鼠标悬停、可见性和控件尺寸

Question

WPF:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <local:BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter"
                                            True="Visible"
                                            False="Collapsed" />
    </Window.Resources>

    <Canvas>
        <StackPanel Canvas.Left="100" Canvas.Top="100" Width="200" Height="100">
            <ListBox>
                <ListBoxItem>one</ListBoxItem>
                <ListBoxItem>two</ListBoxItem>
                <ListBoxItem>three</ListBoxItem>
            </ListBox>
            <StackPanel Orientation="Horizontal"
                        Visibility="{Binding
                                     RelativeSource={RelativeSource AncestorType={x:Type StackPanel}},
                                     Path=IsMouseOver,
                                     Converter={StaticResource BooleanToVisibilityConverter}}">
                <Button>one</Button>
                <Button>two</Button>
                <Button>three</Button>
            </StackPanel>
        </StackPanel>
    </Canvas>
</Window>

代码：

public abstract class BooleanConverter<T> : IValueConverter
{
    public BooleanConverter(T trueValue, T falseValue)
    {
        True = trueValue;
        False = falseValue;
    }

    public T True { get; set; }
    public T False { get; set; }

    public virtual object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is bool && ((bool)value) ? True : False;
    }

    public virtual object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is T && EqualityComparer<T>.Default.Equals((T)value, True);
    }
}

public class BooleanToVisibilityConverter : BooleanConverter<Visibility>
{
    public BooleanToVisibilityConverter()
        : base(Visibility.Visible, Visibility.Collapsed)
    { }
}

当鼠标悬停在ListBox上方时，按钮按预期显示。如果鼠标移到ListBox右侧下方，则按钮消失。为什么那里的IsMouseOver是false？当内部StackPanel的Visibility属性从Collapsed更改为Visible时，外部StackPanel的高度不应该增加吗？

如果您想尝试，请查看此项目：http://dl.dropbox.com/u/4220513/WpfApplication1.zip

- epalm

Answer 1

您需要将StackPanel（外部）的背景设置为透明，以便检测鼠标悬停。如果背景为空，就像您的示例一样，命中测试将失败。

- Wallstreet Programmer

Answer 2

为你的StackPanel使用背景，例如<StackPanel Background="Transparent">...

- Navid Rahmani