equivalent of Control.CreateGraphics() for Compact framework 2.0

equivalent of Control.CreateGraphics() for Compact framework 2.0

• robydx

  Hello how can i override the OnPaint method
  Here is my problem:
  First I setup some circles on a panel with the paint event
  
  Rectangle[] Circles;
  private void panel1_Paint(object sender, PaintEventArgs e)
          {
              Graphics Draw = e.Graphics;
              Circles = new Rectangle[ 8 ];
              for (int i = 0; i < 8; i++)
              {
                  Circles[ i ] = new Rectangle(10, 200 - (i * 24), 20, 20);
                  Brush brWhite = new SolidBrush(Color.White);
                  Pen penBlack = new Pen(Color.Black); 
  
                  Draw.FillEllipse(brWhite, Circles[ i ]);
                  Draw.DrawEllipse(penBlack, Circles[ i ]);
              }
           }
  ///////////////////////////////////////////////////////////////////////////////////////////////
  Then I create a method to update the color of those circle depending if it's a one or a zero
  
  private void UpdateCircle (Graphics Update, int OneIndex, int ZeroIndex)
          {
              Brush brWhite = new SolidBrush(Color.White);
              Pen penBlack = new Pen(Color.Black); 
              Brush brRed = new SolidBrush(Color.Red);
            
              if (OneIndex > -1)                          // Draw red circle if one
              {
                  Update.FillEllipse(brRed, Circles[OneIndex]);
                  Update.DrawEllipse(penBlack, Circles[OneIndex]);
              }
  
              else if (ZeroIndex > -1)                    // Draw white circle if zero
              {
                  Update.FillEllipse(brWhite, Circles[ZeroIndex]);
                  Update.DrawEllipse(penBlack, Circles[ZeroIndex]);
              }
          }
  ////////////////////////////////////////////////////////////////////////////////////
  On the method where i read in the 1 and 0 i just need to call the UpdateCircle method and pass in the the graphics object to precise where i want it to draw and the the variables to read the index of 1 and 0.
  
  Graphics Update = this.panel1.CreateGraphics();
  int OneIndex  =........
  int ZeroIndex =.......
  UpdateCircle(Update, OneIndex, ZeroIndex);
  
  It works fine on the desktop but in the CF world i only can draw on a form.
  Anyway to go around this
  
  

• LamptonWorm

  In my example code I just simply called panel1.Invalidate() for simplicity. If you only want to invalidate a portion of a control you can use the Invalidate(Rectangle) override, passing it the rectangle (of the ellipse in your case) that needs to be updated.

  You can do a series of calles to Invalidate(Rectangle) if you want more than one rectangle to be updated on the next paint event.

  
  
  

• donWong

  You need to store the colors that you want to change in UpdateCircle() in member variables that will be used by the Paint event handler. For example:

  Brush circleBrushes[] = new Brush[ 8 ]; Pen circlePen = new Pen(Color.Blank); //... presumably in constructor for(int i = 0; i < circleBrushes.Length; ++i) { circleBrushes[ i ] = new SolidBrush(Color.Wite); } private void panel1_Paint(object sender, PaintEventArgs e) { // ... Debug.Assert(Circles.Length == circleBrushes.Length); for(int i = 0; i < Circles.Length; ++i) { e.Graphics.FillEllipse(circleBrushes[ i ], Circles[ i ]); e.Graphics.DrawEllipse(circlePen, Circles[ i ]); } // ... } private void UpdateCircle(int OneIndex, int ZeroIndex) { if (OneIndex > -1) // Draw red circle if one { circleBrushes[OneIndex] = new SolidBrush(Color.Red); panel1.Invalidate(); } else if (ZeroIndex > -1) // Draw white circle if zero { circleBrushes[ZeroIndex] = new SolidBrush(Color.White); panel1.Invalidate(); } }

  
  
  

• FRED COLES

  Just wanna precise that i want to create graphics on a panel
  
  

• Talyrond

  Handling the Paint event or overriding the OnPaint method is the recommended method.
  
  

• Nat999

  Thank you for your help. It was a great fix and it works. Oh one more thing since i constantly updating the indexes, I notice that the panel and circles got flickered. Is it due to the panel1.Invalidate(). Is there a way to prevent this flickering event
  And again I appreciate you help.
  
  

• khs202968

  great!!! :)
  
  
• equivalent of Control.CreateGraphics() for Compact framework 2.0