winapi doesn't respond to keypress - c++

Question

I recently decided to learn a bit of WinApi, but I hit a snag. I want to display a massage in my window after a keypress, but it doesn't seem to work. If I press the key multiple times or if I hold it down, still nothing happens. Can you tell me what I'm doing wrong?
This is the full code:
#include <windows.h>
#include <string.h>
#include <stdlib.h>
#include <tchar.h>
LRESULT CALLBACK WndProc (HWND hwnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam)
{
PAINTSTRUCT ps;
HDC hdc;
LPCWSTR display_str = L"hello";
switch(uMsg)
{
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
if(GetAsyncKeyState(VK_UP))
{
TextOut(hdc,
15, 15,
display_str,
_tcslen(display_str));
}
EndPaint(hwnd, &ps);
break;
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
return 0;
}
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
HWND hwnd;
MSG uMsg;
HINSTANCE hInst;
WNDCLASSEX wcex;
LPCWSTR class_name = L"myWindowClass";
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_APPLICATION));
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = NULL;
wcex.lpszClassName = class_name;
wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_APPLICATION));
if(!RegisterClassEx(&wcex))
{
MessageBox(NULL, L"Call to RegisterClassEx failed!", L"Win32 Guided Tour!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
hInst = hInstance;
hwnd = CreateWindowEx(
NULL,
class_name,
L"Test",
WS_OVERLAPPEDWINDOW,
200, 200,
740, 540,
NULL,
NULL,
hInstance,
NULL
);
if(!hwnd)
{
MessageBox(NULL, L"Window Creation Failed!", L"Error!",
MB_ICONEXCLAMATION | MB_OK);
return 0;
}
ShowWindow(hwnd, nCmdShow);
UpdateWindow(hwnd);
while(GetMessage(&uMsg, NULL, 0, 0) > 0)
{
TranslateMessage(&uMsg);
DispatchMessage(&uMsg);
}
return uMsg.wParam;
}

Answer 1

Windows sends WM_KEYDOWN message when a key is pressed. In WndProc handle WM_KEYDOWN message, call InvalidateRect with the Client rect of the window and draw the text you want to display in WM_PAINT message handler.

Answer 2

Here's my example, if pressed F11 key, print in console string.:
case WM_KEYDOWN:
if(wParam==VK_F11)
{
std::cout << "Hello in my example!";
}
break;