Dynamic JPanel addition

Question

I am trying to create a dynamic Swing GUI. I need to add/delete JPanels when I click on add/delete button. I am not able to add JPanels dynamically. Initially JPanel loads but the array of JPanels fail to work. How do I do it?

import java.awt.*;
import java.awt.event.*;
import java.io.*;

import javax.print.attribute.standard.JobHoldUntil;
import javax.swing.*;

public class AccessoryFileChooser2 extends JFrame {
  JFileChooser chooser = null;
  JLabel statusbar;
  JLabel file;
  JCheckBox checkBox;
  int count;
  int increment;
  JPanel [] panel = new JPanel[10]; //array

  public AccessoryFileChooser2() {
    setSize(350, 200);
    count=0;
    increment=1;
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    final Container c = getContentPane();

    c.setLayout(new BorderLayout());
    checkBox =new JCheckBox("");
    String fileName = "Choose File Name";
   file = new JLabel(fileName);
    final JButton accButton = new JButton("Browse");
    final JButton add = new JButton("Add");
    final JButton validate = new JButton("Validate");
    final JButton delete = new JButton("Delete");

    accButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent ae) {
        int option = chooser.showOpenDialog(AccessoryFileChooser2.this);
        if (option == JFileChooser.APPROVE_OPTION) {
          statusbar.setText(
           (
            chooser.getSelectedFile().getPath()));
        }
      }
    });

    statusbar = new JLabel("Output of your selection will go here");
    chooser = new JFileChooser();


   final JPanel panels =new JPanel();

   //JPanel panel2 =new JPanel();
   panel[count]=new JPanel();
   panel[count].add(checkBox);
   panel[count].add(file);
   panel[count].add(accButton );
   panel[count].add(statusbar);
   c.add(panel[count],BorderLayout.CENTER);
   panels.add(add);
   panels.add(delete);
   panels.add(validate);

   add.addActionListener(new ActionListener() {

       public void actionPerformed(ActionEvent e)
       {
          count=count+1;;
          increment=increment+1;;
          panel[count]=new JPanel();
           System.out.println("You clicked the ADD button");

           panel[count].add(checkBox);
           panel[count].add(file);
           panel[count].add(accButton );
           panel[count].add(statusbar);
           panel[count].revalidate();
           panel[count].repaint();
           panel[count].updateUI();
           c.add(panel[count]);

       }
   });

   delete.addActionListener(new ActionListener() {

       public void actionPerformed(ActionEvent e)
       {
           increment--;
           System.out.println("You clicked the Delete button");
           System.out.println(checkBox.isSelected());
           for (int i = 0; i < panel.length; i++) {
               JCheckBox box=(JCheckBox) panel[i].getComponent(0);
               if(box.isSelected()){
   c.remove(panel[i]);
   }
        }

       }
   });

   validate.addActionListener(new ActionListener() {

       public void actionPerformed(ActionEvent e)
       {
           System.out.println("You clicked the Validate button");
       }
   });


   c.add(panels,BorderLayout.SOUTH);

  }

  public static void main(String args[]) {
    AccessoryFileChooser2 afc = new AccessoryFileChooser2();
    afc.setVisible(true);
  }
}

score 1 · Answer 1 · answered Jul 27 '11 at 14:23

1

When adding or removing components from a visible GUI the general code should be:

panel.add(...);
panel.revalidate();
panel.repaint();

The revalidate basically invoke the layout manager.

The repaint makes sure the components are repainted in case the layout has changed.

answered Jul 27 '11 at 14:23

camickr

321,443
19
166
288

Hi, it works for me with revalidate(); only, repaint() method is necessary? why ? – Marwen Trabelsi Feb 05 '12 at 20:27
@MarwenTrabelsi, repaint() is generally not necessary when you only add a component. However, sometimes if you remove and then add a component you may need to force the repaint because the layout manager may think the panel is the same size and not invoke repaint(). – camickr Feb 06 '12 at 18:29

score 1 · Accepted Answer · edited May 23 '17 at 10:30

not that not correct, there are lots of newbie mistakes,

1/ because same way as you created array for JPanels

JPanel [] panel = new JPanel[10];

you need to create Array for its JComponents, because one JComponent could be added only once time

EDIT: partial amended/changed code diplayed this issue

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.LineBorder;

public class AccessoryFileChooser2 extends JFrame {

    private static final long serialVersionUID = 1L;
    private JFileChooser chooser = null;
    private JLabel statusbar;
    private JLabel file;
    private JCheckBox checkBox;
    private int count;
    private int increment = 10;
    private JPanel parentPanel = new JPanel();
    private JPanel panels = new JPanel();
    private JPanel[] panel = new JPanel[increment]; //array
    private JButton accButton = new JButton("Browse");
    private JButton addButton = new JButton("Add");
    private JButton validate = new JButton("Validate");
    private JButton delete = new JButton("Delete");

    public AccessoryFileChooser2() {
        count = 0;
        parentPanel.setLayout(new GridLayout(10, 1, 10, 10));
        checkBox = new JCheckBox("");
        String fileName = "Choose File Name";
        file = new JLabel(fileName);
        accButton.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent ae) {
                int option = chooser.showOpenDialog(AccessoryFileChooser2.this);
                if (option == JFileChooser.APPROVE_OPTION) {
                    statusbar.setText((chooser.getSelectedFile().getPath()));
                }
            }
        });
        statusbar = new JLabel("Output of your selection will go here");
        chooser = new JFileChooser();
        panel[count] = new JPanel();
        panel[count].add(checkBox);
        panel[count].add(file);
        panel[count].add(accButton);
        panel[count].add(statusbar);
        panel[count].setPreferredSize(new Dimension(450, 40));
        panel[count].setBorder(new LineBorder(Color.BLACK, 1));
        parentPanel.add(panel[count]);
        addButton.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                if (count < increment - 1) {
                    count += 1;
                    panel[count] = new JPanel();
                    System.out.println("You clicked the ADD button");
                    panel[count].add(checkBox);
                    panel[count].add(file);
                    panel[count].add(accButton);
                    panel[count].add(statusbar);
                    panel[count].revalidate();
                    panel[count].repaint();
                    //panel[count].updateUI();
                    parentPanel.add(panel[count]);
                    parentPanel.revalidate();
                    parentPanel.repaint();
                    pack();
                    if (count == increment - 1) {
                        addButton.setEnabled(false);
                    }
                }
            }
        });
        delete.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                System.out.println("You clicked the Delete button");
                System.out.println(checkBox.isSelected());
                /*for (int i = 0; i < parentPanel.getComponentCount(); i++) {
                JCheckBox box = (JCheckBox) panel[i].getComponent(0);
                if (box.isSelected()) {
                parentPanel.remove(panel[i]);
                }
                }*/
            }
        });
        validate.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                System.out.println("You clicked the Validate button");
            }
        });
        panels.setLayout(new GridLayout(1, 3, 10, 10));
        panels.add(addButton);
        panels.add(delete);
        panels.add(validate);
        add(parentPanel, BorderLayout.CENTER);
        add(panels, BorderLayout.SOUTH);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }

    public static void main(String args[]) {
        AccessoryFileChooser2 afc = new AccessoryFileChooser2();
    }
}

with this output to the GUI

enter image description here

2/ and so on ...

don't do it this way, there is possible a lots of issues with performance, if you add and remove JPanel[] lots of times ..., GUI would be freeze or will be un-responsive

it would be better to look for JTable with one TableColumn as is suggested here

Thanks a lot. Ya i am new to Swings. So trying some things to get familiar. — freepublicview, Jul 28 '11 at 08:44

MByD · Answer 3 · 2011-07-27T12:16:15.433

0

Add c.validate() after c.add(panel[count]); to update the GUI.

It is also recommended to check the current number of JPanels, because this way, you will get ArrayIndexOutOfBoundsException pretty fast...

edited Jul 27 '11 at 12:16

answered Jul 27 '11 at 12:10

MByD

135,866
28
264
277

And does it help? according to docs you have to call it after `add` – MByD Jul 27 '11 at 12:15
I have added c.validate as c.revalidate is not present. But its still not working.Thanks for your reply. – freepublicview Jul 27 '11 at 12:16
try calling `invalidate()` before – MByD Jul 27 '11 at 12:18

score 0 · Answer 4 · answered Jul 27 '11 at 14:00

0

I have had success with:

repaint();
validate();

after making changes to the gui at run time. When I create, remove, move panels I call these two methods on the component/container.

answered Jul 27 '11 at 14:00

Allan

2,889
2
27
38

Dynamic JPanel addition

4 Answers4