c# - KeyDown、KeyUp 和 KeyPressed 不会在托管 WPF 控件的 WinForms 应用程序上触发

Question

我在 C# 中针对 .NET 4.5 做了一个测试 WinForms APP。该应用程序使用 System.Windows.Controls.Canvas 在黑色背景上绘制一个白色矩形。

我遇到了与键盘相关的事件。

完整源码如下

using System;
using System.Drawing;
using System.Windows.Controls;
using System.Windows.Forms;
using System.Windows.Forms.Integration;
using Brushes = System.Windows.Media.Brushes;
using Panel = System.Windows.Forms.Panel;
using Rectangle = System.Windows.Shapes.Rectangle;
using UserControl = System.Windows.Controls.UserControl;

namespace WpfHostApp
{
    internal static class Program
    {
        /// <summary>
        /// Entry point.
        /// </summary>
        [STAThread]
        private static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            var panel = new Panel { Dock = DockStyle.Fill };

            var form = new Form {Size = new Size(800, 600), Text = "WPF Host Form"};
            form.Controls.Add(panel);

            var rectangle = new Rectangle {Fill = Brushes.White, Width = 100, Height = 100};

            var canvas = new Canvas {Background = Brushes.Black};
            canvas.Children.Add(rectangle);

            var userControl = new UserControl {Content = canvas};

            var elementHost = new ElementHost {Child = userControl, Dock = DockStyle.Fill};

            panel.Controls.Add(elementHost);

            form.KeyDown += (sender, args) => MessageBox.Show("Key pressed!");

            Application.Run(form);
        }
    }
}

form.KeyDown 事件不会触发(实际上 form.Key* 不会触发)，但如果我注释行 panel.Controls .Add(elementHost); 事件触发但显然没有绘制 Canvas 。

我看不出上面的示例代码中有什么会导致这个问题。罪魁祸首是什么？

编辑:

我已经添加了一个用于订阅 KeyDown 的递归函数...没有结果

在 Main() 中，在 form.KeyDown 之后:

foreach (Control control in form.Controls)
{
    SuscribeKeyDown(control);
}

SuscribeKeyDown(Control 控件) 函数:

private static void SuscribeKeyDown(Control control)
{
    control.KeyDown += (sender, args) => MessageBox.Show("Key pressed!");
    foreach (Control controlNested in control.Controls)
    {
        SuscribeKeyDown(controlNested);
    }
}

Answer 1

将 canvas.Focusable 设置为 true 并捕获 Canvas 的 KeyDown 事件:

[STAThread]
private static void Main()
{
    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);

    var panel = new System.Windows.Forms.Panel { Dock = DockStyle.Fill };

    var form = new Form { Size = new Size(800, 600), Text = "WPF Host Form" };
    form.Controls.Add(panel);

    var rectangle = new System.Windows.Shapes.Rectangle { Fill = System.Windows.Media.Brushes.White, Width = 100, Height = 100 };

    var canvas = new Canvas { Background = System.Windows.Media.Brushes.Black,
        Focusable = true};
    canvas.Children.Add(rectangle);

    var userControl = new System.Windows.Controls.UserControl { Content = canvas };

    var elementHost = new ElementHost { Child = userControl, Dock = DockStyle.Fill };

    panel.Controls.Add(elementHost);

    // form.KeyDown += (sender, args) => MessageBox.Show("Key pressed!");
    canvas.KeyDown += (sender, args) => MessageBox.Show("Key pressed!");

    Application.Run(form);
}