Java Tutorial/Swing Event/Event Adapter

Multiple sources: A listener can be plugged into several sources.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
class ButtonListener implements ActionListener {
  public void actionPerformed(ActionEvent e) {
    JButton o = (JButton) e.getSource();
    String label = o.getText();
    System.out.println(label + " button clicked");
  }
}
public class MultipleSources {
  public static void main(String[] args) {
    JPanel panel = new JPanel();
    JButton close = new JButton("Close");
    close.addActionListener(new ButtonListener());
    JButton open = new JButton("Open");
    open.addActionListener(new ButtonListener());
    JButton find = new JButton("Find");
    find.addActionListener(new ButtonListener());
    JButton save = new JButton("Save");
    save.addActionListener(new ButtonListener());
    panel.add(close);
    panel.add(open);
    panel.add(find);
    panel.add(save);
    JFrame f = new JFrame();
    f.add(panel);
    f.setSize(400, 300);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
  }
}

Register several listeners for one event.

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSpinner;
public class MultipleListeners {
  JLabel statusbar = new JLabel("0");
  JSpinner spinner = new JSpinner();
  static int count = 0;
  class ButtonListener1 implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      Integer val = (Integer) spinner.getValue();
      spinner.setValue(++val);
    }
  }
  class ButtonListener2 implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      statusbar.setText(Integer.toString(++count));
    }
  }
  public MultipleListeners() {
    JPanel panel = new JPanel();
    JButton add = new JButton("+");
    add.addActionListener(new ButtonListener1());
    add.addActionListener(new ButtonListener2());
    panel.add(add);
    panel.add(spinner);
    JFrame f = new JFrame();
    f.add(panel);
    f.add(statusbar, BorderLayout.SOUTH);
    f.setSize(300, 200);
    f.setLocationRelativeTo(null);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
  }
  public static void main(String[] args) {
    new MultipleListeners();
  }
}

Removing listeners: remove the registered listeners.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class RemoveListener {
  class ButtonListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      System.out.println(++count);
    }
  }
  JButton add = new JButton("+");
  JCheckBox active = new JCheckBox("Active listener");
  ButtonListener buttonlistener = new ButtonListener();
  int count = 0;
  public RemoveListener() {
    JPanel panel = new JPanel();
    active.addItemListener(new ItemListener() {
      public void itemStateChanged(ItemEvent event) {
        if (active.isSelected()) {
          add.addActionListener(buttonlistener);
        } else {
          add.removeActionListener(buttonlistener);
        }
      }
    });
    panel.add(add);
    panel.add(active);
    JFrame f = new JFrame();
    f.add(panel);
    f.setSize(310, 200);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
  }
  public static void main(String[] args) {
    new RemoveListener();
  }
}

void java.awt.Toolkit.addAWTEventListener(AWTEventListener listener, long eventMask)

import java.awt.AWTEvent;
import java.awt.Toolkit;
import java.awt.event.AWTEventListener;
import java.awt.event.ActionEvent;
import java.awt.event.ruponentEvent;
import java.awt.event.WindowEvent;
import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
public class Main implements AWTEventListener {
  public void eventDispatched(AWTEvent evt) {
    if (evt.getID() == WindowEvent.WINDOW_OPENED) {
      ComponentEvent cev = (ComponentEvent) evt;
      if (cev.getComponent() instanceof JFrame) {
        System.out.println("event: " + evt);
        JFrame frame = (JFrame) cev.getComponent();
        loadSettings(frame);
      }
    }
  }
  public static void loadSettings(JFrame frame) {
    System.out.println("loading");
  }
  public static void saveSettings() {
    System.out.println("saving");
  }
  public static void main(String[] args) throws Exception {
    Toolkit tk = Toolkit.getDefaultToolkit();
    final Main main = new Main();
    tk.addAWTEventListener(main, AWTEvent.WINDOW_EVENT_MASK);
    final JFrame frame = new JFrame("");
    frame.setName("your frame");
    JMenuBar mb = new JMenuBar();
    JMenu menu = new JMenu("File");
    menu.add(new AbstractAction("Quit") {
      public void actionPerformed(ActionEvent evt) {
        try {
          main.saveSettings();
          System.exit(0);
        } catch (Exception ex) {
          System.out.println(ex);
        }
      }
    });
    mb.add(menu);
    frame.setJMenuBar(mb);
    frame.pack();
    frame.setVisible(true);
  }
}