发送lparam作为类的指针，并在WndProc（）中使用它， [英] sending lparam as a pointer to class, and use it in WndProc()

问题描述

我有这个抽象代码：
我想在CreateWindowEx（）中使用lParam（最后一个参数）来保存指向main - SaveArr开始时声明的类的指针。然后，我想在函数WndProc中使用它。
在开始我做了一个全局数组，然后我可以使用它在任何地方，但它不是那么聪明到c ++关注，所以我试图升级它一点。

i have this abstract code : i want to use lParam (last parameter) in CreateWindowEx() to save a pointer to a class thats declared in the begining of main - SaveArr. then, i want to use it in the function WndProc. in the begining i did a global array, and then i could use it anywhere, but its not so "clever" as far as c++ concern, so im trying to upgrade it a bit.

class Samples
{
        int arr[ITERATIONS+1];
        int index;
        ...
}

INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine, int nCmdShow)
{
        Samples * SaveArr;
        ...
    hWnd = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW,
                          ClsName,
                          WindowCaption,
                          WS_OVERLAPPEDWINDOW,
                          INITIAL_WIN_LOCAT_X,
                          INITIAL_WIN_LOCAT_Y,
                          WIN_WIDTH,
                          WIN_HIGHT,
                          NULL,
                          NULL,
                          hInstance,
                          NULL);    //here i want to pass SaveArr, so that i can use it in the WndProc(...) function

...
return 0;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
   ...      //here i would like to use lParam as the class pointer, meaning using the 
              SaveArr declared in the main function.

}

}

推荐答案

最佳方式是

    LRESULT CALLBACK WndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
    {
           Samples *savearr = (Samples*)GetWindowLong(hWnd,GWL_USERDATA)
           switch(Msg)
           {
                case WM_CREATE:
                    SetWindowLong(hWnd, GWL_USERDATA, (LONG)lParam);
                    break;
           }
    }

下一次调用WndProc时，在savearr，并可以使用。

The next time the WndProc is called the value would be in savearr, and can be used.

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