JList And JScrollPane in Java

Introduction of JList

In this article, we are going to describe how to use JList and JScrollPane in an application. JList is a component that displays a group of items to the user and allows him/her to select one or more items from the list. A listModel(interface) is used for maintaining the contents of the list. A class DefaultListModel(inherits ListModel) is used for maintaining a contents list. This class actually provides methods to add removeAll elements or a specific elements list and to find the index of an element. A component that allows the user to select one or more objects from a list. A separate model, ListModel, represents the contents of the list. It's easy to display an array or vector of objects, using a JList constructor that builds a ListModel instance for you. A List doesn't support scrolling directly. To create a scrolling list you make the JList the viewport view of a JScrollPane. By default the JList selection model allows any combination of items to be selected at a time, using the constant MULTIPLE_INTERVAL_SELECTION. The selection state is actually managed by a separate delegate object, an instance of ListSelectionModel. However, JList provides convenient properties for managing the selection.

Note - JJList doesn't provide any special support for handling double or triple (or N) mouse clicks however it's easy to handle them using a MouseListener. Use the JList method locationToIndex() to determine what cell was clicked.

Example

import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.*;
import java.awt.event.*;
public class JListExample extends JFrame
{
JList list;
String[] listColorNames = {
"BLACK",
"BLUE",
"GREEN",
"YELLOW",
"WHITE"
};
Color[] listColorValues = {
Color.BLACK,
Color.BLUE,
Color.GREEN,
Color.YELLOW,
Color.WHITE
};
Container contentpane;
public JListExample()
{
super("List Example ");
contentpane = getContentPane();
contentpane.setLayout(new FlowLayout());
list = new JList(listColorNames);
list.setSelectedIndex(0);
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
contentpane.add(new JScrollPane(list));
list.addListSelectionListener(new ListSelectionListener()
{
public void valueChanged(ListSelectionEvent e)
{
contentpane.setBackground(listColorValues[list.getSelectedIndex()]);
}
});
setSize(300, 300);
setVisible(true);
}
public static void main(String[] args)
{
JListExample test = new JListExample();
test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

Output

Cmd output

First or initial output.

When you select the BLUE item of the list.

When you select GREEN item on list.

Introduction of JScrollPane

JScollPane manages a viewport, optional vertical and horizontal scroll bars, and optional row and column heading viewports. The JViewport provides a window, or "viewport" onto a data source -- for example, a text file. That data source is the "scrollable client" (aka data model) displayed by the JViewport view. A JScrollPane basically consists of JScrollBars, a JViewport, and the wiring between them, as shown in the following diagram.

Example

import javax.swing.*;
public class JScrollPaneDemo
{
public static void main(String[] args)
{
String st = "Amit Maheswari\n"
+
"Akshay Tewatiya\n"
+
"Praveen Kumar\n"
+
"Vipendra kumar\n"
+
"Arjun Pawar"
+
"sanjoli\n" + "Deepak Dwij"
+
"Amit\n" + "Anuj\n"
+
"Sourabh Tripathi\n" + "Vaibhav Tripathi\n"
+
"Anamika" + "KRIShana\n"
+
"I have four cars and two computers.";
JFrame frame = new JFrame("Example a JScrollPane ");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
JTextArea area = new JTextArea(st, 8, 12);
JScrollPane spane = new JScrollPane(area);
panel.add(spane);
frame.add(panel);
frame.setSize(400, 400);
frame.setVisible(true);
}
}

Output

Resources