C语言 WinAPI win32编程-按钮不可见

Question

我使用GetLastError()和FormatMessage()来确定按钮是否成功创建。但是，当我运行程序时，它是不可见的。我最初在winMain中创建了按钮，但发现网上的帖子说不这样做，所以我把它注释了出来，并在WM_CREATE中添加了创建。注意，所有ID等都是在resource.h文件中定义的，void ErrorExit()是从MSDN中提取的，以便在像我这样的相对较新的winApi程序员上使用GetLastError()和FormatMessage()。我的代码如下:

#define WIN32_LEAN_AND_MEAN
#define _WIN32_IE 0x0900
#define _WIN32_WINNT 0x0900
#include <strsafe.h>
#include <windows.h>
#include <CommCtrl.h>
#include <iostream>
#include <ShlObj.h>
#include <cstring>
#include "resource.h"
HWND main_hwnd, tab_hwnd, tab0_hwnd, tab1_hwnd, tab2_hwnd, tab3_hwnd, tab4_hwnd;
HINSTANCE tab_hinst;
TCHAR HomePath[MAX_PATH*2], SavePath[MAX_PATH*2];
WNDCLASSEX wc;
bool success=FALSE;
MSG msg;
HWND button;
static HWND text;
TCITEM tie;
int focus = 0, NotifyCase = 0;
void ErrorExit(LPTSTR lpszFunction) 
{ 
    // Retrieve the system error message for the last-error code
    LPVOID lpMsgBuf;
    LPVOID lpDisplayBuf;
    DWORD dw = GetLastError(); 
    FormatMessage(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | 
        FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        dw,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPTSTR) &lpMsgBuf,
        0, NULL );
    // Display the error message and exit the process
    lpDisplayBuf = (LPVOID)LocalAlloc(LMEM_ZEROINIT, 
        (lstrlen((LPCTSTR)lpMsgBuf)+lstrlen((LPCTSTR)lpszFunction)+40)*sizeof(TCHAR)); 
    StringCchPrintf((LPTSTR)lpDisplayBuf, 
        LocalSize(lpDisplayBuf) / sizeof(TCHAR),
        TEXT("%s failed with error %d: %s"), 
        lpszFunction, dw, lpMsgBuf); 
    MessageBox(NULL, (LPCTSTR)lpDisplayBuf, TEXT("Error"), MB_OK); 
    LocalFree(lpMsgBuf);
    LocalFree(lpDisplayBuf);
    ExitProcess(dw); 
}
// Step 4: The Window Procedure
LRESULT CALLBACK WndProc(HWND hwnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
    switch(Msg)
    {
        case WM_CREATE:
            {
                if(tab0_hwnd!=NULL)
                    button = CreateWindow("Button","Navigate to...", BS_PUSHBUTTON | WS_CHILD | WS_VISIBLE ,350,42,100,25,tab0_hwnd,(HMENU)ID_B_HOME,(HINSTANCE)GetWindowLong(tab0_hwnd, GWL_HINSTANCE),0);
                /*if(tab0_hwnd!=NULL)
                    button = CreateWindow("Button","Save to...", BS_PUSHBUTTON | WS_CHILD | WS_VISIBLE ,350,92,100,25,tab0_hwnd,(HMENU)ID_B_SAVE,(HINSTANCE)GetWindowLong(tab0_hwnd, GWL_HINSTANCE), NULL);
                */HMENU hMenu, hSubMenu;
                hMenu = CreateMenu();
                hSubMenu = CreatePopupMenu();
                AppendMenu(hMenu, MF_STRING | MF_POPUP, (UINT)hSubMenu, "&File");
                AppendMenu(hSubMenu, MF_STRING, ID_FILE_EXIT, "&Exit");
                hSubMenu = CreatePopupMenu();
                AppendMenu(hMenu, MF_STRING | MF_POPUP, (UINT)hSubMenu, "&Help");
                AppendMenu(hSubMenu, MF_STRING, ID_HELP_ABOUT, "&About");
                SetMenu(hwnd, hMenu);
            }
            break;
        case WM_NOTIFY:
            switch(((LPNMHDR)lParam) ->code)
            {
                case TCN_SELCHANGING:
                    switch(TabCtrl_GetCurFocus(tab_hwnd))
                    {
                        case 0:
                            ShowWindow(tab0_hwnd,SW_HIDE);
                            break;
                        case 1:
                            ShowWindow(tab1_hwnd,SW_HIDE);
                            break;
                        case 2:
                            ShowWindow(tab2_hwnd,SW_HIDE);
                            break;
                        case 3:
                            ShowWindow(tab3_hwnd,SW_HIDE);
                            break;
                        case 4:
                            ShowWindow(tab4_hwnd,SW_HIDE);
                            break;
                        default:
                            return DefWindowProc(hwnd, Msg, wParam, lParam);
                            break;
                    }
                    break;
                case TCN_SELCHANGE:
                    switch(TabCtrl_GetCurFocus(tab_hwnd))
                    {
                        case 0:
                            ShowWindow(tab0_hwnd,SW_SHOW);
                            break;
                        case 1:
                            ShowWindow(tab1_hwnd,SW_SHOW);
                            break;
                        case 2:
                            ShowWindow(tab2_hwnd,SW_SHOW);
                            break;
                        case 3:
                            ShowWindow(tab3_hwnd,SW_SHOW);
                            break;
                        case 4:
                            ShowWindow(tab4_hwnd,SW_SHOW);
                            break;
                        default:
                            return DefWindowProc(hwnd, Msg, wParam, lParam);
                            break;
                    }
                    break;
                default:
                    return DefWindowProc(hwnd, Msg, wParam, lParam);
            }
            break;
        case WM_COMMAND:
            switch(LOWORD(wParam))
            {
                case ID_FILE_EXIT:
                    PostMessage(hwnd, WM_CLOSE, 0, 0);
                    break;
                case ID_HELP_ABOUT:
                    return MessageBox(0, "This program is an alteration of...", "About", MB_OK);
                    //return DefWindowProc(hwnd2,0,0,0);
                case ID_B_HOME:
                    MessageBox(tab0_hwnd,"HERE","OKAY",NULL);
                    break;
                case ID_B_SAVE:
                    break;
                case ID_B_BLANK:
                    break;
                default:
                    return DefWindowProc(hwnd, Msg, wParam, lParam);
            }
            break;
        case WM_CLOSE:
            DestroyWindow(hwnd);
            break;  
        case WM_DESTROY:
            PostQuitMessage(0);
            break;
        default:
            return DefWindowProc(hwnd, Msg, wParam, lParam);
    }
    return 0;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
    tab_hinst = hInstance;
    //Step 1: Registering the Window Class
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.style         = 0;
    wc.lpfnWndProc   = WndProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInstance;
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = "Home";
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);
    if(!RegisterClassEx(&wc))
        MessageBox(NULL, "Window Registration Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK);
    // Step 2: Creating the Window
    main_hwnd = CreateWindowEx(
        WS_EX_CLIENTEDGE,
        "Home",
        "The Home page",
        WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX,
        CW_USEDEFAULT, CW_USEDEFAULT, 700, 400,
        NULL, NULL, hInstance, NULL);
    tab_hwnd = CreateWindowEx(
        0,
        "SysTabControl32",
        "",
        WS_CHILD|WS_CLIPSIBLINGS,
        CW_USEDEFAULT, CW_USEDEFAULT, 681, 338,
        main_hwnd, NULL, tab_hinst, NULL);
    tab0_hwnd = CreateWindowEx(
        0,
        "SysTabControl32",
        "",
        WS_CHILD|WS_CLIPSIBLINGS,
        1, 22, 679, 315,
        tab_hwnd, NULL, tab_hinst, NULL);
    text = CreateWindow("Static","Home Directory",WS_CHILD | WS_VISIBLE,0,50,150,50,tab0_hwnd, 0, tab_hinst,0);
    text = CreateWindow("Static","C:\",WS_CHILD | WS_VISIBLE,200,50,150,50,tab0_hwnd, 0, tab_hinst,0);
    //button = CreateWindow("Button","Navigate to...", BS_PUSHBUTTON | WS_CHILD | WS_VISIBLE ,350,42,100,25,tab0_hwnd,(HMENU)ID_B_HOME,tab_hinst,0);    
    text = CreateWindow("Static","Save Directory",WS_CHILD | WS_VISIBLE,0,100,150,50,tab0_hwnd, 0, tab_hinst,0);
    text = CreateWindow("Static","C:\",WS_CHILD | WS_VISIBLE,200,100,150,50,tab0_hwnd, 0, tab_hinst,0);
    //button = CreateWindow("Button","Save to...", BS_PUSHBUTTON | WS_CHILD | WS_VISIBLE ,350,92,100,25,tab0_hwnd,(HMENU)ID_B_SAVE,tab_hinst,0);
    tab1_hwnd = CreateWindowEx(
        0,
        "SysTabControl32",
        "",
        WS_CHILD|WS_CLIPSIBLINGS,
        1, 22, 679, 315,
        tab_hwnd, NULL, tab_hinst, NULL);
    tab2_hwnd = CreateWindowEx(
        0,
        "SysTabControl32",
        "",
        WS_CHILD|WS_CLIPSIBLINGS,
        1, 22, 679, 315,
        tab_hwnd, NULL, tab_hinst, NULL);
    tab3_hwnd = CreateWindowEx(
        0,
        "SysTabControl32",
        "",
        WS_CHILD|WS_CLIPSIBLINGS,
        1, 22, 679, 315,
        tab_hwnd, NULL, tab_hinst, NULL);
    tab4_hwnd = CreateWindowEx(
        0,
        "SysTabControl32",
        "",
        WS_CHILD|WS_CLIPSIBLINGS,
        1, 22, 679, 315,
        tab_hwnd, NULL, tab_hinst, NULL);
    tie.mask = TCIF_TEXT;
    tie.pszText = "Paths";
    TabCtrl_InsertItem(tab_hwnd, 0, &tie);
    tie.pszText = "Output";
    TabCtrl_InsertItem(tab_hwnd, 1, &tie);
    tie.pszText = "Parameters";
    TabCtrl_InsertItem(tab_hwnd, 2, &tie);
    tie.pszText = "Configurations";
    TabCtrl_InsertItem(tab_hwnd, 3, &tie);
    tie.pszText = "Run";
    TabCtrl_InsertItem(tab_hwnd, 4, &tie);
    if(main_hwnd == NULL) {
        MessageBox(NULL, "Window Creation Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }
    ShowWindow(main_hwnd, nCmdShow);
    ShowWindow(tab_hwnd, nCmdShow);
    ShowWindow(tab0_hwnd,nCmdShow);
    UpdateWindow(main_hwnd);
    UpdateWindow(tab_hwnd);
    UpdateWindow(tab0_hwnd);
    // Step 3: The Message Loop
    do{
        PeekMessage(&msg, NULL, NULL, NULL, PM_REMOVE);
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&msg);
        /* Send message to WindowProcedure */
        DispatchMessage(&msg);
    } while(msg.message!=WM_CLOSE && msg.message!=WM_QUIT);
    return msg.wParam;
}

我也对UpdateWindow()很好奇，如果我不画画，我需要调用这个吗?

Answer 1

在WM_CREATE描述中，我们读到消息在函数返回之前被发送。

因此main_hwnd的WM_CREATE总是发生在tab0_hwnd之前。

现在让我们看看你的代码处理WM_CREATE:

if(tab0_hwnd!=NULL)
   /* you would create the button here, but it does not happen. */

现在，如果tab0_hwnd是NULL，产生错误消息不是更好吗，而不是静默地忽略错误?

这不一定是代码的唯一问题，但我不会在没有可编译的示例的情况下进一步讨论。

在WndProc的WM_CREATE情况下创建按钮的调用在tab0_hwnd窗口创建之前运行。CreateWindow将不会返回，直到它调用WndProc的窗口类与WM_CREATE，所以你的代码的顺序是:

创建主窗口:main_hwnd
1. 在WndProc
的WM_CREATE情况下运行代码
2. 创建标签控件tab_hwnd
3. 创建标签控件tab0_hwnd

所以你需要重新排序你的代码，这样按钮将不会被创建，直到标签已经创建。

也许你错过了WS_VISIBLE ?这是必需的，否则你不会看到它