In this example we are going to see how to use several components like JRadioButton and JComboBox bundled with an ItemListener. As you know, radio buttons and combo boxes are quite popular in Graphical Applications because they give flexibility to the end users, and it’s very natural to them to interact with them when you want to give specific values to choose from.
In short, to use components with ItemListener you have to:
- Create a new class that implements
ItemListenerinterface. - Override the methods that correspond to the events that you want to monitor on the radio buttons e.g
itemStateChangedand customize as you wish the handling of the respective event - Create a number of new
JRadioButtonscomponents. - Use the
addItemListenerto add theItemListenerto each one of the buttons. - Create
JComboBoxcomponents and use theaddItemListenerto add theItemListenerto each one of the.
Let’s see the code snippet that follows:
package com.javacodegeeks.snippets.desktop;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.ButtonGroup;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
public class ItemListenerExample {
public static void main(String args[]) {
JFrame jFrame = new JFrame();
Container cPane = jFrame.getContentPane();
ItemListener itemListener = new ItemListener() {
@Override
public void itemStateChanged(ItemEvent event) {
System.out.println("Source: " + getName(event.getSource()));
System.out.println("Item: " + getName(event.getItem()));
int state = event.getStateChange();
System.out.println("State: "
+ ((state == ItemEvent.SELECTED) ? "Selected"
: "Deselected"));
}
private String getName(Object o) {
if (o instanceof JComponent) {
JComponent jComponent = (JComponent) o;
return jComponent.getName();
} else {
return o.toString();
}
}
};
JPanel jPanel = new JPanel(new GridLayout(0, 1));
ButtonGroup buttonGroup = new ButtonGroup();
JRadioButton option = new JRadioButton("Option 1", true);
option.setName(option.getText());
option.addItemListener(itemListener);
buttonGroup.add(option);
jPanel.add(option);
option = new JRadioButton("Option 2", false);
option.setName(option.getText());
option.addItemListener(itemListener);
buttonGroup.add(option);
jPanel.add(option);
option = new JRadioButton("Option 3", false);
option.setName(option.getText());
option.addItemListener(itemListener);
buttonGroup.add(option);
jPanel.add(option);
cPane.add(jPanel, BorderLayout.NORTH);
String itemArray[] = {"Item 1", "Item 2", "Item 3"};
JComboBox combobox = new JComboBox(itemArray);
combobox.setName("Combo");
combobox.addItemListener(itemListener);
combobox.setMaximumRowCount(4);
cPane.add(combobox, BorderLayout.SOUTH);
jFrame.pack();
jFrame.setVisible(true);
}
}
This was an example on how to work with ItemListener in Java.
