使用画line的方法介绍HDC CDC CClientDC CWindowDC用法

建立项目，采用单文档结构

HDC:

首先在CYourClassView类中add windows message handler, 一个是LButtonDown, 另一个是LButtonUp. 添加成员变量：m_ptOrigin用来记录初始点位置。

在view结构体中初始化m_ptOrigin变量：

CYourClassView:: CYourClassView ()

{

       // TODO: add construction code here

       m_ptOrigin=0;

}

在LButtonDown函数里面添加代码：

void CYourClassView::OnLButtonDown(UINT nFlags, CPoint point)

{

       // TODO: Add your message handler code here and/or call default

       m_ptOrigin=point;

       CView::OnLButtonDown(nFlags, point);

}

在LButtonUp中添加代码，首先使用HDC:

void CYourClassView::OnLButtonUp(UINT nFlags, CPoint point)

{

       // TODO: Add your message handler code here and/or call default

       HDC hdc;

       hdc=::GetWindowDC(m_hWnd);

       MoveToEx(hdc,m_ptOrigin.x,m_ptOrigin.y,NULL);

       LineTo(hdc,point.x,point.y);

       ::ReleaseDC(m_hWnd,hdc);

       CView::OnLButtonUp(nFlags, point);

}

使用CDC:

void CYourClassView::OnLButtonUp(UINT nFlags, CPoint point)

{

       // TODO: Add your message handler code here and/or call default

       CDC *pdc=GetDC();

       pdc->MoveTo(m_ptOrigin);

       pdc->LineTo(point);

       ReleaseDC(pdc);

       CView::OnLButtonUp(nFlags, point);

}

使用CClientDC:

void CYourClassView::OnLButtonUp(UINT nFlags, CPoint point)

{

       // TODO: Add your message handler code here and/or call default

       CClientDC dc(this);

       dc.MoveTo(m_ptOrigin);

       dc.LineTo(point);

       CView::OnLButtonUp(nFlags, point);

}

使用CWindowDC:

void CYourClassView::OnLButtonUp(UINT nFlags, CPoint point)

{

       // TODO: Add your message handler code here and/or call default

       CWindowDC dc(this);

       dc.MoveTo(m_ptOrigin);

       dc.LineTo(point);

       CView::OnLButtonUp(nFlags, point);

}