CComboBox DDX_CBString行为令人困惑 [英] CComboBox DDX_CBString behavior confusing

问题描述

我在对话框中使用ComboBox控件为用户提供一些有用的值(例如:10; 20; 100; 400; 800)，但如果需要的话，让用户插入确切的值.

I use a ComboBox control in a Dialog to give the user some useful values (Ex: 10; 20; 100; 400; 800) but let the user insert the exact value if needed.

经过很长时间我发现了什么: 如果我在组合框中键入值 40 ，则组合框在UpdataData()总是 400 之后返回. :(( 更好的值为 39 或 41 ，没有问题.

What I have discovered after long time: If I type the value 40 in the Combobox, the Combobox returns after UpdataData() always 400. :(( Ohterwards with the values 39 or 41, there is no problem.

这不是我和用户所期望的行为.
当我键入一个值时，ComboBox应该使用此值，如果从下拉菜单中选择，请使用此值.

That's is not the behaviour what I and the user expected.
When I type a value, ComboBox should take this value, if select from the dropdown Menue, take this.

我现在看到这种行为是由DDX_CBString给出的.

I see now this behaviour is given by DDX_CBString.

我必须编写自己的DDX_CBString还是其他方法?

Do I have to write my own DDX_CBString or is there an another approach?

代码:

void CTestDialog::DoDataExchange(CDataExchange* pDX)
{
    CDialogEx::DoDataExchange(pDX);
    DDX_Control(pDX, IDC_IFBANDWIDTH, m_cIFBandWidth);
    DDX_CBString(pDX, IDC_IFBANDWIDTH, m_sIFBandWidth);  // Bahavior confusing
}

BOOL CTestDialog::OnInitDialog()
{
    CDialogEx::OnInitDialog();

    m_cIFBandWidth.ResetContent();

    m_cIFBandWidth.AddString(_T("10"));
    m_cIFBandWidth.AddString(_T("20"));
    m_cIFBandWidth.AddString(_T("100"));
    m_cIFBandWidth.AddString(_T("400"));
    m_cIFBandWidth.AddString(_T("800"));


    return TRUE;  // return TRUE unless you set the focus to a control
    // EXCEPTION: OCX Property Pages should return FALSE
}

void CTestDialog::OnBnClickedApply()
{   
    UpdateData(TRUE);     // m_sIFBandWidth now 4 ok!
    UpdateData(FALSE);    // m_sIFBandWidth still 4, but control show 400, so the next OnOk() or Apply() take this value. Wrong!
}

推荐答案

我通过修改DDX_CBtring解决了这个问题.

I solved this with modify the DDX_CBtring.

void DDX_CBString_Normal(CDataExchange* pDX, int nIDC, CString& value)
{
    ..    
    if (pDX->m_bSaveAndValidate)
    {
        ..      
    }
    else
    {
        // Behaviour as we expect: Type a value and keep it
        // Select it form dropwon, or take the value the user type it
        AfxSetWindowText(hWndCtrl, value);
        return; 

        /* Disable original MS behavior 
        // set current selection based on model string
        if (::SendMessage(hWndCtrl, CB_SELECTSTRING, (WPARAM)-1,
            (LPARAM)(LPCTSTR)value) == CB_ERR)
        {
            // just set the edit text (will be ignored if DROPDOWNLIST)
            AfxSetWindowText(hWndCtrl, value);
        } 
       */
    }
}

如果有人有其他方法，请告诉我.

If anyone has an another aproach let me know.

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