标  题: 如何实现一个橡皮区矩形                           
发信人: Pacific (无情~~~Nolove), 信区: VisualC
发信站: BBS 水木清华站 (Fri Oct 16 17:20:08 1998)


    CRectTracker是一个很有用的类，可以通过调用CRectTracker::                     
TrackRubberBand                                                                  
响应WM_LBUTTONDOWN消息来创建一个橡皮区矩形。下例表明使用CRectTracker移动         
和重置视窗中的蓝色椭圆的大小是很容易的事情。                                     
    首先，在文件档中声明一个CRectTracker数据成员：                               
class CSampleView : Public CView                                                 
{                                                                                
                                                                                 
    …                                                                           
                                                                                 
    public :                                                                     
         CrectTracker m_tracker;                                                 
                                                                                 
    …                                                                           
};                                                                               
    其次，在文档类的构造函数中初始化CRectTracker 对象：                          
CSampleDoc:: CSampleDOC ()                                                       
{                                                                                
     //Initialize tracker position, size and style.                              
     m_tracker.m_rect.SetRect (0, 0, 10, 10);                                    
     m_tracker.m_nStyle=CRectTracker:: resizeInside  |                           
           CRectTracker:: dottedLine;                                            
}                                                                                
    然后，在OnDraw函数中画椭圆和踪迹矩形：                                       
void CSampleView:: OnDraw (CDC* pDC)                                             
{                                                                                
     CSampleDoc* pDoc=GetDocument ();                                            
     ASSERT_VALID (pDoc);                                                        
                                                                                 
     //Select blue brush into device context.                                    
     CBrush brush (RGB (0, 0, 255));                                             
     CBrush* pOldBrush=pDC->SelectObject (&brush);                               
                                                                                 
     //draw ellipse in tracking rectangle.                                       
     Crect rcEllipse;                                                            
     pDoc->m_tracker.GetTrueRect (rcEllipse);                                    
     pDC->Ellipse (rcEllipse);                                                   
                                                                                 
     //Draw tracking rectangle.                                                  
     pDoc->m_tracker.Draw (pDC);                                                 
     //Select blue brush out of device context.                                  
     pDC->Selectobject (pOldBrush);                                              
}                                                                                
    最后，使用ClassWizard处理WM_LBUTTONDOWN消息，并增加下述代码。该段代码        
根据鼠标击键情况可以拖放、移动或者重置椭圆的大小。                               
void CSampleView::OnLButtonDown (UINT nFlags, CPoint point)                      
{                                                                                
     //Get pointer to document.                                                  
     CSampleDoc* pDoc=GetDocument ();                                            
     ASSERT_VALID (pDoc);                                                        
                                                                                 
     //If clicked on ellipse, drag or resize it. Otherwise create a              
     //rubber-band rectangle nd create a new ellipse.                            
     BOOL bResult=pDoc->m_tracker.HitTest (point)!=                              
         CRectTracker::hitNothing;                                               
                                                                                 
     //Tracker rectangle changed so update views.                                
     if (bResult)                                                                
     {                                                                           
        pDoc->m_tracker.Track (this,point,TRue);                                 
        pDoc->SetModifiedFlag ();                                                
        pDoc->UpdateAllViews (NULL);                                             
     }                                                                           
                                                                                 
     else                                                                        
        pDoc->m-tracker.TrackRubberBand (this,point,TRUE);                       
     CView:: onLButtonDown (nFlags,point);                                       
}                                                                                
    
--
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--
☆ 来源:．哈工大紫丁香 bbs.hit.edu.cn．[FROM: yazhou.bbs@bbs.net.t]
※ 修改:．fzx 于 Aug  9 16:51:17 修改本文．[FROM: heart.hit.edu.cn]