In this Java Swing tutorial, you will learn how to use button that allows the user to perform action in a desktop application.

You know, JButtonis a fundamental Swing component that renders a button on screen and responds to user’s clicking event for performing a specific task. This article summarizes common programming practices for using JButton in Swing.

Table of content:

1. 1. Creating a JButton object
   2. Adding the button to a container
   3. Adding event listener for JButton
   4. Setting mnemonic and hotkey for JButton
   5. Setting a JButton as the default button
   6. Customizing JButton’s apperance
   7. JButton demo program

 

1. Creating a JButton object

• • Create a default button with a caption:
    

    JButton button = new JButton("Edit");

    
    Image:
  • Create a button with only an icon in the file system:
    

    JButton button = new JButton(new ImageIcon("images/start.gif"));

    Here the icon file start.gifis placed under images directory which is relative to the program.
    
    Image:

  • Create a button with only icon inside a jar file or in classpath:
    

    String iconPath = "/net/codejava/swing/jbutton/stop.jpg";
    Icon icon = new ImageIcon(getClass().getResource(iconPath));
    JButton button = new JButton(icon);

    Here the icon file stop.jpgis placed under a specific package in the classpath.
    
    Image:

  • Create a button with a caption and an icon:
    

    JButton button = new JButton("Start", new ImageIcon("images/start.gif"));

    
    Image:
     

 

2. Adding the button to a container

• A JButton is usually added to a JPanel, a JFrame, a JDialog or a JApplet:
  

  frame.add(button);
  dialog.add(button);
  panel.add(button);
  applet.getContentPane().add(button);

   

• Adding a JButton to a container with a specific layout manager:

frame.add(button, BorderLayout.CENTER);
panel.add(button, gridbagConstraints);

  

3. Adding event listener for JButton

• Adding an event listener using anonymous class (shortcut way):
  

  button.addActionListener(new ActionListener() {
  	@Override
  	public void actionPerformed(ActionEvent evt) {
  		// do everything here...
  	}
  });

   

• Adding an event listener using anonymous class and an event handler method (recommended):
  

  button.addActionListener(new ActionListener() {
  	@Override
  	public void actionPerformed(ActionEvent evt) {
  		// delegate to event handler method
  		buttonActionPerformed(evt);
  	}
  });

   
  The event handler method is declared as follows:

  private void buttonActionPerformed(ActionEvent evt) {
  	// do something here...
  }

   

• Let the container listens to JButton’s click event (not recommended):

public class App extends JFrame implements ActionListener {
	public App() {
		// creates the button...

		// adds event listener:
		button.addActionListener(this);
	}

	@Override
	public void actionPerformed(ActionEvent evt) {
		// do something here...
	}
}

 

Here the container (JFrame) must implement the ActionListener interface and override the method actionPerformed().

 

4. Setting mnemonic and hotkey for JButton

• Set mnemonic key Alt + Efor the button whose caption is “Edit”:
  

  button.setMnemonic(KeyEvent.VK_E);

  
  The letter E is underlined: so user can invoke that button’s action by pressing Alt + Einstead of clicking mouse.  

• Set F2 as the hot key to invoke the button’s action:

String mapKey = "KEY_F2";
InputMap inputMap = button.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
inputMap.put(KeyStroke.getKeyStroke("F2"), mapKey);

button.getActionMap().put(mapKey, new AbstractAction() {
	public void actionPerformed(ActionEvent evt) {
		buttonActionPerformed(evt);
	}
});

 

5. Setting a JButton as the default button

A window can have a default button whose action will be invoked when the user hits Enter key. Here is the code to set the button as default button in the frame window:

getRootPane().setDefaultButton(button);

 

The default button is bold in the window like the 3^rd button in this screenshot:

6. Customizing JButton’s appearance

• Change font style, background color and foreground color of the button:
  

  button.setFont(new java.awt.Font("Arial", Font.BOLD, 14));
  button.setBackground(Color.YELLOW);
  button.setForeground(Color.BLUE);

  
  Image:  

• Change font style using HTML code:

button.setText("<html><color=blue><b>Edit</b></font></html>");

 

7. JButton demo program

For reference, we created a demo program which incorporates all the practices mentioned above. The program looks like this:

You can download source code of this program in the attachment section.

 

Other Java Swing Tutorials:

• Java Swing Hello World Tutorial for Beginners Using Text Editor
• JFrame basic tutorial and examples
• JPanel basic tutorial and examples
• JLabel basic tutorial and examples
• JTextField basic tutorial and examples
• JComboBox basic tutorial and examples
• JList basic tutorial and examples
• JTree basic tutorial and examples
• A Simple JTable Example for Display