跟进Jobi Joy的回答,你不能直接在Xaml中使用OneWayToSource
绑定只读依赖属性ActualHeight,但有许多解决方法。我最喜欢的是Kent Boogaart在这个问题中提供的答案。它使用一个附加行为来监听任何FrameworkElement
的SizeChanged
事件,并相应地更新两个附加属性,即Width和Height。
例如,对于TextBlock
,可以使用ActualHeight
将其推入到ViewModel的Height属性中。
<TextBlock local:ActualSizeBehavior.ObserveActualSize="True"
local:ActualSizeBehavior.ActualHeight="{Binding Path=Height,
Mode=OneWayToSource}"
.../>
同步两个ScrollViewers
您可以使用DependencyPropertyDescriptor
来监听VerticalOffsetProperty
属性的更改,或者订阅ScrollChanged
事件并调用ScrollToVerticalOffset
。示例:
Xaml
<ScrollViewer Name="scrollViewerLeft"
ScrollChanged="scrollViewerLeft_ScrollChanged">
<ScrollViewer Name="scrollViewerRight"
ScrollChanged="scrollViewerRight_ScrollChanged">
代码后置事件处理程序
private void scrollViewerLeft_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
scrollViewerRight.ScrollToVerticalOffset(scrollViewerLeft.VerticalOffset);
}
private void scrollViewerRight_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
scrollViewerLeft.ScrollToVerticalOffset(scrollViewerRight.VerticalOffset);
}
实际大小行为
public static class ActualSizeBehavior
{
public static readonly DependencyProperty ActualSizeProperty =
DependencyProperty.RegisterAttached("ActualSize",
typeof(bool),
typeof(ActualSizeBehavior),
new UIPropertyMetadata(false, OnActualSizeChanged));
public static bool GetActualSize(DependencyObject obj)
{
return (bool)obj.GetValue(ActualSizeProperty);
}
public static void SetActualSize(DependencyObject obj, bool value)
{
obj.SetValue(ActualSizeProperty, value);
}
private static void OnActualSizeChanged(DependencyObject dpo,
DependencyPropertyChangedEventArgs e)
{
FrameworkElement element = dpo as FrameworkElement;
if ((bool)e.NewValue == true)
{
element.SizeChanged += element_SizeChanged;
}
else
{
element.SizeChanged -= element_SizeChanged;
}
}
static void element_SizeChanged(object sender, SizeChangedEventArgs e)
{
FrameworkElement element = sender as FrameworkElement;
SetActualWidth(element, element.ActualWidth);
SetActualHeight(element, element.ActualHeight);
}
private static readonly DependencyProperty ActualWidthProperty =
DependencyProperty.RegisterAttached("ActualWidth", typeof(double), typeof(ActualSizeBehavior));
public static void SetActualWidth(DependencyObject element, double value)
{
element.SetValue(ActualWidthProperty, value);
}
public static double GetActualWidth(DependencyObject element)
{
return (double)element.GetValue(ActualWidthProperty);
}
private static readonly DependencyProperty ActualHeightProperty =
DependencyProperty.RegisterAttached("ActualHeight", typeof(double), typeof(ActualSizeBehavior));
public static void SetActualHeight(DependencyObject element, double value)
{
element.SetValue(ActualHeightProperty, value);
}
public static double GetActualHeight(DependencyObject element)
{
return (double)element.GetValue(ActualHeightProperty);
}
}