可以通过以下步骤实现:
class CMyComboBox : public CComboBox
{
DECLARE_DYNAMIC(CMyComboBox)
public:
CMyComboBox();
virtual ~CMyComboBox();
protected:
afx_msg HBRUSH CtlColor(CDC* pDC, UINT nCtlColor);
DECLARE_MESSAGE_MAP()
};
IMPLEMENT_DYNAMIC(CMyComboBox, CComboBox)
CMyComboBox::CMyComboBox()
{
}
CMyComboBox::~CMyComboBox()
{
}
BEGIN_MESSAGE_MAP(CMyComboBox, CComboBox)
ON_WM_CTLCOLOR()
END_MESSAGE_MAP()
HBRUSH CMyComboBox::CtlColor(CDC* pDC, UINT nCtlColor)
{
HBRUSH hbr = CComboBox::CtlColor(pDC, nCtlColor);
// 根据需要设置边框颜色
if (nCtlColor == CTLCOLOR_EDIT)
{
// 设置错误状态下的边框颜色为红色
if (IsWindowEnabled() && IsWindowVisible() && GetEditSel() == 0)
{
pDC->SetTextColor(RGB(255, 0, 0));
pDC->SetBkColor(RGB(255, 255, 255));
pDC->SetBkMode(TRANSPARENT);
CPen pen(PS_SOLID, 1, RGB(255, 0, 0));
CPen* pOldPen = pDC->SelectObject(&pen);
CRect rect;
GetClientRect(rect);
rect.DeflateRect(1, 1);
pDC->Rectangle(rect);
pDC->SelectObject(pOldPen);
}
// 设置警告状态下的边框颜色为黄色
else if (IsWindowEnabled() && IsWindowVisible() && GetEditSel() != 0)
{
pDC->SetTextColor(RGB(0, 0, 0));
pDC->SetBkColor(RGB(255, 255, 0));
pDC->SetBkMode(TRANSPARENT);
CPen pen(PS_SOLID, 1, RGB(255, 255, 0));
CPen* pOldPen = pDC->SelectObject(&pen);
CRect rect;
GetClientRect(rect);
rect.DeflateRect(1, 1);
pDC->Rectangle(rect);
pDC->SelectObject(pOldPen);
}
}
return hbr;
}
通过以上步骤,当CMyComboBox控件处于错误状态时,边框颜色将显示为红色;当处于警告状态时,边框颜色将显示为黄色。这样可以更直观地向用户展示错误和警告信息。
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