如何使用 Visual Studio C++ 将 2 个列表框添加到 1 window？

Question

I have this code that works for 1 listbox but adding another one right below the first one is problematic. This is C code that works fine in C++. Also, duplicating the hwndList just erases the first listbox.

#include "framework.h"
#include "environ.h"

#define ID_LIST 1
#define ID_TEXT 2

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("Environ");
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;
    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"),
            szAppName, MB_ICONERROR);
        return 0;
    }
    hwnd = CreateWindow(szAppName, TEXT("Environment List Box"),
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT,
        CW_USEDEFAULT, CW_USEDEFAULT,
        NULL, NULL, hInstance, NULL);
    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}

fills the content of the listbox

void FillListBox(HWND hwndList)
{
    int iLength;

    TCHAR* pVarBlock, * pVarBeg, * pVarEnd, * pVarName;

    TCHAR* pVarBlockCopy = GetEnvironmentStrings(); // Get pointer to environment block
    pVarBlock = GetEnvironmentStrings(); // Get pointer to environment block
    while (*pVarBlock)
    {
        if (*pVarBlock != '=') // Skip variable names beginning with `=`
        {
            pVarBeg = pVarBlock; // Beginning of variable name
                while (*pVarBlock++ != '='); // Scan until `=`
            pVarEnd = pVarBlock - 1; // Points to `=` sign
            iLength = pVarEnd - pVarBeg; // Length of variable name
            // Allocate memory for the variable name and terminating
            // zero. Copy the variable name and append a zero.
            pVarName = (TCHAR*)(calloc(iLength + 1, sizeof(TCHAR)));
            CopyMemory(pVarName, pVarBeg, iLength * sizeof(TCHAR));
            pVarName[iLength] = '\0' ;
                // Put the variable name in the list box and free memory.
                SendMessage(hwndList, LB_ADDSTRING, 0, (LPARAM)pVarName);
            free(pVarName);
        }
        while (*pVarBlock++ != '\0') ; // Scan until terminating zero
    }
    FreeEnvironmentStrings(pVarBlockCopy);
}

This section of the code seems to handle the creation of the listbox and the text box. I attempted to copy the listbox code and modify the code with a 2 to see if adjusting the location of the listbox might make the code function as two listbox windows program.

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HWND hwndList, hwndText;
    int iIndex, iLength, cxChar, cyChar;
    TCHAR* pVarName, * pVarValue;
    switch (message)
    {
    case WM_CREATE:
        cxChar = LOWORD(GetDialogBaseUnits());
        cyChar = HIWORD(GetDialogBaseUnits());
        // Create listbox and static text windows.
        hwndList = CreateWindow(TEXT("listbox"), NULL,
            WS_CHILD | WS_VISIBLE | LBS_STANDARD,
            cxChar, cyChar * 3,
            cxChar * 16 + GetSystemMetrics(SM_CXVSCROLL),
            cyChar * 5,
            hwnd, (HMENU)ID_LIST,
            (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE),
            NULL);
        hwndText = CreateWindow(TEXT("static"), NULL,
            WS_CHILD | WS_VISIBLE | SS_LEFT,
            cxChar, cyChar,
            GetSystemMetrics(SM_CXSCREEN), cyChar,
            hwnd, (HMENU)ID_TEXT,
            (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE),
            NULL);
        FillListBox(hwndList);
        return 0;
    case WM_SETFOCUS:
        SetFocus(hwndList);
        return 0;
    case WM_COMMAND:
        if (LOWORD(wParam) == ID_LIST && HIWORD(wParam) == LBN_SELCHANGE)
        {
            // Get current selection.
            iIndex = SendMessage(hwndList, LB_GETCURSEL, 0, 0);
            iLength = SendMessage(hwndList, LB_GETTEXTLEN, iIndex, 0) + 1;
            pVarName = (TCHAR*)(calloc(iLength, sizeof(TCHAR)));
            SendMessage(hwndList, LB_GETTEXT, iIndex, (LPARAM)pVarName);
            // Get environment string.
            iLength = GetEnvironmentVariable(pVarName, NULL, 0);
            pVarValue = (TCHAR *) (calloc(iLength, sizeof(TCHAR)));
            GetEnvironmentVariable(pVarName, pVarValue, iLength);
            // Show it in window.
            SetWindowText(hwndText, pVarValue);
            free(pVarName);
            free(pVarValue);
        }
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

Answer 1

I added a new ID_NEWLIST to your source code and created a listbox in the same way.

Here is the sample:

#include <windows.h>

#define ID_LIST 1
#define ID_TEXT 2
#define ID_NEWLIST 3
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
void FillListBox(HWND hwndList)
{
    int iLength;

    TCHAR* pVarBlock, * pVarBeg, * pVarEnd, * pVarName;

    TCHAR* pVarBlockCopy = GetEnvironmentStrings(); // Get pointer to environment block
    pVarBlock = GetEnvironmentStrings(); // Get pointer to environment block
    while (*pVarBlock)
    {
        if (*pVarBlock != '=') // Skip variable names beginning with `=`
        {
            pVarBeg = pVarBlock; // Beginning of variable name
            while (*pVarBlock++ != '='); // Scan until `=`
            pVarEnd = pVarBlock - 1; // Points to `=` sign
            iLength = pVarEnd - pVarBeg; // Length of variable name
            // Allocate memory for the variable name and terminating
            // zero. Copy the variable name and append a zero.
            pVarName = (TCHAR*)(calloc(iLength + 1, sizeof(TCHAR)));
            CopyMemory(pVarName, pVarBeg, iLength * sizeof(TCHAR));
            pVarName[iLength] = '\0';
            // Put the variable name in the list box and free memory.
            SendMessage(hwndList, LB_ADDSTRING, 0, (LPARAM)pVarName);
            free(pVarName);
        }
        while (*pVarBlock++ != '\0'); // Scan until terminating zero
    }
    FreeEnvironmentStrings(pVarBlockCopy);
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("Environ");
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;
    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"),
            szAppName, MB_ICONERROR);
        return 0;
    }
    hwnd = CreateWindow(szAppName, TEXT("Environment List Box"),
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT,
        CW_USEDEFAULT, CW_USEDEFAULT,
        NULL, NULL, hInstance, NULL);
    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HWND hwndList, hwndText, hwndNewList;
    int iIndex, iLength, cxChar, cyChar;
    TCHAR* pVarName, * pVarValue;
    switch (message)
    {
    case WM_CREATE:
        cxChar = LOWORD(GetDialogBaseUnits());
        cyChar = HIWORD(GetDialogBaseUnits());
        // Create listbox and static text windows.
        hwndList = CreateWindow(TEXT("listbox"), NULL,
            WS_CHILD | WS_VISIBLE | LBS_STANDARD,
            cxChar, cyChar * 3,
            cxChar * 16 + GetSystemMetrics(SM_CXVSCROLL),
            cyChar * 5,
            hwnd, (HMENU)ID_LIST,
            (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE),
            NULL);
        hwndNewList = CreateWindow(TEXT("listbox"), NULL,
            WS_CHILD | WS_VISIBLE | LBS_STANDARD,
            cxChar, cyChar * 8,
            cxChar * 16 + GetSystemMetrics(SM_CXVSCROLL),
            cyChar * 5,
            hwnd, (HMENU)ID_NEWLIST,
            (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE),
            NULL);
        hwndText = CreateWindow(TEXT("static"), NULL,
            WS_CHILD | WS_VISIBLE | SS_LEFT,
            cxChar, cyChar,
            GetSystemMetrics(SM_CXSCREEN), cyChar,
            hwnd, (HMENU)ID_TEXT,
            (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE),
            NULL);
        FillListBox(hwndList);
        FillListBox(hwndNewList);
        return 0;
    case WM_SETFOCUS:
        SetFocus(hwndList);
        return 0;
    case WM_COMMAND:
        if (LOWORD(wParam) == ID_LIST && HIWORD(wParam) == LBN_SELCHANGE)
        {
            // Get current selection.
            iIndex = SendMessage(hwndList, LB_GETCURSEL, 0, 0);
            iLength = SendMessage(hwndList, LB_GETTEXTLEN, iIndex, 0) + 1;
            pVarName = (TCHAR*)(calloc(iLength, sizeof(TCHAR)));
            SendMessage(hwndList, LB_GETTEXT, iIndex, (LPARAM)pVarName);
            // Get environment string.
            iLength = GetEnvironmentVariable(pVarName, NULL, 0);
            pVarValue = (TCHAR*)(calloc(iLength, sizeof(TCHAR)));
            GetEnvironmentVariable(pVarName, pVarValue, iLength);
            // Show it in window.
            SetWindowText(hwndText, pVarValue);
            free(pVarName);
            free(pVarValue);
        }
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

If you encounter other problems during the creation, I hope you can further point them out so that we can solve them for you.