C2440无法在C ++ WinApi中将LRESULT转换为WNDPROC [英] C2440 Can't convert LRESULT to WNDPROC in C++ WinApi

问题描述

我试图用WinApi写这个win32程序，我被困住，因为我下面的教程似乎有一个问题。

I'm trying to write this win32 program with WinApi and I'm stuck because the tutorial I'm following seems to have a problem.

MainWindow.h ：

MainWindow.h:

class MainWindow
{
  public:
    MainWindow(HINSTANCE);
   ~MainWindow(void);

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

    // [...]

MainWindow.cpp：

MainWindow.cpp:

MainWindow::MainWindow(HINSTANCE hInstance) : hwnd(0)
{
  WNDCLASSEX WndClsEx;
  // [...]
  WndClsEx.lpfnWndProc = &MainWindow::WndProcedure;
  // [...]
}

LRESULT CALLBACK MainWindow::WndProcedure(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
  // [...]
}

我必须引用MainWindow :: WndProcedure错误，因为我遵循的签名完全符合教程说，但是lpfnWndProc行在构造函数中给出一个编译时错误：

I must be referencing MainWindow::WndProcedure wrong because I'm following the signature exactly as the tutorial says, however the lpfnWndProc line in the constructor gives a compile-time error:

错误C2440： '='：无法从'LRESULT（__stdcall MainWindow :: *）（HWND，UINT，WPARAM，LPARAM）'转换为'WNDPROC'

error C2440: '=' : cannot convert from 'LRESULT (__stdcall MainWindow::* )(HWND,UINT,WPARAM,LPARAM)' to 'WNDPROC'

推荐答案

替换

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

由

static LRESULT CALLBACK WndProcedure(HWND, UINT, WPARAM, LPARAM);

此指针是函数调用中的一个隐藏参数，通过声明它静态this指针不是一个参数和两个函数的签名匹配。

The this pointer is a hidden parameter in your function call and by declaring it static the this pointer is not a parameter anymore and the signature of the two functions match.

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