MFC OnEnChange 处理函数 - 无限循环

发布于 2024-07-30 04:23:53 字数 1399 浏览 3 评论 0原文

（我使用的是 VS++2005）

我将编辑框控件（带有 ID - ID_edit_box）放在对话框中，并为其关联（与处理程序向导）两个变量： control (c_editbox）和值（v_editbox）变量。此外，我还将处理函数 OnEnChangeedit_box 与该编辑框控件相关联。假设我们可以在编辑框中只输入一位数字，并且该数字可以是 0 或 1。如果我们输入其他值 - 我想要的是该编辑框的内容被自动清除，所以用户看不到他输入任何内容（换句话说，用户不能在编辑框中输入除 0/1 之外的任何内容）。我在 onEnChangeedit_box 函数中进行了检查。这是代码：

void CSDRDlg::OnEnChangeedit_box()
{
   CWnd* pWnd;
   CString edit_box_temp;

   pWnd = GetDlgItem(ID_edit_box);
   pWnd->GetWindowText(edit_box_temp);

   if ((edit_box_temp == "0" || edit_box_temp == "1")
   {...do something - i.e. setfocus on some other edit box }
   else
   {
       pWnd->SetWindowText(""); // clear the content of edit box
       //... any other statement below will not be executed because the 
       //above line cause again call of this function
   }
}

我调试并发现该行： pWnd->SetWindowText(""); 导致无限循环，因为我们更改了该函数中的控制内容，这再次触发了她的调用。

但我像这样更改上面的代码：

void CSDRDlg::OnEnChangeedit_box()
{
   UpdateData(TRUE);
   if ((v_editbox == "0" || v_editbox== "1")
   {...do something - i.e. setfocus on some other edit box }
   else
   { 
      v_editbox = "";
      UpdateData(FALSE);
   }
}

这符合我想要的效果，但是有人可以向我解释为什么当我们调用

  v_editbox = "";
  UpdateData(FALSE);

它时不会导致无限循环。

原文

(I'm using VS++2005)

I put edit box control (with ID - ID_edit_box) on my dialog, and associate (with handler wizard) two varibles for it: control (c_editbox) and value (v_editbox) variable. Also I associate handler function OnEnChangeedit_box with that edit box control. Suppose that we may enter just one digit in edit box, and that digit can be 0 or 1. If we enter some other value - what I want is that content of that edit box is automaticaly cleared, so user can't see that he type anything (in other words user can not enter anything except 0/1 in edit box). I do that check in onEnChangeedit_box function. Here is the code:

void CSDRDlg::OnEnChangeedit_box()
{
   CWnd* pWnd;
   CString edit_box_temp;

   pWnd = GetDlgItem(ID_edit_box);
   pWnd->GetWindowText(edit_box_temp);

   if ((edit_box_temp == "0" || edit_box_temp == "1")
   {...do something - i.e. setfocus on some other edit box }
   else
   {
       pWnd->SetWindowText(""); // clear the content of edit box
       //... any other statement below will not be executed because the 
       //above line cause again call of this function
   }
}

I debug and discover that line: pWnd->SetWindowText(""); cause an infinite loop because we change control content in this function which triggers again her call.

But I change above code like this:

void CSDRDlg::OnEnChangeedit_box()
{
   UpdateData(TRUE);
   if ((v_editbox == "0" || v_editbox== "1")
   {...do something - i.e. setfocus on some other edit box }
   else
   { 
      v_editbox = "";
      UpdateData(FALSE);
   }
}

and that works what I want but can someone explain to me why when we call

  v_editbox = "";
  UpdateData(FALSE);

that doesn't cause an infinite loop.

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音栖息无 2024-08-06 04:23:53

当您为编辑框添加变量时，为什么不将最小/最大值设置为 0/1 或将值类型设置为 bool

回复收藏 0 原文

泅渡 2024-08-06 04:23:53

您可能应该通过子类化 CEdit 并过滤掉无效字符来做到这一点。例如：

class CSDREdit public CEdit
{
    afx_msg void OnChar(UINT nChar, UINT nRepCnt, UINT nFlags);
    DECLARE_MESSAGE_MAP()
};

BEGIN_MESSAGE_MAP(CSDREdit, CEdit)
    ON_WM_CHAR()
END_MESSAGE_MAP()

void CSDREdit::OnChar(UINT nChar, UINT nRepCnt, UINT nFlags)
{
    if (nChar != _T('0') && nChar != _T('1'))
        return;
    CEdit::OnChar(nChar, nRepCnt, nFlags);
}

You should probably do this by subclassing CEdit and filter out invalid characters. eg:

class CSDREdit public CEdit
{
    afx_msg void OnChar(UINT nChar, UINT nRepCnt, UINT nFlags);
    DECLARE_MESSAGE_MAP()
};

BEGIN_MESSAGE_MAP(CSDREdit, CEdit)
    ON_WM_CHAR()
END_MESSAGE_MAP()

void CSDREdit::OnChar(UINT nChar, UINT nRepCnt, UINT nFlags)
{
    if (nChar != _T('0') && nChar != _T('1'))
        return;
    CEdit::OnChar(nChar, nRepCnt, nFlags);
}

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