为什么OnKeyDown不会在基于对话框的MFC项目中捕获关键事件？ [英] Why doesn't OnKeyDown catch key events in a dialog-based MFC project?

问题描述

我只是在MFC（VS2008）中创建一个基于对话框的项目，并添加 OnKeyDown 事件到对话框。
当我运行项目并按键盘上的键，没有任何反应。但是，如果我从对话框中删除所有的控件，并重新运行项目它的工作原理。
即使我有对话框上的控件，我该怎么做才能得到关键事件？

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

它，对话框本身永远不会得到焦点。它被孩子控制被盗。当你按下一个按钮， WM_KEYDOWN 消息被发送到控件的焦点，所以你的 CgDlg :: OnKeyDown 从来没有称为。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);  
}

另请参阅有关CodeProject的文章：http://www.codeproject.com/KB/dialog/pretransdialog01.aspx

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

这篇关于为什么OnKeyDown不会在基于对话框的MFC项目中捕获关键事件？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！