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JPanel basic tutorial and examples
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- Written by Nam Ha Minh
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Last Updated on 06 July 2019   |  
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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:
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
or
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: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.
Other Java Swing Tutorials:
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
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To add GUI components such as JLabel JButton … to the panel, we use themethod. There are different versions of themethod, so which method to be used is depending on the layout manager of the panel.The panel cannot stand alone. It must be added to a parent container such as a JFrame or another. For example:Normally, adoes not render its own GUI. However we can set its background color, transparent background or border when necessary.We created the following program to demonstrate the typical usages ofin a Swing application. The program uses ato group some labels, textfields and a button to form a login panel as follows:As you can notice, the panel used in this program has a titled border “Login Panel”. Here is complete source code of the program:You can download the code as well as an executable jar file of this program in the attachments section.