2

我正在尝试使用 C++ 设置一个简单的窗口，但我对CreateWindowEx返回的调用NULL。我使用的大部分代码来自MSDN 网站上的示例。我尝试过的任何方法都没有奏效，任何帮助将不胜感激。

这是代码：

//Include the windows header
#include <Windows.h>

//Forward declaration of the WndProc function
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

//Main entry point
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow) {
    //Window class name
    const wchar_t windowName[] = L"Window Class";

    //Set up window class
    WNDCLASS wnd;
    wnd.lpfnWndProc = WndProc;
    wnd.hInstance = hInstance;
    wnd.lpszClassName = windowName;

    //Register window class
    RegisterClass(&wnd);

    //Create window
    //! This returns NULL
    HWND hWnd = CreateWindowEx(
        0,
        windowName,
        L"Windows Programming",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL
        );

    //Simple check to see if window creation failed
    if(hWnd == NULL) {
            //Pause
        system("PAUSE");
        return -1;
    }

    //Show the window
    ShowWindow(hWnd, nCmdShow);

    //Main message loop
    MSG msg;
    while(GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
}

//WndProc function
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch(msg) {
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hDc = BeginPaint(hWnd, &ps);

            FillRect(hDc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW + 1));

            EndPaint(hWnd, &ps);

            return 0;
        }
    case WM_DESTROY:
        {
            PostQuitMessage(0);
            return 0;
        }
    }

    return DefWindowProc(hWnd, msg, wParam, lParam);
}
4

2 回答 2

9

请注意，来自 MSDN 的示例在设置它关心的字段之前将 WNDCLASS 的所有字段清零。

WNDCLASS wnd = { };  // from MSDN example

空大括号是用于将整个结构初始化为 0 的 C 和 C++ 简写。通常将其写为{ 0 }，这在技术上略有不同，但具有相同的净效果。

在您的代码中，您删除了初始化：

WNDCLASS wnd;  // your code

因此，您可能会在其他重要字段之一（例如cbClsExtraor ）中获得一些垃圾值cbWndExtra，从而使该类无法注册。由于该类未注册，因此您无法创建该类的窗口。

于 2012-12-01T18:16:43.850 回答
8

我已经让你的代码工作了。基本上我在使用 WNDCLASS（或 WNDCLASSEX）结构时所做的就是使用所有参数来确保不会遗漏任何东西。

//Include the windows header
#include <Windows.h>

//Forward declaration of the WndProc function
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

//Main entry point
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow) {
    //Window class name
    const wchar_t windowName[] = L"Window Class";

    //Set up window class
    WNDCLASS wnd;
    wnd.cbClsExtra = 0;
    wnd.cbWndExtra = 0;
    wnd.hCursor = LoadCursor(0, IDC_ARROW);
    wnd.hIcon = LoadIcon(0, IDI_WINLOGO);
    wnd.lpszMenuName = 0;
    wnd.style = 0;
    wnd.hbrBackground = 0;
    wnd.lpfnWndProc = WndProc;
    wnd.hInstance = hInstance;
    wnd.lpszClassName = windowName;

    //Register window class
    RegisterClass(&wnd);

    //Create window
    //! This returns NULL
    HWND hWnd = CreateWindowEx(
        0,
        windowName,
        L"Windows Programming",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL
        );

    //Simple check to see if window creation failed
    if(hWnd == NULL) {
            //Pause
        system("PAUSE");
        return -1;
    }

    //Show the window
    ShowWindow(hWnd, nCmdShow);

    //Main message loop
    MSG msg;
    while(GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
}

//WndProc function
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch(msg) {
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hDc = BeginPaint(hWnd, &ps);

            FillRect(hDc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW + 1));

            EndPaint(hWnd, &ps);

            return 0;
        }
    case WM_DESTROY:
        {
            PostQuitMessage(0);
            return 0;
        }
    }

    return DefWindowProc(hWnd, msg, wParam, lParam);
}
于 2012-12-01T17:58:26.573 回答