Question

这是我的代码，在WinMain入口点我注册了一个类并尝试创建一个窗口，但CreateWindow（）函数总是返回NULL。但是RegisterClass（）函数确实成功了。我做错了什么？

#include <Windows.h>
#include <stdio.h>


LRESULT CALLBACK event(HWND, UINT, WPARAM, LPARAM)
{


    return 0;
}

int CALLBACK WinMain(
    _In_ HINSTANCE hInstance,
    _In_ HINSTANCE hPrevInstance,
    _In_ LPSTR     lpCmdLine,
    _In_ int       nCmdShow
    )
{
    WNDCLASS wndClass;
    wndClass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndClass.hInstance = hInstance;
    wndClass.lpszMenuName = NULL;
    wndClass.lpfnWndProc = event;
    wndClass.lpszClassName = L"ME";
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.style = CS_HREDRAW | CS_VREDRAW;

    int err = RegisterClass(&wndClass);
    if (err < 0)
    {
        MessageBox(NULL, L"Can not register window class!", L"Error", 0);
        return -1;
    }
    HWND hwnd;
    hwnd = CreateWindow(L"ME",
    L"Test",
    WS_OVERLAPPEDWINDOW, 
    100,
    100, 
    300, 
    300, 
    NULL,
    NULL,
    hInstance, 
    NULL);
    if (hwnd == NULL)
    {
        MessageBox(NULL, L"Can not create window!", L"Error", 0);
        return -1;
    }
    ShowWindow(hwnd, SW_NORMAL);
    UpdateWindow(hwnd);

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return 0;
}

Answer 1

LRESULT CALLBACK event(HWND, UINT, WPARAM, LPARAM)
{
    return 0;
}

这是一个根本破坏的窗口程序。为自己没有处理的邮件调用DefWindowProc（）是不可选。

现在它不会创建窗口，因为因为WM_NCCREATE消息返回FALSE。它应该返回TRUE以允许创建窗口。您也不会从GetLastError（）获取错误代码，就操作系统而言，您故意拒绝允许创建窗口。修正：

LRESULT CALLBACK event(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
    return DefWindowProc(hwnd, msg, wparam, lparam);
}

Visual C ++中的CreateWindow（）始终返回null

1 个答案: