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JPanel basic tutorial and examples

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Written by Nam Ha Minh

Last Updated on 06 July 2019 &nbsp | &nbsp

JPanel

is a Swing’s lightweight container which is used to group a set of components together.

JPanel

is a pretty simple component which, normally, does not have a GUI (except when it is being set an opaque background or has a visual border).In this article, we summarize the common practices when working with

JPanel

in Swing. At the end, we will create a sample program looks like this: JPanel demo program 2

Table of content:

1. Creating a new JPanel

is a Swing’s lightweight container which is used to group a set of components together.is a pretty simple component which, normally, does not have a GUI (except when it is being set an opaque background or has a visual border).In this article, we summarize the common practices when working within Swing. At the end, we will create a sample program looks like this:

The JPanel class resides in the package javax.swing and it’s a subclass of the javax.swing.JComponent class.

Normally we create new
JPanel

object as simple as follows:
```
JPanel newPanel = new JPanel();
```
That creates a new

JPanel

with double enabled by default.

Often, we create a class that extends from

JPanel

as follows:

public class UserDetail extends JPanel {

	// code to add components to the panel

}

If we want to specify the double buffering strategy explicitly, use the constructor

JPanel(boolean isDoubleBuffered)

JPanel newPanel = new JPanel(true);		// enable double buffering

JPanel newPanel = new JPanel(false);	// disable double buffering

We also can specify a layout manager when creating the panel:
```
JPanel newPanel = new JPanel(new GridBagLayout());
JPanel newPanel = new JPanel(new BorderLayout());
```
By default, the panel has a flow layout manager.
Another constructor allows us to specify both the double buffering strategy and a layout manager:

// use grid bag layout and no double buffering:
JPanel newPanel = new JPanel(new GridBagLayout(), false);

2. Setting a layout manager for JPanel

We can call the method
setLayout(LayoutManager)

to specify a layout manager for the panel (after the panel is created):
```
JPanel newPanel = new JPanel();
newPanel.setLayout(new GridBagLayout()); 
```

However it’s recommended to specify the layout manager when creating the panel to avoid creating the default

FlowLayout

object:

// NOT recommended:
JPanel newPanel = new JPanel(); // a FlowLayout manager is created by default
newPanel.setLayout(new GridBagLayout());

// RECOMMENDED:
JPanel newPanel = new JPanel(new GridBagLayout());

One exception is the
BoxLayout

, whose constructor requires an existing container, so we cannot specify a

BoxLayout

when creating the panel. For example:

// exception:
JPanel newPanel = new JPanel();
newPanel.setLayout(new BoxLayout(newPanel, BoxLayout.X_AXIS));

3. Adding components to JPanel

To add GUI components such as JTextField,

add()

method. There are different versions of the

add()

method, so which method to be used is depending on the layout manager of the panel.

Use the

add(Component)

method for the following layout managers:

FlowLayout

BoxLayout

GridLayout

, or

SpringLayout

. For example:

JLabel label = new JLabel("Enter username:");
JTextField userName = new JTextField(20);

newPanel.add(label);
newPanel.add(userName);

Use the

add(Component comp, Object constraints)

method for the following layout managers:

BorderLayout

CardLayout

GridBagLayout

. For example:

JPanel newPanel = new JPanel(new BorderLayout());
JLabel label = new JLabel("Enter username:");
JTextField userName = new JTextField(20);

newPanel.add(label, BorderLayout.NORTH);
newPanel.add(userName, BorderLayout.SOUTH);

For

GridBagLayout

, we have to pass a

GridBagConstraints

object as the second argument. For example:

GridBagConstraints constraints = new GridBagConstraints();
constraints.anchor = GridBagConstraints.WEST;
constraints.insets = new Insets(10, 10, 10, 10);
constraints.gridx = 0;
constraints.gridy = 0;

newPanel.add(labelUsername, constraints);

For
CardLayout

, use the

add(String name, Component comp)

method with the first argument is name of a card. For example:

JPanel wizardPanel = new JPanel(new CardLayout());
wizardPanel.add("Step1", step1Panel);
wizardPanel.add("Step2", step2Panel);

4. Adding JPanel to a parent container

The panel cannot stand alone. It must be added to a parent container such as a

JPanel

. For example:

frame.add(newPanel);
anotherPanel.add(newPanel);

5. Customizing appearance for JPanel

Normally, a

JPanel

does not render its own GUI. However we can set its background color, transparent background or border when necessary.

Set background color:
```
newPanel.setBackground(Color.CYAN); 
```
Set transparent background:
```
newPanel.setOpaque(false);	// make transparent background
```
By default, the panel’s background is opaque.

Set a raised bevel border:

newPanel.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));

Set an etched border:

newPanel.setBorder(BorderFactory.createEtchedBorder());

Set a line border:

newPanel.setBorder(BorderFactory.createLineBorder(Color.RED));

Set a titled and etched border:

newPanel.setBorder(BorderFactory.createTitledBorder(
		BorderFactory.createEtchedBorder(), "Login Panel"));

6. JPanel Sample application

We created the following program to demonstrate the typical usages of

JPanel

in a Swing application. The program uses a

JPanel

to group some labels, textfields and a button to form a login panel as follows: JPanel demo program As you can notice, the panel used in this program has a titled border “Login Panel”. Here is complete source code of the program:

package net.codejava.swing.jpanel;

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

/**
 * This program demonstrates how to use JPanel in Swing. 
 * @author www.codejava.net
 */
public class SwingJPanelDemo extends JFrame {
	
	private JLabel labelUsername = new JLabel("Enter username: ");
	private JLabel labelPassword = new JLabel("Enter password: ");
	private JTextField textUsername = new JTextField(20);
	private JPasswordField fieldPassword = new JPasswordField(20);
	private JButton buttonLogin = new JButton("Login");
	
	public SwingJPanelDemo() {
		super("JPanel Demo Program");
		
		// create a new panel with GridBagLayout manager
		JPanel newPanel = new JPanel(new GridBagLayout());
		
		GridBagConstraints constraints = new GridBagConstraints();
		constraints.anchor = GridBagConstraints.WEST;
		constraints.insets = new Insets(10, 10, 10, 10);
		
		// add components to the panel
		constraints.gridx = 0;
		constraints.gridy = 0;		
		newPanel.add(labelUsername, constraints);

		constraints.gridx = 1;
		newPanel.add(textUsername, constraints);
		
		constraints.gridx = 0;
		constraints.gridy = 1;		
		newPanel.add(labelPassword, constraints);
		
		constraints.gridx = 1;
		newPanel.add(fieldPassword, constraints);
		
		constraints.gridx = 0;
		constraints.gridy = 2;
		constraints.gridwidth = 2;
		constraints.anchor = GridBagConstraints.CENTER;
		newPanel.add(buttonLogin, constraints);
		
		// set border for the panel	
		newPanel.setBorder(BorderFactory.createTitledBorder(
				BorderFactory.createEtchedBorder(), "Login Panel"));
		
		// add the panel to this frame
		add(newPanel);
		
		pack();
		setLocationRelativeTo(null);
	}
	
	public static void main(String[] args) {
		// set look and feel to the system look and feel
		try {
			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		
		SwingUtilities.invokeLater(new Runnable() {
			@Override
			public void run() {
				new SwingJPanelDemo().setVisible(true);
			}
		});
	}
}

You can download the code as well as an executable jar file of this program in the attachments section.

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He started programming with Java in the time of Java 1.4 and has been falling in love with Java since then. Make friend with him on

is certified Java programmer (SCJP and SCWCD). He started programming with Java in the time of Java 1.4 and has been falling in love with Java since then. Make friend with him on Facebook and watch his Java videos you YouTube.

Attachments:SwingJPanelDemo.zip[Source code and runnable jar file]7 kB