Handle Focus events with FocusListener

import java.applet.Applet;
import java.awt.*;
import java.awt.event.FocusListener;
import java.awt.event.FocusEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.WindowEvent;
import java.awt.event.WindowAdapter;


public class FocusEventExample extends Applet
		            implements FocusListener,
				       ActionListener {

    TextArea textAreaObj;
    FocusFrame frameObj;
    Button btnOne, btnTwo;
    static final String SHOW = "show";
    static final String CLEAR = "clear";
    String lineSep;

    public void init() {
	btnOne = new Button("Click to show frame");
	btnOne.setActionCommand(SHOW);
	btnOne.addActionListener(this);

	btnTwo = new Button("Clear");
	btnTwo.setActionCommand(CLEAR);
	btnTwo.addActionListener(this);

	textAreaObj = new TextArea(5, 20);
	textAreaObj.setEditable(false);

	setLayout(new BorderLayout());
	add("North", btnOne);
	add("Center", textAreaObj);
	add("South", btnTwo);

	//Create but don't show window.
	frameObj = new FocusFrame(this);

	lineSep = System.getProperty("line.separator");
    }

    public void stop() {
	frameObj.setVisible(false);
    }

    public void focusGained(FocusEvent e) {
	showStatus("Focus On ", e);
    }

    public void focusLost(FocusEvent e) {
	showStatus("Focus Off ", e);
    }

    void showStatus(String prefix, FocusEvent e) {
	textAreaObj.append(prefix
		       + ": "
		       + e.getComponent()
		       + lineSep); 
    }

    public void actionPerformed(ActionEvent e) {
	if (e.getActionCommand() == SHOW) {
	    frameObj.pack();
	    frameObj.setVisible(true);
	} else { //CLEAR
	    textAreaObj.setText("");
	}
    }
}
class FocusFrame extends Frame {
    class FocusFrameListener extends WindowAdapter {
        public void windowClosing(WindowEvent e) {
    	    setVisible(false);
        }
    }

    public FocusFrame(FocusListener listener) {
	super("Focus Event Frame");
	this.addFocusListener(listener);
	this.addWindowListener(new FocusFrameListener());

	GridBagLayout gridbag = new GridBagLayout();
	GridBagConstraints gridBagConstObj = new GridBagConstraints();
	setLayout(gridbag);

	gridBagConstObj.fill = GridBagConstraints.HORIZONTAL;
	gridBagConstObj.weightx = 1.0;   
	TextField textField = new TextField("A TextField");
	textField.addFocusListener(listener);
	gridbag.setConstraints(textField, gridBagConstObj);
	add(textField);

	gridBagConstObj.weightx = 0.1;   
	gridBagConstObj.fill = GridBagConstraints.NONE;
	Label labelObj = new Label("Label:");
	labelObj.addFocusListener(listener);
	gridbag.setConstraints(labelObj, gridBagConstObj);
	add(labelObj);

	Choice choiceObj = new Choice();
	String choiceprefix = "Choice item #";
	for (int i = 0; i < 10; i++) {
	    choiceObj.addItem(choiceprefix + i);
	}
	choiceObj.addFocusListener(listener);
	gridbag.setConstraints(choiceObj, gridBagConstObj);
	add(choiceObj);

	gridBagConstObj.gridwidth = GridBagConstraints.REMAINDER;
	Button btnObj = new Button("Button: ");
	btnObj.addFocusListener(listener);
	gridbag.setConstraints(btnObj, gridBagConstObj);
	add(btnObj);

	gridBagConstObj.weighty = 1.0;   
	gridBagConstObj.weightx = 0.0;   
	gridBagConstObj.fill = GridBagConstraints.BOTH;
	List list = new List();
	String listprefix = "List item #";
	for (int i = 0; i < 10; i++) {
	    list.addItem(listprefix + i);
	}
	list.addFocusListener(listener);
	gridbag.setConstraints(list, gridBagConstObj);
	add(list);
    }
}