时间戳

首页 > 解决方案 > Windows API 子类化 - Win Docs 示例不起作用

c++ - Windows API 子类化 - Win Docs 示例不起作用

问题描述

我是 Windows Api 的新手，仍在学习基础知识。在我的项目中，我遇到了一个需要子类化的问题，所以我决定找一个示例代码，编译它，看看它在实践中是如何工作的。我在 Windows Docs 网页How to Subclass a Combo Box找到了一个相对简单的示例。在创建了一个父窗口并对要编译的代码进行了一些调整之后，我设法运行了它，但该程序似乎表现得好像没有进行子类化。

这不是第一次在网页上找到的示例代码不起作用。我错过了什么吗？

我的 WinMain 例程：

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

WNDCLASSEX wc = { 0 };
wc.lpszClassName = "MyClassName";
wc.hInstance = hInstance;
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wc.cbSize = sizeof(WNDCLASSEX);
wc.lpfnWndProc = ToolbarWindowProc;
RegisterClassEx(&wc)

hwndMain = CreateWindow(
    "MyClassName",
    "Title",
    WS_POPUPWINDOW | WS_CAPTION,
    0,
    0,
    500,
    210,
    nullptr,
    nullptr,
    hInstance,
    NULL
);
ShowWindow(hwndMain, nCmdShow);
UpdateWindow(hwndMain);

MSG msg;
while (GetMessageW(&msg, NULL, 0, 0) > 0) {
    TranslateMessage(&msg);
    DispatchMessageW(&msg);
}
return (int)msg.wParam;
}

标签： c++winapisubclassing

解决方案

你需要知道为什么我们需要子类化控件。

对现有控件进行子类化是创建自定义控件的另一种方法。子类过程可以通过处理影响选定行为的那些消息来改变控件的选定行为。所有其他消息都传递给控件的原始窗口过程。例如，应用程序可以通过子类化控件并处理WM_PAINT消息，在只读单行编辑控件中的文本旁边显示一个小位图。

参考：继承现有控件的窗口类

从您提供的链接来看，您似乎没有按照教程学习如何对控件进行子类化。

但是现在看来你需要一个完整的例子来学习。

所以第一步是使用官方模板，看下面的截图：

1

创建后，您可以从子类化静态控件开始。

将以下消息事件添加到WndProc函数中。

case WM_CREATE:
       {
           hWndStatic = CreateWindowEx(0, L"Static", NULL, WS_CHILD | WS_VISIBLE | SS_LEFT, 10, 130, 200, 40, hWnd, (HMENU)IDC_OWNERDRAWBUTTON, hInst, NULL);
           SetWindowSubclass(hWndStatic, &OwnerDrawButtonProc, IDC_OWNERDRAWBUTTON, 0);
        return TRUE;
    }
    break;

最后，添加子类控件的回调函数。

TCHAR szText[] = _T("TestString");
LRESULT CALLBACK OwnerDrawButtonProc(HWND hWnd, UINT uMsg, WPARAM wParam,
    LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
    switch (uMsg)
    {
    case WM_PAINT:
    {
        RECT rc;
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hWnd, &ps);
        GetClientRect(hWnd, &rc);
        SetTextColor(hdc, RGB(255, 0, 255));
        DrawText(hdc, szText, _tcslen(szText), &rc, DT_CENTER | DT_VCENTER);
        EndPaint(hWnd, &ps);
        return 0;
    }
    case WM_NCDESTROY:
        RemoveWindowSubclass(hWnd, &OwnerDrawButtonProc, 1);
        break;
    }
    return DefSubclassProc(hWnd, uMsg, wParam, lParam);
}

注意：不要忘记声明新创建的函数

完整示例：

// Test_SetWindowSubclass.cpp : Defines the entry point for the application.
//

#include "stdafx.h"
#include "Test_SetWindowSubclass.h"
#include <commctrl.h>
#pragma comment(lib,"Comctl32.lib")

#define MAX_LOADSTRING 100
#define IDC_OWNERDRAWBUTTON 101

// Global Variables:
HINSTANCE hInst;                                // current instance
WCHAR szTitle[MAX_LOADSTRING];                  // The title bar text
WCHAR szWindowClass[MAX_LOADSTRING];            // the main window class name
HWND hWndStatic;
// Forward declarations of functions included in this code module:
ATOM                MyRegisterClass(HINSTANCE hInstance);
BOOL                InitInstance(HINSTANCE, int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK OwnerDrawButtonProc(HWND hWnd, UINT uMsg, WPARAM wParam,
    LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData);

int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
                     _In_opt_ HINSTANCE hPrevInstance,
                     _In_ LPWSTR    lpCmdLine,
                     _In_ int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // TODO: Place code here.

    // Initialize global strings
    LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
    LoadStringW(hInstance, IDC_TESTSETWINDOWSUBCLASS, szWindowClass, MAX_LOADSTRING);
    MyRegisterClass(hInstance);

    // Perform application initialization:
    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }

    HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TESTSETWINDOWSUBCLASS));

    MSG msg;

    // Main message loop:
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    return (int) msg.wParam;
}



//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
    WNDCLASSEXW 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(hInstance, MAKEINTRESOURCE(IDI_TESTSETWINDOWSUBCLASS));
    wcex.hCursor        = LoadCursor(nullptr, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
    wcex.lpszMenuName   = MAKEINTRESOURCEW(IDC_TESTSETWINDOWSUBCLASS);
    wcex.lpszClassName  = szWindowClass;
    wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

    return RegisterClassExW(&wcex);
}

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   hInst = hInstance; // Store instance handle in our global variable

   HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE: Processes messages for the main window.
//
//  WM_COMMAND  - process the application menu
//  WM_PAINT    - Paint the main window
//  WM_DESTROY  - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
       {
           hWndStatic = CreateWindowEx(0, L"Static", NULL, WS_CHILD | WS_VISIBLE | SS_LEFT, 10, 130, 200, 40, hWnd, (HMENU)IDC_OWNERDRAWBUTTON, hInst, NULL);
           SetWindowSubclass(hWndStatic, &OwnerDrawButtonProc, IDC_OWNERDRAWBUTTON, 0);
        return TRUE;
    }
    break;
    case WM_COMMAND:
        {
            int wmId = LOWORD(wParam);
            // Parse the menu selections:
            switch (wmId)
            {
            case IDM_ABOUT:
                DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, 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 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;
}

TCHAR szText[] = _T("TestString");
LRESULT CALLBACK OwnerDrawButtonProc(HWND hWnd, UINT uMsg, WPARAM wParam,
    LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
    switch (uMsg)
    {
    case WM_PAINT:
    {
        RECT rc;
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hWnd, &ps);
        GetClientRect(hWnd, &rc);
        SetTextColor(hdc, RGB(255, 0, 255));
        DrawText(hdc, szText, _tcslen(szText), &rc, DT_CENTER | DT_VCENTER);
        EndPaint(hWnd, &ps);
        return 0;
    }
    case WM_NCDESTROY:
        RemoveWindowSubclass(hWnd, &OwnerDrawButtonProc, 1);
        break;
    }
    return DefSubclassProc(hWnd, uMsg, wParam, lParam);
}

调试：

2

在了解了控件子类化的过程之后，您可以查看 Remy 给您的评论。

推荐阅读