CEdit数字验证事件C++ MFC

Question

我有一个CEdit文本框,它是属性窗格的一部分,只允许数值(正整数).当人们输入非数字值时,该框工作正常,但当他们删除框中的值时会弹出一个对话框,说:"请输入一个正整数."

情况如下:
1.我在框中有一个数字(比如20).
我删除了这个号码.
3.我收到错误对话框.
有谁能告诉我如何拦截这个事件并在那里放一个默认值？

这是我的属性窗格的样子:

const int DEFAULT_VALUE = 20;

class MyPropertyPane:public CPropertyPane
{
    //....
private:
    CEdit m_NumericBox;
    int   m_value;

    //....
public:
    afx_msg void OnEnChangeNumericBox();

    //....
}
void MyPropertyPane::MyPropertyPane()
{
   // Set a default value
   m_value = DEFAULT_VALUE;
}

//....
void MyPropertyPane::DoDataExchange(CDataExchange* pDX)
{
    DDX_Control(pDX, IDC_NUMERIC_BOX, m_NumericBox);

    // this sets the displayed value to 20
    DDX_Text(pDX, IDC_NUMERIC_BOX, m_value);
}

//....
void MyPropertyPane::OnEnChangeNumericBox()
{
    // Somebody deleted the value in the box and I got an event
    // saying that the value is changed.

    // I try to get the value from the box by updating my data
    UpdateData(TRUE);

    // m_value is still 20 although the value is 
    // deleted inside the text box.
}

Answer 1

您收到的消息来自数据验证例程,而不是数据交换例程.在DoDataExchange()中可能有这样的调用:

void MyPropertyPane::DoDataExchange(CDataExchange* pDX)
{
    DDX_Control(pDX, IDC_NUMERIC_BOX, m_NumericBox);
    DDX_Text(pDX, IDC_NUMERIC_BOX, m_value);
    DDV_MinMaxInt(pDX, m_value, 1, 20); // if the value in m_value is outside the range 1-20, MFC will pop up an error dialog
}

您可以通过删除内置MFC数据验证并添加自己的问题来解决此问题:

void MyPropertyPane::DoDataExchange(CDataExchange* pDX)
{
    DDX_Control(pDX, IDC_NUMERIC_BOX, m_NumericBox);
    DDX_Text(pDX, IDC_NUMERIC_BOX, m_value);

    if( m_value < 1 || m_value > 20 )
    {
        m_value = DefaultValue;
    }
}