CWnd::SubclassWindow

最新推荐文章于 2022-05-12 15:18:27 发布

原创最新推荐文章于 2022-05-12 15:18:27 发布 · 1.2k 阅读

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CC 4.0 BY-SA版权

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#function #null #parameters #windows #object #class

本文详细介绍了CWnd::SubclassWindow成员函数的作用及使用方法。该函数用于动态子类化窗口，并将其附加到CWnd对象上。文章通过一个示例展示了如何对组合框内的编辑控件和列表框进行子类化。

CWnd::SubclassWindow

Call this member function to "dynamically subclass" a window and attach it to this CWnd object.

BOOL SubclassWindow(
   HWND hWnd 
);

Parameters

hWnd

A handle to the window.

Return Value

Nonzero if the function is successful; otherwise 0.

Remarks

When a window is dynamically subclassed, windows messages will route through the CWnd's message map and call message handlers in the CWnd's class first. Messages that are passed to the base class will be passed to the default message handler in the window.

This member function attaches the Windows control to a CWnd object and replaces the window's WndProc and AfxWndProc functions. The function stores a pointer to the old WndProc in the CWnd object.

Note
The window must not already be attached to an MFC object when this function is called.

Example

// The following code shows how to subclass the edit control and list box
// controls inside a combo box. It uses WM_CTLCOLOR for subclassing.
// CSuperComboBox represents the combo box
HBRUSH CSuperComboBox::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
   if (nCtlColor == CTLCOLOR_EDIT)
   {
      //Edit control
      if (m_edit.GetSafeHwnd() == NULL)
         m_edit.SubclassWindow(pWnd->GetSafeHwnd());
   }
   else if (nCtlColor == CTLCOLOR_LISTBOX)
   {
      //ListBox control
      if (m_listbox.GetSafeHwnd() == NULL)
         m_listbox.SubclassWindow(pWnd->GetSafeHwnd());
   }
   HBRUSH hbr = CComboBox::OnCtlColor(pDC, pWnd, nCtlColor);
   return hbr;
}

void CSuperComboBox::OnDestroy()
{
   //unsubclass edit and list box before destruction
   if (m_edit.GetSafeHwnd() != NULL)
      m_edit.UnsubclassWindow();
   if (m_listbox.GetSafeHwnd() != NULL)
      m_listbox.UnsubclassWindow();
   CComboBox::OnDestroy();
}