GetWindowLong(hwnd, GWL_USERDATA)很费解

[亚细亚]

GetWindowLong(hwnd, GWL_USERDATA)
GWL_USERDATA解释是获得窗口一个32位的值.
那这个32位的值是创建窗体是系统分配的还是人工传递的一个参数?真费解!!!

[wocow3]

创建窗口的app可以用GWL_USERDATA存储一个32位值，每个窗口都有这个32bit的空间
一般是窗口的管理者(也就是创建该窗口的程序)负责维护这个值

[HowToP2p]

就是用SetWindowLong设置的值 传递GWL_USERDATA

[亚细亚]

[Quote=引用 1 楼 wocow3 的回复:]

创建窗口的app可以用GWL_USERDATA存储一个32位值，每个窗口都有这个32bit的空间
一般是窗口的管理者(也就是创建该窗口的程序)负责维护这个值
[/Quote]
这个值是哪个变量？

[亚细亚]

[Quote=引用 3 楼 howtop2p 的回复:]

就是用SetWindowLong设置的值 传递GWL_USERDATA
[/Quote]
有些代码一开始就没有用SetWindowLong()设置，而是直接用GetWindowLong(hwnd, GWL_USERDATA)

[Eleven]

GWL_USERDATA
Retrieves the user data associated with the window. This data is intended for use by the application that created the window. Its value is initially zero.

[亚细亚]

[Quote=引用 7 楼 visualeleven 的回复:]

GWL_USERDATA
Retrieves the user data associated with the window. This data is intended for use by the application that created the window. Its value is initially zero.
[/Quote]
这个数据是用户定义的数据，那应该是那个参数？例如下面的代码：

#include <windows.h>
#include <stdio.h>

static const TCHAR	ClassName[] = "Example";
LRESULT CALLBACK WindowProc( HWND hwnd,UINT uMsg,WPARAM wParam,LPARAM lParam);
LRESULT CALLBACK WindowProc( HWND hwnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
        switch(uMsg)
            {
 
             case WM_CLOSE:
                 DestroyWindow(hwnd);
                break;
             case WM_DESTROY:
                PostQuitMessage(0);
                break;
             default:
                return DefWindowProc(hwnd,uMsg,wParam,lParam);   
            } 
            return 0;
}

int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nCmdShow)
{
  
     MSG msg;
	 if (OleInitialize(NULL) == S_OK)
	{
 
        WNDCLASSEX wc;
	    ZeroMemory(&wc, sizeof(WNDCLASSEX));
	    wc.cbSize=sizeof(WNDCLASSEX);
		wc.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
		wc.hCursor=LoadCursor(NULL,IDC_ARROW);
		wc.hIcon=LoadIcon(NULL,IDI_APPLICATION);
	    wc.hInstance = hInstance;
		wc.lpfnWndProc = WindowProc;
		wc.lpszClassName = &ClassName[0];
		RegisterClassEx(&wc);
		
		 
		if ((msg.hwnd = CreateWindowEx(0, &ClassName[0], "web site", WS_OVERLAPPEDWINDOW,
						CW_USEDEFAULT, 0, CW_USEDEFAULT, 0,
						HWND_DESKTOP, NULL, hInstance, 4)))
		 {
                        GetWindowLong(hwnd, GWL_USERDATA);
			ShowWindow(msg.hwnd, nCmdShow);
			UpdateWindow(msg.hwnd);
		}
		
		while(GetMessage(&msg,NULL,0,0))
		{
		   TranslateMessage(&msg);
		   DispatchMessage(&msg);
		}
	
	
	OleUninitialize();
	return(0);
	}
    return 0;
}

[Eleven]

#include <windows.h>
#include <stdio.h>
#include <tchar.h>

static const TCHAR    ClassName[] = TEXT("Example");

typedef struct INFO
{
	int a;
	int b;
}INFO, *PINFO;

INFO info = {11, 22};
LRESULT CALLBACK WindowProc( HWND hwnd,UINT uMsg,WPARAM wParam,LPARAM lParam);
LRESULT CALLBACK WindowProc( HWND hwnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
        switch(uMsg)
            {
		case WM_CREATE:
			SetWindowLong(hwnd, GWL_USERDATA, (LONG)&info);
			break;
		case WM_CLOSE:
			DestroyWindow(hwnd);
			break;
		case WM_DESTROY:
			PostQuitMessage(0);
			break;
		default:
			return DefWindowProc(hwnd,uMsg,wParam,lParam);   
		} 
		return 0;
}

int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nCmdShow)
{
	
	MSG msg;
//	if (OleInitialize(NULL) == S_OK)
  //  {
		
        WNDCLASSEX wc;
        ZeroMemory(&wc, sizeof(WNDCLASSEX));
        wc.cbSize=sizeof(WNDCLASSEX);
        wc.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
        wc.hCursor=LoadCursor(NULL,IDC_ARROW);
        wc.hIcon=LoadIcon(NULL,IDI_APPLICATION);
        wc.hInstance = hInstance;
        wc.lpfnWndProc = WindowProc;
        wc.lpszClassName = &ClassName[0];
        RegisterClassEx(&wc);
        HWND hwnd = NULL;
		
        if ((hwnd = CreateWindowEx(0, &ClassName[0], TEXT("web site"), WS_OVERLAPPEDWINDOW,
			CW_USEDEFAULT, 0, CW_USEDEFAULT, 0,
			HWND_DESKTOP, NULL, hInstance, (LPVOID)4)))
		{
			INFO* pInfo = (INFO*)GetWindowLong(hwnd, GWL_USERDATA);
			TCHAR buf[20] = {0};
			_stprintf(buf, TEXT("a = %d, b = %d"), pInfo->a, pInfo->b);
			MessageBox(hwnd, buf, TEXT("Message"), 0);

            ShowWindow(hwnd, nCmdShow);
            UpdateWindow(hwnd);
        }
        
        while(GetMessage(&msg,NULL,0,0))
        {
			TranslateMessage(&msg);
			DispatchMessage(&msg);
        }
		
		
//		OleUninitialize();
//		return(0);
  ////  }
    return 0;
}

注意上的SetWindowLong()和GetWindowLong的用法

[亚细亚]

[Quote=引用 9 楼 visualeleven 的回复:]

C/C++ code
#include <windows.h>
#include <stdio.h>
#include <tchar.h>

static const TCHAR ClassName[] = TEXT("Example");

typedef struct INFO
{
int a;
int b;
}INFO, *PINFO;

INFO info = {……
[/Quote]
谢谢你的回复！
还有一点不明白，就是GetWindowLong(hwnd, GWL_USERDATA)与创建的窗口有什么关系？

[Eleven]

GetWindowLong(hwnd, GWL_USERDATA)与创建的窗口有什么关系？
-------------------------------------------------------
MSDN这里说的很清楚了：
Retrieves the user data associated with the window. This data is intended for use by the application that created the window. Its value is initially zero.

[亚细亚]

[Quote=引用 11 楼 visualeleven 的回复:]

GetWindowLong(hwnd, GWL_USERDATA)与创建的窗口有什么关系？
-------------------------------------------------------
MSDN这里说的很清楚了：
Retrieves the user data associated with the window. This data is intended for us……
[/Quote]
谢谢！结贴！