Java Gui, gap between elements after hiding some of them

Question

I am developing a GUI in java using Netbeans (7.0).

I have a JFrame including a JPanel and several elements inside this panel.

The layout type is free layout I think.

draft:

-------------------
|JFrame           |
|                 |
| --------------- |
| |JPanel       | |
| |             | |
| | elem1 elem2 | |
| | elem3 elem4 | |
| | elem5 elem6 | |
| |             | |
| |-------------- |
|                 |
-------------------

During my program is running I am hiding some of the elements being in one row (e. g. elem3 and elem4) by using setVisible(false).

Everything resizes as expected (JFrame and JPanel) except for the gaps. It looks like that the elements are hidden correctly but there gaps are remaining so that in my example where I am hiding elem3 and elem4 a bigger gap between the row elem1/elem2 and elem5/6 remains.

Hopefully my problem was understandable :-)

Is there any way to fix this behavior?

Thanks in advance.

Steffen

Answer 1

Try removing that elements from jpanel instead of hiding but remember this will still not work for some layout. It depends on your layout to how to handle adding and removing of component.

Answer 2

with intend to avoid any missinterpretations:

if is TopLayoutContainer once visible then:

1/ for adding new JComponent is needed to call revalidate() and for compound JComponents f.e. with set programatically Item in JComboBox is needed call with repaint() too

2/ after removing JCmponent(s) you have to call revalidate() plus repaint()

3/ for example remove JComponents -> add new JComponents -> revalidate() plus repaint()

@Steffen Kuehn there are lots of possible problems, better would be to sent code that ilustrated your described issue

Answer 3

@Steffen Kuehn please check out the below code which presents the 'possible' problem you are experiencing. i.e. you are not revalidating and repainting the panel which was changed.

Please notice when you click the panel using left mouse button there is no repainting/revalidation, and at first it seems nothing is happening. Try to resize the frame. It calls the operations and you will see that the elements 5 & 6 are in fact visible. Thus if you want the changes to be instant use the right click which does visibility change and validation.

    import java.awt.Color;
    import java.awt.event.MouseAdapter;
    import java.awt.event.MouseEvent;
    import javax.swing.JComponent;
    import javax.swing.JFrame;
    import javax.swing.JPanel;
    import javax.swing.JTextField;
    import javax.swing.SwingUtilities;

    public class FlowComponentsTest
    {
        public static void main(String[] args)
        {
            SwingUtilities.invokeLater(new Runnable()
            {
                @Override
                public void run()
                {
                    final JPanel p = new JPanel();
                    for(int i = 1; i <= 20; i++)
                    {
                        JComponent c = new JTextField("I am element no. " + i);
                        //so any textfield will not steal the focus from the panel p
                        c.setFocusable(false);
                        p.add(c);
                        if(i == 5 || i == 6)
                        {
                            c.setForeground(Color.GREEN);
                            c.setVisible(false);
                        }
                    }
                    JFrame f = new JFrame();
                    f.addMouseListener(new MouseAdapter()
                    {
                        @Override
                        public void mousePressed(MouseEvent e)
                        {
                            JComponent c5 = (JComponent) p.getComponent(4);
                            JComponent c6 = (JComponent) p.getComponent(5);
                            c5.setVisible(!c5.isVisible());
                            c6.setVisible(!c6.isVisible());

                        if(e.getButton() == MouseEvent.BUTTON3)
                        {
                            System.out.println("Right click");
                            p.revalidate();
                            p.repaint();
                        }
                    }
                });
                f.setContentPane(p);
                f.setSize(300, 330);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);
            }
        });
    }
}