How to force JContainer to re-layout itself?

Question

I have JFrame with BorderLayout: JTextArea in the NORTH and JButton in the SOUTH. I pack() it in the beginning.

My code changes font size for the text area. How do I force the dialog window and its components to re-layout itself?

So far I tried some combinations of:

another pack()
repaint()
revalidate()

It does not seem to help.

Is there a guaranteed brute force approach? What is the proper way to achieve such result?

UPDATE:

While creating SCCE (see below) I found two mistakes in my original code and fixed them. The frame is re-sizing nicely now.

I still have a question whether this is the proper way to do it.

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

public class MyFrame extends JFrame implements ActionListener{

    private JTextArea txt;
    private JButton bis;
    private JFrame frame;

    int size = 10;

    private void BuildMainGUI() {
        txt = new JTextArea("This is just a line of text");
        bis = new JButton("Increase size");

        JPanel p1 = new JPanel();
        bis.addActionListener(this);

        BorderLayout bl = new BorderLayout();

        p1.setLayout(bl);
        p1.add(txt, BorderLayout.NORTH);
        p1.add(bis, BorderLayout.SOUTH);

        frame = new JFrame();
        frame.setContentPane(p1);
        frame.setVisible(true);
        frame.pack();
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    @Override
    public void actionPerformed(ActionEvent e) {

        size += 2;
        Font newFont = new Font("Courier", Font.PLAIN, size);
        txt.setFont(newFont);
        frame.revalidate();
        frame.pack();
    }

    /**
     * @param args
     */
    public static void main(String[] args) {

        MyFrame myGUI = new MyFrame(); 
        myGUI.BuildMainGUI();
    }
}

this is correct suggestion, but there are three proper ways, for better help sooner post an [SSCCE](http://sscce.org/), short, runnable, compilable, just about your view — mKorbel, Apr 18 '13 at 19:08
@mKorbel - As many times in my long programming career, all it took to find the problem was to get rid of unrelated code and concentrate on what's left. — PM 77-1, Apr 18 '13 at 19:55
`While creating SCCE (see below) I found two mistakes in my original code and fixed them` - and that is why a SSCCE should be provided with every question. Most of the time creating the SSCCE solves the problem so you don't even need to ask it. — camickr, Apr 18 '13 at 20:11
very good SSCCE, my hat down (missing there Initial Thread, but doesn't matter) — mKorbel, Apr 18 '13 at 20:12
_"I still have a question whether this is the proper way to do it."_ You usually should not be extending JFrame (extend JPanel instead). Also, you should initialize your gui with the `EventQueue`. Also, what is the use of your MyFrame? You're not even using it(it is a JFrame)! — phil, Apr 18 '13 at 20:24

score 3 · Accepted Answer · answered Apr 18 '13 at 20:10

all three alternativer are described in ActionListener, lets work easiest of them, seems like is coordinates is the same (I think that required deepest look into TextLayout ???)

enter image description here

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class ResizeJTextArea {

    private JFrame frame = new JFrame();
    private JScrollPane scrollPane = new JScrollPane();
    private JTextArea textArea = new JTextArea(10, 15);
    private JButton button = new JButton("change");
    private Font newFont = new Font("Courier", Font.PLAIN, 10);

    public ResizeJTextArea() {
        textArea.setText("This is just a line of text");
        textArea.setFont(newFont);
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textArea.setFont(textArea.getFont().deriveFont(20f));

                //2. choice
                //textArea.setColumns(20);
                //textArea.setRows(20);

                //3rd. coice
                //override PreferredScrollableViewportSize
                frame.pack();
            }
        });
        scrollPane.setViewportView(textArea);
        frame.add(scrollPane);
        frame.add(button, BorderLayout.SOUTH);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocation(100, 100);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                ResizeJTextArea fs = new ResizeJTextArea();
            }
        });
    }
}

I'm a bit confused. Are you saying that `pack()` **alone** is all what it takes in my case? — PM 77-1, Apr 18 '13 at 20:34
[(re)validate & repaint is about add, remove, modify JComponents in Container see all possible variations](http://stackoverflow.com/a/6989230/714968), result from this code is are you want to resize JFrame (mentioned JDialog) or not, have to decide :-) — mKorbel, Apr 18 '13 at 20:46
RE: "*JFrame (mentioned JDialog)*" Well, one of the two stupid mistakes in my original code was that I was actually re-sizing a **wrong container**: Dialog (separate window) instead of Frame. — PM 77-1, Apr 18 '13 at 20:52

How to force JContainer to re-layout itself?

1 Answers1