null，若为空则重新通过Application.Current.MainPage设置导航容器：

private async void NewGame_Clicked(object sender, EventArgs e)
{
    if (Navigation == null)
    {
        await MainThread.InvokeOnMainThreadAsync(() =>
        {
            Application.Current.MainPage = new NavigationPage(new EventSetupPage());
        });
        return;
    }
    await MainThread.InvokeOnMainThreadAsync(() => 
        Navigation.PushAsync(new EventSetupPage())
    );
}

3. 替换MessagingCenter为WeakReferenceMessenger（官方推荐） #

.NET MAUI中MessagingCenter已被标记为过时，改用WeakReferenceMessenger可避免内存泄漏和线程问题：

1. 安装CommunityToolkit.Mvvm NuGet包
2. 修改消息发送与订阅逻辑：

using CommunityToolkit.Mvvm.Messaging;

// 发送消息（替代原MessagingCenter.Send）
WeakReferenceMessenger.Default.Send("UpdateMainPage");

// 订阅消息（替代原MessagingCenter.Subscribe）
WeakReferenceMessenger.Default.Register<string>(this, (recipient, message) =>
{
    MainThread.BeginInvokeOnMainThread(() =>
    {
        Application.Current.MainPage = new NavigationPage(new GameList());
    });
});

4. 检查Android项目配置 #

确保MainActivity正确继承MauiAppCompatActivity，无自定义导航拦截：

[Activity(Theme = "@style/Maui.SplashTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize | ConfigChanges.Density)]
public class MainActivity : MauiAppCompatActivity
{
}

5. 清理模拟器缓存并重启 #

Android模拟器缓存可能导致页面渲染异常，执行以下操作：

• 关闭模拟器，在Android Device Manager中选择对应模拟器，点击"清空数据"
• 重启Visual Studio和模拟器，重新编译运行项目

内容的提问来源于stack exchange，提问作者Wallace B. McClure