側邊欄功能實現 #

MainWindowViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;

namespace AvaloniaSideBarEx.ViewModels;

public partial class MainWindowViewModel : ViewModelBase
{
    [ObservableProperty]
    private bool _isSidebarOpen;

    [RelayCommand]
    private void ToggleSidebar()
    {
        IsSidebarOpen = !IsSidebarOpen;
    }
}

  using System;
  using Avalonia;
  using Avalonia.Controls.ApplicationLifetimes;
  using Avalonia.Data.Core;
  using Avalonia.Data.Core.Plugins;
  using System.Linq;
  using Avalonia.Markup.Xaml;
  using AvaloniaSideBarEx.ViewModels;
  using AvaloniaSideBarEx.Views;
  using Microsoft.Extensions.DependencyInjection;

  namespace AvaloniaSideBarEx;

  public partial class App : Application
  {
      // 定義 ServiceProvider
      public IServiceProvider? Services { get; set; }

      public override void Initialize()
      {
          AvaloniaXamlLoader.Load(this);
      }
      public override void OnFrameworkInitializationCompleted()
      {
          // 初始化 DI 容器
          var collection = new ServiceCollection();
          // 註冊 ViewModels
          collection.AddSingleton<MainWindowViewModel>();
          collection.AddSingleton<HomeViewModel>();
          collection.AddSingleton<SettingsViewModel>();
          collection.AddSingleton<AboutViewModel>();

          // 建立 Provider
          Services = collection.BuildServiceProvider();
          if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
          {
              // 解析 MainWindow 並注入 ViewModel
              var mainVm = Services.GetRequiredService<MainWindowViewModel>();
              DisableAvaloniaDataAnnotationValidation();
              desktop.MainWindow = new MainWindow
              {
                  DataContext = mainVm
              };
          }
          base.OnFrameworkInitializationCompleted();
      }
      ...略

public partial class MainWindowViewModel(IServiceProvider services) : ViewModelBase
{
    // ... 內部的程式碼
}

"首頁" => _homeViewModel ??= services.GetRequiredService<HomeViewModel>()

MainWindowViewModel.cs
using System;
using System.Collections.Generic;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using Microsoft.Extensions.DependencyInjection;

namespace AvaloniaSideBarEx.ViewModels;

public partial class MainWindowViewModel(IServiceProvider services) : ViewModelBase
{
    //側邊欄控制
    [ObservableProperty]
    private bool _isSidebarOpen;

    [RelayCommand]
    private void ToggleSidebar()
    {
        IsSidebarOpen = !IsSidebarOpen;
    }

    //側邊欄導航
    private HomeViewModel? _homeViewModel;
    private SettingsViewModel? _settingsViewModel;
    private AboutViewModel? _aboutViewModel;
    public List<string> MenuItems { get; } = ["首頁", "設定", "關於"];

    [ObservableProperty]
    private string? _selectedMenuItem = "首頁";

    [ObservableProperty]
    private ObservableObject? _currentPage = services.GetRequiredService<HomeViewModel>();

    // 這是 CommunityToolkit 自動生成的鉤子方法 (Hook)
    // 當 _selectedMenuItem 改變時，這個函數會被自動呼叫
    partial void OnSelectedMenuItemChanged(string? value)
    {
        // 直接在這裡呼叫你的導航邏輯
        OnMenuSelected();
    }

    [RelayCommand]
    private void OnMenuSelected()
    {
        //Debug.WriteLine($"當前選中：{SelectedMenuItem}");
        Navigate(SelectedMenuItem);
        if (IsSidebarOpen)
        {
            IsSidebarOpen = false;
        }
    }

    private void Navigate(string? target)
    {
        //根據選中的菜單名稱，實例化對應的 ViewModel
        CurrentPage = target switch
        {
            "首頁" => _homeViewModel ??= services.GetRequiredService<HomeViewModel>(), // 如果 _homeViewModel 是 null，則創建新的並賦值
            "設定" => _settingsViewModel ??= services.GetRequiredService<SettingsViewModel>(),
            "關於" => _aboutViewModel ??= services.GetRequiredService<AboutViewModel>(),
            _ => _homeViewModel ??= services.GetRequiredService<HomeViewModel>()
        };
    }
}