问题描述

C#做上位机时自定义了一个控件，控件对↑键做出反应，发现方向键不好使，按键事件进不去，求助大神！

控件主要是想做一个显示速度的条，当按↑时格子文本框变色
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace SpeedBar
{
public partial class SpeedBar : UserControl
{
private Int16 SpeedBarflag = 0;
public SpeedBar()
{

        InitializeComponent();
    }

    private void SpeedBar_KeyDown(object sender, KeyEventArgs e)
    {
        Keys key = e.KeyCode;

        switch (key)
        {
                //↑按键
                case Keys.Up:
                SpeedBarflag ++;
                if(SpeedBarflag >5)
                       SpeedBarflag=5;
                if (SpeedBarflag >= 1 && SpeedBarflag<6)
                {
                    switch(SpeedBarflag)
                    {
                        case 1:
                            SpeedBar1.BackColor=System.Drawing.Color.Red;
                            break;
                        case 2:
                            SpeedBar2.BackColor=System.Drawing.Color.Yellow;
                            break;
                        case 3:
                            SpeedBar3.BackColor=System.Drawing.Color.Green;
                            break;
                        case 4:
                            SpeedBar4.BackColor=System.Drawing.Color.Blue;
                            break;
                        case 5:
                            SpeedBar5.BackColor=System.Drawing.Color.Black;
                            break;
                    }
                }

                if (SpeedBarflag > -5 && SpeedBarflag< 1)
                {

                    switch(SpeedBarflag)
                    {
                        case -4:
                            SpeedBarminus5.BackColor=System.Drawing.Color.White;
                            break;
                        case -3:
                            SpeedBarminus4.BackColor=System.Drawing.Color.White;
                            break;
                        case -2:
                            SpeedBarminus3.BackColor=System.Drawing.Color.White;
                            break;
                        case -1:
                            SpeedBarminus2.BackColor=System.Drawing.Color.White;
                            break;
                        case 0:
                            SpeedBarminus1.BackColor=System.Drawing.Color.White;
                            break;
                    }
                }
                break;

                //↓按键

                case Keys.Down:
                SpeedBarflag --;
                if(SpeedBarflag <-5)
                       SpeedBarflag=-5;
                if (SpeedBarflag <= -1 && SpeedBarflag>-6)
                {
                    switch(SpeedBarflag)
                    {
                        case -1:
                            SpeedBarminus1.BackColor=System.Drawing.Color.Red;
                            break;
                        case -2:
                            SpeedBarminus2.BackColor=System.Drawing.Color.Yellow;
                            break;
                        case -3:
                            SpeedBarminus3.BackColor=System.Drawing.Color.Green;
                            break;
                        case -4:
                            SpeedBarminus4.BackColor=System.Drawing.Color.Blue;
                            break;
                        case -5:
                            SpeedBarminus5.BackColor=System.Drawing.Color.Black;
                            break;
                    }
                }

                if (SpeedBarflag < 5 && SpeedBarflag> -1)
                {
                    switch(SpeedBarflag)
                    {
                        case 4:
                            SpeedBar5.BackColor=System.Drawing.Color.White;
                            break;
                        case 3:
                            SpeedBar4.BackColor=System.Drawing.Color.White;
                            break;
                        case 2:
                            SpeedBar3.BackColor=System.Drawing.Color.White;
                            break;
                        case 1:
                            SpeedBar2.BackColor=System.Drawing.Color.White;
                            break;
                        case 0:
                            SpeedBar1.BackColor=System.Drawing.Color.White;
                            break;
                    }
                }
                break;
        }
    }

}

}
一直想不通为啥按键无效，一直找不到焦点一样，Form有一个keypreview好像是管这个的，可自定义控件里没这个选项。。。求助求助，谢了

解决方案

这个原因太简单了，因为你的控件没有获取到焦点，你这样的功能，一般要使用钩子，否则一失去焦点，功能就失灵了，除非你保证焦点总在这个程序的这个控件上