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Neither Key Listener nor Document Listener fires for ComboBox

Found a simple JComboBox sample on java2 and expanded it to include both a DocumentListener and KeyListener
hoping to capture keystrokes done within the JComboBox.
Eventually those keystrokes will be captured to display the data which matches the keys entered.
For example, as the user types APP, all records beginning with A is return then AP is return and then all data beginning with APP. Basically doing a Filter on "APP*".
But for now, I am unable to get either a KeyListener or DocumentListener working.
Actually, it works sporadically and can't narrow down why. It seems to only work for the Enter key but would like for it to capture for all keystrokes.
Here is the code.
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.ComboBoxEditor;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.plaf.metal.MetalFileChooserUI;
public class JComboBoxFilter extends JPanel implements ItemListener {
public JComboBoxFilter () {
JComboBox jc = new JComboBox();
jc.addItem("A");
jc.addItem("AA");
jc.addItem("AAA");
jc.addItem("C");
jc.addItem("CC");
jc.addItem("CCC");
jc.addItem("B");
jc.addItem("BB");
jc.addItem("BBB");
jc.addItemListener(this);
add(jc);
ComboBoxEditor editor = jc.getEditor();
JTextField textField = (JTextField)editor.getEditorComponent();
textField.addKeyListener(new KeyListener()
{
#Override
public void keyPressed(KeyEvent arg0) {
runThisKeyListener();
}
#Override
public void keyReleased(KeyEvent arg0) {
runThisKeyListener();
}
#Override
public void keyTyped(KeyEvent arg0) {
runThisKeyListener();
}
private void runThisKeyListener()
{
System.out.println("Inside runThisKeyListener() : " + textField.getText());
}
});
DocumentListener textFieldDL = new DocumentListener()
{
#Override
public void insertUpdate(DocumentEvent e)
{
runThis();
}
#Override
public void removeUpdate(DocumentEvent e)
{
runThis();
}
#Override
public void changedUpdate(DocumentEvent e)
{
runThis();
}
private void runThis()
{
System.out.println("Inside runThis() : " + textField.getText());
}
};
textField.getDocument().addDocumentListener(textFieldDL);
}
public void itemStateChanged(ItemEvent ie) {
String s = (String)ie.getItem();
System.out.println(s);
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.getContentPane().add(new JComboBoxFilter ());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setVisible(true);
}
}
Is there anything wrong with the code or is there a Java rule or restriction not allowing this type of functionality?

How to change the icon of a dynamically generated JButton

I have this java swing program, and im trying to figure out how can i create a button that upon clicking it will clear the text areas & change the icon of the person to put their hand down.
The buttons are dynamically generated using a for loop
And this
// To create buttons
for(int i=0 ; i < list.length; i++){
Participant pa = list[i];
JButton b = new JButton(pa.getNameButton(),participant);
b.addActionListener(e ->
{
String s = pa.toString() + questionPane.getText();
final ImageIcon raise = resizeIcon(new ImageIcon("src/raise.png"),30,30);
b.setIcon(raise);
JOptionPane.showMessageDialog(null,s,"Welcome to Chat Room",JOptionPane.INFORMATION_MESSAGE,pa.getImage());
});
p.add(b);
}
// Clear button logic
clearButton.addActionListener(e ->{
questionPane.setText("");
hostPane.setText("");
});

Okay, this is going to be a bit of fun.
The following example decouples much of the concept and makes use of a basic "observer pattern" to notify interested parties that the state has changed (ie, the chat's been cleared).
This is a basic concept where by you decouple the "what" from the "how", ie, "what" it is you want done (update the model) from the "how" it gets done (ie, button push). This makes it easier to adapt to more complex systems.
The example contains a ChatService, which has a single listener, which, for this example, simple tells interested parties that the chat has been cleared.
A more complex solution might have the ChatService generating events for when a user "raises" their hand, which allows the interested parties to deal with it in what ever way is relevant to them.
The example makes use of the Action API to decouple the work performed by each action from the UI itself. This helps create a single unit of work which is easier to deal with when you have a dynamic data set.
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.add(new TestPane());
frame.pack();
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
ChatService chatService = new ChatService();
JPanel panel = new JPanel();
String[] names = new String[] {"Bryan", "Alan", "George", "Henry"};
List<PeopleAction> actions = new ArrayList<>(names.length);
for (String name : names) {
PeopleAction action = new PeopleAction(chatService, name, false);
actions.add(action);
}
Random rnd = new Random();
actions.get(rnd.nextInt(names.length)).setRaised(true);
for (Action action : actions) {
JButton btn = new JButton(action);
panel.add(btn);
}
setLayout(new GridLayout(2, 1));
add(panel);
JPanel hostPane = new JPanel();
JButton clearButton = new JButton(new ClearAction(chatService));
hostPane.add(clearButton);
add(hostPane);
}
}
public class ChatService {
private List<ChatListener> listeners = new ArrayList<>(25);
public void addChatListeners(ChatListener listener) {
listeners.add(listener);
}
public void removeChatListener(ChatListener listener) {
listeners.remove(listener);
}
protected void fireChatCleared() {
if (listeners.isEmpty()) {
return;
}
for (ChatListener listener : listeners) {
listener.chatCleared();
}
}
public void clear() {
// Do what's required
fireChatCleared();
}
}
public interface ChatListener {
public void chatCleared();
}
public class PeopleAction extends AbstractAction implements ChatListener {
private String name;
private boolean raised;
public PeopleAction(ChatService chatService, String name, boolean raised) {
// You can use either LARGE_ICON_KEY or SMALL_ICON to set the icon
this.name = name;
if (raised) {
putValue(NAME, "* " + name);
} else {
putValue(NAME, name);
}
chatService.addChatListeners(this);
}
public void setRaised(boolean raised) {
if (raised) {
putValue(NAME, "* " + name);
} else {
putValue(NAME, name);
}
}
public boolean isRaised() {
return raised;
}
#Override
public void actionPerformed(ActionEvent evt) {
// Do what ever needs to be done
setRaised(!isRaised());
}
#Override
public void chatCleared() {
setRaised(false);
}
}
public class ClearAction extends AbstractAction {
private ChatService chatService;
public ClearAction(ChatService chatService) {
this.chatService = chatService;
putValue(NAME, "Clear");
}
#Override
public void actionPerformed(ActionEvent evt) {
chatService.clear();
}
}
}

How do I make Java jtables, cell editors and undo work together w/o creating extranious undo event?

In the following code, I create a jtable with a custom cell editor for the first column and then add undo capabilities to the table. When you run the program, the program allows you to change the values in the first column (test by appending a "d" and then an "e" to the "abc" already there). Now enter control-z (undo) and enter control-z again. It works as expected. But now enter control-z (undo) again. This time the "abc" is erased. It looks like the swing system is setting the initial value of the column and creating an undo event for that action which the user can then undo. My question - how do I write my code so that the user only can undo the actions the user makes?
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.DefaultCellEditor;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JRootPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.KeyStroke;
import javax.swing.SwingUtilities;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableCellEditor;
import javax.swing.undo.AbstractUndoableEdit;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;
import javax.swing.undo.UndoableEdit;
public class UndoExample extends JFrame {
private static final long serialVersionUID = 1L;;
static Boolean objEnableUndoRedoActions = true;
UndoExample rootFrame;
public UndoExample() {
// This procedure starts the whole thing off.
//Create table
final String[] tableColumns = {"Column 1", "Column 2"};
JTable tabUndoExample = new JTable(
new DefaultTableModel(null, tableColumns) {
private static final long serialVersionUID = 1L;
});
final DefaultTableModel tabUndoExampleModel = (DefaultTableModel) tabUndoExample
.getModel();
tabUndoExampleModel.addRow(new Object[]{"abc", true});
tabUndoExampleModel.addRow(new Object[]{"zyw", false});
// Create the undo/redo manager
UndoManager objUndoManager = new UndoManager();
// Create a cell editor
JTextField tfTabField = new JTextField();
TableCellEditor objEditor = new DefaultCellEditor(tfTabField);
// Make the cell editor the default editor for this table's first column
tabUndoExample.getColumnModel().getColumn(0)
.setCellEditor(objEditor);
// Create the undo action on the field's document for the column
tfTabField.getDocument().addUndoableEditListener(
new uelUndoRedoTableCellField(objUndoManager, tabUndoExample));
// Allow undo and redo to be entered by the user
UndoRedoSetKeys(this, "Example", objUndoManager);
tabUndoExample.setInheritsPopupMenu(true);
//Add the table to the frame and show the frame
this.add(tabUndoExample);
this.pack();
setLocationRelativeTo(null);
}
public static void main(final String[] args) {
// Launches the application. This is required syntax.
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
try {
final UndoExample rootFrame = new UndoExample();
rootFrame.setVisible(true);
} catch (final Exception e) {
}
}
});
}
#SuppressWarnings("serial")
static class aueUndoRedoTableCellField extends AbstractUndoableEdit {
// Wrap the text edit action item as we need to add the table
// row and column information. This code is invoked when the
// code sees an undo event created and then later when the
// user requests an undo/redo.
JTable objTable = null;
UndoableEdit objUndoableEdit;
int objCol = -1;
int objRow = -1;
public aueUndoRedoTableCellField(UndoableEdit undoableEdit,
JTable table, int row, int col) {
super();
objUndoableEdit = undoableEdit;
objTable = table;
objCol = col;
objRow = row;
}
public void redo() throws CannotRedoException {
// When the user enters redo (or undo), this code sets
// that we are doing an redo (or undo), sets the cursor
// to the right location, and then does the undo (or redo)
// to the table cell.
UndoRedoManagerSetEnabled(false);
super.redo();
#SuppressWarnings("unused")
boolean success = objTable.editCellAt(objRow, objCol);
objTable.changeSelection(objRow, objCol, false, false);
objUndoableEdit.redo();
UndoRedoManagerSetEnabled(true);
}
public void undo() throws CannotUndoException {
super.undo();
UndoRedoManagerSetEnabled(false);
#SuppressWarnings("unused")
boolean success = objTable.editCellAt(objRow, objCol);
objTable.changeSelection(objRow, objCol, false, false);
objUndoableEdit.undo();
UndoRedoManagerSetEnabled(true);
}
}
static class aUndoRedo extends AbstractAction {
// This code is bound to the undo/redo keystrokes and tells
// Java what commands to run when the keys are later entered
// by the user.
private static final long serialVersionUID = 1L;
Boolean objUndo = true;
UndoManager objUndoManager = null;
final String objLocation;
public aUndoRedo(Boolean Undo, UndoManager undoManager, String location) {
super();
objUndo = Undo;
objUndoManager = undoManager;
objLocation = location;
}
#Override
public void actionPerformed(ActionEvent ae) {
try {
// See if operation allowed
if (!objUndoManager.canUndo() && objUndo
|| !objUndoManager.canRedo() && !objUndo)
return;
UndoRedoManagerSetEnabled(false);
if (objUndo) {
objUndoManager.undo();
} else {
objUndoManager.redo();
}
UndoRedoManagerSetEnabled(true);
// Catch errors and let user know
} catch (Exception e) {
UndoRedoManagerSetEnabled(true);
}
}
}
static class uelUndoRedoTableCellField implements UndoableEditListener {
// This action is called when the user changes the table's
// text cell. It saves the change for later undo/redo.
private UndoManager objUndoManager = null;
private JTable objTable = null;
public uelUndoRedoTableCellField(UndoManager undoManager,
JTable table) {
objUndoManager = undoManager;
objTable = table;
}
#Override
public void undoableEditHappened(UndoableEditEvent e) {
// Remember the edit but only if the code isn't doing
// an undo or redo currently.
if (UndoRedoManagerIsEnabled()) {
objUndoManager.addEdit(new aueUndoRedoTableCellField(e
.getEdit(), objTable, objTable.getSelectedRow(),
objTable.getSelectedColumn()));
}
}
}
static public Boolean UndoRedoManagerIsEnabled() {
// See if we are currently doing an undo/redo.
// Return true if so.
return objEnableUndoRedoActions;
}
static public void UndoRedoManagerSetEnabled(Boolean state) {
// Set the state of whether we are in undo/redo code.
objEnableUndoRedoActions = state;
}
static void UndoRedoSetKeys(JFrame frame, final String location, UndoManager undoManager) {
// Allow undo and redo to be called via these keystrokes for this dialog
final String cntl_y = "CNTL_Y";
final KeyStroke ksCntlY = KeyStroke.getKeyStroke("control Y");
final String cntl_z = "CNTL_Z";
final KeyStroke ksCntlZ = KeyStroke.getKeyStroke("control Z");
JRootPane root = frame.getRootPane();
root.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)
.put(ksCntlZ, cntl_z);
root.getActionMap().put(
cntl_z,
new aUndoRedo(true, undoManager, location));
root.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)
.put(ksCntlY, cntl_y);
root.getActionMap().put(
cntl_y,
new aUndoRedo(false, undoManager, location));
}
}

When you press a key, a series of things occur. The JTable, process the key stroke, it checks to see if the cell is editable (as the TableModel), it then asks the editor for the currently selected cell if the event should edit the cell (CellEditor#isCellEditable(EventObject)).
If this method returns true, the editor is prepared, the value from the TableModel is applied to the editor (ie setText is called), and the editor is added to the JTable, finally, the event which triggered the edit mode is re-dispatched to the editor, in your case the Ctrl+Z, which then triggers and undo event, returning the editor it's initial state (before setText was called).
You can try and use something like...
TableCellEditor objEditor = new DefaultCellEditor(tfTabField) {
#Override
public boolean isCellEditable(EventObject anEvent) {
boolean isEditable = super.isCellEditable(anEvent); //To change body of generated methods, choose Tools | Templates.
if (isEditable && anEvent instanceof KeyEvent) {
KeyEvent ke = (KeyEvent) anEvent;
if (ke.isControlDown() && ke.getKeyCode() == KeyEvent.VK_Z) {
isEditable = false;
}
}
return isEditable;
}
};
to prevent the JTable from been placed into edit when a specific key stroke occurs
Updated
So based on Andrew's answer from JTextArea setText() & UndoManager, I devised a "configurable" UndoableEditListener which can be set to ignore undoable actions, for example...
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.text.Document;
import javax.swing.text.PlainDocument;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;
public class FixedField {
public static void main(String[] args) {
new FixedField();
}
public FixedField() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public static class UndoableEditHandler implements UndoableEditListener {
private static final int MASK
= Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();
private UndoManager undoManager = new UndoManager();
private boolean canUndo = true;
public UndoableEditHandler(JTextField field) {
Document doc = field.getDocument();
doc.addUndoableEditListener(this);
field.getActionMap().put("Undo", new AbstractAction("Undo") {
#Override
public void actionPerformed(ActionEvent evt) {
try {
if (undoManager.canUndo()) {
undoManager.undo();
}
} catch (CannotUndoException e) {
System.out.println(e);
}
}
});
field.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_Z, MASK), "Undo");
field.getActionMap().put("Redo", new AbstractAction("Redo") {
#Override
public void actionPerformed(ActionEvent evt) {
try {
if (undoManager.canRedo()) {
undoManager.redo();
}
} catch (CannotRedoException e) {
System.out.println(e);
}
}
});
field.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_Y, MASK), "Redo");
}
#Override
public void undoableEditHappened(UndoableEditEvent e) {
if (canUndo()) {
undoManager.addEdit(e.getEdit());
}
}
public void setCanUndo(boolean canUndo) {
this.canUndo = canUndo;
}
public boolean canUndo() {
return canUndo;
}
}
public class TestPane extends JPanel {
public TestPane() {
JTextField field = new JTextField(10);
UndoableEditHandler handler = new UndoableEditHandler(field);
handler.setCanUndo(false);
field.setText("Help");
handler.setCanUndo(true);
add(field);
}
}
}
Now, you're going to have to devices your own TableCellEditor to support this, for example...
public static class MyCellEditor extends AbstractCellEditor implements TableCellEditor {
private JTextField editor;
private UndoableEditHandler undoableEditHandler;
public MyCellEditor(JTextField editor) {
this.editor = editor;
undoableEditHandler = new UndoableEditHandler(editor);
editor.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
fireEditingStopped();
}
});
}
#Override
public Object getCellEditorValue() {
return editor.getText();
}
#Override
public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column) {
undoableEditHandler.setCanUndo(false);
editor.setText(value == null ? null : value.toString());
undoableEditHandler.setCanUndo(true);
return editor;
}
}

Can't figure out error with ActionListener

The following is my program. the goal is to convert from a roman numeral to an Arabic number after a user types in the numeral and presses the enter key.
This is a homework assignment and we are forced to user JTextAreas in lieu of JTextFields.
My error exists on the line: enterRomanNumber.addActionListener(handler);
The error reads:
"The method addActionListener(ArabicToRomanGUI.HandlerForTextArea) is
undefined for the type JTextArea"
I can't seem to figure out why I am getting this error or how to correct it, can someone please advise.
import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class ArabicToRomanGUI extends JFrame
{
private static final long serialVersionUID = 1L;
private JTextArea enterRomanNumber = new JTextArea();
JLabel label = new JLabel();
JPanel panel = new JPanel();
JFrame frame = new JFrame();
//TestArea contructor adds jtextArea to jframe
public ArabicToRomanGUI()
{
super("Convert a Roman Numeral");
setLayout(new FlowLayout());
//Text field to enter a roman numeral
enterRomanNumber = new JTextArea(1,25);
enterRomanNumber.setText("Delete this text and Enter a Roman Numerial Here!");
//enterRomanNumber.setAlignmentX(0);
//enterRomanNumber.setAlignmentY(0);
add(enterRomanNumber);
HandlerForTextArea handler = new HandlerForTextArea();
enterRomanNumber.addActionListener(handler);
}
private class HandlerForTextArea implements ActionListener
{
//used to process textArea events
#Override
public void actionPerformed(ActionEvent e)
{
String userInput = "";
userInput = enterRomanNumber.getText();
userInput = userInput.toUpperCase();
ConversionLogic.ConvertFromRomanToArabic(userInput); //converts user string of Roman numerals to an int in arabic
String arabicNumberAsString = ConversionLogic.getConvertedRomanNumeral();
enterRomanNumber.setText(arabicNumberAsString);
//user pressed enter in JTextField enterNumberField
if(e.getSource() == enterRomanNumber)
{
//enterRomanNumber.setText(arabicNumberAsString);
if (ConversionLogic.getCheckFail() == true)
{
JOptionPane.showMessageDialog(frame, "The Roman Numeral entered is Invalid", "Error", JOptionPane.ERROR_MESSAGE);
}
else
{
JOptionPane.showMessageDialog(frame, "The arabic equivalent is " + arabicNumberAsString + "." , "Conversion Successful", JOptionPane.PLAIN_MESSAGE);
}
}
}
}
}//end inner class TextAreaHandler

For a better answer, see #MadProgrammer 's answer.
My solution:
There is no ActionListener for JTextArea.
So just use KeyListener instead
HandlerForTextArea handler = new HandlerForTextArea();
enterRomanNumber.addKeyListener(handler);
Implements KeyListener
private class HandlerForTextArea implements KeyListener
{
#Override
public void keyPressed(KeyEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void keyReleased(KeyEvent arg0) {
// TODO Auto-generated method stub
if (arg0.getKeyCode() == VK_ENTER){
// TODO Your bussiness
}
}
#Override
public void keyTyped(KeyEvent arg0) {
// TODO Auto-generated method stub
}
}

KeyListeners are NEVER appropriate solutions to use with text components, if you want to be notified when a text component changes, you use a DocumentListener, if you want to change/filter what can be entered into a text component, you use a DocumentFilter, if you need to change a special key, like Enter, you should use a key binding
See How to Use Key Bindings for more details.
One of the problems you could have with KeyListener is not knowing when the key stroke is processed by the text component, in your case, it may not be a major issue, but it could change the way the program works on different platforms.
Instead, you can override the JTextArea's key binding for the Enter key (named insert-break). This provides you with the ability to actually change the behavior of the key stroke, or, in your case, manage how you process the event. For example, this replaces the Action for the text area's Enter key, but retains the previous/default behavior...
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class KeyBindingsTest {
public static void main(String[] args) {
new KeyBindingsTest();
}
public KeyBindingsTest() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextArea ta;
public TestPane() {
ta = new JTextArea(10, 20);
ActionMap am = ta.getActionMap();
Action proxy = am.get("insert-break");
am.put("insert-break", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
// You can process the event through the original action BEFORE
// you do your own processing
//proxy.actionPerformed(e);
System.out.println("You pressed the enter key, you can have candy");
// Or you can process the event through the original action AFTER
// you do your own processing, you have now gained control
proxy.actionPerformed(e);
}
});
setLayout(new BorderLayout());
add(ta);
}
}
}
Now, you could even go to the extent for creating your own JTextArea which supported ActionPerformed...
public class ActionableTextArea extends JTextArea {
private String actionCommand;
public ActionableTextArea() {
installKeyBindings();
}
public ActionableTextArea(String text) {
super(text);
installKeyBindings();
}
public ActionableTextArea(int rows, int columns) {
super(rows, columns);
installKeyBindings();
}
public ActionableTextArea(String text, int rows, int columns) {
super(text, rows, columns);
installKeyBindings();
}
public ActionableTextArea(Document doc) {
super(doc);
installKeyBindings();
}
public ActionableTextArea(Document doc, String text, int rows, int columns) {
super(doc, text, rows, columns);
installKeyBindings();
}
protected void installKeyBindings() {
ActionMap am = getActionMap();
Action proxy = am.get("insert-break");
am.put("insert-break", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
// You can process the event through the original action BEFORE
// you do your own processing
//proxy.actionPerformed(e);
fireActionPerformed();
// Or you can process the event through the original action AFTER
// you do your own processing, you have now gained control
proxy.actionPerformed(e);
}
});
}
public void addActionListener(ActionListener listener) {
listenerList.add(ActionListener.class, listener);
}
public void removeActionListener(ActionListener listener) {
listenerList.remove(ActionListener.class, listener);
}
public void setActionCommand(String actionCommand) {
this.actionCommand = actionCommand;
}
public String getActionCommand() {
return actionCommand;
}
protected void fireActionPerformed() {
ActionListener[] listeners = listenerList.getListeners(ActionListener.class);
if (listeners.length > 0) {
ActionEvent evt = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, getActionCommand());
for (ActionListener listener : listeners) {
listener.actionPerformed(evt);
}
}
}
}

Dynamically updating Jlist

I've been reading a lot on Swing but I've hit a dead end and I know you can help me.
I've read lots of questions like Updating an JList but still I'm clueless as how to proceed.
My problem is the same as the guy who asked the question I mentioned. I'm making a server and users will access it.
This are my classes.
Server
private string name;
private string dateOfAccess;
#Override
public String toString() {
// TODO Auto-generated method stub
return nombreAmigo;
}
Main
private DefaultListModel listModel = new DefaultListModel();
private JList list=new JList(listModel);
and my ClientHandler
public static List<Conexion> clientes=new ArrayList<Conexion>();
So, I'm going to be filling the clientes list from different threads as they connect to my server and I need to show them in my Jlist. Any suggestions on how to update it? I'm really stuck here
Thanks!

Personally, I would have some kind of "client manager" that is responsible for collating all the clients into a centralised repository. This would be a singleton within your server. It could be queried at any time for a list of currently active users (and other management functions), but there should only ever be one active.
The manager would then fire notification events to interested parties (using an observe pattern).
One of these parties would be your UI. When a "connect" or "disconnect" event is raised, you will need to ensure that this is synced back the Event Dispatching Thread BEFORE you try and update the list model, for example...
public void userConnected(UserManagerEvent evt) { // You would need to define all this yourself...
final Conexion user = evt.getConnection(); // You would need to define this event yourself...
EventQueue.invokeLater(new Runnable() {
public void run() {
listModel.addElement(user);
}
});
}
The actually implementation will come down to what it is you want to achieve and the way you want to achieve it, but this is the basic concept...
Updated with conceptual example
This is a basic, conceptual, example. An event is raised by the button, which simulates (for example) a connection. This event is then sent to the list, via an listener interface, where the model is updated
Events are generated from some other source and the UI is updated when they occur, classic observer pattern
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import org.w3c.dom.ls.LSInput;
public class UpdateListOnEvent {
public static void main(String[] args) {
new UpdateListOnEvent();
}
public UpdateListOnEvent() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class ConnectionEvent {
private Date date;
public ConnectionEvent(Date date) {
this.date = date;
}
public Date getDate() {
return date;
}
}
public interface ConnectionListener {
public void connectionEstablished(ConnectionEvent evt);
}
public class TestPane extends JPanel implements ConnectionListener {
private JList list;
private DefaultListModel<String> model;
public TestPane() {
setLayout(new BorderLayout());
model = new DefaultListModel<>();
list = new JList(model);
add(new JScrollPane(list));
EventPane eventPane = new EventPane();
eventPane.addConnectionListener(this);
add(eventPane, BorderLayout.SOUTH);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.dispose();
}
#Override
public void connectionEstablished(ConnectionEvent evt) {
model.addElement(DateFormat.getDateTimeInstance().format(evt.getDate()));
}
}
public class EventPane extends JPanel {
private List<ConnectionListener> listeners;
private JButton update;
public EventPane() {
listeners = new ArrayList<>(5);
setLayout(new GridBagLayout());
update = new JButton("Update");
update.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// connectionEstablished(new Date());
fireConnectionEstablished(new Date());
}
});
add(update);
}
public void addConnectionListener(ConnectionListener listener) {
listeners.add(listener);
}
public void removeConnectionListener(ConnectionListener listener) {
listeners.remove(listener);
}
protected ConnectionListener[] getConnectionListeners() {
return listeners.toArray(new ConnectionListener[listeners.size()]);
}
protected void fireConnectionEstablished(Date date) {
ConnectionListener[] listeners = getConnectionListeners();
if (listeners != null && listeners.length > 0) {
ConnectionEvent evt = new ConnectionEvent(date);
for (ConnectionListener listener : listeners) {
listener.connectionEstablished(evt);
}
}
}
}
}