[Avalonia] 练习一：搭建Avalonia+Prism+Material项目

　　这是个练手项目，初次接触Avalonia，决定搭建一个架构由Prism实现，UI基于Material，演示基本控件、自定义控件、遮罩、弹窗、标签页等UI基础的桌面项目，实现这些UI基础，基于WPF转Avalonia应该就没太大的问题了。

一、新建项目。

　　（推荐编辑器：JetBrains Rider，智能提示更友好）

新建空白解决方案AvaloniaApps。
新建项目，选择Avalonia .NET MVVM App (AvaloniaUl)，下一步。
在创建之前勾选“Remove View Locator”，使用Prism的View Locator就可以了，同样的，MVVM Toolkit也是使用Prism，但由于引入CefGlue.Avalonia隐式引入了ReactiveUI，所以这里选择ReactiveUI。

项目建好后，右键项目“管理 Nuget 程序包”，将已安装的“CommunityToolkit.Mvvm”卸载掉。
安装 Nuget 包：Prism.DryIoc.Avalonia、Material.Avalonia.DataGrid。

二、集成Prism。

基于Prism的BindableBase实现ViewModel-First的ViewModelBase。

public abstract class PrismViewModelBase : BindableBase
{
    /// <summary>
    /// 创建视图
    /// </summary>
    /// <returns></returns>
    /// <exception cref="Exception"></exception>
    public virtual Control CreateView()
    {
        var type = this.GetType();

        // 按命名规则获取View的类型
        string? nameSpace = null;
        if (type.Namespace is { } ns)
        {
            nameSpace = ns.Replace("ViewModel", "View");
        }

        var name = type.Name.Replace("ViewModel", "View");
        var fullName = nameSpace == null ? name : $"{nameSpace}.{name}";

        var definedTypes = type.Assembly.DefinedTypes.ToList();
        var viewType = definedTypes.FirstOrDefault(q => q.FullName == fullName);

        if (viewType == null)
        {
            fullName = fullName.Replace("ViewModel", "View");
            viewType = definedTypes.FirstOrDefault(q => q.FullName == fullName);

            if (viewType == null)
            {
                throw new Exception(type.FullName + "对应的View未找到！");
            }
        }

        if (Activator.CreateInstance(viewType) is not Control { } control)
        {
            throw new Exception(
                $"{Activator.CreateInstance(viewType)?.GetType().FullName}无法转换为类型{typeof(Control).FullName}。");
        }

        control.DataContext = this;
        Control = control;
        return control;
    }

    /// <summary>
    /// 视图
    /// </summary>
    public Control? Control { get; set; }
}

CreateView是public方法，调用CreateView方法根据命名规则自动查找View，并将View的DataContext设为当前ViewModel。
不调用CreateView方法则可以兼容Prism的View-First方式，比如在axaml中使用prism:ViewModelLocator.AutoWireViewModel="True"，或者IRegionManager.RegisterViewWithRegion方法；

那么使用Prism的View-First方式创建的ViewModel如何对Control（视图）赋值呢？使用ViewModelLocationProvider.SetDefaultViewModelFactory监听ViewModel实例化，代码如下：

ViewModelLocationProvider.SetDefaultViewModelFactory((view, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] viewModelType) =>
{
    var viewModel = Activator.CreateInstance(viewModelType);
    if (viewModel is PrismViewModelBase myViewModel && view is Control control)
    {
        myViewModel.Control = control;
    }
    return viewModel;
});

启动App。

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Data.Core.Plugins;
using Avalonia.Markup.Xaml;
using AvaloniaDesktopApp.ViewModels;
using GntAvaloniaCore.Mvvm;
using GntAvaloniaCore.Utils;
using Prism.DryIoc;
using Prism.Ioc;
using Prism.Mvvm;
using System;
using System.Diagnostics.CodeAnalysis;

namespace AvaloniaDesktopApp
{
    public class App : PrismApplication
    {
        public override void Initialize()
        {
            AvaloniaXamlLoader.Load(this);

            // Required when overriding Initialize
            base.Initialize();
        }

        [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "<Pending>")]
        public override void OnFrameworkInitializationCompleted()
        {
            if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
            {
                // Line below is needed to remove Avalonia data validation.
                // Without this line you will get duplicate validations from both Avalonia and CT
                BindingPlugins.DataValidators.RemoveAt(0);
                var mainWindowViewModel = Container.Resolve<MainWindowViewModel>();
                desktop.MainWindow = mainWindowViewModel.View;
            }

            base.OnFrameworkInitializationCompleted();
        }

        protected override AvaloniaObject CreateShell()
        {
            // 获取主窗口的 ViewModel 并启动相应的 View

            // ViewModel-First
            var mainWindowViewModel = Container.Resolve<MainWindowViewModel>();
            return mainWindowViewModel.CreateView();
        }

        protected override void RegisterTypes(IContainerRegistry containerRegistry)
        {
            // Register you Services, Views, Dialogs, etc.
            // 注册 MainWindowViewModel
            containerRegistry.RegisterSingleton<ILog, NLogWrapper>();
            containerRegistry.RegisterSingleton<MainWindowViewModel>();
        }

        protected override void OnInitialized()
        {
            base.OnInitialized();

            ViewModelLocationProvider.SetDefaultViewModelFactory((view, [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] viewModelType) =>
            {
                var viewModel = Activator.CreateInstance(viewModelType);
                if (viewModel is PrismViewModelBase myViewModel && view is Control control)
                {
                    myViewModel.Control = control;  // 将 View 注入 ViewModel
                }
                return viewModel;
            });

            // Register Views to the Region it will appear in. Don't register them in the ViewModel.
            //var regionManager = Container.Resolve<IRegionManager>();

            // WARNING: Prism v11.0.0-prev4
            // - DataTemplates MUST define a DataType or else an XAML error will be thrown
            // - Error: DataTemplate inside of DataTemplates must have a DataType set
            //regionManager.RegisterViewWithRegion(nameof(RegionNames.MainWindowContentRegion), typeof(WindowTestView));
        }
    }
}

App集成PrismApplication。
注册 MainWindowViewModel 为单例，在CreateShell初始化MainWindowViewModel单例，并通过CreateView返回对应的View，在OnFrameworkInitializationCompleted中再次获取MainWindowViewModel单例，并将View设为MainWindow。

三、引入Material主题。

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:themes="clr-namespace:Material.Styles.Themes;assembly=Material.Styles"
             x:Class="AvaloniaDesktopApp.App">
  <Application.Styles>
    <themes:MaterialTheme BaseTheme="Light" PrimaryColor="Blue" SecondaryColor="Yellow" />
    <StyleInclude Source="avares://GntAvaloniaUI/Styles/Generic.axaml"/>
  </Application.Styles>
</Application>

使用Material主题色。

Git代码仓库：AvaloniaApps: C#跨平台Avalonia演示Demo

# cd到项目输出目录AvaloniaDesktop/bin/x64/Debug/net80
# 添加执行权限，主要是浏览器
chmod +x AvaloniaDesktopApp
chmod +x ./CefGlueBrowserProcess/Xilium.CefGlue.BrowserProcess

# 执行APP
./AvaloniaDesktopApp

由于Avalonia在国产系统UOS上表现不一，Ubuntu上可以完美呈现Demo，但UOS在窗口最大化时，窗口尺寸不变且移至左上角，在渲染阴影上一片漆黑，渲染通知窗口底色是灰色的，而且在两台不同设备同样都是x86_x64的UOS系统上渲染也是不一致，所以放弃该移植方案，该系列不再更新。