Question

<Grid.RowDefinitions>
            <RowDefinition Height="10"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="240"/>
</Grid.RowDefinitions>

这是我的用户控制器的行定义。我需要将第二行的高度设置为我的Viewmodel。我怎么能得到它？

谢谢。

Answer 1

Kent Boogaart写了附加属性来观察元素的大小：

https://stackoverflow.com/a/1083733/4049478

这可能是使用MVVM时的最佳解决方案

观察者适应了你的问题（非常便宜的解决方案，但仍然是一个解决方案）：

public class RowDefinitionObserver {

    public static readonly DependencyProperty ObserveRowProperty = DependencyProperty.RegisterAttached(
        "ObserveRow",
        typeof(bool),
        typeof(RowDefinitionObserver),
        new FrameworkPropertyMetadata(OnObserveChanged));

    public static readonly DependencyProperty ObservedRowHeightProperty = DependencyProperty.RegisterAttached(
        "ObservedRowHeight",
        typeof(double),
        typeof(RowDefinitionObserver));

    public static bool GetObserveRow(FrameworkElement frameworkElement) {
        return (bool)frameworkElement.GetValue(ObserveRowProperty);
    }

    public static void SetObserveRow(FrameworkElement frameworkElement, bool observe) {
        frameworkElement.SetValue(ObserveRowProperty, observe);
    }

    public static double GetObservedRowHeight(FrameworkElement frameworkElement) {
        return (double)frameworkElement.GetValue(ObservedRowHeightProperty);
    }

    public static void SetObservedRowHeight(FrameworkElement frameworkElement, double observedHeight) {
        frameworkElement.SetValue(ObservedRowHeightProperty, observedHeight);
    }

    private static void OnObserveChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e) {
        var frameworkElement = (FrameworkElement)dependencyObject;

        if ((bool)e.NewValue) {
            frameworkElement.SizeChanged += OnFrameworkElementSizeChanged;
            UpdateObservedSizesForFrameworkElement(frameworkElement);
        } else {
            frameworkElement.SizeChanged -= OnFrameworkElementSizeChanged;
        }
    }

    private static void OnFrameworkElementSizeChanged(object sender, SizeChangedEventArgs e) {
        UpdateObservedSizesForFrameworkElement((FrameworkElement)sender);
    }

    private static void UpdateObservedSizesForFrameworkElement(FrameworkElement frameworkElement) {
        Grid g = frameworkElement as Grid;
        if (g != null) {
            if (g.RowDefinitions.Count > 1) {
                SetObservedRowHeight(g, g.RowDefinitions[1].ActualHeight);
            }
        }
    }
}

用法：

<Grid attachedProperties:RowDefinitionObserver.ObserveRow="True"
      attachedProperties:RowDefinitionObserver.ObservedRowHeight="{Binding RowHeight, Mode=OneWayToSource}"><!--RowHeight is a double Property in your ViewModel-->
    <Grid.RowDefinitions>
        <RowDefinition Height="10"/>
        <RowDefinition Height="*"/>
        <RowDefinition Height="240"/>
    </Grid.RowDefinitions>
    <Grid/>
    <Grid Grid.Row="1" Background="Red"/>
    <Grid Grid.Row="2"/>
</Grid>

为了使其适应性，您必须为RowDefinition的索引添加DP

动态获取rowdefinition WPF MVVM的高度

1 个答案: