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c# - 覆盖默认的 ComboBoxItem 颜色

问题描述

这可以覆盖 Xamarin Forms WPF 应用程序中的 ComboBoxItem 背景颜色，但不是很优雅，因为我必须在自定义渲染器中手动将模板应用到 ComboBoxItems：

Application.Resources 中的 App.xaml：

    <ControlTemplate TargetType="{x:Type ComboBoxItem}" x:Key="CustomComboBoxItem">
        <Border BorderThickness="{TemplateBinding Border.BorderThickness}" Padding="{TemplateBinding Control.Padding}" BorderBrush="{TemplateBinding Border.BorderBrush}" Background="{TemplateBinding Panel.Background}" Name="Bd" SnapsToDevicePixels="True">
            <ContentPresenter Content="{TemplateBinding ContentControl.Content}" ContentTemplate="{TemplateBinding ContentControl.ContentTemplate}" ContentStringFormat="{TemplateBinding ContentControl.ContentStringFormat}" HorizontalAlignment="{TemplateBinding Control.HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding Control.VerticalContentAlignment}" SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}" />
        </Border>
        <ControlTemplate.Triggers>
              ... All the regular triggers here override with new colors ...
        </ControlTemplate.Triggers>
    </ControlTemplate>

    <Style TargetType="{x:Type ComboBoxItem}">
        <Setter Property='OverridesDefaultStyle' Value='True'/>
        <Setter Property="Template" Value="{StaticResource CustomComboBoxItem}">
        </Setter>
    </Style>

在自定义 PickerRenderer 中：

    protected override void UpdateNativeWidget()
    {
        base.UpdateNativeWidget();
        var c = Control;
        if (p == null)
        {
            template = System.Windows.Application.Current.Resources["CustomComboBoxItem"] as System.Windows.Controls.ControlTemplate;
            ItemsPresenter presenter = GetVisualChild<ItemsPresenter>(c);
            Popup p = VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(c, 0), 0) as Popup;
            var a = (((((p.Child) as Decorator).Child as Border).Child as ScrollViewer).Content as System.Windows.Controls.Grid).Children;
            presenter = a[1] as ItemsPresenter;
            this.p = presenter;
            this.p.Loaded += Presenter_Loaded;
        }
    }

    ItemsPresenter p;
    ComboBoxItem[] items;
    System.Windows.Controls.ControlTemplate template;

    private void Presenter_Loaded(object sender, RoutedEventArgs e)
    {
        items = new ComboBoxItem[Control.ItemContainerGenerator.Items.Count];
        for(int i=0;i<items.Length;i++)
        {
            items[i] = Control.ItemContainerGenerator.ContainerFromIndex(i) as ComboBoxItem;
            if (template != null)
            {
                items[i].Template = template;
            }
        }
    }

我不能执行以下操作，否则我会得到以下异常：

ArgumentException：已添加项目。字典中的键：'System.Windows.Controls.ComboBoxItem' 添加的键：'System.Windows.Controls.ComboBoxItem'

    <ControlTemplate TargetType="{x:Type ComboBoxItem}" x:Key="{x:Type ComboBoxItem}">
    </ControlTemplate>

或者这个，默认值不会被覆盖：

    <ControlTemplate TargetType="{x:Type ComboBoxItem}" x:Key="CustomComboBoxItem">
    </ControlTemplate>

    <Style TargetType="{x:Type ComboBoxItem}" x:Key="{x:Type ComboBoxItem}">
        <Setter Property='OverridesDefaultStyle' Value='True'/>
        <Setter Property="Template" Value="{StaticResource CustomComboBoxItem}">
        </Setter>
    </Style>

有没有更简单、更优雅的方式来做我想做的事情？

标签： c#wpfxamlxamarin

解决方案

如果您想将整个应用程序中的默认comBoxItem 模板设置为customComboxItem。您只需将样式资源放在 app.xaml 中。

<Application.Resources>
<Style TargetType="{x:Type ComboBoxItem}" x:Key="{x:Type ComboBoxItem}">
    <Setter Property='OverridesDefaultStyle' Value='True'/>
    <Setter Property="Template" Value="{StaticResource CustomComboBoxItem}">
    </Setter>
</Style>
</Application.Resources>

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