当我有一个按钮时，C＃keydown无法正常工作

问题描述

我在互联网上看到了问题，解决方案是将KeyPreview设置为true。我试过了，它仍然没有用。为什么当我按下其中一个箭头（向下，向上，向左或向右）时，标签仍然没有显示？



更新：

谢谢你的回答Peter Vegter，但它仍然不起作用。

为了清楚说明：常规字母确实工作并使标签显示出来。问题是箭头（向下，向上，向左或向右）不能工作。

我想我知道为什么 - 焦点在按钮上而不是在表格上。

我在网上搜索过这个，我发现我需要将KeyPreview设置为true。我做了它，当我按下箭头时，它仍然没有显示标签，只有当我按下字母时。

如果我删除按钮，箭头做工作。



我尝试了什么：

I saw in the internet the problem, and the solution was setting the "KeyPreview" to "true". I have tried it, and it still didn't work. Why when I press one of the arrows (down, up, left or right) the lable still doesn't show off?

Updated:
Thank you for your answer Peter Vegter, but It still doesn't work.
To make this clear: regular letter does work and makes the label show off. The thing is that the arrows (down, up, left or right) don't work.
I think I know why - the "focus" is on the the button and not on the form.
I searched for this in the internet, and I found that I need to make the "KeyPreview" set as "true". I did it, and still it doesn't show the label when I press the arrows, only when I press letters.
If i remove the button, the arrows do work.

What I have tried:

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            label1.Visible = false;
            this.KeyPreview = true;
            this.KeyDown += Form1_KeyDown;
        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            label1.Visible = true;
        }

        private void button1_Click(object sender, EventArgs e)
        {

        }
    }

推荐答案

public Form1()
{
    InitializeComponent();
    label1.Visible = false;
}

protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
    switch (keyData)
    {
        case Keys.Left: // left arrow key
            label1.Visible = true;
            return true;

        case Keys.Right: // right arrow key
            label1.Visible = true;
            return true;

        // etc.
    }
    return base.ProcessCmdKey(ref msg, keyData);
}

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