Question

I have a JPanel parent with 3 JPanel children inside. They all currently make use of GridLayout and together represent a UML class. Problem is that when I add a new attribute or method, all 3 JPanel grow to the same size.

Desire behaviour is that:

1. The title box’s size always remain the same whenever a method or attribute is added.
2. When a method is added, only the method panel grows and title and attribute panel’s size stay the same.
3. When an attribute is added, only the attribute panel grows and other panels size stay the same.

The parent JPanel already can automatically grow/shrink whenever a method/attribute is added. I’m toying around with GridBagLayout atm but I’m getting nowhere near the desire results.

Is there a simple (or simpler) way for me to solve this?!

Here is few pics to show my situation.

A newly created UML class =>
this is how it currently behaves =>

But I want this => or this=> or this =>

Edit2: added new pics for clarity. Im terribly sorry if original version was misleading.

Edit3: YESS! I have sorted it! Felt like forever!! Here is the SSEEC:

Child panel

    import java.awt.Component;
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.MouseEvent;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.event.MouseInputAdapter;
import javax.swing.event.MouseInputListener;

    public class APanel extends JPanel{
        private JTextField tf;

    public APanel() {
        this.setLayout(new GridLayout(0,1));
        this.addMouseListener(mouseInputListener);
      }

    MouseInputListener mouseInputListener = new MouseInputAdapter() {
        @Override
        public void mouseClicked(MouseEvent e) {
        System.out.println("Adding a new text field!");
        tf = MyTF.create("Double click");
        addNewTF(tf);
        Component source = (Component) e.getSource();
        Container c = source.getParent();
        while(true) {
            if(c instanceof PPanel)
                break;
            else
                c=c.getParent();
        }
        PPanel p = (PPanel) c;
        p.expand();
        }
    };

    public void addNewTF(JTextField tf) {
        this.add(tf);
        this.setSize(this.getWidth(), this.getHeight()+tf.getHeight());
        this.revalidate();
        this.repaint();

    }
}

Parent panel:

    import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class PPanel extends JPanel{
    //private APanel panel1;
    private JPanel panel1;
    private APanel panel2;
    private APanel panel3;
    public PPanel() {

        this.setLayout(new BoxLayout(this , BoxLayout.Y_AXIS));
        this.setBackground(Color.black);

        panel1 = new JPanel();
        panel1.setLayout(new GridLayout(0,1));
        panel1.add(new JTextField("title"));
        panel2 = new APanel();
        panel2.setBorder(BorderFactory.createLineBorder(Color.red));
        panel3 = new APanel();
        panel3.setBorder(BorderFactory.createLineBorder(Color.black));

        this.add(panel1);
        this.add(Box.createRigidArea(new Dimension(0,1)));
        this.add(panel2);
        this.add(panel3);


    }
    public void expand() {
        this.setSize(this.getWidth(), this.getHeight()+33);
        this.revalidate();
        this.repaint();
    }
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        PPanel panel = new PPanel();
        panel.setBounds(10, 10, 100, 150);
        JPanel c = new JPanel(null);
        c.add(panel);
        frame.add(c);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(new Dimension(350, 300));
        frame.setTitle("Demo");
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

A helping class:

    import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.event.MouseEvent;
import javax.swing.JTextField;
import javax.swing.event.MouseInputAdapter;
import javax.swing.event.MouseInputListener;

public class MyTF {
    public static JTextField create(String name) {
        final JTextField tf = new JTextField(name);
        System.out.println(tf.getPreferredSize());
        tf.setPreferredSize(new Dimension(100,33));
        tf.addMouseListener(mouseInputListener);
        return tf;
    }

    static MouseInputListener mouseInputListener = new MouseInputAdapter() {
        @Override
            public void mouseClicked(MouseEvent e) {
                Component source = (Component) e.getSource();
                Container c = source.getParent();
                while(true) {
                    if(c instanceof PPanel)
                        break;
                    else if(c instanceof APanel)
                    {
                        c.dispatchEvent(e);
                        c = c.getParent();
                        break;

                    }
                    else
                        c=c.getParent();
                }
                c.dispatchEvent(e);
        }

    };
}

I gave up the efford playing with GridBagLayout, it was just too much for me. Then I tried borderLayout as suggested but couldn’t get it to work like I want it either. Then finally BoxLayout, it should had worked but there was a bug in my code! So when I tried out 0verbose code suggest and playing around with it, it failed! Not until, I finished up the SSEEC, did the final compile and run it before I decided to post (I practically gave up at this point) then I realised that it worked…The panel that can grow in their own space, they dont interfere with each other.

I was like WTF!

Went back to my code and compared it SSEEC and there was a bug, the code to expand the height of the panel was in wrong place so they sort of like eating into each other spaces.

Better yet! I can specify the distance between the middle box with the box above and below it by one pixel. That means I can still use the trick by mKorbel to draw the back line seperating those boxes!

Edit 4: is there a way for me to set size of a component? If you run the SSEEC, you will notice that once the JTextField is added in, it’s huge! It’s bigger than the container…

Answer 1

I suggest you to use BoxLayout. Here’s a tutorial. Playing around with glues and rigid area you can obtain almost all desired layout. In your case the code should be somthing like this:

JPanel container = new JPanel();
container .setLayout(new BoxLayout(container , BoxLayout.Y_AXIS));

JPanel childTop = new JPanel();
JPanel childCenter = new JPanel();
JPanel childBottom = new JPanel();


childTop.setMaximumSize(...);
childBottom.setMaximumSize(...);

container.add(childTop);
container.add(Box.createVerticalGlue());
container.add(childCenter);
container.add(Box.createVerticalGlue());
container.add(childBottom);

When you need to insert a new child, remember to insert it into the right position: between one of the glues and childCenter.
For example:

container.add(newChild, 2) ;