CDC中的SelectObject

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1、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 from CGdiObject, 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 defaultm_ptBegin=point;//m_ptBegin是类的成员，类型为CPointCView::OnLButtonDown(nFlags, point);}void CDrawView::OnLButtonUp(UINT nFlags, CPoint point){// TODO: Add your message handler code here and/or call defaultCPen 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CPendc.MoveTo(m_ptBegin);dc.LineTo(point);dc.SelectObject(pOldPen);//恢复原始的CPendc.MoveTo(m_ptBegin);dc.LineTo(point.x+100, point.y);CView::OnLButtonUp(nFlags, point);}

3、运行结果：