功能说明

一个用于 WPF TextBox 的附加行为，实现 TextBox 与 Popup 控件的联动效果：

1. 自动弹出/关闭：

   • TextBox 获得焦点时自动打开关联的 Popup
   • TextBox 失去焦点时自动关闭关联的 Popup

2. 点击外部关闭：

   • 点击 TextBox 和 Popup 外部区域时关闭 Popup

3. 焦点状态处理：

   • 解决 TextBox 保持焦点但 Popup 关闭后的重新触发问题

核心代码解析

        // 解决在 TextBox 外其他地方点击时，仅关闭 Popup，但是 TextBox 还是 Focused 状态，导致再点击进来时不会触发弹出 Popup
        private void AssociatedObject_PreviewMouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e) {
            if (AssociatedObject?.IsFocused == true && Popup != null && !Popup.IsOpen) {
                Popup.IsOpen = true;
            }
        }

        private void Window_PreviewMouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e) {
            if (Popup == null || !Popup.IsOpen || AssociatedObject == null || _parentWindow == null) { return; }

            Point position = e.GetPosition(null);
            Rect textBoxRect = new Rect(AssociatedObject.TranslatePoint(new Point(0, 0), _parentWindow), AssociatedObject.RenderSize);
            Rect popupRect = new Rect(Popup.TranslatePoint(new Point(0, 0), _parentWindow), Popup.RenderSize);
            if (!textBoxRect.Contains(position) && !popupRect.Contains(position)) {
                Popup.SetCurrentValue(Popup.IsOpenProperty, false);
            }
        }

使用方法

<TextBox x:Name="SearchBox"
         Width="400"
         Height="30"
         Text="{Binding ElementName=list, Path=SelectedItem.Content}">
    <hc:Interaction.Behaviors>
        <controls:TextBoxPopupBehavior Popup="{Binding ElementName=SuggestionsPopup}" />
    </hc:Interaction.Behaviors>
</TextBox>

<Popup x:Name="SuggestionsPopup"
       Placement="Bottom"
       PlacementTarget="{Binding ElementName=SearchBox}"
       StaysOpen="True">
    <Border Background="White"
            BorderBrush="Gray"
            BorderThickness="1">
        <ListBox x:Name="list"
                 Width="200"
                 Height="150">
            <ListBoxItem>选项1</ListBoxItem>
            <ListBoxItem>选项2</ListBoxItem>
            <ListBoxItem>选项3</ListBoxItem>
        </ListBox>
    </Border>
</Popup>

注意事项

• 确保 Popup 的 PlacementTarget 正确绑定
• 在 MVVM 模式下可通过绑定设置 Popup 属性
• 控件卸载时会自动清理事件监听