CDC中的SelectObject

、看MSDN中的解释：

Selects an object into the device context（选择一个对象到设备上下文中去）.

 CPen* SelectObject(
    CPen* pPen
 );
 CBrush* SelectObject(
    CBrush* pBrush
 );
 virtual CFont* SelectObject(
    CFont* pFont
 );
 CBitmap* SelectObject(
    CBitmap* pBitmap
 );
 int SelectObject(
    CRgn* pRgn
 );
 CGdiObject* SelectObject(
    CGdiObject* pObject
 );

 

参数：

pPen

A pointer to a CPen object to be selected.

pBrush

A pointer to a CBrush object to be selected.

pFont

A pointer to a CFont object to be selected.

pBitmap

A pointer to a CBitmap object to be selected.

pRgn

A pointer to a CRgn object to be selected.

pObject

A pointer to a CGdiObject object to be selected.

 

返回值：

A pointer to the object being replaced. This is a pointer to an object of one of the classes derived fromCGdiObject, such as CPen, depending on which version of the function is used.

 

返回一个指向被代替的对象的指针。这个真正指向的对象是重载于CGdiObject类的一种，比如CPen，具体以来与所使用的函数版本。

 

2、测试代码

 void CDrawView::OnLButtonDown(UINT nFlags, CPoint point)
 {
     // TODO: Add your message handler code here and/or call default
     m_ptBegin=point;//m_ptBegin是类的成员，类型为CPoint

     CView::OnLButtonDown(nFlags, point);
 }

 void CDrawView::OnLButtonUp(UINT nFlags, CPoint point)
 {
     // TODO: Add your message handler code here and/or call default
     CPen pen(PS_SOLID, 1, RGB(255, 0, 0));
     CClientDC dc(this);
     CPen* pOldPen=dc.SelectObject(&pen);//保存原始的CPen，即黑色的CPen
     dc.MoveTo(m_ptBegin);
     dc.LineTo(point);
     dc.SelectObject(pOldPen);//恢复原始的CPen
     dc.MoveTo(m_ptBegin);
     dc.LineTo(point.x+100, point.y);
     CView::OnLButtonUp(nFlags, point);
 }

 

3、运行结果：