如何无休止地检查是否按下了键？

Question

我正在制作一个小程序，显示 numlock 或 capslock 是打开还是关闭（因为我的笔记本电脑没有这些 LED，所以我想制作这样的东西会很有趣）。我想要实现的是，无论是否按下键，文本都会改变。到目前为止，我所拥有的是显示它们在运行程序本身之前是打开还是关闭的程序。如何让程序对变化做出反应？

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Runtime.InteropServices;


namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {

        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.Winapi)]
       public static extern short GetKeyState(int keyCode);


        public Form1()
        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)
        {
            looper();
        }

        public void looper()
        {
            cLock_check();
            nLock_check();
            sLock_check();
        }

        public void cLock_check()
        {
            bool CapsLock = (((ushort)GetKeyState(0x14)) & 0xffff) != 0;

            if (CapsLock)
                lbl_cLock_onOff.Text = "ON";
            else
                lbl_cLock_onOff.Text = "OFF";
        }
        public void nLock_check()
        {
            bool NumLock = (((ushort)GetKeyState(0x90)) & 0xffff) != 0;
            if (NumLock)
                lbl_nLock_onOff.Text = "ON";
            else
                lbl_nLock_onOff.Text = "OFF";
        }
        public void sLock_check()
        {
            bool ScrollLock = (((ushort)GetKeyState(0x91)) & 0xffff) != 0;
            if (ScrollLock)
                lbl_sLock_onOff.Text = "ON";
            else
                lbl_sLock_onOff.Text = "OFF";
        }
    }
}

Answer 1

创建一个定时器对象，给它一个合理的时间间隔（对于大多数'responsive'UI问题，300毫秒是合适的），并设置Tick处理程序来调用looper方法：

Timer checkState;

public Form1()
{
    InitializeComponent();

    checkState = new Timer { Interval = 300};
    checkState.Tick += (o,e) => looper();
    chechState.Start();
}

Answer 2

您应该实现全局键盘挂钩，如 this article 中所述。比较 vkCode 与 VK_NUMLOCK、VK_CAPITAL 和 VK_SCROLL 并调用您的相关更新函数。

如何无休止地检查是否按下了键？

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