为什么 OnKeyDown 不捕获基于对话框的 MFC 项目中的关键事件?

Why doesn#39;t OnKeyDown catch key events in a dialog-based MFC project?(为什么 OnKeyDown 不捕获基于对话框的 MFC 项目中的关键事件?)

问题描述

我只是在 MFC (VS2008) 中创建了一个基于对话框的项目并将 OnKeyDown 事件添加到对话框中.当我运行项目并按下键盘上的键时，没有任何反应.但是，如果我从对话框中删除所有控件并重新运行项目，它就可以工作.即使对话框上有控件，我应该怎么做才能获取关键事件?

I just create a dialog-based project in MFC (VS2008) and add OnKeyDown event to the dialog. When I run the project and press the keys on the keyboard, nothing happens. But, if I remove all the controls from the dialog and rerun the project it works. What should I do to get key events even when I have controls on the dialog?

这是一段代码:

void CgDlg::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
{
    // TODO: Add your message handler code here and/or call default
    AfxMessageBox(L"Key down!");
    CDialog::OnKeyDown(nChar, nRepCnt, nFlags);
}

推荐答案

当对话框上有控件时，对话框本身永远不会获得焦点.它被儿童控件偷走了.当您按下一个按钮时，一个 WM_KEYDOWN 消息将发送到具有焦点的控件，因此您的 CgDlg::OnKeyDown 永远不会被调用.如果您希望对话框处理 WM_KEYDOWN 消息，请覆盖对话框的 PreTranslateMessage 函数:

When a dialog has controls on it, the dialog itself never gets the focus. It's stolen by the child controls. When you press a button, a WM_KEYDOWN message is sent to the control with focus so your CgDlg::OnKeyDown is never called. Override the dialog's PreTranslateMessage function if you want dialog to handle the WM_KEYDOWN message:

BOOL CgDlg::PreTranslateMessage(MSG* pMsg)
{
   if(pMsg->message == WM_KEYDOWN   )  
   {
      if(pMsg->wParam == VK_DOWN)
      {
         ...
      }
      else if(pMsg->wParam == ...)
      {
         ...                      
      }
      ...
      else
      {
         ...                   
      }
   }

   return CDialog::PreTranslateMessage(pMsg);  
}

另请参阅 CodeProject 上的这篇文章:http://www.codeproject.com/KB/dialog/pretransdialog01.aspx

Also see this article on CodeProject: http://www.codeproject.com/KB/dialog/pretransdialog01.aspx

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