C ++ MFC如何使用GetDlgItem() [英] C++ MFC how to use GetDlgItem()

问题描述

这在主"example dlg.cpp"文件中:

This is in the main "example dlg.cpp" file:

void CHelixV3Dlg::OnBnClickedCancel()
{
   CEdit* editbox = (CEdit*)GetDlgItem(IDC_EDIT1); 
  //works fine, defined as: *CWnd GetDlgItem(int nID); in this file
}

这是test.cpp源文件

This is test.cpp source file

void test()
{
   CEdit* editbox = (CEdit*)GetDlgItem(IDC_EDIT1);
   //does not work at all, seems to be a winAPI function instead of MFC...
   //defined as: HWND __stdcall GetDlgItem(HWND hDlg, int nIDDlgItem);
}

两个源文件都在同一个项目中，使用相同的头，但是test()的GetDlgItem显然是Win32 API函数，在MFC中不起作用. 我该如何在test.cpp文件中使用GetDlgItem()?

both source files are in the same project, use the same headers, but test()'s GetDlgItem is obviously a Win32 API function, which does not work in MFC... How could I get GetDlgItem() working in the test.cpp file?

推荐答案

您不了解C ++范围规则.

You don't understand C++ scoping rules.

在第一次使用时，您最终会调用CWnd :: GetDlgItem()，因为您是从CHelixV3Dlg进行调用的.您的对话框类是从CDialog派生的，而CDialog是从CWnd派生的.使用普通的C ++范围规则，如果有一个成员函数以GetDlgItem作为其名称，它将被使用.

In your first usage, you end up calling CWnd::GetDlgItem() because you are making your call from CHelixV3Dlg. Your dialog class is derived from CDialog which is derived from CWnd. Using normal C++ scoping rules, if there is a member function that has GetDlgItem as its name, it will be the one to be used.

在第二种用法中，您最终按照WINAPI标头中的定义调​​用GetDlgItem().那是因为CWnd :: GetDlgItem()不在您的范围内.

In your second usage, you end up calling GetDlgItem() as defined in the WINAPI headers. That is because CWnd::GetDlgItem() is not in your scope.

如果要在第二次使用中调用CWnd版本，则必须以某种方式获取指向已创建并具有有效HWND的CHelixV3Dlg实例的指针或引用.有了该指针后:

If you want to call the CWnd version in your second usage, somehow you will have to get a pointer or reference to an instance of CHelixV3Dlg that has been created and has a valid HWND. Once you have that pointer:

void test(CHelixV3Dlg* pDlg)
{
   CEdit* editbox = (CEdit*)pDlg->GetDlgItem(IDC_EDIT1);
   // do some stuff with editbox...
}

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