增加ViewModelBase 生命周期控制View

Source/Store.Management.Framework/Controls/ConfirmDialog.cs

@@ -32,7 +32,7 @@ public static class IDialogServiceExtension
 /// <summary>
 /// 确定取消对话框 ViewModel
 /// </summary>
-public class ConfirmDialogViewModel : BindableBase, IDialogAware
+public class ConfirmDialogViewModel : ViewModelBase, IDialogAware
 {
 	public ConfirmDialogViewModel()
 	{
@@ -286,4 +286,4 @@ public abstract class ConfirmDialogViewModel<TParameter, TResult> : ConfirmDialo
 //public abstract class ConfirmDialogParameterViewModel : ConfirmDialogViewModel<ConfirmDialogParameterViewModel.Parameter>
 //{
 //	public abstract class Parameter;
-//}
+//}

Source/Store.Management.Framework/Controls/ViewLifecycle.cs

@@ -0,0 +1,85 @@
+using Prism.Services.Dialogs;
+using System.ComponentModel;
+using System.Windows;
+using System.Windows.Controls;
+
+namespace Store.Management.Framework.Controls;
+
+internal static class ViewLifecycle
+{
+    // 卸载时 DataContext 可能已改变，记录实际收到 OnLoaded 的实例。
+    private static readonly DependencyProperty LoadedViewModelProperty =
+        DependencyProperty.RegisterAttached("LoadedViewModel", typeof(ViewModelBase), typeof(ViewLifecycle));
+
+    internal static void Register()
+    {
+        foreach (Type type in new[] { typeof(UserControl), typeof(Window) })
+        {
+            FrameworkElement.DataContextProperty.OverrideMetadata(type,
+                new FrameworkPropertyMetadata(null, OnDataContextChanged));
+        }
+    }
+
+    private static void OnDataContextChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
+    {
+        if (sender is Window window)
+        {
+            if (e.OldValue is ViewModelBase)
+            {
+                window.Activated -= OnActivated;
+                window.Deactivated -= OnDeactivated;
+                window.Closing -= OnClosing;
+                window.Closed -= OnClosed;
+            }
+            if (e.NewValue is ViewModelBase)
+            {
+                window.Activated += OnActivated;
+                window.Deactivated += OnDeactivated;
+                window.Closing += OnClosing;
+                window.Closed += OnClosed;
+            }
+            if (window is IDialogWindow) return; // Prism 弹窗由内容页接收加载与卸载。
+        }
+        var view = (FrameworkElement)sender;
+        if (e.OldValue is ViewModelBase)
+        {
+            view.Loaded -= OnLoaded;
+            view.Unloaded -= OnUnloaded;
+        }
+        if (e.NewValue is ViewModelBase)
+        {
+            view.Loaded += OnLoaded;
+            view.Unloaded += OnUnloaded;
+        }
+        if (view.IsLoaded || view.GetValue(LoadedViewModelProperty) != null)
+            UpdateViewModel(view);
+    }
+
+    private static void OnLoaded(object sender, RoutedEventArgs e)
+        => UpdateViewModel((FrameworkElement)sender);
+
+    private static void OnActivated(object? sender, EventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnActivated();
+    private static void OnDeactivated(object? sender, EventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnDeactivated();
+    private static void OnClosing(object? sender, CancelEventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnClosing(e);
+    private static void OnClosed(object? sender, EventArgs e) => (((Window)sender!).DataContext as ViewModelBase)?.OnClosed();
+
+    private static void UpdateViewModel(FrameworkElement view)
+    {
+        // 共享父级 DataContext 的页眉、导航栏等子控件不拥有页面生命周期。
+        var source = DependencyPropertyHelper.GetValueSource(view, FrameworkElement.DataContextProperty);
+        var next = source.BaseValueSource == BaseValueSource.Inherited ? null : view.DataContext as ViewModelBase;
+        var previous = (ViewModelBase?)view.GetValue(LoadedViewModelProperty);
+        if (ReferenceEquals(previous, next)) return;
+        view.SetValue(LoadedViewModelProperty, next);
+        previous?.OnUnloaded();
+        next?.OnLoaded();
+    }
+
+    private static void OnUnloaded(object sender, RoutedEventArgs e)
+    {
+        var view = (FrameworkElement)sender;
+        var previous = (ViewModelBase?)view.GetValue(LoadedViewModelProperty);
+        view.ClearValue(LoadedViewModelProperty);
+        previous?.OnUnloaded();
+    }
+}

Source/Store.Management.Framework/Controls/ViewModelBase.cs

@@ -0,0 +1,14 @@
+using Prism.Mvvm;
+using System.ComponentModel;
+
+namespace Store.Management.Framework.Controls;
+
+public abstract class ViewModelBase : BindableBase
+{
+    protected internal virtual void OnLoaded() { }
+    protected internal virtual void OnUnloaded() { }
+    protected internal virtual void OnActivated() { }
+    protected internal virtual void OnDeactivated() { }
+    protected internal virtual void OnClosing(CancelEventArgs e) { }
+    protected internal virtual void OnClosed() { }
+}

Source/Store.Management.Framework/FrameworkApplication.cs

@@ -26,6 +26,8 @@ public abstract class FrameworkApplication : PrismApplication
 	private IStatusBarService StatusBarService;
 	private IMessageBoxService MessageBoxService;
 	private static bool FatalShutdown = false;
+	static FrameworkApplication() => Controls.ViewLifecycle.Register();
+
 	protected FrameworkApplication()
 	{
 		DispatcherUnhandledException += OnDispatcherUnhandledException;