c++ - WIN32对话框抛出异常
问题描述
我正在尝试使用 Microsoft 文档学习 win32 api。我已经到了第 4 章,我似乎遇到了一个我正在努力调试的问题。about 按钮触发的对话框抛出异常:
在 practice.exe 中在 0x773BDCFF (ntdll.dll) 处引发异常:0xC0000005:访问冲突读取位置 0x00905A4C。
这是 WndProc 和 About 回调的声明:
static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
static INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
以下是 WndProc 和 About 回调的实现代码:
LRESULT CALLBACK App::WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
App* pApp;
if (message == WM_CREATE)
{
LPCREATESTRUCT pcs = (LPCREATESTRUCT)lParam;
pApp = (App*)pcs->lpCreateParams;
::SetWindowLongPtrW(hWnd, GWLP_USERDATA, PtrToUlong(pApp));
return TRUE;
}
else
{
pApp = reinterpret_cast<App*>(static_cast<LONG_PTR>(::GetWindowLongPtrW(hWnd, GWLP_USERDATA)));
if (!pApp)
return DefWindowProc(hWnd, message, wParam, lParam);
}
int wmld, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
switch (message)
{
case WM_COMMAND:
{
int wmId = LOWORD(wParam);
// Parse the menu selections:
switch (wmId)
{
case IDM_ABOUT:
DialogBox(pApp->getInstance(), MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, pApp->About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
}
break;
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code that uses hdc here...
EndPaint(hWnd, &ps);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
// Message handler for about box.
INT_PTR CALLBACK App::About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
UNREFERENCED_PARAMETER(lParam);
switch (message)
{
case WM_INITDIALOG:
return (INT_PTR)TRUE;
case WM_COMMAND:
if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
{
EndDialog(hDlg, LOWORD(wParam));
return (INT_PTR)TRUE;
}
break;
}
return (INT_PTR)FALSE;
我希望错误在这些片段中。如果没有,我很乐意提供更多代码。我做过研究,我真的不知道问题是什么。我知道 about 函数的回调必须是静态的,我相信它是静态的。除此之外,我不知道什么会导致它抛出异常。谢谢你能给我的任何帮助。
解决方案
使用您提供的代码无法重现此问题。以下是基于您的代码片段的示例,它适用于我。你可以参考。
应用程序.h
class App
{
public:
App(HINSTANCE hInstance, CONST WCHAR* clsName);
private:
static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
static INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
ATOM MyRegisterClass(HINSTANCE hInstance, CONST WCHAR* clsName);
};
应用程序.cpp
#include "App.h"
App::App(HINSTANCE hInstance, CONST WCHAR* clsName)
{
App::MyRegisterClass(hInstance, clsName);
}
ATOM App::MyRegisterClass(HINSTANCE hInstance, CONST WCHAR* clsName)
{
WNDCLASSEXW wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = App::WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_DIALOGBOXEXCEPTION));
wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wcex.lpszMenuName = MAKEINTRESOURCEW(IDC_DIALOGBOXEXCEPTION);
wcex.lpszClassName = clsName;
wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassExW(&wcex);
}
LRESULT CALLBACK App::WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
App* pApp;
if (message == WM_CREATE)
{
LPCREATESTRUCT pcs = (LPCREATESTRUCT)lParam;
pApp = (App*)pcs->lpCreateParams;
::SetWindowLongPtrW(hWnd, GWLP_USERDATA, (LONG_PTR)pApp);
return TRUE;
}
else
{
pApp = reinterpret_cast<App*>(static_cast<LONG_PTR>(::GetWindowLongPtrW(hWnd, GWLP_USERDATA)));
if (!pApp)
return DefWindowProc(hWnd, message, wParam, lParam);
}
switch (message)
{
case WM_COMMAND:
{
int wmId = LOWORD(wParam);
// Parse the menu selections:
switch (wmId)
{
case IDM_ABOUT:
DialogBox(NULL, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, pApp->About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
}
break;
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code that uses hdc here...
EndPaint(hWnd, &ps);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
// Message handler for about box.
INT_PTR CALLBACK App::About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
UNREFERENCED_PARAMETER(lParam);
switch (message)
{
case WM_INITDIALOG:
return (INT_PTR)TRUE;
case WM_COMMAND:
if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
{
EndDialog(hDlg, LOWORD(wParam));
return (INT_PTR)TRUE;
}
break;
}
return (INT_PTR)FALSE;
}
创建主窗口:
App pApp = App(hInst, szWindowClass);
HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, &pApp);
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);