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