扩展WPF工具包ColorPicker：如何使用ContextMenu事件？ [英] Extended WPF Toolkit ColorPicker: How to use ContextMenu events?

问题描述

情况：我在Canvas中有ColorPicker。

目标：使用ContextMenu的事件。

问题：ContextMenuOpening事件不会触发和ContextMenu.Opened事件结果错误很多其他事件。

注意：

1.我的意思是ContextMenu的下拉菜单，但我不知道ContextMenu究竟是什么。

2.它是扩展WPF工具包并使用它你需要添加扩展dll。

代码：

Situation: I have ColorPicker in Canvas.
Goal: To use events of ContextMenu.
Problem: The ContextMenuOpening event doesn't fire and the ContextMenu.Opened event results error as many other events.
Notes:
1. I mean a drop menu by "ContextMenu", but i don't know what "ContextMenu" exactly is.
2. It is Extended WPF Toolkit and to use it you need to add extended dlls.
Code:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        canvas.Background = Brushes.Black;
        this.Content = canvas;

        ColorPicker colorpicker = new ColorPicker();
        canvas.Children.Add(colorpicker);
        colorpicker.ContextMenuOpening += delegate { System.Windows.MessageBox.Show("a"); }; // Doesn't fire.
        colorpicker.ContextMenu.Opened += delegate { System.Windows.MessageBox.Show("a"); }; // Error: Object reference not set to an instance of an object.
    }

    Canvas canvas = new Canvas();
}

推荐答案

上下文菜单是右键单击某些内容时出现的菜单。颜色选择器的弹出窗口不是上下文菜单，这就是 ContextMenuOpening 事件不会触发的原因。除非你明确设置 ContextMenu 属性，否则它将返回 null ，这就是为什么你得到一个 NullReferenceException 当您尝试订阅它的已打开的事件时。



查看源代码 [ ColorPicker 控件，title =新窗口> ^ ]，当弹出窗口打开时，它似乎不会触发事件。您最好的选择可能是订阅 IsOpen 属性的属性更改事件：

A context menu is the menu that appears when you right-click on something. The color-picker's popup isn't a context menu, which is why the ContextMenuOpening event doesn't fire. And unless you've explicitly set the ContextMenu property, it will return null, which is why you're getting a NullReferenceException when you try to subscribe to it's Opened event.

Looking at the source code[^] for the ColorPicker control, it doesn't seem to fire an event when the popup opens. Your best bet is probably to subscribe to the property change event for the IsOpen property:

DependencyPropertyDescriptor descriptor = DependencyPropertyDescriptor.FromProperty(ColorPicker.IsOpenProperty, typeof(ColorPicker));
descriptor.AddValueChanged(colorpicker, delegate 
{ 
    if (colorpicker.IsOpen)
    {
        // Do something here...
    }
});

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