Java/Swing JFC/Focus

Button Focus

   <source lang="java">
 

import java.awt.Container; import java.awt.FlowLayout; import javax.swing.JButton; import javax.swing.JFrame; public class ButtonFocus {

 public static void main(String args[]) {
   JFrame frame = new JFrame("Action Sample");
   JButton focusButton = new JButton("Focused");
   JButton notFocusButton = new JButton("Not Focused");
   Container contentPane = frame.getContentPane();
   contentPane.setLayout(new FlowLayout());
   contentPane.add(focusButton);
   contentPane.add(notFocusButton);
   frame.setSize(300, 100);
   frame.setVisible(true);
 }

}

 </source>
   
  
 
  

Focus Concepts Demo

   <source lang="java">
 

/* From http://java.sun.ru/docs/books/tutorial/index.html */ /*

* Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* -Redistribution of source code must retain the above copyright notice, this
*  list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduce the above copyright notice,
*  this list of conditions and the following disclaimer in the documentation
*  and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
* AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
* REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
* INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
* OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
* EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed, licensed or intended
* for use in the design, construction, operation or maintenance of any
* nuclear facility.
*/

import java.awt.BorderLayout; import java.awt.GridLayout; import javax.swing.BorderFactory; import javax.swing.JButton; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JTextArea; import javax.swing.JTextField; /*

* FocusConceptsDemo.java is a 1.4 example that requires no other files.
*/

public class FocusConceptsDemo extends JPanel {

 static JFrame frame;
 JTextField t1, t2, t3, t4;
 JButton b1, b2, b3, b4;
 JTextArea text1;
 public FocusConceptsDemo() {
   super(new BorderLayout());
   b1 = new JButton("JButton");
   b2 = new JButton("JButton");
   b3 = new JButton("JButton");
   b4 = new JButton("JButton");
   JPanel buttonPanel = new JPanel(new GridLayout(1, 1));
   buttonPanel.add(b1);
   buttonPanel.add(b2);
   buttonPanel.add(b3);
   buttonPanel.add(b4);
   text1 = new JTextArea("JTextArea", 15, 40);
   JPanel textAreaPanel = new JPanel(new BorderLayout());
   textAreaPanel.add(text1, BorderLayout.CENTER);
   t1 = new JTextField("JTextField");
   t2 = new JTextField("JTextField");
   t3 = new JTextField("JTextField");
   t4 = new JTextField("JTextField");
   JPanel textFieldPanel = new JPanel(new GridLayout(1, 1));
   textFieldPanel.add(t1);
   textFieldPanel.add(t2);
   textFieldPanel.add(t3);
   textFieldPanel.add(t4);
   add(buttonPanel, BorderLayout.PAGE_START);
   add(textAreaPanel, BorderLayout.CENTER);
   add(textFieldPanel, BorderLayout.PAGE_END);
   setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
 }
 /**
  * Create the GUI and show it. For thread safety, this method should be
  * invoked from the event-dispatching thread.
  */
 private static void createAndShowGUI() {
   //Make sure we have nice window decorations.
   JFrame.setDefaultLookAndFeelDecorated(true);
   //Create and set up the window.
   frame = new JFrame("FocusConceptsDemo");
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   //Create and set up the content pane.
   JComponent newContentPane = new FocusConceptsDemo();
   newContentPane.setOpaque(true); //content panes must be opaque
   frame.setContentPane(newContentPane);
   //Display the window.
   frame.pack();
   frame.setVisible(true);
 }
 public static void main(String[] args) {
   //Schedule a job for the event-dispatching thread:
   //creating and showing this application"s GUI.
   javax.swing.SwingUtilities.invokeLater(new Runnable() {
     public void run() {
       createAndShowGUI();
     }
   });
 }

}

 </source>
   
  
 
  

Focus Cycle Sample

   <source lang="java">
 

import java.awt.Container; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.GridLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; public class FocusCycleSample {

 public static void main(String args[]) {
   JFrame frame = new JFrame("Focus Cycle Sample");
   Container contentPane = frame.getContentPane();
   contentPane.setLayout(new GridLayout(3,3));
   for (int i = 0; i < 8; i++) {
     JButton button = new JButton("" + i);
     contentPane.add(button);
   }
   JPanel panel = new FocusCycleConstrainedJPanel();
   panel.setLayout(new GridLayout(1, 3));
   for (int i = 0; i < 3; i++) {
     JButton button = new JButton("" + (i + 3));
     panel.add(button);
   }
   contentPane.add(panel);
   frame.setSize(300, 200);
   frame.setVisible(true);
 }

} class FocusCycleConstrainedJPanel extends JPanel {

 public boolean isFocusCycleRoot() {
   return true;
 }

}

 </source>
   
  
 
  

Focus Example

   <source lang="java">
 

import java.awt.AWTKeyStroke; import java.awt.BorderLayout; import java.awt.Color; import java.awt.Container; import java.awt.Dimension; import java.awt.GridLayout; import java.awt.KeyboardFocusManager; import java.awt.event.KeyEvent; import javax.swing.JButton; import javax.swing.JDesktopPane; import javax.swing.JFrame; import javax.swing.JInternalFrame; import javax.swing.JPanel; public class FocusExample extends JFrame {

 public FocusExample() {
   super("Focus Example");
   setDefaultCloseOperation(EXIT_ON_CLOSE);
   MyPanel mypanel = new MyPanel();
   JButton button1 = new JButton("One");
   JButton button2 = new JButton("Two");
   JButton button3 = new JButton("Three");
   JButton button4 = new JButton("Four");
   JButton button5 = new MyButton("Five*");
   JButton button6 = new MyButton("Six*");
   JButton button7 = new JButton("Seven");
   mypanel.add(button2);
   mypanel.add(button3);
   JInternalFrame frame1 = new JInternalFrame("Internal Frame 1", true,
       true, true, true);
   frame1.setBackground(Color.lightGray);
   frame1.getContentPane().setLayout(new GridLayout(2, 3));
   frame1.setSize(300, 200);
   frame1.getContentPane().add(button1);
   frame1.getContentPane().add(mypanel);
   frame1.getContentPane().add(button4);
   frame1.getContentPane().add(button5);
   frame1.getContentPane().add(button6);
   frame1.getContentPane().add(button7);
   JDesktopPane desktop = new JDesktopPane();
   desktop.add(frame1, new Integer(1));
   desktop.setOpaque(true);
   //  Now set up the user interface window.
   Container contentPane = getContentPane();
   contentPane.add(desktop, BorderLayout.CENTER);
   setSize(new Dimension(400, 300));
   frame1.setVisible(true);
   setVisible(true);
 }
 public static void main(String[] args) {
   new FocusExample();
 }
 class MyButton extends JButton {
   public MyButton(String s) {
     super(s);
   }
   public boolean isFocusable() {
     return false;
   }
 }
 class MyPanel extends JPanel {
   public MyPanel() {
     super(true);
     java.util.Set upKeys = new java.util.HashSet(1);
     upKeys.add(AWTKeyStroke.getAWTKeyStroke(KeyEvent.VK_UP, 0));
     setFocusTraversalKeys(KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS,
         upKeys);
   }
   public boolean isFocusCycleRoot() {
     return true;
   }
 }

}

 </source>
   
  
 
  

Focus Traversal Demo

   <source lang="java">
 

/* From http://java.sun.ru/docs/books/tutorial/index.html */ /*

* Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* -Redistribution of source code must retain the above copyright notice, this
*  list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduce the above copyright notice,
*  this list of conditions and the following disclaimer in the documentation
*  and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
* AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
* REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
* INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
* OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
* EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed, licensed or intended
* for use in the design, construction, operation or maintenance of any
* nuclear facility.
*/

import java.awt.BorderLayout; import java.awt.ruponent; import java.awt.Container; import java.awt.FocusTraversalPolicy; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.BorderFactory; import javax.swing.JCheckBox; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTable; import javax.swing.JTextField; /*

* FocusTraversalDemo.java is a 1.4 example that requires no other files.
*/

public class FocusTraversalDemo extends JPanel implements ActionListener {

 static JFrame frame;
 JTextField tf1, tf2, tf3, tf4, tf5, tf6;
 JTable table;
 JLabel label;
 JCheckBox togglePolicy;
 static MyOwnFocusTraversalPolicy newPolicy;
 public FocusTraversalDemo() {
   super(new BorderLayout());
   newPolicy = new MyOwnFocusTraversalPolicy();
   tf1 = new JTextField("Field 1");
   tf2 = new JTextField("A Bigger Field 2");
   tf3 = new JTextField("Field 3");
   tf4 = new JTextField("A Bigger Field 4");
   tf5 = new JTextField("Field 5");
   tf6 = new JTextField("A Bigger Field 6");
   table = new JTable(4, 3);
   togglePolicy = new JCheckBox("Custom FocusTraversalPolicy");
   togglePolicy.setActionCommand("toggle");
   togglePolicy.addActionListener(this);
   togglePolicy.setFocusable(false); //Remove it from the focus cycle.
   //Note that HTML is allowed and will break this run of text
   //across two lines.
   label = new JLabel(

"<html>Use Tab (or Shift-Tab) to navigate from component to component.

Control-Tab (or Control-Shift-Tab) allows you to break out of the JTable.</html>"); JPanel leftTextPanel = new JPanel(new GridLayout(3, 2)); leftTextPanel.add(tf1, BorderLayout.PAGE_START); leftTextPanel.add(tf3, BorderLayout.CENTER); leftTextPanel.add(tf5, BorderLayout.PAGE_END); leftTextPanel.setBorder(BorderFactory.createEmptyBorder(0, 0, 5, 5)); JPanel rightTextPanel = new JPanel(new GridLayout(3, 2)); rightTextPanel.add(tf2, BorderLayout.PAGE_START); rightTextPanel.add(tf4, BorderLayout.CENTER); rightTextPanel.add(tf6, BorderLayout.PAGE_END); rightTextPanel.setBorder(BorderFactory.createEmptyBorder(0, 0, 5, 5)); JPanel tablePanel = new JPanel(new GridLayout(0, 1)); tablePanel.add(table, BorderLayout.CENTER); tablePanel.setBorder(BorderFactory.createEtchedBorder()); JPanel bottomPanel = new JPanel(new GridLayout(2, 1)); bottomPanel.add(togglePolicy, BorderLayout.PAGE_START); bottomPanel.add(label, BorderLayout.PAGE_END); add(leftTextPanel, BorderLayout.LINE_START); add(rightTextPanel, BorderLayout.CENTER); add(tablePanel, BorderLayout.LINE_END); add(bottomPanel, BorderLayout.PAGE_END); setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20)); } //Turn the custom focus traversal policy on/off, //according to the checkbox public void actionPerformed(ActionEvent e) { if ("toggle".equals(e.getActionCommand())) { frame.setFocusTraversalPolicy(togglePolicy.isSelected() ? newPolicy  : null); } } /** * Create the GUI and show it. For thread safety, this method should be * invoked from the event-dispatching thread. */ private static void createAndShowGUI() { //Make sure we have nice window decorations. JFrame.setDefaultLookAndFeelDecorated(true); //Create and set up the window. frame = new JFrame("FocusTraversalDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane. JComponent newContentPane = new FocusTraversalDemo(); newContentPane.setOpaque(true); //content panes must be opaque frame.setContentPane(newContentPane); //Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { //Schedule a job for the event-dispatching thread: //creating and showing this application"s GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } public class MyOwnFocusTraversalPolicy extends FocusTraversalPolicy { public Component getComponentAfter(Container focusCycleRoot, Component aComponent) { if (aComponent.equals(tf1)) { return tf2; } else if (aComponent.equals(tf2)) { return tf3; } else if (aComponent.equals(tf3)) { return tf4; } else if (aComponent.equals(tf4)) { return tf5; } else if (aComponent.equals(tf5)) { return tf6; } else if (aComponent.equals(tf6)) { return table; } else if (aComponent.equals(table)) { return tf1; } return tf1; } public Component getComponentBefore(Container focusCycleRoot, Component aComponent) { if (aComponent.equals(tf1)) { return table; } else if (aComponent.equals(tf2)) { return tf1; } else if (aComponent.equals(tf3)) { return tf2; } else if (aComponent.equals(tf4)) { return tf3; } else if (aComponent.equals(tf5)) { return tf4; } else if (aComponent.equals(tf6)) { return tf5; } else if (aComponent.equals(table)) { return tf6; } return tf1; } public Component getDefaultComponent(Container focusCycleRoot) { return tf1; } public Component getLastComponent(Container focusCycleRoot) { return table; } public Component getFirstComponent(Container focusCycleRoot) { return tf1; } } } </source>

Focus Traversal Example

   <source lang="java">
 

/* Java Swing, 2nd Edition By Marc Loy, Robert Eckstein, Dave Wood, James Elliott, Brian Cole ISBN: 0-596-00408-7 Publisher: O"Reilly

• /

// FocusTraversalExample.java //Similar to the FocusExample, this class uses the custom AlphaButtonPolicy //focus traversal policy to navigate another small set of buttons. // import java.awt.Color; import java.awt.ruponent; import java.awt.Container; import java.awt.FocusTraversalPolicy; import java.awt.GridLayout; import java.util.Map; import java.util.SortedMap; import java.util.TreeMap; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; public class FocusTraversalExample extends JPanel {

 public FocusTraversalExample() {
   setLayout(new GridLayout(6, 1));
   JButton button1 = new JButton("Texas");
   JButton button2 = new JButton("Vermont");
   JButton button3 = new JButton("Florida");
   JButton button4 = new JButton("Alabama");
   JButton button5 = new JButton("Minnesota");
   JButton button6 = new JButton("California");
   setBackground(Color.lightGray);
   add(button1);
   add(button2);
   add(button3);
   add(button4);
   add(button5);
   add(button6);
 }
 public static void main(String[] args) {
   JFrame frame = new JFrame("Alphabetized Button Focus Traversal");
   frame.setFocusTraversalPolicy(new AlphaButtonPolicy());
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   frame.setContentPane(new FocusTraversalExample());
   frame.setSize(400, 300);
   frame.setVisible(true);
 }

} //AlphaButtonPolicy.java //A custom focus traversal policy that uses alphabetical ordering of button //labels to determine "next" and "previous" buttons for keyboard traversal. // class AlphaButtonPolicy extends FocusTraversalPolicy {

 private SortedMap getSortedButtons(Container focusCycleRoot) {
   if (focusCycleRoot == null) {
     throw new IllegalArgumentException("focusCycleRoot can"t be null");
   }
   SortedMap result = new TreeMap(); // Will sort all buttons by text.
   sortRecursive(result, focusCycleRoot);
   return result;
 }
 private void sortRecursive(Map buttons, Container container) {
   for (int i = 0; i < container.getComponentCount(); i++) {
     Component c = container.getComponent(i);
     if (c instanceof JButton) { // Found another button to sort.
       buttons.put(((JButton) c).getText(), c);
     }
     if (c instanceof Container) { // Found a container to search.
       sortRecursive(buttons, (Container) c);
     }
   }
 }
 // The rest of the code implements the FocusTraversalPolicy interface.
 public Component getFirstComponent(Container focusCycleRoot) {
   SortedMap buttons = getSortedButtons(focusCycleRoot);
   if (buttons.isEmpty()) {
     return null;
   }
   return (Component) buttons.get(buttons.firstKey());
 }
 public Component getLastComponent(Container focusCycleRoot) {
   SortedMap buttons = getSortedButtons(focusCycleRoot);
   if (buttons.isEmpty()) {
     return null;
   }
   return (Component) buttons.get(buttons.lastKey());
 }
 public Component getDefaultComponent(Container focusCycleRoot) {
   return getFirstComponent(focusCycleRoot);
 }
 public Component getComponentAfter(Container focusCycleRoot,
     Component aComponent) {
   if (!(aComponent instanceof JButton)) {
     return null;
   }
   SortedMap buttons = getSortedButtons(focusCycleRoot);
   // Find all buttons after the current one.
   String nextName = ((JButton) aComponent).getText() + "\0";
   SortedMap nextButtons = buttons.tailMap(nextName);
   if (nextButtons.isEmpty()) { // Wrapped back to beginning
     if (!buttons.isEmpty()) {
       return (Component) buttons.get(buttons.firstKey());
     }
     return null; // Degenerate case of no buttons.
   }
   return (Component) nextButtons.get(nextButtons.firstKey());
 }
 public Component getComponentBefore(Container focusCycleRoot,
     Component aComponent) {
   if (!(aComponent instanceof JButton)) {
     return null;
   }
   SortedMap buttons = getSortedButtons(focusCycleRoot);
   SortedMap prevButtons = // Find all buttons before this one.
   buttons.headMap(((JButton) aComponent).getText());
   if (prevButtons.isEmpty()) { // Wrapped back to end.
     if (!buttons.isEmpty()) {
       return (Component) buttons.get(buttons.lastKey());
     }
     return null; // Degenerate case of no buttons.
   }
   return (Component) prevButtons.get(prevButtons.lastKey());
 }

}

 </source>
   
  
 
  

Handling Focus Changes

   <source lang="java">
  

import java.awt.event.FocusAdapter; import java.awt.event.FocusEvent; import javax.swing.JFrame; import javax.swing.JTextField; public class Main {

 public static void main(String[] argv) throws Exception {
   JTextField component = new JTextField();
   component.addFocusListener(new MyFocusListener());
   JFrame f = new JFrame();
   f.add(component);
   f.setSize(300, 300);
   f.setVisible(true);
 }

} class MyFocusListener extends FocusAdapter {

 public void focusGained(FocusEvent evt) {
   System.out.println("component gained the focus");
 }
 public void focusLost(FocusEvent evt) {
   System.out.println("component lost the focus");
 }

}

 </source>
   
  
 
  

Requests focus for a component

   <source lang="java">
  

import java.awt.ruponent; import java.awt.Container; import java.awt.FocusTraversalPolicy; import java.awt.KeyboardFocusManager; import javax.swing.JComponent; /**

* Copyright (C) 2004 NNL Technology AB
* Visit www.infonode.net for information about InfoNode(R) 
* products and how to contact NNL Technology AB.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, 
* MA 02111-1307, USA.
*/

// $Id: ComponentUtil.java,v 1.25 2005/12/04 13:46:04 jesper Exp $

public class Util {

 /**
  * Requests focus for a component. If that"s not possible it"s
  * {@link FocusTraversalPolicy}is checked. If that doesn"t work all it"s
  * children is recursively checked with this method.
  *
  * @param component the component to request focus for
  * @return the component which has focus or probably will obtain focus, null
  *         if no component will receive focus
  */
 public static Component smartRequestFocus(Component component) {
   if (requestFocus(component))
     return component;
   if (component instanceof JComponent) {
     FocusTraversalPolicy policy = ((JComponent) component).getFocusTraversalPolicy();
     if (policy != null) {
       Component focusComponent = policy.getDefaultComponent((Container) component);
       if (focusComponent != null && requestFocus(focusComponent)) {
         return focusComponent;
       }
     }
   }
   if (component instanceof Container) {
     Component[] children = ((Container) component).getComponents();
     for (int i = 0; i < children.length; i++) {
       component = smartRequestFocus(children[i]);
       if (component != null)
         return component;
     }
   }
   return null;
 }
 /**
  * Requests focus unless the component already has focus. For some weird
  * reason calling {@link Component#requestFocusInWindow()}when the
  * component is focus owner changes focus owner to another component!
  *
  * @param component the component to request focus for
  * @return true if the component has focus or probably will get focus,
  *         otherwise false
  */
 public static boolean requestFocus(Component component) {
   /*
    * System.out.println("Owner: " +
    * System.identityHashCode(KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner()) + ", " +
    * System.identityHashCode(component) + ", " +
    * (KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner() ==
    * component));
    */
   return KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner() == component ||
          component.requestFocusInWindow();
 }

}

 </source>
   
  
 
  

Requests focus unless the component already has focus

   <source lang="java">
  

import java.awt.ruponent; import java.awt.KeyboardFocusManager; /**

* Copyright (C) 2004 NNL Technology AB
* Visit www.infonode.net for information about InfoNode(R) 
* products and how to contact NNL Technology AB.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, 
* MA 02111-1307, USA.
*/

// $Id: ComponentUtil.java,v 1.25 2005/12/04 13:46:04 jesper Exp $

public class Util {

 /**
  * Requests focus unless the component already has focus. For some weird
  * reason calling {@link Component#requestFocusInWindow()}when the
  * component is focus owner changes focus owner to another component!
  *
  * @param component the component to request focus for
  * @return true if the component has focus or probably will get focus,
  *         otherwise false
  */
 public static boolean requestFocus(Component component) {
   /*
    * System.out.println("Owner: " +
    * System.identityHashCode(KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner()) + ", " +
    * System.identityHashCode(component) + ", " +
    * (KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner() ==
    * component));
    */
   return KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner() == component ||
          component.requestFocusInWindow();
 }

}

 </source>
   
  
 
  

Track Focus Demo

   <source lang="java">
 

/* From http://java.sun.ru/docs/books/tutorial/index.html */ /*

* Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* -Redistribution of source code must retain the above copyright notice, this
*  list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduce the above copyright notice,
*  this list of conditions and the following disclaimer in the documentation
*  and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
* AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
* REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
* INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
* OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
* EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed, licensed or intended
* for use in the design, construction, operation or maintenance of any
* nuclear facility.
*/

/*

* TrackFocusDemo.java is a 1.4 example that requires the following files:
* Picture.java images/Maya.jpg images/Anya.jpg images/Laine.jpg
* images/Cosmo.jpg images/Adele.jpg images/Alexi.jpg
*/

import java.awt.BorderLayout; import java.awt.Color; import java.awt.ruponent; import java.awt.Dimension; import java.awt.Graphics; import java.awt.GridLayout; import java.awt.Image; import java.awt.KeyboardFocusManager; import java.awt.event.FocusEvent; import java.awt.event.FocusListener; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import javax.accessibility.Accessible; import javax.swing.BorderFactory; import javax.swing.ImageIcon; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; public class TrackFocusDemo extends JPanel {

 Picture pic1, pic2, pic3, pic4, pic5, pic6;
 JLabel info;
 static String mayaString = "Maya";
 static String anyaString = "Anya";
 static String laineString = "Laine";
 static String cosmoString = "Cosmo";
 static String adeleString = "Adele";
 static String alexiString = "Alexi";
 String[] comments = { "Oops. What is this?", "This is Maya",
     "This is Anya", "This is Laine", "This is Cosmo", "This is Adele",
     "This is Alexi" };
 public TrackFocusDemo() {
   super(new BorderLayout());
   JPanel mugshots = new JPanel(new GridLayout(2, 3));
   pic1 = new Picture(createImageIcon("images/" + mayaString + ".jpg",
       mayaString).getImage());
   pic1.setName("1");
   mugshots.add(pic1);
   pic2 = new Picture(createImageIcon("images/" + anyaString + ".jpg",
       anyaString).getImage());
   pic2.setName("2");
   mugshots.add(pic2);
   pic3 = new Picture(createImageIcon("images/" + laineString + ".jpg",
       laineString).getImage());
   pic3.setName("3");
   mugshots.add(pic3);
   pic4 = new Picture(createImageIcon("images/" + cosmoString + ".jpg",
       cosmoString).getImage());
   pic4.setName("4");
   mugshots.add(pic4);
   pic5 = new Picture(createImageIcon("images/" + adeleString + ".jpg",
       adeleString).getImage());
   pic5.setName("5");
   mugshots.add(pic5);
   pic6 = new Picture(createImageIcon("images/" + alexiString + ".jpg",
       alexiString).getImage());
   pic6.setName("6");
   mugshots.add(pic6);
   info = new JLabel("Nothing selected");
   setPreferredSize(new Dimension(450, 350));
   add(mugshots, BorderLayout.CENTER);
   add(info, BorderLayout.PAGE_END);
   setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
   KeyboardFocusManager focusManager = KeyboardFocusManager
       .getCurrentKeyboardFocusManager();
   focusManager.addPropertyChangeListener(new PropertyChangeListener() {
     public void propertyChange(PropertyChangeEvent e) {
       String prop = e.getPropertyName();
       if (("focusOwner".equals(prop)) && (e.getNewValue() != null)
           && ((e.getNewValue()) instanceof Picture)) {
         Component comp = (Component) e.getNewValue();
         String name = comp.getName();
         Integer num = new Integer(name);
         int index = num.intValue();
         if (index < 0 || index > comments.length) {
           index = 0;
         }
         info.setText(comments[index]);
       }
     }
   });
 }
 /** Returns an ImageIcon, or null if the path was invalid. */
 protected static ImageIcon createImageIcon(String path, String description) {
   java.net.URL imageURL = TrackFocusDemo.class.getResource(path);
   if (imageURL == null) {
     System.err.println("Resource not found: " + path);
     return null;
   } else {
     return new ImageIcon(imageURL, description);
   }
 }
 /**
  * Create the GUI and show it. For thread safety, this method should be
  * invoked from the event-dispatching thread.
  */
 private static void createAndShowGUI() {
   //Make sure we have nice window decorations.
   JFrame.setDefaultLookAndFeelDecorated(true);
   //Create and set up the window.
   JFrame frame = new JFrame("TrackFocusDemo");
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   JComponent newContentPane = new TrackFocusDemo();
   newContentPane.setOpaque(true); //content panes must be opaque
   frame.setContentPane(newContentPane);
   //Display the window.
   frame.pack();
   frame.setVisible(true);
 }
 public static void main(String[] args) {
   //Schedule a job for the event-dispatching thread:
   //creating and showing this application"s GUI.
   javax.swing.SwingUtilities.invokeLater(new Runnable() {
     public void run() {
       createAndShowGUI();
     }
   });
 }

} /*

* Picture.java is used by the 1.4 TrackFocusDemo.java and DragPictureDemo.java
* examples.
*/

class Picture extends JComponent implements MouseListener, FocusListener,

   Accessible {
 Image image;
 public Picture(Image image) {
   this.image = image;
   setFocusable(true);
   addMouseListener(this);
   addFocusListener(this);
 }
 public void mouseClicked(MouseEvent e) {
   //Since the user clicked on us, let"s get focus!
   requestFocusInWindow();
 }
 public void mouseEntered(MouseEvent e) {
 }
 public void mouseExited(MouseEvent e) {
 }
 public void mousePressed(MouseEvent e) {
 }
 public void mouseReleased(MouseEvent e) {
 }
 public void focusGained(FocusEvent e) {
   //Draw the component with a red border
   //indicating that it has focus.
   this.repaint();
 }
 public void focusLost(FocusEvent e) {
   //Draw the component with a black border
   //indicating that it doesn"t have focus.
   this.repaint();
 }
 protected void paintComponent(Graphics graphics) {
   Graphics g = graphics.create();
   //Draw in our entire space, even if isOpaque is false.
   g.setColor(Color.WHITE);
   g.fillRect(0, 0, image == null ? 125 : image.getWidth(this),
       image == null ? 125 : image.getHeight(this));
   if (image != null) {
     //Draw image at its natural size of 125x125.
     g.drawImage(image, 0, 0, this);
   }
   //Add a border, red if picture currently has focus
   if (isFocusOwner()) {
     g.setColor(Color.RED);
   } else {
     g.setColor(Color.BLACK);
   }
   g.drawRect(0, 0, image == null ? 125 : image.getWidth(this),
       image == null ? 125 : image.getHeight(this));
   g.dispose();
 }

}

 </source>
   
  
 
  

Use this method to determine whether a particular component has the focus

   <source lang="java">
 

import javax.swing.JFrame; public class Main {

 public static void main() {
   JFrame f = new JFrame();
   boolean b = f.isFocusOwner();
 }

}

 </source>