Develop Reference

How to call an Action from a different class in Java

How would I call an Action from another class in Java? I got a CloseTabButton class online that allows a simple close tab button on each JTabbedPane, but when the tab is closed, I would like a dialog to pop up based on information (if file is not saved, ask to save it, etc.). This is the file:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class CloseTabButton extends JPanel implements ActionListener {
private JTabbedPane pane;
public CloseTabButton(JTabbedPane pane, int index) {
this.pane = pane;
setOpaque(false);
// CloseIcon class just had a button with an x painted on it
Icon closeIcon = new CloseIcon();
JButton close = new JButton(closeIcon);
close.setPreferredSize(new Dimension(closeIcon.getIconWidth(), closeIcon.getIconHeight()));
close.addActionListener(this);
add(new JLabel(pane.getTitleAt(index), pane.getIconAt(index), JLabel.LEFT));
add(close);
pane.setTabComponentAt(index, this);
}
#Override
public void actionPerformed(ActionEvent e) {
int i = pane.indexOfTabComponent(this);
String fileName = pane.getToolTipTextAt(i);
// Where I want to ask if user wants to save, etc.
if (fileName == "Untitled") {
// Do stuff
}
pane.remove(i); // Removes the tab
// If tab count < 1, then disable the save and save as buttons on menu
if (pane.getTabCount() < 1) {
JFrame frame = (JFrame) pane.getParent().getParent().getParent().getParent().getParent(); // Yes, there is that many in my code to get the parent JFrame
int menuCount = frame.getJMenuBar().getMenuCount();
for (int a = 0; a < menuCount; a++) {
int itemCount = frame.getJMenuBar().getMenu(a).getItemCount();
for (int b = 0; b < itemCount; b++) {
Component component = frame.getJMenuBar().getMenu(a).getMenuComponent(b);
if (!(component instanceof JSeparator)) {
// Not a seperator
String itemName = frame.getJMenuBar().getMenu(a).getItem(b).getAccessibleContext().getAccessibleName();
if (itemName == "Save As..") {
frame.getJMenuBar().getMenu(a).getItem(b).setEnabled(false);
}
}
}
}
}
}
}
In my main class I have actions listed like this:
static Action Close = new AbstractAction("Close") {
public void actionPerformed(ActionEvent e) {
closeCurrentWindow(); // function that will close tab
}
}
The other menu items are Actions as well, and as you can see, what I'm currently doing in the CloseTabButton class is quite frustrating, and most likely the wrong way to code it. Is there a much simpler way to do what I'm doing?

The first thing I might do is provide ActionListener support to the CloseTabButton, for example...
public class CloseTabButton extends JPanel {
private JTabbedPane pane;
public CloseTabButton(JTabbedPane pane, int index) {
this.pane = pane;
setOpaque(false);
// CloseIcon class just had a button with an x painted on it
Icon closeIcon = new CloseIcon();
JButton close = new JButton(closeIcon);
close.setPreferredSize(new Dimension(closeIcon.getIconWidth(), closeIcon.getIconHeight()));
close.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
fireActionPerformed();
}
});
add(new JLabel(pane.getTitleAt(index), pane.getIconAt(index), JLabel.LEFT));
add(close);
pane.setTabComponentAt(index, this);
}
public void addActionListener(ActionListener listener) {
listenerList.add(ActionListener.class, listener);
}
public void removeActionListener(ActionListener listener) {
listenerList.remove(ActionListener.class, listener);
}
protected void fireActionPerformed() {
ActionListener[] listeners = listenerList.getListeners(ActionListener.class);
ActionEvent evt = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "You could provide you own action command for each tab here");
for (ActionListener listener : listeners) {
listener.actionPerformed(evt);
}
}
}
Basically, this now allows you to register your own ActionListeners to the CloseTabButton
Next, this, fileName == "Untitled", is not how you compare Strings in Java, you should be using something more like "Untitled".equals(fileName)
If you're menus are based on actual Actions, then you can simply disable the Actions themselves. This would require a little bit of work, but a lot less of "guess" work then you're doing now.
Basically, you would monitor the JTabbedPane itself, monitoring for changes to the selected tab and updating the states of the individual Actions themselves
There a number of ways you could do this, like passing a reference of the JTabbedPane to the Actions so they can perform there own monitoring (but I'd use some kind of management interface which could more easily provide information to the Actions and decouple the code and the reliance on JTabbedPane directly, then you could be free to use JInternalFrames instead).
You could have a "menu manager" which did a similar job, monitoring changes to the document container and changing the state of the menu Actions based on the current state, as an example
Updated
If you're making use of the Action API (which I would recommend), then you could simply do something like...
public class CloseTabButton extends JPanel {
private JTabbedPane pane;
public CloseTabButton(JTabbedPane pane, Action action, int index) {
this.pane = pane;
setOpaque(false);
// CloseIcon class just had a button with an x painted on it
Icon closeIcon = new CloseIcon();
JButton close = new JButton(action);
close.setIcon(closeIcon);
close.setPreferredSize(new Dimension(closeIcon.getIconWidth(), closeIcon.getIconHeight()));
add(new JLabel(pane.getTitleAt(index), pane.getIconAt(index), JLabel.LEFT));
add(close);
pane.setTabComponentAt(index, this);
}
}
Passing in the Action for the close operation, then use the same action for both the JMenuItem and JTabbedPane.
The "core" issue would be how you would identify the "current" tab and document in a uniform manner

Implementing a JMenu with actionPerformed using TextAction

I have a Java Swing interface with multiple JTextArea's and I am implementing an "Edit" menu with various different functions like "Find", "Copy", "Paste", etc. When I click on the JMenuItem I need to know which JTextArea had the focus which is achievable through a TextAction (I haven't gone down the route of a FocusListener and keeping track of what last had the focus):
JMenuItem miFind = new JMenuItem(new EditHandler("Find"));
class EditHandler extends TextAction {
private String s = null;
public EditHandler(String vs) {
super(vs);
s = vs;
}
#Override
public void actionPerformed(ActionEvent e) {
JTextComponent c = getFocusedComponent();
if (s.equals("Find")) {
showFindDialog(c);
}
}
}
This works well and good but I want to be able to disable the "Find" JMenuItem under certain contexts (i.e. if the specific JTextArea is disabled or is empty. I can implement an ActionListener on a JMenu but I can't use getFocusedComponent() to identify what JTextArea has the focus.
According to the Java docs the JMenu constructor takes an Action (like a JMenuItem) and I have tried the following:
mEdit = new JMenu(new EditHandler("Edit"));
However, although the constructor fires, the actionPerformed() event isn't firing within my EditHandler for the JMenu. If I can get it to fire then I was planning to either enable or disable my "Find" JMenuItem.

The best way for you is using of actions map of the text component to place the corresponding action. In this case you can disable it for some text components.
#Override
public void actionPerformed(ActionEvent e) {
JTextComponent c = getFocusedComponent();
if (s.equals("Find")) {
Action a = c.getActionMap().get("Find");
if (a.isEnabled()) {
// generate new event to modify the source (menu item -> text component)
ActionEvent ae = new ActionEvent(c, e.getID(), e.getCommand());
a.actionPerformed(ae);
}
}
}
For each your text component you must provide an action and register it using the action map of the component.
public class UniversalFindAction extends AbstractAction {
public void actionPerformed(ActionEvent ae) {
JTextComponent c = (JTextComponent) ae.getSource();
showFindDialog(c);
}
}
// registering of action
JTextComponent comp = new JTextArea();
comp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_F, InputEvent.CTRL_DOWN_MASK), "Find");
comp.getActionMap().put("Find", new UniversalFindAction());

Thanks to #sergiy-medvynskyy I have implemented a Global Focus Listener to keep track of the last JTextArea to be focused:
KeyboardFocusManager.getCurrentKeyboardFocusManager().addPropertyChangeListener("permanentFocusOwner", new PropertyChangeListener() {
#Override
public void propertyChange(final PropertyChangeEvent e) {
if (e.getNewValue() instanceof JTextArea) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
tFocused = (JTextArea)e.getNewValue();
}
});
}
}
});
I then check the tFocused object using a MenuListener on my JMenu to verify what JTextArea currently has the focus. I can then call setEnabled() on my respective JMenuItem's depending on the context.

JPanel Action Listener

I have a JPanel with a bunch of different check boxes and text fields, I have a button that's disabled, and needs to be enabled when specific configurations are setup.
What I need is a listener on the the whole JPanel looking for events, whenever anything changes.
I believe I need an action listener but I can't find anything to bridge the action Listener with the JPanel
JPanel Window = new JPanel();
Window.addActionListener(new ActionListener(){
//Check if configurations is good
}
I figure I can copy and paste my code a bunch of times into every listener in the panel, but that seems like bad coding practice to me.

First off as #Sage mention in his comment a JPanel is rather a container than a component which do action. So you can't attach an ActionListener to a JPanel.
I figure I can copy and paste my code a bunch of times into every
listener in the panel, but that seems like bad coding practice to me.
You're totally right about that, it's not a good practice at all (see DRY principle). Instead of that you can define just a single ActionListener and attach it to your JCheckBoxes like this:
final JCheckBox check1 = new JCheckBox("Check1");
final JCheckBox check2 = new JCheckBox("Check2");
final JCheckBox check3 = new JCheckBox("Check3");
final JButton buttonToBeEnabled = new JButton("Submit");
buttonToBeEnabled.setEnabled(false);
ActionListener actionListener = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
boolean enable = check1.isSelected() && check3.isSelected();
buttonToBeEnabled.setEnabled(enable);
}
};
check1.addActionListener(actionListener);
check2.addActionListener(actionListener);
check3.addActionListener(actionListener);
This means: if check1 and check3 are both selected, then the button must be enabled, otherwise must be disabled. Of course only you know what combination of check boxes should be selected in order to set the button enabled.
Take a look to How to Use Buttons, Check Boxes, and Radio Buttons tutorial.

A suggestion could be to derive a class from each of the components you're using and add an ActionListener that bubbles up the Container tree and looks for the first Container that implements a custom interface like this:
public interface MyCommandProcessor {
void execute(String actionCommand);
}
public class MyButton extends JButton {
public MyButton(string actionCommand) {
setActionCommand(actionCommand);
addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
Container traverser = MyButton.this;
while (traverser != null && !(traverser instanceof MyCommandProcessor))
traverser = traverser.getParent();
if (traverser != null)
((CommandListener)traverser).execute(ae.getActionCommand());
}
});
}
}
public class MyApp extends JFrame implements MyCommandListener {
public MyApp() {
JPanel panel = new Panel();
panel.add(new MyButton("MyButton got pressed"));
}
public void execute(String actionCommand) {
System.out.println(actionCommand);
}
}

You need to create custom component listener. Look here:
Create a custom event in Java
Creating Custom Listeners In Java
http://www.javaworld.com/article/2077333/core-java/mr-happy-object-teaches-custom-events.html
I do it throw the standard ActionListener
Example
public class MyPanel extends JPanel {
private final JComboBox<String> combo1;
private final JButton btn2;
.......
//catch the actions of inside components
btn2.addActionListener(new MyPanelComponentsActionListener());
........
//assign actionlistener to panel class
public void addActionListener(ActionListener l) {
listenerList.add(ActionListener.class, l);
}
public void removeActionListener(ActionListener l) {
listenerList.remove(ActionListener.class, l);
}
//handle registered listeners from components used MyPanel class
protected void fireActionPerformed(ActionEvent event) {
// Guaranteed to return a non-null array
Object[] listeners = listenerList.getListenerList();
ActionEvent e = null;
// Process the listeners last to first, notifying
// those that are interested in this event
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==ActionListener.class) {
// Lazily create the event:
if (e == null) {
String actionCommand = event.getActionCommand();
if(actionCommand == null) {
actionCommand = "FontChanged";
}
e = new ActionEvent(FontChooserPanel.this,
ActionEvent.ACTION_PERFORMED,
actionCommand,
event.getWhen(),
event.getModifiers());
}
// here registered listener executing
((ActionListener)listeners[i+1]).actionPerformed(e);
}
}
}
//!!! here your event generator
class MyPanelComponentsActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
//do something usefull
//.....
fireActionPerformed(e);
}
}
....
}

MouseExited event triggers when crossing an inner separator?

I have a JPopupMenu which contains an inner JMenu and a separator with addSeparator(). Due to some odd handling, I've added a MouseListener to the JPopupMenu which makes it invisible on a mouseExited event. This works fine, except that when the mouse tries to cross over the separator, it's triggering the event (even though the JPopupMenu is the super component).
If I remove the addSeparator() line, it works as expected.
Is there any way to work around this? Or have I not set up the listener properly?
The code is like the following:
JPopupMenu popupMenu = new JPopupMenu();
JMenu innerMenu = new JMenu("Inner");
// ... add JMenuItems
popupMenu.add(innerMenu);
popupMenu.addSeparator();
popupMenu.add(new JMenuItem("Exit"));
popupMenu.addMouseListener(new MouseAdapter() {
#Override
public void mouseExited(MouseEvent e) {
popupMenu.setVisible(false);
}
});
Full Compilable Example
Simply comment and uncomment the popupMenu.addSeparator() line to notice the different behaviors
public class Test {
public static void main(String[] args) throws Exception {
if(!SystemTray.isSupported()) {
throw new UnsupportedOperationException("SystemTray is not supported.");
}
final TrayIcon trayIcon = new TrayIcon(ImageIO.read(new File("resources/icon.gif")));
final JPopupMenu popupMenu = new JPopupMenu();
JMenu intervalMenu = new JMenu("Interval");
ButtonGroup itemGroup = new ButtonGroup();
JRadioButtonMenuItem oneSecondMenuItem = new JRadioButtonMenuItem("1 sec");
itemGroup.add(oneSecondMenuItem);
JRadioButtonMenuItem twoSecondMenuItem = new JRadioButtonMenuItem("2 sec");
itemGroup.add(twoSecondMenuItem);
intervalMenu.add(oneSecondMenuItem);
intervalMenu.add(twoSecondMenuItem);
popupMenu.add(intervalMenu);
popupMenu.addSeparator();
JMenuItem exitMenuItem = new JMenuItem("Exit");
exitMenuItem.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
SystemTray.getSystemTray().remove(trayIcon);
System.exit(0);
}
});
popupMenu.add(exitMenuItem);
//Thanks to Artem Ananiev for this implementation idea
//https://weblogs.java.net/blog/ixmal/archive/2006/05/using_jpopupmen.html
trayIcon.addMouseListener(new MouseAdapter() {
#Override
public void mouseReleased(MouseEvent e) {
if(e.getButton() == MouseEvent.BUTTON3) {
popupMenu.setLocation(e.getX() - 40, e.getY() - 40);
popupMenu.setInvoker(popupMenu);
popupMenu.setVisible(true);
}
}
});
popupMenu.addMouseListener(new MouseAdapter() {
#Override
public void mouseExited(MouseEvent e) {
popupMenu.setVisible(false);
}
});
SystemTray.getSystemTray().add(trayIcon);
}
}

Wow, you are using a sytem tray icon. That information might have been important to know. That is why a SSCCE should be posted with EVERY question.
Anyway the following seems to work:
if (! popupMenu.contains( e.getPoint() ) )
popupMenu.setVisible(false);
Edit:
It looks like the problem is that the JSeparator does not listen for MouseEvents by default so all the mouse events are passed to its parent. So when you leave a JMenuItem, the mouseEntered() event is generated for the popup menu and then when you re-enter another JMenuItem the mouseExited() event is generated.
If you enable MouseEvents for the JSeparator then it look like the JPopupMenu doesn't get the event
//popupMenu.addSeparator();
popupMenu.add( new MySeparator() );
...
static class MySeparator extends JSeparator
{
public MySeparator( )
{
super( JSeparator.HORIZONTAL );
enableEvents(AWTEvent.MOUSE_EVENT_MASK);
}
/**
* Returns the name of the L&F class that renders this component.
*
* #return the string "PopupMenuSeparatorUI"
* #see JComponent#getUIClassID
* #see UIDefaults#getUI
*/
public String getUIClassID()
{
return "PopupMenuSeparatorUI";
}
}

How do I create a right click context menu in Java Swing?

I'm currently creating a right-click context menu by instantiating a new JMenu on right click and setting its location to that of the mouse's position... Is there a better way?

You are probably manually calling setVisible(true) on the menu. That can cause some nasty buggy behavior in the menu.
The show(Component, int x, int x) method handles all of the things you need to happen, (Highlighting things on mouseover and closing the popup when necessary) where using setVisible(true) just shows the menu without adding any additional behavior.
To make a right click popup menu simply create a JPopupMenu.
class PopUpDemo extends JPopupMenu {
JMenuItem anItem;
public PopUpDemo() {
anItem = new JMenuItem("Click Me!");
add(anItem);
}
}
Then, all you need to do is add a custom MouseListener to the components you would like the menu to popup for.
class PopClickListener extends MouseAdapter {
public void mousePressed(MouseEvent e) {
if (e.isPopupTrigger())
doPop(e);
}
public void mouseReleased(MouseEvent e) {
if (e.isPopupTrigger())
doPop(e);
}
private void doPop(MouseEvent e) {
PopUpDemo menu = new PopUpDemo();
menu.show(e.getComponent(), e.getX(), e.getY());
}
}
// Then on your component(s)
component.addMouseListener(new PopClickListener());
Of course, the tutorials have a slightly more in-depth explanation.
Note: If you notice that the popup menu is appearing way off from where the user clicked, try using the e.getXOnScreen() and e.getYOnScreen() methods for the x and y coordinates.

This question is a bit old - as are the answers (and the tutorial as well)
The current api for setting a popupMenu in Swing is
myComponent.setComponentPopupMenu(myPopupMenu);
This way it will be shown automagically, both for mouse and keyboard triggers (the latter depends on LAF). Plus, it supports re-using the same popup across a container's children. To enable that feature:
myChild.setInheritsPopupMenu(true);

There's a section on Bringing Up a Popup Menu in the How to Use Menus article of The Java Tutorials which explains how to use the JPopupMenu class.
The example code in the tutorial shows how to add MouseListeners to the components which should display a pop-up menu, and displays the menu accordingly.
(The method you describe is fairly similar to the way the tutorial presents the way to show a pop-up menu on a component.)

The following code implements a default context menu known from Windows with copy, cut, paste, select all, undo and redo functions. It also works on Linux and Mac OS X:
import javax.swing.*;
import javax.swing.text.JTextComponent;
import javax.swing.undo.UndoManager;
import java.awt.*;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
public class DefaultContextMenu extends JPopupMenu
{
private Clipboard clipboard;
private UndoManager undoManager;
private JMenuItem undo;
private JMenuItem redo;
private JMenuItem cut;
private JMenuItem copy;
private JMenuItem paste;
private JMenuItem delete;
private JMenuItem selectAll;
private JTextComponent textComponent;
public DefaultContextMenu()
{
undoManager = new UndoManager();
clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
addPopupMenuItems();
}
private void addPopupMenuItems()
{
undo = new JMenuItem("Undo");
undo.setEnabled(false);
undo.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Z, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
undo.addActionListener(event -> undoManager.undo());
add(undo);
redo = new JMenuItem("Redo");
redo.setEnabled(false);
redo.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Y, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
redo.addActionListener(event -> undoManager.redo());
add(redo);
add(new JSeparator());
cut = new JMenuItem("Cut");
cut.setEnabled(false);
cut.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
cut.addActionListener(event -> textComponent.cut());
add(cut);
copy = new JMenuItem("Copy");
copy.setEnabled(false);
copy.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_C, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
copy.addActionListener(event -> textComponent.copy());
add(copy);
paste = new JMenuItem("Paste");
paste.setEnabled(false);
paste.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_V, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
paste.addActionListener(event -> textComponent.paste());
add(paste);
delete = new JMenuItem("Delete");
delete.setEnabled(false);
delete.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_DELETE, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
delete.addActionListener(event -> textComponent.replaceSelection(""));
add(delete);
add(new JSeparator());
selectAll = new JMenuItem("Select All");
selectAll.setEnabled(false);
selectAll.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_A, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
selectAll.addActionListener(event -> textComponent.selectAll());
add(selectAll);
}
private void addTo(JTextComponent textComponent)
{
textComponent.addKeyListener(new KeyAdapter()
{
#Override
public void keyPressed(KeyEvent pressedEvent)
{
if ((pressedEvent.getKeyCode() == KeyEvent.VK_Z)
&& ((pressedEvent.getModifiersEx() & Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()) != 0))
{
if (undoManager.canUndo())
{
undoManager.undo();
}
}
if ((pressedEvent.getKeyCode() == KeyEvent.VK_Y)
&& ((pressedEvent.getModifiersEx() & Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()) != 0))
{
if (undoManager.canRedo())
{
undoManager.redo();
}
}
}
});
textComponent.addMouseListener(new MouseAdapter()
{
#Override
public void mousePressed(MouseEvent releasedEvent)
{
handleContextMenu(releasedEvent);
}
#Override
public void mouseReleased(MouseEvent releasedEvent)
{
handleContextMenu(releasedEvent);
}
});
textComponent.getDocument().addUndoableEditListener(event -> undoManager.addEdit(event.getEdit()));
}
private void handleContextMenu(MouseEvent releasedEvent)
{
if (releasedEvent.getButton() == MouseEvent.BUTTON3)
{
processClick(releasedEvent);
}
}
private void processClick(MouseEvent event)
{
textComponent = (JTextComponent) event.getSource();
textComponent.requestFocus();
boolean enableUndo = undoManager.canUndo();
boolean enableRedo = undoManager.canRedo();
boolean enableCut = false;
boolean enableCopy = false;
boolean enablePaste = false;
boolean enableDelete = false;
boolean enableSelectAll = false;
String selectedText = textComponent.getSelectedText();
String text = textComponent.getText();
if (text != null)
{
if (text.length() > 0)
{
enableSelectAll = true;
}
}
if (selectedText != null)
{
if (selectedText.length() > 0)
{
enableCut = true;
enableCopy = true;
enableDelete = true;
}
}
if (clipboard.isDataFlavorAvailable(DataFlavor.stringFlavor) && textComponent.isEnabled())
{
enablePaste = true;
}
undo.setEnabled(enableUndo);
redo.setEnabled(enableRedo);
cut.setEnabled(enableCut);
copy.setEnabled(enableCopy);
paste.setEnabled(enablePaste);
delete.setEnabled(enableDelete);
selectAll.setEnabled(enableSelectAll);
// Shows the popup menu
show(textComponent, event.getX(), event.getY());
}
public static void addDefaultContextMenu(JTextComponent component)
{
DefaultContextMenu defaultContextMenu = new DefaultContextMenu();
defaultContextMenu.addTo(component);
}
}
Usage:
JTextArea textArea = new JTextArea();
DefaultContextMenu.addDefaultContextMenu(textArea);
Now the textArea will have a context menu when it is right-clicked on.

I will correct usage for that method that #BullyWillPlaza suggested. Reason is that when I try to add add textArea to only contextMenu it's not visible, and if i add it to both to contextMenu and some panel it ecounters: Different parent double association if i try to switch to Design editor.
TexetObjcet.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
if (SwingUtilities.isRightMouseButton(e)){
contextmenu.add(TexetObjcet);
contextmenu.show(TexetObjcet, 0, 0);
}
}
});
Make mouse listener like this for text object you need to have popup on. What this will do is when you right click on your text object it will then add that popup and display it. This way you don't encounter that error. Solution that #BullyWillPlaza made is very good, rich and fast to implement in your program so you should try it our see how you like it.