This is a very short tutorial on the creation of JButtons. JButtons are just as you'd think, buttons on the screen that your user can press to change properties of your program. We need to move onto a brand new example now. Technically JPanels shouldn't be used as a widget, they are widget containers. Now we have enough widgets to create a half decent program, for this tutorial we shall do away with our coloured box example. SwingButton.java
SwingButton_Extended (Button Action) Event Listeners are the things that make the GUI come alive. When a user does anything to a GUI like re-size it, press a mouse button or enter text into a textfield, an 'event' will occur. We use an Event Listener to listen for certain events and edit the GUI on the occurrence of the event. There are many different Event Listeners, each looking out for a specific type of event. The Event Listener a JButton uses is an ActionListener. This covers the events created by Buttons, TextFields and MenuItems. In this tutorial we shall look at how to put one in practise for Buttons so you will be familiar with the concept when we cover the other widgets. SwingButton_Extended.java
package java9r.blogspot.com;Output
import javax.swing.*;
import java.awt.Color;
public class SwingButton{
public JPanel createContentPane (){
// We create a bottom JPanel to place everything on.
JPanel totalGUI = new JPanel();
totalGUI.setLayout(null);
// Creation of a Panel to contain the title labels
JPanel titlePanel = new JPanel();
titlePanel.setLayout(null);
titlePanel.setLocation(10, 0);
titlePanel.setSize(250, 30);
totalGUI.add(titlePanel);
JLabel redLabel = new JLabel("Red Team");
redLabel.setLocation(0, 0);
redLabel.setSize(100, 30);
redLabel.setHorizontalAlignment(0);
redLabel.setForeground(Color.red);
titlePanel.add(redLabel);
JLabel blueLabel = new JLabel("Blue Team");
blueLabel.setLocation(120, 0);
blueLabel.setSize(100, 30);
blueLabel.setHorizontalAlignment(0);
blueLabel.setForeground(Color.blue);
titlePanel.add(blueLabel);
// Creation of a Panel to contain the score labels.
JPanel scorePanel = new JPanel();
scorePanel.setLayout(null);
scorePanel.setLocation(10, 40);
scorePanel.setSize(250, 30);
totalGUI.add(scorePanel);
JLabel redScore = new JLabel("0");
redScore.setLocation(0, 0);
redScore.setSize(100, 30);
redScore.setHorizontalAlignment(0);
scorePanel.add(redScore);
JLabel blueScore = new JLabel("0");
blueScore.setLocation(120, 0);
blueScore.setSize(100, 30);
blueScore.setHorizontalAlignment(0);
scorePanel.add(blueScore);
// Creation of a label to contain all the JButtons.
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(null);
buttonPanel.setLocation(10, 80);
buttonPanel.setSize(250, 70);
totalGUI.add(buttonPanel);
// We create a button and manipulate it using the syntax we have
// used before.
JButton redButton = new JButton("Red Score!");
redButton.setLocation(0, 0);
redButton.setSize(100, 30);
buttonPanel.add(redButton);
JButton blueButton = new JButton("Blue Score!");
blueButton.setLocation(120, 0);
blueButton.setSize(100, 30);
buttonPanel.add(blueButton);
JButton resetButton = new JButton("Reset Score");
resetButton.setLocation(0, 40);
resetButton.setSize(220, 30);
buttonPanel.add(resetButton);
totalGUI.setOpaque(true);
return totalGUI;
}
private static void createAndShowGUI() {
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("--------- JButton Scores! ---------");
//Create and set up the content pane.
SwingButton demo = new SwingButton();
frame.setContentPane(demo.createContentPane());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(250, 190);
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
package java9r.blogspot.com;Output
import javax.swing.*;
import java.awt.Color;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class SwingButton_Extended implements ActionListener{
// Definition of global values and items that are part of the GUI.
int redScoreAmount = 0;
int blueScoreAmount = 0;
JPanel titlePanel, scorePanel, buttonPanel;
JLabel redLabel, blueLabel, redScore, blueScore;
JButton redButton, blueButton, resetButton;
public JPanel createContentPane (){
// We create a bottom JPanel to place everything on.
JPanel totalGUI = new JPanel();
totalGUI.setLayout(null);
// Creation of a Panel to contain the title labels
titlePanel = new JPanel();
titlePanel.setLayout(null);
titlePanel.setLocation(10, 0);
titlePanel.setSize(250, 30);
totalGUI.add(titlePanel);
redLabel = new JLabel("Red Team");
redLabel.setLocation(0, 0);
redLabel.setSize(120, 30);
redLabel.setHorizontalAlignment(0);
redLabel.setForeground(Color.red);
titlePanel.add(redLabel);
blueLabel = new JLabel("Blue Team");
blueLabel.setLocation(130, 0);
blueLabel.setSize(120, 30);
blueLabel.setHorizontalAlignment(0);
blueLabel.setForeground(Color.blue);
titlePanel.add(blueLabel);
// Creation of a Panel to contain the score labels.
scorePanel = new JPanel();
scorePanel.setLayout(null);
scorePanel.setLocation(10, 40);
scorePanel.setSize(260, 30);
totalGUI.add(scorePanel);
redScore = new JLabel(""+redScoreAmount);
redScore.setLocation(0, 0);
redScore.setSize(120, 30);
redScore.setHorizontalAlignment(0);
scorePanel.add(redScore);
blueScore = new JLabel(""+blueScoreAmount);
blueScore.setLocation(130, 0);
blueScore.setSize(120, 30);
blueScore.setHorizontalAlignment(0);
scorePanel.add(blueScore);
// Creation of a Panel to contain all the JButtons.
buttonPanel = new JPanel();
buttonPanel.setLayout(null);
buttonPanel.setLocation(10, 80);
buttonPanel.setSize(260, 70);
totalGUI.add(buttonPanel);
// We create a button and manipulate it using the syntax we have
// used before. Now each button has an ActionListener which posts
// it's action out when the button is pressed.
redButton = new JButton("Red Score!");
redButton.setLocation(0, 0);
redButton.setSize(120, 30);
redButton.addActionListener(this);
buttonPanel.add(redButton);
blueButton = new JButton("Blue Score!");
blueButton.setLocation(130, 0);
blueButton.setSize(120, 30);
blueButton.addActionListener(this);
buttonPanel.add(blueButton);
resetButton = new JButton("Reset Score");
resetButton.setLocation(0, 40);
resetButton.setSize(250, 30);
resetButton.addActionListener(this);
buttonPanel.add(resetButton);
totalGUI.setOpaque(true);
return totalGUI;
}
// This is the new ActionPerformed Method.
// It catches any events with an ActionListener attached.
// Using an if statement, we can determine which button was pressed
// and change the appropriate values in our GUI.
public void actionPerformed(ActionEvent e) {
if(e.getSource() == redButton)
{
redScoreAmount = redScoreAmount + 1;
redScore.setText(""+redScoreAmount);
}
else if(e.getSource() == blueButton)
{
blueScoreAmount = blueScoreAmount + 1;
blueScore.setText(""+blueScoreAmount);
}
else if(e.getSource() == resetButton)
{
redScoreAmount = 0;
blueScoreAmount = 0;
redScore.setText(""+redScoreAmount);
blueScore.setText(""+blueScoreAmount);
}
}
private static void createAndShowGUI() {
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("------- JButton Scores! ----------");
//Create and set up the content pane.
SwingButton_Extended demo = new SwingButton_Extended();
frame.setContentPane(demo.createContentPane());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(280, 190);
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
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