我在wxPaintDC绘图中得到了一个奇怪的东西

Question

我有一些关于wxpaintDC绘图的代码。

我有这样一些相关的绘图类：

IMPLEMENT_CLASS(MapView, wxWindow) 

BEGIN_EVENT_TABLE(MapView, wxWindow) 
EVT_PAINT(MapView::OnPaint) 
END_EVENT_TABLE() 

void MapView::OnPaint(wxPaintEvent & event) 
{ 

    wxPaintDC dc(this); 
    wxRect m_Rect = this->GetRect(); //get the rect 

    wxCoord x1 = 50, y1 = 60; 
    wxCoord x2 = 190, y2 = 60; 

    dc.DrawLine(x1, y1, x2, y2); 


    //draw line 
    //draw point 
    //draw polygon 

    if(m_ly->lineSVector.size()>0) 
    { 
     wxString tmp = wxString::Format(_T("%d"), m_ly->lineSVector.size()); 

     for(int i =0 ; i < m_ly->lineSVector.size(); i++) 
     { 
      wxArrayString strArrTmp = m_ly->lineSVector.at(i); 

      wxPoint *pts = new wxPoint; 

      wxPoint p1; 
      wxPoint p2; 

      wxPaintDC dc_k(this); 
      wxRect m_Rect = this->GetRect(); 

      wxCoord xx1 = 40, yy1 = 50; 
      wxCoord xx2 = 180, yy2 = 70; 
      dc_k.DrawLine(xx1, yy1,xx2,yy2); 

      for(int j = 0; j < strArrTmp.size(); j++) 
      { 

       wxString strPt = strArrTmp.Item(j); 

       int p = strPt.Find(" "); 

       wxString strX = strPt.substr(0,p); 
       wxString strY = strPt.substr(p+1,strPt.Length()-p); 

       double a = atof(strX); 
       double b = atof(strY); 

       a = a - m_ly->m_rect->GetLeft(); 
       b = b - m_ly->m_rect->GetBottom(); 

       a = m_Rect.GetLeft() + ((double)m_Rect.GetWidth()/(double)m_ly->m_rect->GetWidth()) * (double)a; 
       b = m_Rect.GetBottom() + ((double)m_Rect.GetHeight()/(double)m_ly->m_rect->GetHeight())* (double)b; 

       (pts + j)->x = a; 
       (pts + j)->y = b; 
       if(j==0) 
       { 
        //xx1 = a; 
        //yy1 = b; 
       } 
       else if(j==1) 
       { 
        //xx2 = a; 
        //yy2 = b; 
       }  
      } 
      //dc.DrawLines(strArrTmp.size(), pts); 
      //dc.DrawLine(p1, p2); 

    /*  dc.DrawLine(xx1, yy1,xx2,yy2);*/ 
     } 
     //wxMessageBox(tmp); 
    } 
    else 
    { 

    } 



} 

我尝试各种方法，但我发现，只有

wxPaintDC dc(this); 
wxRect m_Rect = this->GetRect(); //get the rect 

wxCoord x1 = 50, y1 = 60; 
wxCoord x2 = 190, y2 = 60; 

dc.DrawLine(x1, y1, x2, y2); 

生效。

它借鉴（50,60）一行（190,60）

我调试代码，并发现该代码可以进入

if(m_ly->lineSVector.size()>0) 
    {.... 
.... 
} 

而且它可以进入该代码 [code] wxPaintDC dc_k（this）; wxRect m_Rect = this-> GetRect（）;

 wxCoord xx1 = 40, yy1 = 50; 
     wxCoord xx2 = 180, yy2 = 70; 
     dc_k.DrawLine(xx1, yy1,xx2,yy2); 

我调试，并观看他们的价值毫无疑问，他们有正确的价值，并运行它们，

，但我真的不明白，为什么在我如果{}块不会生效我的绘制代码。

Answer 1

您不得创建两次wxPaintDC，您应该使用已有的同一个DC，而不是在if内重新创建另一个。