关于WM_KEYDOWN的消息中传递的是该键的虚拟扫描码,不是ASCII码。它传递了键被按下时的特征,细节的描述如下:
wParamThe virtual-key code of the nonsystem key. See Virtual-Key Codes.
lParamThe repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown following.例如,我们实现一个打印输入的virtual code的程序,只要在前面的程序中,填入:
1 case WM_KEYDOWN: 2 { 3 char virtual_code = wparam; 4 int key_state = lparam; 5 6 // get a graphics context 7 hdc = GetDC(hwnd); 8 9 // set the foreground color to green 10 SetTextColor(hdc, RGB(0,255,0)); 11 12 // set the background color to black 13 SetBkColor(hdc, RGB(0,0,0)); 14 15 // set the transparency mode to OPAQUE 16 SetBkMode(hdc, OPAQUE); 17 18 // print the virtual code and key state 19 sprintf(buffer,"WM_KEYDOWN: Character = 0X%X ",virtual_code); 20 TextOut(hdc, 0,32, buffer, strlen(buffer)); 21 22 // release the dc back 23 ReleaseDC(hwnd, hdc); 24 25 }break;
最后要介绍的是键盘状态函数:GetAsyncKeyState(). 函数的原型如下:
short GetAsyncKeyState(int virtual_key); 返回值的最高位为1表示该键被按下,否则该键被松开。一般我们可以采用简单的宏代替来完成测试。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#define KEYDOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0) #define KEYUP(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 0 : 1)