Resizing window erases content of Graphics2d

[Fernando Piovani]

Every time i resize the window, or open a new window in front of it, the content (drawed lines) are erased. How can i avoid that?

Also, can some explain why this happens in technical terms?

[ ]´s

[Campbell Ritchie]

Please post some code, because we shall need more details to work on.

I shall move this thread to our GUIs forum, because it sounds a GUI-related question.

[Maneesh Godbole]

Most probably you are missing the call to super.paintComponent()
If that doesn't fix the problem post your SSCCE code like Campbell suggested.

[Fernando Piovani]

Maneesh Godbole wrote:Most probably you are missing the call to super.paintComponent()
If that doesn't fix the problem post your SSCCE code like Campbell suggested.

public class GMI_JFrame extends javax.swing.JFrame {

    /** Creates new form GMI_JFrame */
    public GMI_JFrame() {
        initComponents();
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 523, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 430, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>                        

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(GMI_JFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(GMI_JFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(GMI_JFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(GMI_JFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new GMI_JFrame().setVisible(true);
                
            }
        });
    }
    // Variables declaration - do not modify                     
    // End of variables declaration                   
}

class Drawing extends GMI_JFrame{
  JLabel label;  
  Parser parser;
  

  public Drawing(Parser prs) {  
    parser=prs;
    Container c = getContentPane();
    c.setLayout(new BorderLayout());

    label = new JLabel();
    c.add(label, BorderLayout.CENTER);

    JButton btn = new 
      JButton("Draw Lines");
    btn.addActionListener(
      new ActionListener(){
        public void actionPerformed(ActionEvent e){
          
          Graphics graphics = label.getGraphics();
          Graphics2D g2 = (Graphics2D) graphics;
          g2.setStroke(new BasicStroke(4));
          for (int j=0;j<=parser.wayCounter();j++)
          {
              parser.loader(parser.wayList(j));
              int count=parser.way.getId().size();
              for (int i=0; i<count-1;i++)
              {
                  g2.drawLine(parser.coord2pixel(true, i, parser.way.getId().size())
                  , parser.coord2pixel(false, i, parser.way.getId().size())
                  , parser.coord2pixel(true, i+1, parser.way.getId().size())
                  , parser.coord2pixel(false, i+1, parser.way.getId().size()));  
              }
              
          }

        }
      }
    );
    c.add(btn, BorderLayout.SOUTH);
    setSize(700,700);
    setVisible(true);
  }
}

I didnt start to work on the GUI yet. I am using netBeans as you can see in the code-generated below. The only thing the program does is display lines that represents a map, using gps coordinates.

Every time i resize the window, or open a new window in front of it, all the drawing is gone.

Oh, and one more question, how can i transform the label that i've draw on into a image, so i can work on the pixels to zoom it and etc.

[Darryl Burke]

:groan:

Never never never use getGraphics() of a Component. Learn about Performing Custom Painting the correct way.

[Darryl Burke]

I am using netBeans as you can see in the code-generated below.

You have every right to take the hard road, but at least you could remove the inane commencts and make your code shorter for posting.

[Fernando Piovani]

Maneesh Godbole wrote:Most probably you are missing the call to super.paintComponent()
If that doesn't fix the problem post your SSCCE code like Campbell suggested.

Yeah, that definitely works. I dont yet understand how and why but its ok... Still, resizing cause the program to reload all drawing, and since i've been working with a huge amout of data it take several time to resize (when growing to larger dimen. ).

My question is:

Why, when i resize to a smaller dimensions didnt reload the drawing process and how does exactly super.paintComponent() works on this matter?

[Darryl Burke]

Why, when i resize to a smaller dimensions didnt reload the drawing process and how does exactly super.paintComponent() works on this matter?

Still using getGraphics(), huh?

[Rob Camick]

and how does exactly super.paintComponent() works on this matter?

I have no idea because this should NOT have fixed your problem. Plus your posted code doesn't even have a paintComponent() method so I have no idea what you are doing.

The whole point of invoking super.paintComponent() is to clear the background of the panel by repainting the panel in its background color which is gray(ish).

Darryl has twice given you the solution.

[Fernando Piovani]

Darryl Burke wrote:

Why, when i resize to a smaller dimensions didnt reload the drawing process and how does exactly super.paintComponent() works on this matter?

Still using getGraphics(), huh?

Actually, no. I've read the perform custom painting that you show to me, and i done what it says so now it looks like that:

protected void paintComponent(Graphics g) {
          super.paintComponent(g);      
          int way_count;
          parser = new Parser();
          Graphics2D g2 = (Graphics2D) g;
          g2.setStroke(new BasicStroke(1));
          way_count=parser.wayCounter();
          for (int j=0;j<=way_count;j++)
          {
              parser.loader(parser.wayList(j));
              int count=parser.way.getId().size();
              for (int i=0; i<count-1;i++)
              {
                  g2.drawLine(parser.coord2pixel(true, i, parser.way.getId().size())
                  , parser.coord2pixel(false, i, parser.way.getId().size())
                  , parser.coord2pixel(true, i+1, parser.way.getId().size())
                  , parser.coord2pixel(false, i+1, parser.way.getId().size())); 
              }
          }
      }

[On Drawing class]

private static void createAndShowGUI() {
        JFrame f = new JFrame("GMI");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        f.add(new Drawing());
        f.pack();
        f.setVisible(true);
    } 

[On Custom_JFrame class]


Its working, but still got this issue with resizing to a bigger window.>

[Ranganathan Kaliyur Mannar]

In that case, this is a performance problem and you should follow what is mentioned in the tutorial:
"To keep our custom painting as efficient as possible, we will track the mouse coordinates and repaint only the areas of the screen that have changed. This is a recommended best practice that will keep your application running as efficiently as possible. "

Refer: Clipping