MFC 画线

// 鼠标是否按下标志 点位变量

private:
    // 是否按下
    bool m_isPress;
    // 存点数据
    CPoint m_myPoint;

消息：

BEGIN_MESSAGE_MAP(CMFCApplication1View, CView)
	// 标准打印命令
	ON_COMMAND(ID_FILE_PRINT, &CView::OnFilePrint)
	ON_COMMAND(ID_FILE_PRINT_DIRECT, &CView::OnFilePrint)
	ON_COMMAND(ID_FILE_PRINT_PREVIEW, &CView::OnFilePrintPreview)
    ON_WM_LBUTTONDOWN()  // 左键按下
    ON_WM_LBUTTONUP()    // 左键抬起
    ON_WM_MOUSEMOVE()    // 鼠标移动
END_MESSAGE_MAP()

消息实现：

void CMFCApplication1View::OnLButtonDown(UINT nFlags, CPoint point)
{
    m_myPoint = point;
    m_isPress = true;

    CView::OnLButtonDown(nFlags, point);
}


void CMFCApplication1View::OnLButtonUp(UINT nFlags, CPoint point)
{
#ifdef MASK_THIS_BLOCK
    CClientDC dc(this);
    dc.MoveTo(m_myPoint);
    dc.LineTo(point);
#endif // 0

    m_isPress = false;
    CView::OnLButtonUp(nFlags, point);
}


void CMFCApplication1View::OnMouseMove(UINT nFlags, CPoint point)
{
    if (m_isPress) {
        CClientDC dc(this);
        dc.MoveTo(m_myPoint);
        dc.LineTo(point);

        // 更新起点
        m_myPoint = point;
    }

    CView::OnMouseMove(nFlags, point);
}