Swing Focus Adapter

1. FocusAdapter class is an abstract adapter class in Java Swing.
2. FocusAdapter class is for receiving keyboard focus events.
3. Methods specified in FocusAdapter class are empty.
4. FocusAdapter class exists as convenience for creating listener objects

Class declaration

Below is the declaration for java.awt.event.FocusAdapter class -

public abstract class FocusAdapter
   extends Object
      implements FocusListener

Class constructors

FocusAdapter()

Class methods

Methods inherited

This class inherits methods from the following classes:

java.lang.Object

Swing Focus Adapter Example

AdapterExample.java

package com.c4learn;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class AdapterExample {
   private JFrame baseFrame;
   private JLabel headLabel;
   private JLabel msgLabel;
   private JPanel controlPanel;
   public AdapterExample() {
      initializeUI();
   }
   public static void main(String[] args) {
      AdapterExample adapterDemo = new AdapterExample();
      adapterDemo.showFocusApapter();
   }
   private void initializeUI() {
      baseFrame = new JFrame("Java Swing Examples");
      baseFrame.setSize(500, 500);
      baseFrame.setLayout(new GridLayout(3, 1));
      headLabel = new JLabel("", JLabel.CENTER);
      msgLabel = new JLabel("", JLabel.CENTER);
      msgLabel.setSize(300, 100);
      baseFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent) {
            System.exit(0);
         }
      });
      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());
      baseFrame.add(headLabel);
      baseFrame.add(controlPanel);
      baseFrame.add(msgLabel);
      baseFrame.setVisible(true);
   }
   private void showFocusApapter() {
      headLabel.setText("FocusAdapter Example");
      JButton btn1 = new JButton("Button 1");
      JButton btn2 = new JButton("Button 2");
      btn1.addFocusListener(new FocusAdapter() {
         public void focusGained(FocusEvent e) {
            msgLabel.setText("Button 1 - Got focus.");
         }
      });
      btn1.addFocusListener(new FocusAdapter() {
         public void focusLost(FocusEvent e) {
            msgLabel.setText("Button 1 - Lost focus.");
         }
      });
      controlPanel.add(btn1);
      controlPanel.add(btn2);
      baseFrame.setVisible(true);
   }
}

After running program in the eclipse you will see below output

Explanation

In this example consider below two buttons -

JButton btn1 = new JButton("Button 1");
JButton btn2 = new JButton("Button 2");

Now we have added focus listener for the button 1 -

btn1.addFocusListener(new FocusAdapter() {
   public void focusGained(FocusEvent e) {
	msgLabel.setText("Button 1 - Got focus.");
   }
   public void focusLost(FocusEvent e) {
	msgLabel.setText("Button 1 - Lost focus.");
   }
});

Now focusLost() method will provide the code to be executed when button1 will lost its focus. Similarly focusGained() method would be executed when button 1 gains focus.

Swing Key Adapter

1. KeyAdapter class is an abstract adapter class in Java Swing.
2. KeyAdapter class is for receiving keyboard events.
3. Methods specified in KeyAdapter class are empty.
4. KeyAdapter class exists as convenience for creating listener objects

Class declaration

Below is the declaration for java.awt.event.KeyAdapter class -

public abstract class KeyAdapter
   extends Object
      implements KeyListener

Class constructors

KeyAdapter()

Class methods

Methods inherited

This class inherits methods from the following classes:

java.lang.Object

Key Adapter Example

AdapterExample.java

package com.c4learn;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class AdapterExample {
   private JFrame baseFrame;
   private JLabel headLabel;
   private JLabel msgLabel;
   private JPanel controlPanel;
   public AdapterExample() {
      initializeUI();
   }
   public static void main(String[] args) {
      AdapterExample adapterDemo = new AdapterExample();
      adapterDemo.showMouseApapter();
   }
   private void initializeUI() {
      baseFrame = new JFrame("Java Swing Examples");
      baseFrame.setSize(500, 500);
      baseFrame.setLayout(new GridLayout(3, 1));
      headLabel = new JLabel("", JLabel.CENTER);
      msgLabel = new JLabel("", JLabel.CENTER);
      msgLabel.setSize(300, 100);
      baseFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent) {
            System.exit(0);
         }
      });
      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());
      baseFrame.add(headLabel);
      baseFrame.add(controlPanel);
      baseFrame.add(msgLabel);
      baseFrame.setVisible(true);
   }
   private void showMouseApapter() {
      headLabel.setText("KeyAdapter Example");
      final JTextField textField = new JTextField(10);
      JButton displayButton = new JButton("Display");
      displayButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            msgLabel.setText("You entered : " + textField.getText());
         }
      });
      textField.addKeyListener(new KeyAdapter() {
         public void keyPressed(KeyEvent e) {
            if (e.getKeyCode() == KeyEvent.VK_ENTER) {
               msgLabel.setText("You entered : " + textField.getText());
            }
         }
      });
      controlPanel.add(textField);
      controlPanel.add(displayButton);
      baseFrame.setVisible(true);
   }
}

After running program in the eclipse you will see below output

Swing MouseAdapter

1. MouseAdapter class is an abstract adapter class in Java Swing.
2. MouseAdapter class is for receiving mouse events.
3. Methods specified in MouseAdapter class are empty.
4. MouseAdapter class exists as convenience for creating listener objects

Class declaration

Below is the declaration for java.awt.event.MouseAdapter class -

public abstract class MouseAdapter
   extends Object
      implements MouseListener, 
                 MouseWheelListener, 
                 MouseMotionListener

Class constructors

MouseAdapter()

Class methods

Methods inherited

This class inherits methods from the following classes:

java.lang.Object

Mouse Adapter Example

AdapterExample.java

package com.c4learn;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class AdapterExample {
   private JFrame baseFrame;
   private JLabel headLabel;
   private JLabel msgLabel;
   private JPanel controlPanel;
   public AdapterExample() {
      initializeUI();
   }
   public static void main(String[] args) {
      AdapterExample adapterDemo = new AdapterExample();
      adapterDemo.showMouseApapter();
   }
   private void initializeUI() {
      baseFrame = new JFrame("Java Swing Examples");
      baseFrame.setSize(500, 500);
      baseFrame.setLayout(new GridLayout(3, 1));
      headLabel = new JLabel("", JLabel.CENTER);
      msgLabel = new JLabel("", JLabel.CENTER);
      msgLabel.setSize(300, 100);
      baseFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent) {
            System.exit(0);
         }
      });
      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());
      baseFrame.add(headLabel);
      baseFrame.add(controlPanel);
      baseFrame.add(msgLabel);
      baseFrame.setVisible(true);
   }
   private void showMouseApapter() {
      headLabel.setText("Listener in action : MouseAdapter");
      JPanel panel = new JPanel();
      panel.setBackground(Color.gray);
      panel.setLayout(new FlowLayout());
      JLabel msglabel = new JLabel("www.c4learn.com", JLabel.CENTER);
      msglabel.addMouseListener(new MouseAdapter() {
         public void mouseClicked(MouseEvent e) {
            msgLabel.setText("Mouse Clicked: (" + e.getX() + ", "
                  + e.getY() + ")");
         }
      });
      panel.add(msglabel);
      controlPanel.add(panel);
      baseFrame.setVisible(true);
   }
}

After running program in the eclipse you will see below output