窗口未显示WM_PAINT行

Question

我对这个领域有点陌生，所以…我做了下面的代码，据我所知，在WM_PAINT我正在创建一条线，但是我看不到这条线，因为窗口根本不显示。我有一个线程，调用WM_PAINT每2秒，但每次没有显示一旦运行程序。

thanks in advance .

#include <windows.h>
#include <stdio.h>
DWORD WINAPI StartThread1(LPVOID LPElm); 
//---------------------------------------------------------------------------
HWND hWnd;
LPCTSTR ClsName = L"WndMsg";
LPCTSTR WindowCaption = L"Windows and Controls Messages";
LRESULT CALLBACK WndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
//---------------------------------------------------------------------------
INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine, int nCmdShow)
{
    MSG         Msg;
    WNDCLASSEX  WndClsEx;
    WndClsEx.cbSize        = sizeof(WNDCLASSEX);
    WndClsEx.style         = CS_HREDRAW | CS_VREDRAW;
    WndClsEx.lpfnWndProc   = WndProc;
    WndClsEx.cbClsExtra    = NULL;
    WndClsEx.cbWndExtra    = NULL;
    WndClsEx.hInstance     = hInstance;
    WndClsEx.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    WndClsEx.hCursor       = LoadCursor(NULL, IDC_ARROW);
    WndClsEx.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    WndClsEx.lpszMenuName  = NULL;
    WndClsEx.lpszClassName = ClsName;
    WndClsEx.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);
    RegisterClassEx(&WndClsEx);
    hWnd = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW,
                          ClsName,
                          WindowCaption,
                          WS_OVERLAPPEDWINDOW,
                          100,
                          120,
                          640,
                          480,
                          NULL,
                          NULL,
                          hInstance,
                          NULL);
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);
    DWORD ThreadId1, ThreadId2;
    HANDLE HandleThread1 = CreateThread(0,0,StartThread1,0,0,&ThreadId1);
    while( GetMessage(&Msg, NULL, 0, 0) )
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;
}
//---------------------------------------------------------------------------
LRESULT CALLBACK WndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
        HDC hDC;
    PAINTSTRUCT Ps;
    switch(Msg)
    {
    case WM_CREATE:
    //MessageBox(NULL, L"The window is being created", WindowCaption, MB_OK);
    break;
    case WM_SHOWWINDOW:
        break;
    case WM_PAINT:
    hDC = BeginPaint(hWnd, &Ps);
    MoveToEx(hDC, 0, 0, NULL);
    LineTo(hDC, 10, 10);
    EndPaint(hWnd, &Ps);
    break;
    case WM_DESTROY:
        PostQuitMessage(WM_QUIT);
        break;
    default:
        return DefWindowProc(hWnd, Msg, wParam, lParam);
    }
    return 0;
}
//---------------------------------------------------------------------------

DWORD WINAPI StartThread1(LPVOID LPElm)
{
    int n = 5000,i,j;
    for (i=0; i<n; i++)
    {
        SendMessage(hWnd,WM_PAINT,NULL,NULL);
        Sleep(2000);
        /*for (j=0;j<10;j++)
            a[j] = (rand() % 100);
        printf("n");*/
    }
    return 0;
}

Answer 1

你不应该自己发送WM_PAINT。你需要使用InvalidateRect。你还需要用一些来绘制 -你需要使用SelectObject来选择一个有效的笔对象到DC。

Answer 2

WM_PAINT消息是系统在重绘窗口时发送的，所以您不需要自己发送消息。如果你想重新绘制窗口，使用InvalidateRect。如果在程序中使用Thread，则应该使用ExitProcess(ThreadID)退出线程，然后执行以下代码。钢笔的默认颜色是黑色，所以你可以看到它。在您的例子中，您的线程没有退出，因此程序停止在那里。这窗户永远也刷不上了。您可以在程序中使用MessageBox()来测试当前运行的位置