Content
Create and capture events in JList
Additions element in JList

JList allows to display a list of objects and groups. In this lesson we will learn the basics about it.

Create and capture events in JList

We will create a program that contains 1 JList including color, click to select a color, the background color of the JFrame will change the color name.

package nguyenvanquan7826.JList;

import java.awt.Color;
import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

public class JListDemo extends JFrame {
	private int width = 200;
	private int height = 250;

	// create array string color to show in list
	String[] colorName = { "blue", "green", "red" };
	// create array color
	Color[] backGroundColor = { Color.blue, Color.green, Color.red };
	JList<String> myJList;

	// create JList width array color
	public JListDemo() {
		// set layout for contenPane
		getContentPane().setLayout(new FlowLayout());

		// add list color
		add(createJList());

		// set display
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(width, height);
		setLocationRelativeTo(null);
		setVisible(true);
	}

	private JList createJList() {
		// create list
		myJList = new JList<String>(colorName);
		// add listen to get action when select item in JList
		myJList.addListSelectionListener(new ListSelectionListener() {
			@Override
			public void valueChanged(ListSelectionEvent e) {
				changeBackGround();
			}
		});
		return myJList;
	}

	// change background JFrame
	private void changeBackGround() {
		getContentPane().setBackground(
				backGroundColor[myJList.getSelectedIndex()]);
	}

	public static void main(String[] args) {
		new JListDemo();
	}
}

* The constructor method of JList:
– JList(): create an empty JList
– JList(And[] listData): create 1 JList with an array of data
– JList(ListModel dataModel): JList to create a model has
– JList(Vector listData): JList with data created in vector

* Catching Event when selecting an item in the list we add methods addListSelectionListener for JList. Then will override methods value changed to perform the desired. Using methods getSelectedIndex for selected locations in JList

* Attention in the above example because we use directly JFrame should want to change the background color of the frame we need setLayout for JFrame and when performing background instead need to make call getContentPane().setBackground.

Additions element in JList

The next example below will accomplish more in less element JList. JFrame containing 1 JPanel (main panel), This panel is the main pharmaceutical setLayout BorderLayout and contains objects in the picture below:

When Selecting from the JList and then press Delete or Add to delete the selected element or elements in addition to the JList JTextFiel.

package nguyenvanquan7826.JList;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;

public class JListAddOrRemoveItem extends JFrame implements ActionListener {
	private int width = 200;
	private int height = 250;
	private JTextField tfAdd;
	private JList<String> myList;

	public JListAddOrRemoveItem() {
		// add main panel
		add(createMainPanel());

		// display
		setTitle("Add - remove item in JList");
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(width, height);
		setLocationRelativeTo(null);
		setVisible(true);
	}

	private JPanel createMainPanel() {
		// create main panel
		JPanel panel = new JPanel(new BorderLayout());
		// set border empty for main panel
		panel.setBorder(new EmptyBorder(0, 10, 10, 10));
		// add content
		panel.add(createDeletePanel(), BorderLayout.PAGE_START);
		panel.add(createAddPanel(), BorderLayout.PAGE_END);
		panel.add(createList(), BorderLayout.CENTER);
		return panel;
	}

	// delete panel in top of frame
	private JPanel createDeletePanel() {
		JPanel panel = new JPanel();
		panel.add(createButton("Delete"));
		return panel;
	}

	// add panel in bottom of frame
	private JPanel createAddPanel() {
		JPanel panel = new JPanel(new GridLayout(0, 1));
		panel.add(tfAdd = new JTextField());
		panel.add(createButton("Add"));
		return panel;
	}

	// create Jlist
	private JList<String> createList() {
		// create defaultListModel
		DefaultListModel<String> model = new DefaultListModel<>();
		// add element to model
		model.addElement("Java");
		model.addElement("C#");
		// set model to JList
		myList = new JList<String>(model);
		return myList;
	}

	// create a button
	private JButton createButton(String btnName) {
		JButton btn = new JButton(btnName);
		btn.addActionListener(this);
		return btn;
	}

	private void deleteItem() {
		// get model of Jlist
		DefaultListModel<String> model = (DefaultListModel<String>) myList
				.getModel();
		// delete item is selected
		if (!model.isEmpty() && myList.getSelectedIndex() >= 0) {
			model.remove(myList.getSelectedIndex());
		}
		// set model for JList
		myList.setModel(model);
	}

	private void addItem() {
		String item = tfAdd.getText().trim();
		if (item.equals("")) {
			JOptionPane.showMessageDialog(null,
					"Pleas enter item add to Jlist", "Error",
					JOptionPane.ERROR_MESSAGE);
		} else {
			DefaultListModel model = (DefaultListModel) myList.getModel();
			model.addElement(item);
			myList.setModel(model);
			tfAdd.setText("");
		}
	}

	@Override
	public void actionPerformed(ActionEvent e) {
		if (e.getActionCommand() == "Delete") {
			deleteItem();
			return;
		}
		if (e.getActionCommand() == "Add") {
			addItem();
		}
	}

	public static void main(String[] args) {
		new JListAddOrRemoveItem();
	}
}

In this example JList is initialized with 1 model is DefaultListModel, That is 1 model that Java built for us, it is very easy to use. The additions to the JList mandatory element we have done through the JList model can not directly be (Unless every time you add or remove users 1 list (or array) molecules and then re-create the JList). Details of these steps are clearly annotate in the code, you keep track of which.

Read more: use JList, class JList, custom JList