Catch a key event in JFrame

hi,
i am coding a GUI application for some FSM(Finite State Machine) simulation purpose. the app can load the FSM and display it. i can selecte some part of FSM and using "delete" key to delete the selected states. i did register the KeyEventListener to the the JFrame. but when i try to press the "del" key the app doesn't do anything. after few tests, i think JFrame never listene to my key event. how can i make it possible to let the JFrame to listene to my "key event"?
Thanks~~~

Read this, it is very useful for things like this:
[url http://java.sun.com/docs/books/tutorial/uiswing/misc/keybinding.html]How to Use Key Bindings
In your case you can add a key binding to the frame's root pane, and bind the delete key to the action you want to perform.

Similar Messages

Catch several key events

hi...how do i catch several keys events?
Example:
i have a menubar with a menuitem Pan and need to catch the keys UP,DOWN,RIGHT,LEFT.
I know how to catch one key using a menushortcut.
Thanks.

Like this :
menubaritem.addKeyListener(new KeyListener(){
   public void keyPressed(KeyEvent evt){
      int keyCode = evt.getKeyCode();
      switch(keyCode){
         case KeyEvent.VK_UP:
            //your code here...
            break;
         case KeyEvent.VK_DOWN:
            //your code here...
            break;
         case KeyEvent.VK_LEFT:
            //your code here
            break;
         case KeyEvent.VK_RIGHT:
            //your code here
            break;
   public void keyTyped(KeyEvent evt){}
   public void keyReleased(KeyEvent evt){}

Which components catch a key-event?

Hello,
I've a question. I've a panel with severall sub-panels with textfield-editors. These have listeners to respond on a enter-key pressed event.
When I input an illegal value somewhere, I invoke a messagedialog with a warning message. The problem is that when I press enter , the oke-button of the messagepane has the focus, the enter-key pressed event is also caught by my first panel with all the editors and shows the same message dialog again. Kinda like a loop.
I thought that key-pressed event only where caught by the component/frame which has the focus, or am I wrong.
Can anyone help me out here?
Much Thanks
Hugo Hendriks

Normally an ActionListener is installed to an OK button, not a KeyListener. Check if you have implemented the same error handling in two places!
Generally you can "eat" key events by e.consume(), maybe this helps:
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_ENTER) {
// ... do some error handling on ENTER
e.consume();
I think then the Frame GUI will no get the key event anymore. A modal JDialog has a local event queue (to be modal), but maybe it forwards events to the main queue ...

Catching window closing events from JFrame

I'm having problems catching windowClosing() events from a JFrame (just doesn't get to my event listener it would seem!).
I register and setup a window listener in the constructor of my JFrame class. Prior to this I set the default close operation as DO_NOTHING_ON_CLOSE (as you're suppose to if tyou want to handle window closing events).
When user clicks on x (window terminate) button (in WIN systems), nothing is dispatched to my event listener. Any ideas?
Extract from constructor:
setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
addWindowListener(new MainWindowListener(this));
MainWindowListener looks as follows (EDImemConvert extends JFrame):
class MainWindowListener extends WindowAdapter
private EDImemConvert f;
public MainWindowListener(EDImemConvert f)
this.f = f;
public void windowClosing(WindowEvent e)
System.out.println("gets here...");
f.ReturnResources();
f.dispose();
System.exit(0);
}

This works for meimport java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test extends JFrame {
public Test() {
    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent we) { System.exit(0); }
    setSize(300,300);
    setVisible(true);
public static void main(String args[]) { new Test(); }
}Normally, I just use this line
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
instead of adding a listener. It will clean up everything nicely.

JPanel key events blocked by JToolBar?

I have a JPanel that I'm drawing on, and the frame containing the panel also holds a JToolBar. The JPanel doesn't catch any KeyEvents, which I really would like to monitor.
I have overridden isFocusable() as suggested in another thread like so:
public boolean isFocusable()
return true;
}My JPanel still doesn't catch KeyEvents, unless I get rid of the JToolBar. It seems that the controls in the toolbar don't pass the focus on to the panel. How do I change this behavior, without removing the toolbar?

Found the answer elsewhere.
I now add a "requestFocus()" call in my mousePressed event handler, and the JPanel catches the key events again.

Catching key events in application

I have a JFrame with a JDesktop containing lots of JInternalFrame with various of components such as JTextFields etc.
Now, i want to have a "main" listener that will catch key events no matter which component that has focus. For example pressing CTRL+A should produce something in the application no matter which component that has focus.
How do I implement this in an easy way?

It doesnt seem to work to add a KeyListener to the JFrame...
this.addKeyListener(new KeyAdapter(){
               public void keyTyped(KeyEvent e){
                    System.out.println("KeyTyped()");
               public void keyPressed(KeyEvent e){
                    System.out.println("KeyTyped()");
          });Adding that to the JFrame gives nothing to System.out when a JTextArea inside an JInternalFrame has focus.

How to catch key events in JWindow???

Can somebody please suggest me how do I catch key events in a JWindow. I tried without success with addKeyListener( ) method. My sample code is attached below. I've j2sdk1.4.2_03 in my PC.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class EventCatcher extends JWindow implements KeyListener {
     public EventCatcher() {
          super();
          Container c = getContentPane();
          setBounds(100,100,400,400);
          c.setLayout(new FlowLayout());
          JButton button = new JButton("Hello");
          c.add(button);
addKeyListener(this);
requestFocus();
setVisible(true);
     public void keyReleased(KeyEvent ke) {
System.out.println("**************");
     public void keyPressed(KeyEvent ke) {}
     public void keyTyped(KeyEvent ke) {}
     public static void main(String str[]) {
          new EventCatcher();
Regards,
Koushik

Hi GraemeHook!
This is Khurram. I tried your code on my problem that is 95% like this problem but it could not be solved.
can u please take view on my code.
I m trying to move a frame that extends from JWindow on runtime with Key Board Arrow keys. but this only works when I extend this MainApp class from JFrame, but not when from JWindow.
can u please help me. I also posted my own topic but no one response so found it resambling to my problem.
hoping to hear from u soon
you can also tell me at my email address
[email protected]
thanks
===========================================================
MainApp.java
*MainApp.java
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class MainApp extends JWindow {
static LocationManager appLoc = new LocationManager();
public MainApp() {
    try {
      jbInit();
    catch(Exception e) {
      e.printStackTrace();
public static void main(String[] args) {
   MainApp frm = new MainApp();
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        int width = screenSize.width;
        int height = 45;
          frm.setFocusableWindowState(true);
        frm.setFocusable(true);
        frm.setSize(width, height);
        frm.setLocation(appLoc.setAppAtBottomCentered(width, height));
        frm.setLocation(appLoc.moveAppUpward(100));
        frm.setVisible(true);
private void jbInit() throws Exception {
    this.getContentPane().setBackground(Color.white);
     addKeyListener(new java.awt.event.KeyAdapter(){
      int moveSpeed = 4;//must be even
      public void keyPressed(KeyEvent e){
        //JOptionPane.showMessageDialog(null,""+e.getKeyCode());
         if(e.getKeyCode() == KeyEvent.VK_SHIFT)
          if(moveSpeed==4)
            moveSpeed = 12;
          else
            moveSpeed = 4;
        if(e.getKeyCode() == KeyEvent.VK_UP)
          setLocation(appLoc.moveAppUpward(moveSpeed));
        else if(e.getKeyCode() == KeyEvent.VK_DOWN)
          setLocation(appLoc.moveAppDownward(moveSpeed));
        else if(e.getKeyCode() == KeyEvent.VK_LEFT)
          setLocation(appLoc.moveAppToLeft(moveSpeed));
        else if(e.getKeyCode() == KeyEvent.VK_RIGHT)
          setLocation(appLoc.moveAppToRight(moveSpeed));
        else if(e.getKeyCode() == 107) {//NUMPAD '+' Key For Vertically Increasing
          setSize(appLoc.increaseSize(0,moveSpeed));
          setLocation(appLoc.updateLocation());
        else if(e.getKeyCode() == 109) {//NUMPAD '-' Key For Vertically Decreasing
          setSize(appLoc.decreaseSize(0,moveSpeed));
          setLocation(appLoc.updateLocation());
        else if(e.getKeyCode() == 61) {// '+' Key For Horizontal Increasing
          setSize(appLoc.increaseSize(moveSpeed,0));
          setLocation(appLoc.updateLocation());
        else if(e.getKeyCode() == 45) {// '-' Key For Horizontal Decreasing
          setSize(appLoc.decreaseSize(moveSpeed,0));
          setLocation(appLoc.updateLocation());
}====================================================================
LocationManager.java
* LocationManager.java
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
    import java.util.*;
    import java.sql.*;
public class LocationManager {
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    static Point newPoint = new Point();
    static Dimension newDim = new Dimension();
    static Dimension minDim = new Dimension();
    /** Creates a new instance of LocationManager */
    public LocationManager() {
    public LocationManager(int width, int height){
        this.setAppCenteredWithDim(width, height);
    public Point setAppCenteredWithDim(int width, int height){
        //Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
      newDim.width = width;
      newDim.height = height;
        int sWidth = screenSize.width;
        int sHeight = screenSize.height;
        newPoint.x = (sWidth-width)/2;
        newPoint.y = (sHeight-height)/2;
        return newPoint;
        //return new Point(this.x, this.y);
    public Point setAppAtTopCentered(int width, int height){
        //Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
      newDim.width = width;
      newDim.height = height;
        int sWidth = screenSize.width;
        int sHeight = screenSize.height;
        newPoint.x = (sWidth-width)/2;
        newPoint.y = 0;
        return newPoint;
        //return new Point(this.x, this.y);
    public Point setAppAtBottomCentered(int width, int height){
        //Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
      newDim.width = width;
      newDim.height = height;
        int sWidth = screenSize.width;
        int sHeight = screenSize.height;
        newPoint.x = (sWidth-width)/2;
        newPoint.y = (sHeight-height);
        return newPoint;
        //return new Point(this.x, this.y);
    public Point setAppAtRightCentered(int width, int height){
        //Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
      newDim.width = width;
      newDim.height = height;
        int sWidth = screenSize.width;
        int sHeight = screenSize.height;
        newPoint.x = 0;
        newPoint.y = (sHeight-height)/2;
        return newPoint;
        //return new Point(this.x, this.y);
    public Point setAppAtLeftCentered(int width, int height){
        //Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
      newDim.width = width;
      newDim.height = height;
        int sWidth = screenSize.width;
        int sHeight = screenSize.height;
        newPoint.x = (sWidth-width);
        newPoint.y = (sHeight-height)/2;
        return newPoint;
        //return new Point(this.x, this.y);
    public Point moveAppUpward(int step){
        newPoint.y -= step;
        return newPoint;
        //return new Point(this.x, this.y);
    public Point moveAppDownward(int step){
        newPoint.y += step;
        return newPoint;
        //return new Point(this.x, this.y);
    public Point moveAppToLeft(int step){
        newPoint.x -= step;
        return newPoint;
        //return new Point(this.x, this.y);
    public Point moveAppToRight(int step){
        newPoint.x += step;
        return newPoint;
        //return new Point(this.x, this.y);
    public Dimension increaseSize(int w, int h){
      minDim.width = 116;
      minDim.height = 56;
      newDim.width += w;
      newDim.height +=h;
      if(w==0 && newDim.height > minDim.height)
        newPoint.y -= h/2;
      else if(newDim.width > minDim.width )
        newPoint.x -= w/2;
      return newDim;
    public Dimension decreaseSize(int w, int h){
      minDim.width = 116;
      minDim.height = 56;
      if(newDim.width > minDim.width )
        newDim.width -= w;
      if(newDim.height > minDim.height)
        newDim.height -= h;
      if(w==0 && newDim.height > minDim.height)
        newPoint.y += h/2;
      else if(newDim.width > minDim.width)
        newPoint.x += w/2;
      return newDim;
    public Point updateLocation(){
      return newPoint;
        //return new Point(this.x, this.y);
}===================================================================

2nd JFrame at Full Screen not registering key events

I've written an application that launches other applications distributed as JARs with a particular method (replacing the main method). These other applications run at full screen.
Whilst I have got these other applications to work in that they display correctly and do everything else, I require them to register key events. If I run these applications on their own (i.e. having not been launched by the primary application) then the key events are processed correctly. However when they are launched from the primary application the key events are not registered.
I have tried requesting focus from the full screen JFrame but it doesn't seem to be able to.
Any ideas?

Possible that the keystrokes are really being trapped by the other gui, which stops registering them when it's not visible.
IF that's the case, you'll need to re-design your keyboard trap as part of the second JFrame, wholly independent of the original JFrame or originating app. Also, it may be thread-starved i.e. operating off the originating program, which thread may be stopping when it has no focus.
That's all the ideas I have.

Catching Alt Key Press with the Key Down Filter Event

I am writing an application that requires specific key combinations using ctrl, shift, and alt in addition to a function key (F1, F2, F3, etc). The application works great except for when I try to catch an alt key press. The alt key press does not seem to fire an event eventhough it is an option in the PlatMods cluster as well as the VKey enum. When I press the alt key when my application is running the cursor changes to a normal mouse pointer from the usual finger pointer and prevents any other key presses from going through (in addition to not firing an event itself).
I have tried completely removing the run-time menu, which doesn't seem to help. I currently discard all keys after I handle them in my event structure.
I really hope that the only solution isn't using a Windows DLL. Any suggestions or ideas at all would be greatly appreciated.
Thanks,
Ames

Hi Ames
As Kileen has said Khalid has already given you a good solution to detect the ALT key.
I have another approach that might let you stick to your event-driven approach. I suggest that you have another loop in your app that polls the keyboard using the Input Device utility vi's. When this poll loop sees an ALT + KEY combo it raises a dynamic user event and will be processed in your event structure. This means you can keep your key down filter event to process the CTRL + KEY and SHIFT + KEY events.
Example attached in 7.1
cheers
David
Attachments:
Catching Alt Key Press Poll with Events(151551).vi ‏89 KB

How to catch a key down event in TextEdit UI element ?

Is it possible for me to catch 'Enter' and 'Esc' key when I input something ?
Best regads ,

hi, Shishir ,
I see the on key event in input field , yes , the TextEdit does not has any event . But how can I meet such requirement ?
When the user click enter on TextEdit , I should do something , When the user click escape , I should do something ?
Best regards ,

How to catch key events

Hello!
I have a component which extends JPanel. Now I dynamically add a JTextField as a child to this component. The problem is: when the textfield has focus, how can I get key events in my panel before the textfield gets them (and maybe intercept them so that the textfield doesn't get them at all)?
Background: the component is a self written table and the textfield is an editor. Now I have to make sure that when I am editing and press e.g. "cursor up", that not the textfield will get this key event but the table (which should traverse the current cell then ...)
The problem is: I cannot change the textfield (extend it or something) because a possible solution has to work with any java awt "Component" (or at least with JComponent).
Any help very appreciated.
Michael

Hello,
implement the keyListener interface for the Extended component...
and in Keypressed method
keyPressed(keyEvent){
// do all ur reuirements here
//and comsume the keyEvent...
hope this helps

Need key events in JPanel

I can't receive key events in a JPanel, and need to figure out how. While the JDialog I added my JPanel to originally could catch these, once I added more components (like a JTextBox and JCheckBox), neither my panel nor dialog caught any key events at all. Isn't there some way when my panel has focus to capture and respond to key press events?
Thanks,
Mark McKay
http://www.kitfox.com

This works for a JFrame, didn't test it on a JDialog:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class PanelEvents extends JFrame
     public PanelEvents()
          JPanel main = new JPanel();
          main.setPreferredSize( new Dimension(300, 300) );
          main.setFocusable(true);
          getContentPane().add( main );
          main.addMouseListener( new MouseAdapter()
               public void mousePressed(MouseEvent e)
                    e.getComponent().requestFocusInWindow();
                    System.out.println(e.getPoint());
          main.addKeyListener( new KeyAdapter()
               public void keyTyped(KeyEvent e)
                    System.out.println(e.getKeyChar());
          getContentPane().add(new JTextField(), BorderLayout.NORTH);
     public static void main(String[] args)
          JFrame frame = new PanelEvents();
          frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
          frame.pack();
          frame.setLocationRelativeTo( null );
          frame.setVisible(true);
}

Getting Key Events during animation loop

I'm having a problem recieving Key events during my animation loop. Here is my example program
import java.awt.*;
import java.awt.image.BufferStrategy;
import javax.swing.JPanel;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import java.util.ArrayList;
import java.awt.event.*;
import java.util.Iterator;
import GAME.graphics.Animation;
import GAME.sprites.MainPlayer;
import GAME.util.MapData;
import GAME.input.*;
public class ImageTest extends JFrame {
    private static final long DEMO_TIME = 20000;
    private Animation      anim;
    private MainPlayer     mPlayer;
    private MapData               mapData;
    private InputManager      inputManager;
    private GameAction moveLeft;
    private GameAction moveRight;
    private GameAction exit;
    public ImageTest()
     requestFocus();
     initInput();
     setSize(1024, 768);
     setUndecorated(true);
     setIgnoreRepaint(true);
     setResizable(false);
     loadImages();
     anim = new Animation();
        mPlayer = new MainPlayer(anim);
        setVisible(true);
        createBufferStrategy(2);
        animationLoop();
     // load the player images
     private void loadImages()
          // code that loads images...
     // Initialize input controls
     private void initInput() {
        moveLeft = new GameAction("moveLeft");
        moveRight = new GameAction("moveRight");
        exit = new GameAction("exit",
            GameAction.DETECT_INITAL_PRESS_ONLY);
        inputManager = new InputManager(this);
        inputManager.setCursor(InputManager.INVISIBLE_CURSOR);
        inputManager.mapToKey(moveLeft, KeyEvent.VK_LEFT);
        inputManager.mapToKey(moveRight, KeyEvent.VK_RIGHT);
        inputManager.mapToKey(exit, KeyEvent.VK_ESCAPE);
    // Check player input
    private void checkInput(long elapsedTime) {
        if (exit.isPressed()) {
            System.exit(0);
        if (mPlayer.isAlive()) {
            float velocityX = 0;
            if (moveLeft.isPressed()) {
                velocityX-=mPlayer.getMaxSpeed();
            if (moveRight.isPressed()) {
                velocityX+=mPlayer.getMaxSpeed();
            mPlayer.setVelocityX(velocityX);
    // main animation loop
    public void animationLoop() {
        long startTime = System.currentTimeMillis();
        long currTime = startTime;
        while (currTime - startTime < DEMO_TIME) {
            long elapsedTime =
                System.currentTimeMillis() - currTime;
            currTime += elapsedTime;
            checkInput(elapsedTime);
            mPlayer.update(elapsedTime);
            // draw and update screen
            BufferStrategy strategy = this.getBufferStrategy();
            Graphics2D g = (Graphics2D)strategy.getDrawGraphics();
            if (!(bgImage == null))
                 draw(g);
                 g.dispose();
                 if (!strategy.contentsLost()) {
                     strategy.show();
            // take a nap
            try {
                Thread.sleep(20);
            catch (InterruptedException ex) { }
    public void draw(Graphics g) {
        // draw background
        if (bgImage != null)
                     // draw image
             g.drawImage(mPlayer.getImage(), (int)mPlayer.getX(), (int)mPlayer.getY(), null);
}My InputManager implements KeyListener. When running print statements on my Key events, they are not being called until after the animation demo is done running. Can someone help me with getting the Key events to update during the animation loop? Thank you!

I've used the post from Abuse on the following thread with success. Maybe it will clue you in to what you might be doing wrong:
http://forum.java.sun.com/thread.jsp?forum=406&thread=498527

Detect key events on anything

If I have a JFrame with many components on it, how do I detect if a key is pressed, without having to add a listener to every component? For example, how can I check for the escape key being pressed, but not having to have componentN.addKeyListener(this); for everything?
Thanks
US101

The correct way to collect the key events is the following:
from java 1.2 to java 1.3 use the FocusManager. This class can be found in the javax.swing package. You would then need to extend the DefaultFocusManager and override specific behavior.
for java 1.4 use the KeyBoardFocusManager. This class can be found in the java.awt package.
Please see the following for a better explanation:
http://java.sun.com/j2se/1.4/docs/api/java/awt/doc-files/FocusSpec.html
Thanks for your time,
Nate

How to catch the mouse event from the JTable cell of the DefaultCellEditor

Hi, my problem is:
I have a JTable with the cells of DefaultCellEditor(JComboBox) and added the mouse listener to JTable. I can catch the mouse event from any editor cell when this cell didn't be focused. However, when I click the editor to select one JComboBox element, all the mouse events were intercepted by the editor.
So, how can I catch the mouse event in this case? In other word, even if I do the operation over the editor, I also need to catch the cursor position.
Any idea will be highly appreciated!
Thanks in advance!

Hi, bbritta,
Thanks very much for your help. Really, your code could run well, but my case is to catch the JComboBox event. So, when I change the JTextField as JComboBox, it still fail to catch the event. The following is my code. Could you give me any other suggestion?
Also, any one has a good idea for my problem? I look forward to the right solution to this problem.
Thanks.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test3
extends JFrame {
// JTextField jtf = new JTextField();
Object[] as = {"aa","bb","cc","dd"};
JComboBox box = new JComboBox(as);
public Test3() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container content = getContentPane();
String[] head = {
"One", "Two", "Three"};
String[][] data = {
"R1-C1", "R1-C2", "R1-C3"}
"R2-C1", "R2-C2", "R2-C3"}
JTable jt = new JTable(data, head);
box.addMouseListener(new MouseAdapter() {
// jtf.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e)
System.out.println("-------------------JComboBox mouseclick....");
jt.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e)
System.out.println("-------------------JTable mouseclick....");
// jt.setDefaultEditor(Object.class, new DefaultCellEditor(jtf));
jt.setDefaultEditor(Object.class, new DefaultCellEditor(box));
content.add(new JScrollPane(jt), BorderLayout.CENTER);
setSize(300, 300);
public static void main(String[] args) {
new Test3().setVisible(true);
}

Catch a key event in JFrame

Similar Messages

Maybe you are looking for