Develop Reference

How would I use the radio button in jswing to make a listener capable of placing an S or O in the given cell depending on what is selected?

package SOS;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
public class BoardPanel {
private JFrame frame;
private void createAndDisplayGui() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createTopPanel(), BorderLayout.PAGE_START);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private void createBoard(ActionEvent event) {
Object source = event.getSource();
if (source instanceof JTextField) {
JTextField textField = (JTextField) source;
String text = textField.getText();
int dimension = Integer.parseInt(text);
JPanel board = new JPanel(new GridLayout(dimension, dimension));
for (int row = 0; row < dimension; row++) {
for (int col = 0; col < dimension; col++) {
JLabel square = new JLabel(" ");
square.setBackground(Color.white);
square.setOpaque(true);
square.setBorder(BorderFactory.createLineBorder(Color.black));
board.add(square);
}
}
frame.add(board, BorderLayout.CENTER);
frame.pack();
}
}
private JPanel createTopPanel() {
JRadioButton optionS = new JRadioButton("S");
JRadioButton optionO = new JRadioButton("O");
ButtonGroup group = new ButtonGroup();
group.add(optionS);
group.add(optionO);
JPanel topPanel = new JPanel();
JLabel label = new JLabel("Board size:");
topPanel.add(label);
JTextField boardSize = new JTextField(6);
boardSize.addActionListener(this::createBoard);
topPanel.add(boardSize);
topPanel.add(optionS, BorderLayout.NORTH);
topPanel.add(optionO, BorderLayout.CENTER);
return topPanel;
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new BoardPanel().createAndDisplayGui());
}
}
I know I am supposed to make an action listener for each radio button and that seems pretty straightforward, but I am confused on how I would do that and then translate that to placing an S or O on the game boards given cell depending on what is selected. I think the more confusing part is being able to draw in the given cell either the S or the O depending on what is selected. This is for an SOS game, sort of like tic tac toe. I tried following a simple tic tac toe example but got lost as there is no radio buttons like this and I am using a different createboard method.

You can declare your radioButton globally so you can check the selected status. Then in a listener in your cells check that and place the appropriate letter:
package SOS;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
public class BoardPanel {
private JFrame frame;
private JRadioButton optionS;
private JRadioButton optionO;
private void createAndDisplayGui() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(createTopPanel(), BorderLayout.PAGE_START);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private void createBoard(ActionEvent event) {
Object source = event.getSource();
if (source instanceof JTextField) {
JTextField textField = (JTextField) source;
String text = textField.getText();
int dimension = Integer.parseInt(text);
JPanel board = new JPanel(new GridLayout(dimension, dimension));
for (int row = 0; row < dimension; row++) {
for (int col = 0; col < dimension; col++) {
JLabel square = new JLabel(" ");
square.setBackground(Color.white);
square.setOpaque(true);
square.setBorder(BorderFactory.createLineBorder(Color.black));
board.add(square);
square.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
square.setText(optionS.isSelected() ? " S " : " O ");
}
});
}
}
frame.getContentPane().add(board, BorderLayout.CENTER);
frame.pack();
}
}
private JPanel createTopPanel() {
optionS = new JRadioButton("S");
optionO = new JRadioButton("O");
ButtonGroup group = new ButtonGroup();
group.add(optionS);
group.add(optionO);
JPanel topPanel = new JPanel();
JLabel label = new JLabel("Board size:");
topPanel.add(label);
JTextField boardSize = new JTextField(6);
boardSize.addActionListener(this::createBoard);
topPanel.add(boardSize);
topPanel.add(optionS, BorderLayout.NORTH);
topPanel.add(optionO, BorderLayout.CENTER);
return topPanel;
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new BoardPanel().createAndDisplayGui());
}
}

There are few ways you might be able to do this, personally, I like to decouple the workflows and remove dependencies where I can.
For example, your createBoard method is making an assumption about how the dimension value is captured by the user. What happens if you want to change that workflow to use a JSpinner or JCombobox? You'd then have to modify this method as well.
Better to pass the method the information it needs to do its job. In fact, I'd make it return an instance of JPanel, so as to remove all the dependencies, after all createBoard should do just that, nothing else.
I've changed the workflow so there is now a dedicated "create" button, this will collect the information it needs in order to be able to create the board itself. Not as dynamic as the other approach, but it gives the user time to consider their inputs
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
public class BoardPanel {
private JFrame frame;
enum State {
S, O;
}
private JPanel board;
private void createAndDisplayGui() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createTopPanel(), BorderLayout.PAGE_START);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createBoard(int dimension, State state) {
JPanel board = new JPanel(new GridLayout(dimension, dimension));
for (int row = 0; row < dimension; row++) {
for (int col = 0; col < dimension; col++) {
JLabel square = new JLabel(" " + state.name() + " ");
square.setBackground(Color.white);
square.setOpaque(true);
square.setBorder(BorderFactory.createLineBorder(Color.black));
board.add(square);
}
}
return board;
}
private JPanel createTopPanel() {
JRadioButton optionS = new JRadioButton("S");
JRadioButton optionO = new JRadioButton("O");
JTextField boardSize = new JTextField(6);
JPanel topPanel = new JPanel();
ButtonGroup group = new ButtonGroup();
group.add(optionS);
group.add(optionO);
// Default state
optionS.setSelected(true);
JButton createButton = new JButton("Make it so");
createButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
State state = State.O;
if (optionS.isSelected()) {
state = State.S;
}
try {
int dimension = Integer.parseInt(boardSize.getText());
if (board != null) {
frame.remove(board);
}
board = createBoard(dimension, state);
frame.add(board, BorderLayout.CENTER);
frame.pack();
} catch (NumberFormatException exp) {
JOptionPane.showMessageDialog(topPanel, "Invalid board size", "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
JLabel label = new JLabel("Board size:");
topPanel.add(label);
topPanel.add(boardSize);
topPanel.add(optionS);
topPanel.add(optionO);
topPanel.add(createButton);
return topPanel;
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new BoardPanel().createAndDisplayGui());
}
}
If you'd prefer something a little more dynamic, then you could add shared ActionListener to the buttons and text field, for example...
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
public class BoardPanel {
private JFrame frame;
enum State {
S, O;
}
private JPanel board;
private void createAndDisplayGui() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createTopPanel(), BorderLayout.PAGE_START);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createBoard(int dimension, State state) {
JPanel board = new JPanel(new GridLayout(dimension, dimension));
for (int row = 0; row < dimension; row++) {
for (int col = 0; col < dimension; col++) {
JLabel square = new JLabel(" " + state.name() + " ");
square.setBackground(Color.white);
square.setOpaque(true);
square.setBorder(BorderFactory.createLineBorder(Color.black));
board.add(square);
}
}
return board;
}
private JPanel createTopPanel() {
JRadioButton optionS = new JRadioButton("S");
JRadioButton optionO = new JRadioButton("O");
JTextField boardSize = new JTextField(6);
JPanel topPanel = new JPanel();
ButtonGroup group = new ButtonGroup();
group.add(optionS);
group.add(optionO);
ActionListener actionListener = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
State state = State.O;
if (optionS.isSelected()) {
state = State.S;
}
try {
int dimension = Integer.parseInt(boardSize.getText());
if (board != null) {
frame.remove(board);
}
board = createBoard(dimension, state);
frame.add(board, BorderLayout.CENTER);
frame.pack();
} catch (NumberFormatException exp) {
// Not yet ready
}
}
};
optionS.addActionListener(actionListener);
optionO.addActionListener(actionListener);
boardSize.addActionListener(actionListener);
// Default state
optionS.setSelected(true);
JLabel label = new JLabel("Board size:");
topPanel.add(label);
topPanel.add(boardSize);
topPanel.add(optionS);
topPanel.add(optionO);
return topPanel;
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new BoardPanel().createAndDisplayGui());
}
}

Jlabel change color on mouse click Java

I am adding multiple Jlabel using for loop. What I want is on mouse click, the color of the selected JLabel should change and set to the default color on click of anotherJLabel.

Since you changed the state of the label, you need someway to change it back. The simplest solution is to maintain a reference to the last label that was changed and when the new label is clicked, reset it's state
import java.awt.Color;
import java.awt.Component;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
HighlightMouseListener hml = new HighlightMouseListener();
for (int index = 0; index < 10; index++) {
JLabel label = new JLabel("Hello " + index);
label.addMouseListener(hml);
add(label, gbc);
}
}
}
public class HighlightMouseListener extends MouseAdapter {
private JLabel previous;
#Override
public void mouseClicked(MouseEvent e) {
Component source = e.getComponent();
if (!(source instanceof JLabel)) {
return;
}
JLabel label = (JLabel) source;
if (previous != null) {
previous.setBackground(null);
previous.setForeground(null);
previous.setOpaque(false);
}
previous = label;
label.setForeground(Color.WHITE);
label.setBackground(Color.BLUE);
label.setOpaque(true);
}
}
}
I still wonder if a JList would be a better and simpler solution, but since I don't know what you're doing, it's all I can do

why is repaint() not working?

I am trying to add the buttons to the centerPanel that I created, then add that panel to the main center borderlayout. for some reason though my tab will not repaint anymore. It worked fine a while ago when I had the DrawFieldsListener class in the same class file as the MagicSquare, but nothing in the code has changed from my splitting them into two class files. So i really don't know what is going on. When it did repaint before, it would also take a long time. Any help? thanks!
All source for the project is on GitHub if it is easier to read and understand there: https://github.com/andrefecto/Academic-Convivium-Project
MagicSquare Class:
package magicSquare;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class MagicSquare extends JPanel {
JLabel sizeLabel = new JLabel("Enter A Square Size: ");
JButton setSize;
static JButton calculate;
static JButton reset;
static JTextField squareSize;
static JTextField field;
public static ArrayList<JTextField> inputFields = new ArrayList<JTextField>();
public static ArrayList<Integer> inputs = new ArrayList<Integer>();
public static ArrayList<Integer> totals = new ArrayList<Integer>();
public static int squared = 0;
public static int square = 0;
public static JPanel centerPanel = new JPanel();
public static JPanel bottomPanel = new JPanel();
public MagicSquare (){
setLayout(new BorderLayout());
JPanel subPanel = new JPanel();
subPanel.add(sizeLabel);
squareSize = new JTextField();
squareSize.setColumns(6);
subPanel.add(squareSize);
setSize = new JButton("Enter");
subPanel.add(setSize);
setSize.addActionListener(new DrawFieldsListener());
add(subPanel, BorderLayout.NORTH);
add(new DrawFieldsListener(), BorderLayout.CENTER);
}
}
my DrawFieldsListener class:
package magicSquare;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JTextField;
class DrawFieldsListener extends JPanel implements ActionListener {
int square = MagicSquare.square;
int squared = MagicSquare.squared;
JPanel centerPanel = MagicSquare.centerPanel;
JTextField squareSize = MagicSquare.squareSize;
JTextField field = MagicSquare.field;
ArrayList<JTextField> inputFields = MagicSquare.inputFields;
JButton calculate = MagicSquare.calculate;
JButton reset = MagicSquare.reset;
JPanel bottomPanel = MagicSquare.bottomPanel;
public void actionPerformed(ActionEvent e){
square = Integer.parseInt(squareSize.getText());
squared = square*square;
centerPanel.setLayout(new GridLayout(square, square));
for(int i = 0; i < squared; i++){
field = new JTextField();
field.setColumns(3);
inputFields.add(field);
centerPanel.add(inputFields.get(i));
System.out.println("DRAWING");
}
add(centerPanel, BorderLayout.CENTER);
System.out.println("ADDING ADDITINOAL BUTTONS");
additionalButtons();
System.out.println("ADDED ADDITINOAL BUTTONS");
System.out.println("REPAINTING");
repaint();
System.out.println("REPAINTED");
}
public void additionalButtons(){
calculate = new JButton("Calculate");
reset = new JButton("Reset");
bottomPanel.setLayout(new GridLayout(2, 2));
bottomPanel.add(reset);
bottomPanel.add(calculate);
add(bottomPanel, BorderLayout.SOUTH);
calculate.addActionListener(new CalculateListener());
reset.addActionListener(new ResetListener());
}
}

Mistake #1
public static JPanel centerPanel = new JPanel();
Followed by...
class DrawFieldsListener extends JPanel implements ActionListener {
//...
JPanel centerPanel = MagicSquare.centerPanel;
static is not a cross object communication mechanism...and now I have no idea who is suppose to be responsible for managing the centerPanel...
Remember, static is not your friend, beware of how it is used
Mistake #2
setSize.addActionListener(new DrawFieldsListener());
add(subPanel, BorderLayout.NORTH);
add(new DrawFieldsListener(), BorderLayout.CENTER);
You are creating two instances of DrawFieldsListener (which is a panel), one is acting as the ActionListener and one is acting as the view, but which one is actually housing MagicSquare.centerPanel as a component can only have one parent...
Mistake #3
Not revalidating the container after you have changed it...
public void actionPerformed(ActionEvent e) {
square = Integer.parseInt(squareSize.getText());
squared = square * square;
centerPanel.setLayout(new GridLayout(square, square));
for (int i = 0; i < squared; i++) {
field = new JTextField();
field.setColumns(3);
inputFields.add(field);
centerPanel.add(inputFields.get(i));
System.out.println("DRAWING");
}
add(centerPanel, BorderLayout.CENTER);
System.out.println("ADDING ADDITINOAL BUTTONS");
additionalButtons();
System.out.println("ADDED ADDITINOAL BUTTONS");
System.out.println("REPAINTING");
revalidate();
repaint();
System.out.println("REPAINTED");
}
Swing is lazy when it comes to container management, it assumes that you will want to do a number of adds or removes, so it won't update the container hierarchy layout until you ask it to, as the operation can be expensive
A better solution...
Isolate responsibility and provide information to your objects in a de-coupled manner.
For example, the DrawFieldsListener shouldn't care about MagicSquare, but should provide a means by which "some body" can tell it how many squares it should create.
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSpinner;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class MagicSquare extends JPanel {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new MagicSquare());
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
JLabel sizeLabel = new JLabel("Enter A Square Size: ");
JButton setSize;
private JSpinner squareSize;
JTextField field;
public MagicSquare() {
setLayout(new BorderLayout());
JPanel subPanel = new JPanel();
subPanel.add(sizeLabel);
squareSize = new JSpinner();
subPanel.add(squareSize);
setSize = new JButton("Enter");
subPanel.add(setSize);
DrawFieldsListener dfl = new DrawFieldsListener();
setSize.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
int gridSize = (int) squareSize.getValue();
dfl.makeGrid(gridSize);
}
});
add(subPanel, BorderLayout.NORTH);
add(dfl, BorderLayout.CENTER);
}
class DrawFieldsListener extends JPanel {
private JButton calculate;
private JButton reset;
private ArrayList<JTextField> inputFields = new ArrayList<JTextField>();
private ArrayList<Integer> inputs = new ArrayList<Integer>();
private ArrayList<Integer> totals = new ArrayList<Integer>();
private int squared = 0;
private int square = 0;
private JPanel centerPanel = new JPanel();
private JPanel bottomPanel = new JPanel();
public void makeGrid(int gridSize) {
square = gridSize;
squared = square * square;
centerPanel.setLayout(new GridLayout(square, square));
for (int i = 0; i < squared; i++) {
field = new JTextField();
field.setColumns(3);
inputFields.add(field);
centerPanel.add(inputFields.get(i));
System.out.println("DRAWING");
}
add(centerPanel, BorderLayout.CENTER);
System.out.println("ADDING ADDITINOAL BUTTONS");
additionalButtons();
System.out.println("ADDED ADDITINOAL BUTTONS");
System.out.println("REPAINTING");
revalidate();
repaint();
System.out.println("REPAINTED");
}
public void additionalButtons() {
calculate = new JButton("Calculate");
reset = new JButton("Reset");
bottomPanel.setLayout(new GridLayout(2, 2));
bottomPanel.add(reset);
bottomPanel.add(calculate);
add(bottomPanel, BorderLayout.SOUTH);
// calculate.addActionListener(new CalculateListener());
// reset.addActionListener(new ResetListener());
}
}
}

How to a new element to JFrame and have it show

I have a GUI with a scroll pane in it. The Scroll Pane is scrolling though a JPanel of JPanels. I would like the ability to add one more to the list of subJPanels and have the JFrame update to do it.
Right now I have the array updating, but not the JFrame.
package SSCCE;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
public class Add extends JFrame{
private JPanel[] branches;
private JPanel pane; //Pane that stores accounts
private JScrollPane scroller;
private JButton newBranch;
public static void main(String[] args) {
JFrame frame = new Add();
}
public Add(){
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(500, 500);
this.setTitle("How Do I add?");
this.setLayout(new BorderLayout());
this.add(statusBar(), BorderLayout.NORTH);
populateBranches();
pane = new JPanel();
pane.setLayout(new GridLayout(branches.length,1));
for (int i = 0; i < branches.length; i++){
pane.add(branches[i]);
}
scroller = new JScrollPane(pane);
scroller.createVerticalScrollBar();
this.add(scroller,BorderLayout.CENTER);
this.setVisible(true);
}
private JPanel statusBar(){
JPanel statusBar = new JPanel();
statusBar.setLayout(new FlowLayout());
newBranch = new JButton("New Branch");
newBranch.addActionListener(new ButtonEventHandler());
statusBar.add(newBranch);
return statusBar;
}
private void populateBranches(){
branches = new JPanel[2];
for (int i = 0; i < branches.length; i++){
branches[i] = new JPanel();
branches[i].setLayout(new FlowLayout());
branches[i].add(new JTextField(20));
}
}
private void newBranch(){
JPanel[] tempBranches = new JPanel[branches.length + 1];
System.out.println(tempBranches.length);
for (int i = 0; i < branches.length; i++){
tempBranches[i] = branches[i];
}
tempBranches[branches.length] = new JPanel();
tempBranches[branches.length].setLayout(new FlowLayout());
tempBranches[branches.length].add(new JTextField(20));
branches = tempBranches;
pane = new JPanel();
pane.setLayout(new GridLayout(branches.length, 1));
for (int i = 0; i < branches.length; i++){
pane.add(branches[i]);
}
pane.repaint();
pane.validate();
scroller = new JScrollPane(pane);
this.add(scroller, BorderLayout.CENTER);
this.repaint();
this.validate();
}
private class ButtonEventHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent event) {
String btnClkd = event.getActionCommand();
if (btnClkd.equals("New Branch")){
newBranch();
}
}
}
}

If you allow the GridLayout to grow, You can simply add more components to it:
// 0 means new rows are added as needed
pane.setLayout(new GridLayout(0, 1));
// ...
private void newBranch(){
// Create the component
JPanel branch = new JPanel();
branch.add(new JTextField(20));
// + any additional subcomponents
// and just add it where the others already are
pane.add(branch);
pane.revalidate();
}

How can I build 2 JButton instances of the same width

I have 2 buttons, one named btnShort and one named btnLong. I'd like them to be of the same width, so what would be the best option?
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class TestCode2 {
public static void main(String[] args) {
JFrame window = new JFrame("Test2");
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setSize(400, 200);
// ---------------------------------------------------------------------
GridBagLayout layout = new GridBagLayout();
GridBagConstraints constraints = new GridBagConstraints();
JPanel container = new JPanel(layout);
window.add(container);
constraints.gridy = 0;
JButton btnShort = new JButton("Short");
layout.setConstraints(btnShort, constraints);
container.add(btnShort);
constraints.gridy = 1;
JButton btnLong = new JButton("That's a long button");
layout.setConstraints(btnLong, constraints);
container.add(btnLong);
//This one won't work because button dimension is not known yet...
//btnShort.setPreferredSize(new Dimension(btnLong.getWidth(), btnLong.getHeight()));
// ---------------------------------------------------------------------
window.setVisible(true);
}
}

Set the GridBagConstraints fill property to GridBagConstraints.HORIZONTAL so that both JButton components occupy equal width in the container
constraints.fill = GridBagConstraints.HORIZONTAL;

Make use of an appropriate layout manager, like GridBagLayout and it's constraints...
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Buttons {
public static void main(String[] args) {
new Buttons();
}
public Buttons() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.fill = GridBagConstraints.HORIZONTAL;
add(new JButton("I'm a very long button"), gbc);
add(new JButton("I'm not"), gbc);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
}