import java.awt.Dimension;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.util.Vector;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
public class Main extends JPanel implements FocusListener {
public Main() {
JTextField textField = new JTextField("A TextField");
textField.addFocusListener(this);
JLabel label = new JLabel("A Label");
label.addFocusListener(this);
add(label);
String comboPrefix = "ComboBox Item #";
final int numItems = 15;
Vector vector = new Vector(numItems);
for (int i = 0; i < numItems; i++) {
vector.addElement(comboPrefix + i);
}
JComboBox comboBox = new JComboBox(vector);
comboBox.addFocusListener(this);
add(comboBox);
JButton button = new JButton("A Button");
button.addFocusListener(this);
add(button);
String listPrefix = "List Item #";
Vector listVector = new Vector(numItems);
for (int i = 0; i < numItems; i++) {
listVector.addElement(listPrefix + i);
}
JList list = new JList(listVector);
list.setSelectedIndex(1);
list.addFocusListener(this);
JScrollPane listScrollPane = new JScrollPane(list);
listScrollPane.getVerticalScrollBar().setFocusable(false);
listScrollPane.getHorizontalScrollBar().setFocusable(false);
add(listScrollPane);
setPreferredSize(new Dimension(450, 450));
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
}
void displayMessage(String prefix, FocusEvent e) {
System.out.println(prefix
+ (e.isTemporary() ? " (temporary):" : ":")
+ e.getComponent().getClass().getName()
+ "; Opposite component: "
+ (e.getOppositeComponent() != null ? e.getOppositeComponent().getClass().getName()
: "null") );
}
public static void main(String[] args) {
JFrame frame = new JFrame("FocusEventDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new Main();
newContentPane.setOpaque(true); // content panes must be opaque
frame.setContentPane(newContentPane);
frame.pack();
frame.setVisible(true);
}
public void focusGained(FocusEvent e) {
displayMessage("Focus gained", e);
}
public void focusLost(FocusEvent e) {
displayMessage("Focus lost", e);
}
}