In this tutorial we are going to see how ActionListener works in Java. This is one the most important components you have to work with when you’re developing a GUI Application. The ActionListener in able to monitor a number of important events that occur in GUI Apps.
In short, all you have to do to work with an ActionListener in Java is:
- Create an
ActionListenerinstance. - Override the methods that correspond to the events that you want to monitor about the components e.g,
actionPerformedand customize as you wish the handling of the respective events. Now every time one of these events occurs, the corresponding method will be executed. - Use
addActionListenerto add theActionListenerto a specific component.
Let’s take a closer look a the code snippet that follows:
package com.javacodegeeks.snippets.desktop;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class Main {
public static void main(String args[]) {
JFrame jFrame = new JFrame();
Container cPane = jFrame.getContentPane();
ActionListener actListener = new ActionListener() {
@Override
public void actionPerformed(ActionEvent event) {
System.out.println("Command: " + event.getActionCommand());
System.out.println("Modifiers: ");
int mods = event.getModifiers();
System.out.println(" Alt : "
+ cmodifiers(mods, ActionEvent.ALT_MASK));
System.out.println(" Ctrl : "
+ cmodifiers(mods, ActionEvent.CTRL_MASK));
System.out.println(" Meta : "
+ cmodifiers(mods, ActionEvent.META_MASK));
System.out.println(" Shift: "
+ cmodifiers(mods, ActionEvent.SHIFT_MASK));
Object obj = event.getSource();
if (obj instanceof JComboBox) {
JComboBox jb = (JComboBox) obj;
System.out.println("Combo: " + jb.getSelectedItem());
}
}
private boolean cmodifiers(int mods, int mask) {
return ((mods & mask) == mask);
}
};
String array[] = {"Item 1", "Item 2", "Item 3"};
JComboBox box = new JComboBox(array);
box.setMaximumRowCount(10);
box.setEditable(true);
box.addActionListener(actListener);
cPane.add(box, BorderLayout.NORTH);
JButton jButton = new JButton("Button!");
jButton.addActionListener(actListener);
cPane.add(jButton, BorderLayout.CENTER);
JPanel jPanel = new JPanel();
JLabel label = new JLabel("");
JTextField text = new JTextField("Type here", 22);
text.addActionListener(actListener);
label.setDisplayedMnemonic(KeyEvent.VK_1);
label.setLabelFor(text);
jPanel.add(label);
jPanel.add(text);
cPane.add(jPanel, BorderLayout.SOUTH);
jFrame.pack();
jFrame.setVisible(true);
}
}
This was an example on how to work with ActionListener in Java.
