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Java graphics redraw problem

You are having trouble with a simple panel for drawing in java. Problems getting my clear redraw button. The array clears but does not redraw. Can anyone identify my problem or is there any other way to create a clear button for this code.

public class DrawingPanel extends JPanel {
  private double x1=0;
  private double x2=0;
  private double y1=0;
  private double y2=0;

  private ArrayList<Shape> myArr = new ArrayList<Shape>();
  //private ArrayList<Shape> clearMyArr = new ArrayList<Shape>();
  ButtonPanel buttonPress;

   public void paintComponent(Graphics g) 
  {
     for (Shape i : myArr)
     {
        Graphics2D g2d = (Graphics2D)g;
        g2d.draw(i);
     }   
         /*for (Shape i : clearMyArr)
     {
        Graphics2D g2d = (Graphics2D)g;
        g2d.draw(i);
     }   */

  }         
    //inner class

   class Listener1 extends MouseAdapter
  {
      public void mousePressed(MouseEvent e)
     {
        x1=e.getX();
        y1=e.getY();
        System.out.println("Mouse Pressed");
     }

      public void mouseReleased(MouseEvent e)
     {
        x2=e.getX();
        y2=e.getY();
        Shape shape = null;
        if (buttonPress.buttonType.equals("Rectangle"))
        {
        // Rectangles cannot have a zero width or height
           if (x1 != x2 || y1 != y2)
           {
              double width = Math.abs(x1 -x2);
              double height = Math.abs(y1-y2);
              shape = new Rectangle2D.Double(Math.min(x1,x2),Math.min(y1,y2), width, height);
           }
        } 
        if (buttonPress.buttonType.equals("Eclipse"))
        {
           double width = Math.abs(x1 -x2);
           double height = Math.abs(y1-y2);
           shape = new Ellipse2D.Double(Math.min(x1,x2),Math.min(y1,y2), width, height);;
       } 
        if (buttonPress.buttonType.equals("Lines"))
        {
           shape = new Line2D.Double(x1, y1, x2, y2);

        } 
            if (buttonPress.buttonType.equals("Clear"))
        {
                for( int i = 0;i <= myArr.size(); i++ )
                {
                System.out.println("ArrayList Size :"+myArr.size());

                myArr.clear(); // clear all elements from arraylist 
                //clearMyArr.addAll(myArr);
                System.out.println("ArrayList Size :"+myArr.size()); 

                //myArr.removeAll();
                revalidate();
                repaint();
                }


        } 

        if (shape != null)
        {
           myArr.add(shape);

        }
        repaint();
     }


  }
//end of inner class

   public DrawingPanel(ButtonPanel reference)
  {
     buttonPress = reference;
     setBorder(BorderFactory.createLineBorder(Color.black,4));
     addMouseListener(new Listener1());      
  }

}

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3 answers

If you forget to call super.paintComponent(g);, the background will not be cleared, so the old image will still be visible. And all JButton and everything you added will not be drawn. To fix this, let the panel draw first, then you can draw your stuff on top of it.

@Override
protected void paintComponent(Graphics g) {
     super.paintComponent(g);// <-- let panel draw itself
     Graphics2D g2d = (Graphics2D)g;
     for (Shape i : myArr)
     {
        g2d.draw(i);
     }   
  }

( , , DrawingPanel.add(..)). :

@Override
protected void paintComponent(Graphics g)
     Graphics2D g2d = (Graphics2D)g;
     g2d.setColor(Color.grey);
     g2d.fillRect(0,0,this.getWidth(),this.getHeight()); //<-- clear the background
     for (Shape i : myArr)
     {
        g2d.draw(i);
     }   
  }

.

if (buttonPress.buttonType.equals("Clear"))
{
   myArr.clear();
   repaint();
}

revalidate();.

+7

super.paintcomponent(g) paintcomponent. , revalidate repaint JPanel.

+2

Try calling repaint (); your jpanel.

+1
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