ContextMenu IsOpen 属性始终为 false

Question

我有一个 ContextMenu 设置如下的按钮：

<Button
    x:Name="TestButton"
    Click="TestButton_Click">
    <Button.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Sample Menu Item 1" />
            <MenuItem Header="Sample Menu Item 2" />
            <MenuItem Header="Sample Menu Item 3" />
        </ContextMenu>
    </Button.ContextMenu>
</Button>

后面的代码：

private void TestButton_Click(object sender, RoutedEventArgs e)
{
    // This always prints false, even though the contextmenu is currently opened
    System.Console.WriteLine(button.ContextMenu.IsOpen);

    if (sender is Button button)
    {
        button.ContextMenu.Placement = PlacementMode.Bottom;
        button.ContextMenu.PlacementTarget = button;
        button.ContextMenu.StaysOpen = true;
        button.ContextMenu.IsOpen = !button.ContextMenu.IsOpen; // Doesn't work!
    }
}

所以我已将 ContextMenu 设置为单击鼠标即可打开并且有效，但是我想在每次单击按钮时切换 ContextMenu 可见性。为此，我想使用 IsOpen 属性 - 如果当前值为真，则将其设置为假，反之亦然。

我的问题是，即使 IsOpen 属性值在第一次点击时从 false 设置为 true，它始终保持 false在第二次点击时，就像它永远不会被设置一样。

我认为这是关于失去焦点（如果我错了请纠正我）- 那么我怎样才能解决这个问题并将其标记为打开状态，直到发生另一次点击？

Answer 1

试试这个。

private bool _isOpen = false;

private void TestButton_Click(object sender, RoutedEventArgs e)
{
    // This always prints false, even though the contextmenu is currently opened
    //System.Console.WriteLine(button.ContextMenu.IsOpen);

    if (sender is Button button)
    {
        if (_isOpen)
        {
            button.ContextMenu.IsOpen = false;
            _isOpen = false;
        }
        else
        {
            button.ContextMenu.Placement = PlacementMode.Bottom;
            button.ContextMenu.PlacementTarget = button;
            button.ContextMenu.StaysOpen = true;
            _isOpen = true;
            button.ContextMenu.IsOpen = _isOpen;
        }
    }
}

Answer 2

I assume it's about the losing focus ...

是的，ContextMenu 的 StaysOpen 属性没有像您预期的那样工作。当您点击 Button 时，ContextMenu 确实关闭了。

您可以通过使用跟踪 ContextMenu 何时关闭的 DependencyPropertyDescriptor 解决此问题，然后将经过的时间与事件处理程序中的某个常量值进行比较。这应该有效：

private DependencyPropertyDescriptor _dpd;
private DateTime _closeTime;

private void TestButton_Click(object sender, RoutedEventArgs e)
{
    if (sender is Button button)
    {
        button.ContextMenu.Placement = PlacementMode.Bottom;
        button.ContextMenu.PlacementTarget = button;
        button.ContextMenu.IsOpen = !button.ContextMenu.IsOpen && DateTime.UtcNow.Subtract(_closeTime).TotalMilliseconds > 250;

        if (_dpd == null)
        {
            _dpd = DependencyPropertyDescriptor.FromProperty(ContextMenu.IsOpenProperty, typeof(ContextMenu));
            _dpd.AddValueChanged(button.ContextMenu, OnContextMenuClosed);
        }
    }
}

private void OnContextMenuClosed(object sender, EventArgs e) => _closeTime = DateTime.UtcNow;

ContextMenu IsOpen 属性始终为 false

ContextMenu IsOpen property is always false

c#

wpf

contextmenu

ContextMenu IsOpen 属性 始终为 false

ContextMenu IsOpen property is always false

c#

wpf

contextmenu

ContextMenu IsOpen 属性始终为 false