windows 将值设置为对象属性时发生读访问冲突，该对象属性作为LPARAM传递给回调函数

lg40wkob  于 9个月前  发布在  Windows
关注(0)|答案(1)|浏览(41)

我正在构建一个小的Windows应用程序，以学习C++ Windows编程。在问题的最后，我提交了完整的代码以供参考，所以你可以在上下文中看到一切（我希望这种方法没有夸大）。
在我的WndProc回调函数中，我解析message如下：

case ID_SETUP_NUMBEROFFILES:
            callback_result = DialogBoxParam(hInst, MAKEINTRESOURCE(IDD_DIALOG3), hWnd, NumberInputDialogProc, (LPARAM)pState);
            if (callback_result) {
                OutputDebugString(L"ID_SETUP_NUMBEROFFILES (pState->N): ");
                OutputDebugString(pState->N.c_str());
                OutputDebugString(L"\n");
            }
            InvalidateRect(hWnd, NULL, TRUE);
            DebugStateDisplay(hWnd);
            break;

字符串
pState作为LPARAM发送到对话框处理（请参阅最后的完整代码中的pState声明和初始化）。对话框处理程序为：

INT_PTR CALLBACK NumberInputDialogProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) {
    StateInfo* pState = reinterpret_cast<StateInfo*>(lParam);
    switch (message) {
    case WM_INITDIALOG:
        SetDlgItemText(hDlg, IDC_NUMBER_EDIT, pState->N.c_str());
        return (INT_PTR)TRUE;
    case WM_COMMAND:
        switch (LOWORD(wParam)) {
        case IDOK:
            TCHAR buffer[MAX_INPUT_NUMBER_SIZE + 1]; // +1 for null-terminator
            GetDlgItemText(hDlg, IDC_NUMBER_EDIT, buffer, MAX_INPUT_NUMBER_SIZE + 1);
            OutputDebugString(L"buffer:");
            OutputDebugString(buffer);
            OutputDebugString(L"\n");
            // pState->N = buffer; // throws exception
            pState->N = std::wstring(buffer); // throws exception
            OutputDebugString(L"********* CALLBACK (pState->N): ");
            OutputDebugString(pState->N.c_str()); //throws exception
            OutputDebugString(L"\n");
            EndDialog(hDlg, IDOK);
            return (INT_PTR)TRUE;
        case IDCANCEL:
            EndDialog(hDlg, IDCANCEL);
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

型
在WM_INITDIALOG消息的情况下，pState->N被正确读取，因此至少我知道我正在访问正确的对象。然而，对pState->N的两次赋值都抛出了读访问冲突，这让我更加困惑，甚至是这样：

OutputDebugString(pState->N.c_str()); //throws exception

型
抛出异常，即使我只是在阅读它。我单独尝试了这三个方法中的每一个（我注解掉了剩下的两个），这样我就可以确认每个方法都抛出了异常。我做错了什么？
我的目标是从dialog中读取值并将其分配给`pState->N'或换句话说：我想从对话框中读取，并将此值设置为应用程序状态。如果不能直接完成，那么间接也可以，如果可能的话，不需要任何额外的全局变量。
完整代码供参考：

#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <tchar.h>
#include <ShObjIdl.h>
#include <ShlObj.h>
#include "resource.h"

#define VERSION _T("v0.2.0")
#define TITLE _T("MP3 Randomizer II")
#define DEFAULT_N  _T("900")
#define MAX_INPUT_NUMBER_SIZE 10

// Global variables
struct StateInfo {
    std::wstring inputFolder;
    std::wstring outputFolder;
    std::wstring N = DEFAULT_N;
    std::wstring selected = _T("0");
    std::wstring found = _T("0");
};

static TCHAR szWindowClass[] = _T("MP3 Randomizer");
static TCHAR szTitle[100];

HINSTANCE hInst;

// Forward declarations of functions :
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
void PaintWindow(HWND hWnd, StateInfo* pState);
INT_PTR CALLBACK AboutDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
INT_PTR CALLBACK NumberInputDialogProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
INT_PTR CALLBACK NotYetProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
std::wstring ShowFolderBrowserDialog(HWND hWnd);
inline StateInfo* GetAppState(HWND hwnd);
void DebugStateDisplay(HWND hWnd);

int WINAPI WinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPSTR lpCmdLine, _In_ int nCmdShow) {

    StateInfo* pState = new (std::nothrow) StateInfo;
    if (pState == NULL) return 0;

    _stprintf_s(szTitle, _T("%s %s"), TITLE, VERSION);

    WNDCLASSEX wcex;
    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(wcex.hInstance, IDI_APPLICATION);
    wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wcex.lpszMenuName = NULL;
    wcex.lpszClassName = szWindowClass;
    wcex.hIconSm = LoadIcon(wcex.hInstance, IDI_APPLICATION);

    if (!RegisterClassEx(&wcex)) {
        MessageBox(NULL, _T("Call to RegisterClassEx failed!"), _T("Windows Desktop Guided Tour"), NULL);
        return 1;
    }

    // Store instance handle in our global variable
    hInst = hInstance;

    // Load the menu resource
    HMENU hMenu = LoadMenu(hInstance, MAKEINTRESOURCE(IDR_MENU1));

    if (!hMenu) {
        MessageBox(NULL, _T("Failed to load menu resource!"), _T("Error"), MB_ICONERROR);
        return 1;
    }

    // Extract the first (and only) menu from the loaded menu resource
    HMENU hSubMenu = GetSubMenu(hMenu, 0);
    if (!hSubMenu) {
        MessageBox(NULL, _T("Failed to get sub-menu!"), _T("Error"), MB_ICONERROR);
        return 1;
    }

    HWND hWnd = CreateWindowEx(
        WS_EX_OVERLAPPEDWINDOW,                                 // WS_EX_OVERLAPPEDWINDOW : An optional extended window style.
        szWindowClass,                                          // szWindowClass: the name of the application
        szTitle,                                                // szTitle: the text that appears in the title bar
        WS_OVERLAPPEDWINDOW,                                    // WS_OVERLAPPEDWINDOW: the type of window to create
        CW_USEDEFAULT, CW_USEDEFAULT,                           // CW_USEDEFAULT, CW_USEDEFAULT: initial position (x, y)
        800, 400,                                               // 500, 100: initial size (width, length)
        NULL,                                                   // NULL: the parent of this window
        hMenu,                                                  // hMenu: the menu handle loaded from resources
        hInstance,                                              // hInstance: the first parameter from WinMain
        pState                                                  // pointer to state
    );

    if (!hWnd) {
        MessageBox(NULL, _T("Call to CreateWindow failed!"), _T("Windows Desktop Guided Tour"), NULL);
        return 1;
    }

    // The parameters to ShowWindow explained:
        // hWnd: the value returned from CreateWindow
        // nCmdShow: the fourth parameter from WinMain
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

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

    delete pState;

    return (int)msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {

    WORD wmId = LOWORD(wParam);
    WORD wmEvent = HIWORD(wParam);
    std::wstring selectedFolderPath;
    INT_PTR callback_result;
    int enteredNumber = 0;

    StateInfo* pState;
    if (message == WM_CREATE) {
        CREATESTRUCT* pCreate = reinterpret_cast<CREATESTRUCT*>(lParam);
        pState = reinterpret_cast<StateInfo*>(pCreate->lpCreateParams);
        SetWindowLongPtr(hWnd, GWLP_USERDATA, (LONG_PTR)pState);
    }
    else {
        pState = GetAppState(hWnd);
    }

    switch (message) {
    case WM_PAINT:
        PaintWindow(hWnd, pState);
        break;
    case WM_DESTROY:
        if (MessageBox(hWnd, L"Really quit?", TITLE, MB_OKCANCEL) == IDOK) {
            PostQuitMessage(0);
        }
        break;
    case WM_COMMAND:
        switch (wmId) {
        case ID_HELP_ABOUT:
            DialogBox(hInst, MAKEINTRESOURCE(IDD_DIALOG1), hWnd, AboutDlgProc);
            break;
        case ID_SETUP_QUIT:
            if (MessageBox(hWnd, L"Really quit?", TITLE, MB_OKCANCEL) == IDOK) {
                PostQuitMessage(0);
            }
            break;
        case ID_SETUP_INPUTFOLDER:
            selectedFolderPath = ShowFolderBrowserDialog(hWnd);
            pState->inputFolder = selectedFolderPath;
            InvalidateRect(hWnd, NULL, TRUE);
            DebugStateDisplay(hWnd);
            break;
        case ID_SETUP_OUTPUTFOLDER:
            selectedFolderPath = ShowFolderBrowserDialog(hWnd);
            pState->outputFolder = selectedFolderPath;
            InvalidateRect(hWnd, NULL, TRUE);
            DebugStateDisplay(hWnd);
            break;
        case ID_SETUP_NUMBEROFFILES:
            callback_result = DialogBoxParam(hInst, MAKEINTRESOURCE(IDD_DIALOG3), hWnd, NumberInputDialogProc, (LPARAM)pState);
            if (callback_result) {
                OutputDebugString(L"ID_SETUP_NUMBEROFFILES (pState->N): ");
                OutputDebugString(pState->N.c_str());
                OutputDebugString(L"\n");
            }
            InvalidateRect(hWnd, NULL, TRUE);
            DebugStateDisplay(hWnd);
            break;
        case ID_ACTION_FINDMUSIC:
        case ID_ACTION_SAVELIST:
        case ID_ACTION_LOADLIST:
        case ID_ACTION_RANDOMIZE:
        case ID_ACTION_COPYTOOUTPUT:
        case ID_HELP_HELP:
            DialogBox(hInst, MAKEINTRESOURCE(IDD_DIALOG2), hWnd, NotYetProc);
            break;

        default:
            return DefWindowProc(hWnd, message, wParam, lParam);
        }
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
        break;
    }

    return 0;
}
void PaintWindow(HWND hWnd, StateInfo* pState) {
    int x1 = 5;
    int x2 = 120;
    int y = 5;
    int dy = 20;
    PAINTSTRUCT ps;
    HDC hdc;
    TCHAR inputFolder[] = _T("Input folder: ");
    TCHAR outputFolder[] = _T("Output folder: ");
    TCHAR selected[] = _T("N Files to copy: ");
    TCHAR selectedNow[] = _T("Files selected: ");
    TCHAR found[] = _T("Files found: ");
    hdc = BeginPaint(hWnd, &ps);
    FillRect(hdc, &ps.rcPaint, (HBRUSH)(COLOR_WINDOW + 1));
    TextOut(hdc, x1, y, inputFolder, (int)_tcslen(inputFolder));
    TextOut(hdc, x2, y, pState->inputFolder.c_str(), static_cast<int>(pState->inputFolder.length()));
    y += dy;
    TextOut(hdc, x1, y, outputFolder, (int)_tcslen(outputFolder));
    TextOut(hdc, x2, y, pState->outputFolder.c_str(), static_cast<int>(pState->outputFolder.length()));
    y += dy;
    TextOut(hdc, x1, y, selected, (int)_tcslen(selected));
    TextOut(hdc, x2, y, pState->N.c_str(), static_cast<int>(pState->N.length()));
    y += dy;
    TextOut(hdc, x1, y, found, (int)_tcslen(found));
    TextOut(hdc, x2, y, pState->found.c_str(), static_cast<int>(pState->found.length()));
    y += dy;
    TextOut(hdc, x1, y, selectedNow, (int)_tcslen(selectedNow));
    TextOut(hdc, x2, y, pState->selected.c_str(), static_cast<int>(pState->selected.length()));
    EndPaint(hWnd, &ps);
}

// Dialog procedure for the About dialog box
INT_PTR CALLBACK AboutDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) {
    switch (message) {
    case WM_INITDIALOG:
        // Initialize dialog box controls and data here
        SetDlgItemText(hDlg, IDC_STATIC2, VERSION);
        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;
}

INT_PTR CALLBACK NumberInputDialogProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) {
    StateInfo* pState = reinterpret_cast<StateInfo*>(lParam);
    switch (message) {
    case WM_INITDIALOG:
        SetDlgItemText(hDlg, IDC_NUMBER_EDIT, pState->N.c_str());
        return (INT_PTR)TRUE;
    case WM_COMMAND:
        switch (LOWORD(wParam)) {
        case IDOK:
            TCHAR buffer[MAX_INPUT_NUMBER_SIZE + 1]; // +1 for null-terminator
            GetDlgItemText(hDlg, IDC_NUMBER_EDIT, buffer, MAX_INPUT_NUMBER_SIZE + 1);
            OutputDebugString(L"buffer:");
            OutputDebugString(buffer);
            OutputDebugString(L"\n");
            // pState->N = buffer; // throws exception
            pState->N = std::wstring(buffer); // throws exception
            OutputDebugString(L"********* CALLBACK (pState->N): ");
            OutputDebugString(pState->N.c_str()); //throws exception
            OutputDebugString(L"\n");
            EndDialog(hDlg, IDOK);
            return (INT_PTR)TRUE;
        case IDCANCEL:
            EndDialog(hDlg, IDCANCEL);
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

INT_PTR CALLBACK NotYetProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) {
    switch (message) {
    case WM_INITDIALOG:
        // Initialize dialog box controls and data here
        return (INT_PTR)TRUE;
    case WM_COMMAND:
        if (LOWORD(wParam) == IDOK) {
            EndDialog(hDlg, LOWORD(wParam));
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

std::wstring ShowFolderBrowserDialog(HWND hWnd) {
    HRESULT hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);
    std::wstring folderPath;

    if (SUCCEEDED(hr)) {
        IFileDialog* pFileDialog;
        hr = CoCreateInstance(CLSID_FileOpenDialog, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pFileDialog));

        if (SUCCEEDED(hr)) {
            // Set options for the folder browser dialog
            DWORD dwOptions;
            pFileDialog->GetOptions(&dwOptions);
            pFileDialog->SetOptions(dwOptions | FOS_PICKFOLDERS);

            // Show the folder browser dialog
            if (pFileDialog->Show(hWnd) == S_OK) {
                IShellItem* pItem;
                if (pFileDialog->GetResult(&pItem) == S_OK) {
                    PWSTR pszFolderPath;
                    if (SUCCEEDED(pItem->GetDisplayName(SIGDN_FILESYSPATH, &pszFolderPath)) && pszFolderPath) {
                        // Convert to std::wstring and store in folderPath variable
                        folderPath = pszFolderPath;
                        CoTaskMemFree(pszFolderPath);
                    }
                    pItem->Release();
                }
            }

            pFileDialog->Release();
        }

        CoUninitialize();
    }

    return folderPath;
}

inline StateInfo* GetAppState(HWND hwnd) {
    LONG_PTR ptr = GetWindowLongPtr(hwnd, GWLP_USERDATA);
    StateInfo* pState = reinterpret_cast<StateInfo*>(ptr);
    return pState;
}

void DebugStateDisplay(HWND hWnd) {
    StateInfo* pState = GetAppState(hWnd);
    OutputDebugString(L"\n******************\n");

    OutputDebugString(L"Input: ");
    OutputDebugString(pState->inputFolder.c_str());
    OutputDebugString(L"\n");

    OutputDebugString(L"Output: ");
    OutputDebugString(pState->outputFolder.c_str());
    OutputDebugString(L"\n");

    OutputDebugString(L"N: ");
    OutputDebugString(pState->N.c_str());
    OutputDebugString(L"\n");

    OutputDebugString(L"Found: ");
    OutputDebugString(pState->found.c_str());
    OutputDebugString(L"\n");

    OutputDebugString(L"Selected: ");
    OutputDebugString(pState->selected.c_str());
    OutputDebugString(L"\n");

    OutputDebugString(L"******************\n");
    return;
}

型

windows

1条答案

按热度按时间
wlwcrazw

wlwcrazw1#

基于@Raymond Chen的有用评论，传递给不同命令的内容是完全不同的，并且基于similar question，我已经能够找到解决方案。
我将pState->N的值复制到gBuffer（以便在对话框中预先填充当前数字），然后将gBuffer的地址作为LPARAM发送到NumberInputDialogProc函数。gBuffer中填充了对话框中的值，我将其写回状态属性pState->N。WndProc的相关更改：

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
    wchar_t gBuffer[MAX_INPUT_NUMBER_SIZE + 1] = { 0 }
    /** other code ... */
    case ID_SETUP_NUMBEROFFILES:
            wcscpy_s(gBuffer, MAX_INPUT_NUMBER_SIZE + 1, pState->N.c_str());
            callback_result = DialogBoxParam(hInst, MAKEINTRESOURCE(IDD_DIALOG3), hWnd, NumberInputDialogProc, (LPARAM)(&gBuffer));
            if (callback_result ==IDOK) {
                pState->N = gBuffer;
            }
            InvalidateRect(hWnd, NULL, TRUE);
            DebugStateDisplay(pState);
            break;
    /** other code ... */
}

字符串
在NumberInputDialogProc函数中，我将此地址存储到WM_INITDIALOG中的DWLP_USER中，并将其检索回WM_COMMAND中，用于将数字存储为文本：

INT_PTR CALLBACK NumberInputDialogProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) {
    int number;
    wchar_t* gBuffer;

    switch (message) {
    case WM_INITDIALOG:
        SetDlgItemText(hDlg, IDC_NUMBER_EDIT, (wchar_t*)lParam);
        SetWindowLongPtr(hDlg, DWLP_USER, lParam);
        return (INT_PTR)TRUE;
    case WM_COMMAND:
        switch (LOWORD(wParam)) {
        case IDOK:
            gBuffer = (wchar_t*)GetWindowLongPtr(hDlg, DWLP_USER);
            GetDlgItemText(hDlg, IDC_NUMBER_EDIT, gBuffer, MAX_INPUT_NUMBER_SIZE+1);
            number = _ttoi(gBuffer);
            if (number >= 1 && number <= 999) {
                EndDialog(hDlg, IDOK);
                return (INT_PTR)TRUE;
            }
            else {
                SetDlgItemText(hDlg, IDC_ERROR_MSG, _T("Enter a number between 1 and 999"));
            }
            break;
        case IDCANCEL:
            EndDialog(hDlg, IDCANCEL);
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

型
如果我在任何地方使用了unidiomatic C++术语，我事先道歉。如果需要的话，我会编辑这篇文章来解决这个问题。

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