C# WPF OnMouseEnter 和 OnMouseLeave 循环

Question

我有 WPF UI 元素，当鼠标光标进入此元素时应隐藏，当鼠标光标离开此元素时可见。为此，我使用事件OnMouseEnter 和OnMouseLeave，如下所示：

private void TextBlock_MouseEnter(object sender, MouseEventArgs e)
{
    (e.Source as UIElement).Visibility = Visibility.Hidden;
}

private void TextBlock_MouseLeave(object sender, MouseEventArgs e)
{
    (e.Source as UIElement).Visibility = Visibility.Visible;
}

（以下代码来自https://docs.microsoft.com/en-us/dotnet/api/system.windows.controls.panel.zindex?view=netframework-4.8）

<Canvas>
            <Rectangle Canvas.ZIndex="1" Width="100" Height="100" Canvas.Top="100" Canvas.Left="100" Fill="blue" MouseEnter="TextBlock_MouseEnter" MouseLeave="TextBlock_MouseLeave"/>
            <Rectangle Canvas.ZIndex="2" Width="100" Height="100" Canvas.Top="150" Canvas.Left="150" Fill="yellow" MouseEnter="TextBlock_MouseEnter" MouseLeave="TextBlock_MouseLeave"/>
            <Rectangle Canvas.ZIndex="3" Width="100" Height="100" Canvas.Top="200" Canvas.Left="200" Fill="green" MouseEnter="TextBlock_MouseEnter" MouseLeave="TextBlock_MouseLeave"/>

            <!-- Reverse the order to illustrate z-index property -->

            <Rectangle Canvas.ZIndex="3" Width="100" Height="100" Canvas.Top="300" Canvas.Left="200" Fill="green" MouseEnter="TextBlock_MouseEnter" MouseLeave="TextBlock_MouseLeave"/>
            <Rectangle Canvas.ZIndex="2" Width="100" Height="100" Canvas.Top="350" Canvas.Left="150" Fill="yellow" MouseEnter="TextBlock_MouseEnter" MouseLeave="TextBlock_MouseLeave"/>
            <Rectangle Canvas.ZIndex="1" Width="100" Height="100" Canvas.Top="400" Canvas.Left="100" Fill="blue" MouseEnter="TextBlock_MouseEnter" MouseLeave="TextBlock_MouseLeave"/>
        </Canvas>

但是当我运行程序并将光标悬停在元素上时，it starts to flicker and eat up quite a lot of CPU resources.

调试显示当我将光标悬停在元素上时，events loops 直到我将光标移出元素。

我看到this article，但我不明白那里附上的解决方案。

我需要做些什么来防止这些事件循环？

Answer 1

当您将 UIElement 的 Visibility 更改为 Hidden 时，您实际上触发了 MouseLeave 事件，因为现在在其后面的元素上执行了鼠标点击测试。然后运行您的事件处理程序，它将 Visibility 设置为 Visible，然后触发 MouseEnter 事件。因此闪烁。

解决这个问题的一个想法是使用不透明度而不是可见性。试试：

private void TextBlock_MouseEnter(object sender, MouseEventArgs e)
{
  (e.Source as UIElement).Opacity = 0;
}

private void TextBlock_MouseLeave(object sender, MouseEventArgs e)
{
  (e.Source as UIElement).Opacity = 1;
}

Answer 2

你可能会因为重复设置相同的值而导致“绘画事件”，试试这个，看看你是否满意

private void TextBlock_MouseEnter(object sender, MouseEventArgs e)
{
   if(e.Source is UIElement element && element.Visibility != Visibility.Hidden )
   {
     element.Visibility = Visibility.Hidden;
   }   
}