Question

我在wpf usercontrol中有几个Expander控件。当我扩展扩展器时，我想自动滚动，以便在可能的情况下可以看到整个扩展器。或至少所以新扩展的扩展器尽可能“向上”。

当我现在在底部时，它会在窗口边缘下方展开，我无法在扩展器中看到控件而无需手动滚动它们。

我想从XAML而不是代码隐藏中做到这一点。有可能吗？我正在使用MVVM模式。

我假设我必须在扩展器上使用触发器，但我不知道如何预先形成BringToView功能

高级布局：

grep

Answer 1

处理Expanded事件并调用BringIntoView()方法：

private void Expander_Expanded(object sender, RoutedEventArgs e)
{
    ((Expander)sender).BringIntoView();
}

请注意，您应该使用StackPanel或其他内容而不是Grid：

<ScrollViewer Name="sv">
    <UserControl>
        <StackPanel>
            <Expander>
                <Border Height="1000" Background="Red"/>
            </Expander>
            <Expander>
                <Border Height="1000" Background="Blue"/>
            </Expander>
            <Expander Expanded="Expander_Expanded">
                <Border Height="1000" Background="Green"/>
            </Expander>
        </StackPanel>
    </UserControl>
</ScrollViewer>

修改

您可能想要使用此附加属性：

public static class ExpanderEx { public static readonly DependencyProperty BringIntoViewOnExpandProperty = DependencyProperty.RegisterAttached("BringIntoViewOnExpand", typeof(bool), typeof(ExpanderEx), new PropertyMetadata(false, OnBringIntoViewOnExpandChanged)); public static bool GetBringIntoViewOnExpand(DependencyObject obj) { return (bool)obj.GetValue(BringIntoViewOnExpandProperty); } public static void SetBringIntoViewOnExpand(DependencyObject obj, bool value) { obj.SetValue(BringIntoViewOnExpandProperty, value); } private static void OnBringIntoViewOnExpandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { if (d is Expander) { Expander obj = (Expander)d; if (e.NewValue.Equals(true)) obj.Expanded += Obj_Expanded; else obj.Expanded -= Obj_Expanded; } } private static void Obj_Expanded(object sender, RoutedEventArgs e) { ((Expander)sender).BringIntoView(); } }

和Xaml：

<ScrollViewer Name="sv"> <UserControl> <StackPanel> <Expander local:ExpanderEx.BringIntoViewOnExpand="True"> <Border Height="1000" Background="Red"/> </Expander> <Expander local:ExpanderEx.BringIntoViewOnExpand="True"> <Border Height="1000" Background="Blue"/> </Expander> <Expander local:ExpanderEx.BringIntoViewOnExpand="True"> <Border Height="1000" Background="Green"/> </Expander> </StackPanel> </UserControl> </ScrollViewer>

Answer 2

为其Expander事件提供每个Expanded此处理程序。看起来您正在UserControl内定义扩展器，因此转到ScrollViewer是个问题。一种选择是为您的UserControl提供ScrollViewer依赖项属性，所有者将绑定到包含它的任何ScrollViewer。我不喜欢那样。相反，我写了一个辅助函数，它查找可视树并找到最近的父ScrollViewer，如果有的话。

private void Expander_Expanded(object sender, RoutedEventArgs e)
{
    var scrollViewer = GetNearestScrollViewerParent();

    if (scrollViewer == null)
        return;

    var expander = (Expander)sender;

    UIElement container = VisualTreeHelper.GetParent(expander) as UIElement;
    Point relativeLocation = expander.TranslatePoint(new Point(0, 0), container);

    scrollViewer.ScrollToVerticalOffset(relativeLocation.Y);
}

public ScrollViewer GetNearestScrollViewerParent()
{
    for (var parent = VisualTreeHelper.GetParent(this); 
         parent != null; 
         parent = VisualTreeHelper.GetParent(parent))
    {
        if (parent is ScrollViewer)
            return parent as ScrollViewer;
    }

    return null;
}

XAML：

<UserControl.Resources>
    <Style TargetType="Expander" BasedOn="{StaticResource {x:Type Expander}}">
        <EventSetter Event="Expanded" Handler="Expander_Expanded" />
    </Style>
</UserControl.Resources>

如何滚动以便在展开扩展器后可以看到控件

2 个答案: