.NET MAUI Windows平台：如何保持Entry hover/点击时的自定义边框

问题场景 #

在MAUI中通过自定义EntryHandler设置Entry的边框粗细为1、边框颜色为红色时，正常状态显示正常，但鼠标hover或点击获取焦点后，边框会恢复默认样式。尝试过绑定焦点事件、全局设置TextControlBorderThemeThickness均无效。

解决思路 #

Windows平台下MAUI的Entry对应原生TextBox控件，其hover、焦点等状态的样式由VisualStateManager管理，直接设置BorderBrush和BorderThickness会被视觉状态的触发器覆盖。需要修改视觉状态中的边框相关设置，或者替换默认样式。

方法一：在EntryHandler中修改VisualState #

直接在自定义Handler映射中，找到TextBox的视觉状态组，覆盖PointerOver（hover）和Focused状态下的边框属性：

Microsoft.Maui.Handlers.EntryHandler.Mapper.AppendToMapping("CustomBorder", (handler, view) =>
{
    if (view is Entry entry)
    {
#if WINDOWS
        var textBox = handler.PlatformView;
        // 设置默认状态边框
        textBox.BorderThickness = new Microsoft.UI.Xaml.Thickness(1);
        var redBrush = new Microsoft.UI.Xaml.Media.SolidColorBrush(Microsoft.Maui.Graphics.Colors.Red.ToWindowsColor());
        textBox.BorderBrush = redBrush;

        // 遍历视觉状态组，修改hover和焦点状态
        var visualStateGroups = Microsoft.UI.Xaml.VisualStateManager.GetVisualStateGroups(textBox);
        foreach (var group in visualStateGroups)
        {
            if (group is Microsoft.UI.Xaml.VisualStateGroup stateGroup && stateGroup.Name == "CommonStates")
            {
                foreach (var state in stateGroup.States)
                {
                    switch (state.Name)
                    {
                        case "PointerOver":
                        case "Focused":
                            state.Setters.Clear();
                            state.Setters.Add(new Microsoft.UI.Xaml.Setter
                            {
                                Property = Microsoft.UI.Xaml.Controls.TextBox.BorderBrushProperty,
                                Value = redBrush
                            });
                            state.Setters.Add(new Microsoft.UI.Xaml.Setter
                            {
                                Property = Microsoft.UI.Xaml.Controls.TextBox.BorderThicknessProperty,
                                Value = new Microsoft.UI.Xaml.Thickness(1)
                            });
                            break;
                    }
                }
            }
        }
#endif
    }
});

方法二：自定义TextBox样式并应用 #

通过自定义完整的TextBox模板，完全控制所有状态下的样式：

1. 在Windows项目的App.xaml中添加自定义样式：

<maui:MauiWinUIApplication.Resources>
    <Style TargetType="TextBox" x:Key="CustomEntryStyle">
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="BorderBrush" Value="Red"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="TextBox">
                    <Grid>
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Normal"/>
                                <VisualState x:Name="PointerOver">
                                    <VisualState.Setters>
                                        <Setter Property="BorderBrush" Value="Red"/>
                                        <Setter Property="BorderThickness" Value="1"/>
                                    </VisualState.Setters>
                                </VisualState>
                                <VisualState x:Name="Focused">
                                    <VisualState.Setters>
                                        <Setter Property="BorderBrush" Value="Red"/>
                                        <Setter Property="BorderThickness" Value="1"/>
                                    </VisualState.Setters>
                                </VisualState>
                                <VisualState x:Name="Disabled">
                                    <VisualState.Setters>
                                        <Setter Property="BorderBrush" Value="Gray"/>
                                    </VisualState.Setters>
                                </VisualState>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Border x:Name="BorderElement" 
                                BorderThickness="{TemplateBinding BorderThickness}"
                                BorderBrush="{TemplateBinding BorderBrush}"
                                Background="{TemplateBinding Background}">
                            <ContentPresenter x:Name="ContentPresenter"
                                              Margin="{TemplateBinding Padding}"
                                              HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                              VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                                              Content="{TemplateBinding Text}"
                                              ContentTemplate="{TemplateBinding ContentTemplate}"/>
                        </Border>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</maui:MauiWinUIApplication.Resources>

2. 在EntryHandler中应用该样式：

Microsoft.Maui.Handlers.EntryHandler.Mapper.AppendToMapping("CustomBorder", (handler, view) =>
{
    if (view is Entry)
    {
#if WINDOWS
        var textBox = handler.PlatformView;
        textBox.Style = (Microsoft.UI.Xaml.Style)textBox.Resources["CustomEntryStyle"];
#endif
    }
});

说明 #

• 方法一无需重新定义控件模板，仅修改目标状态的属性，适合快速调整；
• 方法二通过自定义模板实现完全样式控制，可按需扩展其他视觉效果（如背景色、字体样式等）。

内容的提问来源于stack exchange，提问作者cera36