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class variable not updating after method call

I am quite new to Java and only after researching and googling and reading many answers, I am posting this. I am kinda lost. A little guidance would be of great help. The following is a method from a class that implements the "ActionListener" interface. What I am trying to do is this: There is a button which one clicked should open a new window with two options in the form of two Radio Buttons. I need to know the Radio Button which was selected for further use in my code. I declared, the "scoreOption" variable as a class variable and static, and then attempt to update it in the "actionPerformed" abstract method. But when I refer to it (after the method call), the value stays the same - null, or whatever I set it to initially. Here is the code:
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileNotFoundException;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Scanner;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextArea;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class StartEvents implements ActionListener {
StartPanel startingPanel;
static String scoreOption;
public StartEvents(StartPanel startPanel) {
startingPanel = startPanel;
}
// Scoring System Window - 1
public void scoringSystem() {
startingPanel.scoringSystem.addActionListener(new ActionListener () {
#Override
public void actionPerformed(ActionEvent e) {
Panel scoringSystemPanel = new Panel();
JFrame scoreSystemFrame = scoringSystemPanel.frame(150, 250, "Scoring System", 2, true);
JPanel scoreSystemPanel = scoringSystemPanel.panel(Color.lightGray);
JButton confirmSelection = scoringSystemPanel.button(40, 20, "Confirm");
JRadioButton scoreSystem1 = scoringSystemPanel.radioButton("Option 1: Same Points Per Hit");
scoreSystem1.setActionCommand("Option 1");
JRadioButton scoreSystem2 = scoringSystemPanel.radioButton("Option 2: Unique Points Per Hit");
scoreSystem2.setActionCommand("Option 2");
ButtonGroup scoreSys = new ButtonGroup();
scoreSys.add(scoreSystem1);
scoreSys.add(scoreSystem2);
scoreSystemFrame.getContentPane().add(scoreSystemPanel);
scoreSystemPanel.add(scoreSystem1);
scoreSystemPanel.add(scoreSystem2);
scoreSystemPanel.add(confirmSelection);
// Get Selection Event
// Option 1
scoreSystem1.addActionListener(new ActionListener () {
#Override
public void actionPerformed(ActionEvent e) {
if (scoreSystem1.isSelected()) {
scoreOption = scoreSystem1.getActionCommand();
}
}
});
// Option 2
scoreSystem2.addActionListener(new ActionListener () {
#Override
public void actionPerformed(ActionEvent e) {
if (scoreSystem2.isSelected()) {
scoreOption = scoreSystem2.getActionCommand();
}
}
});
// Confirm Event
confirmSelection.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
scoreSystemFrame.dispose();
}
});
}
});
}
Main Game Class where the method scoringsystem is called.
import java.util.ArrayList;
public class Game {
public static void main(String[] args) {
StartPanel startingPanel = new StartPanel();
startingPanel.makeStartPanel();
StartEvents starter = new StartEvents(startingPanel);
starter.rulesButton();
starter.exitButton();
starter.highScoresButton();
ArrayList<Integer> dimensions = starter.boardSizeSelector();
// Problem Zone
System.out.println(StartEvents.scoreOption);
starter.scoringSystem();
System.out.println(StartEvents.scoreOption);
// The two values of scoreOption should be different
String[] playPanelDetails = {"970", "Player 1", "450"};
// Final Start of the Game
starter.startGameButton(playPanelDetails, dimensions);
}
}
Furthermore, could you please let me know regarding the following questions:
Implementing "ActionListener" within another "ActionListener" is recommended? Good Practice?
Can there only be one declaration of the "actionPerformed" method or can it be overloaded too?
Is it possible to get a return value from "actionPerformed" method?
I would be really grateful if even some hints could be provided. I really tried a lot and only then posting it here. Thank you very much in advance.
Small Edit: When I "System.out.println" the "actioncommand" there itself, it does work perfectly, printing in the console. But not when I try to update the class variable and then try to print it after the method call. Dunno if this helps.

JFrames are not modal -- you create one and display it, it does not block the code flow, and so you are extracting the value of scoreOption right as the JFrame is being displayed and before the user has had any chance to change it. You need to use a modal dialog such as a JDialog that is created as a modal dialog or use a JOptionPane (which is actually just a modal JDialog under the hood). This will block the flow of code so that you extract the data only after it has been changed by the user.
An example that proves the point:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class FooGui01 extends JPanel {
private String frameTest = "";
private String dialogTest = "";
private JFrame mainFrame = new JFrame("Main GUI");
private JFrame subFrame;
private JDialog dialog;
public FooGui01() {
JButton showFrameBtn = new JButton("Show JFrame");
showFrameBtn.addActionListener(e -> {
changeTest1WithJFrame();
System.out.println("frameTest: " + frameTest);
});
JButton showDialogBtn = new JButton("Show JDialog");
showDialogBtn.addActionListener(e -> {
changeTest2WithModalDialog();
System.out.println("dialogTest: " + dialogTest);
});
JPanel panel = new JPanel();
panel.add(showDialogBtn);
panel.add(showFrameBtn);
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainFrame.add(panel);
mainFrame.pack();
mainFrame.setLocationByPlatform(true);
mainFrame.setVisible(true);
}
public void changeTest1WithJFrame() {
if (subFrame == null) {
subFrame = new JFrame("Frame");
JButton button = new JButton("Press me");
button.addActionListener(e -> {
frameTest = "Hello World and frameTest";
subFrame.setVisible(false);
});
JPanel panel = new JPanel();
panel.add(button);
subFrame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
subFrame.add(panel);
subFrame.pack();
subFrame.setLocationByPlatform(true);
}
subFrame.setVisible(true);
}
public void changeTest2WithModalDialog() {
if (dialog == null) {
dialog = new JDialog(mainFrame, "Dialog", Dialog.ModalityType.APPLICATION_MODAL);
JButton button = new JButton("Press me");
button.addActionListener(e -> {
dialogTest = "Hello World and dialogTest";
dialog.setVisible(false);
});
JPanel panel = new JPanel();
panel.add(button);
dialog.add(panel);
dialog.pack();
dialog.setLocationByPlatform(true);
}
dialog.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new FooGui01());
}
}
If you run the code, when you show the sub JFrame, the test text is displayed immediately in the console before the dialog has been dealt with. If you press the button to show the dialog, the test text display is delayed until after the button has been pushed, changing the text.
Pressing the frame button twice will finally show the correct text since the text was set by the first time it was displayed.

A JDialig is just like a JFrame. That is you add components to it like you do any frame.
The difference is that you can make a JDialog modal. This means that when you use:
dialog.setVisible(true);
System.out.println("here");
The code after the setVisible(...) statement will not be executed until the dialog is closed. It also means you can't click on the parent JFrame until the dialog is closed.
An easy way to create a modal JDialog is to use a JOptionPane. It has some predefined methods that make prompting for user input easy.
For example in your case you could do something like:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class SSCCE extends JPanel
{
private int scoringOption = -1;
public SSCCE()
{
JButton button = new JButton("Change Points Option");
add(button);
button.addActionListener((e) -> displayOptionDialog());
}
private void displayOptionDialog()
{
Window window = SwingUtilities.windowForComponent( this );
// Custom button text
Object[] options = {"Option 1: Same Points Per Hit", "Option 2: Unique Points Per Hit"};
scoringOption = JOptionPane.showOptionDialog(
window,
"Select your scoring option:",
"Scoring Option",
JOptionPane.YES_NO_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE,
null,
options,
null);
System.out.println( scoringOption );
}
private static void createAndShowGUI()
{
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new SSCCE());
frame.pack();
frame.setLocationByPlatform( true );
frame.setVisible( true );
}
public static void main(String[] args) throws Exception
{
java.awt.EventQueue.invokeLater( () -> createAndShowGUI() );
}
}
The above is also an example of an "MRE". The code is simple and contained in a single class that you can copy/paste/compile and test.
Read the section from the Swing tutorial on How to Use Dialogs for more examples of using a JOptionPane.
If you really want to use radio buttons, then you can create a panel with the radio buttons and display them on the option pane using the showConfirmDialog(...) method. When the dialog closes you would then need to get the action command from the ButtonModel of the ButtonGroup.
See: how to set & manage the layout of JOptionPane for a basic example of this approach to get you started.

JButton becomes enabled after JTextfield default action

I'm getting to grips with Java again and playing with Swing. Currently trying to understand JList.
When selecting items in a JList, I enable a button (the "Remove" button). When there's no selection, the button should be disabled (can't remove an item if it's not selected, the JVM tends to vomit if you don't have an item index).
When adding a list item through a JTextField default action (enter), the button enables but there's no selection in the JList. The code to enable the button doesn't even run. How is this happening? Maybe I'm missing a listener somewhere?
All the listeners are in the main class, but it doesn't seem to be a problem with the others. I can't see the class instantiating twice, so it's not that. Any ideas would be great?
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.ListSelectionModel;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.event.ListDataEvent;
import javax.swing.event.ListDataListener;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
public class GUI extends JFrame implements Runnable, ActionListener, DocumentListener, ListDataListener, ListSelectionListener {
/**
*
*/
private static final long serialVersionUID = 1L;
//declare and instantiate interface components
DefaultListModel<String> lm=new DefaultListModel<String>();
JList<String> jl=new JList<String>(lm);
JTextField jt=new JTextField(50);
JButton b_add=new JButton("Add");
JButton b_del=new JButton("Remove");
#Override
public void run() {
//FROM RUNNABLE INTERFACE
//set GUI (JFrame) attributes
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setLocationByPlatform(true);
setName("List of Lists");
setSize(1280, 500);
setLayout(new FlowLayout());
//set component attributes
jl.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); //single selection list
jt.getDocument().addDocumentListener(this);
//other interface components
JScrollPane sp=new JScrollPane(jl);
JButton b_exit=new JButton("Exit");
//other component attributes
sp.setSize(500, 500);
b_add.setEnabled(false);
b_del.setEnabled(false);
//set component listeners
b_add.addActionListener(this);
b_del.addActionListener(this);
b_exit.addActionListener(this);
jt.setActionCommand("TXT");
jt.addActionListener(this);
lm.addListDataListener(this);
jl.addListSelectionListener(this);
//add GUI components
add(jt);
add(sp);
add(b_add);
add(b_del);
add(b_exit);
//set GUI visible
setVisible(true);
}
//FROM ACTIONLISTENER INTERFACE
#Override
public void actionPerformed(ActionEvent ae) {
//default action on text field (enter key)
if (ae.getActionCommand()=="TXT") {
lm.addElement(jt.getText());
jt.setText(null);
} else {
//actions from buttons
switch (ae.getActionCommand()) {
//add button
case "Add":
lm.addElement(jt.getText());
jt.setText(null);
break;
//remove button
case "Remove":
if (jl.getSelectedIndex()>=0) {
lm.remove(jl.getSelectedIndex());
}
break;
//exit button
case "Exit":
setVisible(false);
dispose();
break;
//just in case
default:
break;
}
}
}
//FROM DOCUMENTEVENTLISTENER INTERFACE
#Override
public void changedUpdate(DocumentEvent de) {
b_add.setEnabled(de.getDocument().getLength()>0);
}
#Override
public void insertUpdate(DocumentEvent de) {
b_add.setEnabled(de.getDocument().getLength()>0);
}
#Override
public void removeUpdate(DocumentEvent de) {
b_add.setEnabled(de.getDocument().getLength()>0);
}
//FROM LISTDATALISTENER INTERFACE
#Override
public void contentsChanged(ListDataEvent ld) {
b_del.setEnabled(lm.getSize()>0);
}
#Override
public void intervalAdded(ListDataEvent ld) {
b_del.setEnabled(lm.getSize()>0);
}
#Override
public void intervalRemoved(ListDataEvent ld) {
b_del.setEnabled(lm.getSize()>0);
}
//FROM LISTSELECTIONLISTENER INTERFACE
#Override
public void valueChanged(ListSelectionEvent ls) {
b_del.setEnabled(jl.getSelectedIndex()>=0);
}
}
What should happen is that the "Remove" button should only enable when an item in the JList is highlighted (selected).

What should happen is that the "Remove" button should only enable when an item in the JList is highlighted (selected).
Then you have too many listeners in your code.
There is no need for the DocumentListener. It doesn't matter if the data in the text field is changed. When you add the data from the text field to the JList, the selection does not change automatically.
There is no need for the ListDataListener. Again, you don't care if the data changes.
The only listener that is relevant to this requirement is the ListSelectionListener. This listener will fire an event when the selection changes. Then in the listener code you enable/disable the button based on the selection in the list.
Basic code in the listener might be:
int index = list.getSelectedIndex();
button.setEnabled( index = -1 ? false : true );
Read the section from the Swing tutorial on How to Write a ListSelectionListener for more information and a working example.

Just add b_del.setEnabled(false); in Add case.
//add button
case "Add":
lm.addElement(jt.getText());
jt.setText(null);
b_del.setEnabled(false);
break;
Also, I recommend using system.exit(0) instead of dispose (). For memory reasons only (Obviously, it depends on your needs :) ).

ActionPerformed being called when JComboBox is clicked in Jtable cell

I am using JComboBox in Jtable cell. When I click on the JComboBox and select a value from it, it calls the ActionPerformed fuction. Till here it is working fine but as soon as I click on the JComboBox again, it calls the ActionPerformed function, which it should not. What I want is, to call the ActionPerformed function when the item is selected in the JComboBox. In other words it should work as it worked for the first time when the item was selected from the JComboBox and then the ActionPerformed function was called. I cannot figure out why this problem is occurring. Here are the links that I have looked into and I did some other searches also but still could not find any relative answer to the above mentioned problem.
Adding JComboBox to a JTable cell
How to use ActionListener on a ComboBox to give a variable a value
https://coderanch.com/t/339842/java/ComboBox-ItemListener-calling
Here is the code, you can copy paste it and check it.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultCellEditor;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.TableColumn;
public class TableExample implements ActionListener{
JFrame frame;
JComboBox skuNameComboBoxTable;
TableExample() {
frame = new JFrame();
String data[][] = {{"101", "Amit", "Choose"},
{"102", "Jai", "Choose"},
{"101", "Sachin", "Choose"}};
String column[] = {"ID", "Name", "Degree"};
JTable table = new JTable(data, column);
table.setBounds(30, 40, 200, 300);
JScrollPane scrollPane = new JScrollPane(table);
frame.add(scrollPane);
frame.setSize(300, 400);
frame.setVisible(true);
String[] array = {"BS(SE)", "BS(CS)", "BS(IT)"};
skuNameComboBoxTable = new JComboBox(array);
skuNameComboBoxTable.addActionListener(this);
TableColumn col = table.getColumnModel().getColumn(2);
col.setCellEditor(new DefaultCellEditor(skuNameComboBoxTable));
}
public static void main(String[] args) {
new TableExample();
}
#Override
public void actionPerformed(ActionEvent e) {
JOptionPane.showMessageDialog(null, "actionPerformed called");
}
}
Kindly tell me why this problem is occurring and how should I solve it.

Unfortunately, you can't do much when using the DefaultCellEditor - that is how it behaves. Within your code you can add a check to ensure that a change in value occured before handling the event. Something like below:
public void actionPerformed(ActionEvent e) {
if (skuNameSelected == null || skuNameComboBoxTable.getSelectedItem() != skuNameSelected)
JOptionPane.showMessageDialog(null, "actionPerformed called: ");
skuNameSelected = (String) skuNameComboBoxTable.getSelectedItem();
}

You can try using ItemListener and filter your action according to the ItemEvent.
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JComboBox;
import javax.swing.JFrame;
public class JComboBoxTest {
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
String[] items = {"One", "Two", "Three"};
JComboBox cb = new JComboBox(items);
cb.addItemListener(new ItemListener() {
#Override
public void itemStateChanged(ItemEvent e) {
if (e.getStateChange() == ItemEvent.SELECTED) {
System.out.println("Selected " + e.getItem());
} else {
System.out.println("Deselected " + e.getItem());
}
}
});
frame.add(cb);
frame.pack();
frame.setVisible(true);
}
}

This is happening because you are using the same JComboBox as the DefaultCellEditor for column 2.
Whenever you click a cell from column 2 the ComboBox will change to the value that is on the cell at the moment and that triggers the DESELECT (from the old value) and the SELECT (for the new value). This will only happen if the old value and the new value are not the same.
One way to avoid this is to add a CellEditorListener on the DefaultCellEditor that you are using, like below:
TableColumn col = table.getColumnModel().getColumn(2);
DefaultCellEditor cellEditor = new DefaultCellEditor(skuNameComboBoxTable);
col.setCellEditor(cellEditor);
cellEditor.addCellEditorListener(new CellEditorListener() {
#Override
public void editingStopped(ChangeEvent e) {
System.out.println("Value of combo box defined!");
}
#Override
public void editingCanceled(ChangeEvent e) {
System.out.println("Edition canceled, set the old value");
}
});
This way you will be able to only act when the value has been defined by the ComboBox.
I hope this helps.

You should not be using an ActionListener for this. The combo box uses its own ActionListener to update the TableModel when an item is selected.
So instead you should be listening for changes in the TableModel in order to do your custom code. So you should be using a TableModelListener to listen for changes in the data. However, a TableModelListener can fire an event even if just start and stop editing of the cell which might be a problem for you.
In this case you can use the Table Cell Listener. It will only generate an event when the value in the TableModel has changed.

How to select an item from a JList without using a button?

I've been making a program, and one part of it is the ability to choose an item from a JList and have it display a specific icon in a JLabel. I've made it work so that the user has to select the item from the list and then press a button to initiate the action.
I'm just wondering if there's any way to make it so the button isn't necessary? In other words, the user simply has to click the list item and it immediately initiates the action.

Here is my code:
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
public class Example extends JFrame
{
JList list = null;
Example()
{
Container cp = getContentPane();
cp.setLayout(new FlowLayout());
ArrayList data = new ArrayList();
data.add("Py");
data.add("Piper");
list = new JList(data.toArray());
list.addListSelectionListener(new ListSelectionListener()
{
public void valueChanged(ListSelectionEvent evt)
{
// To avoid double value selected
if (evt.getValueIsAdjusting())
return;
System.out.println("Selected: " + list.getSelectedValue());
}
});
cp.add(new JScrollPane(list), BorderLayout.CENTER);
}
public static void main(String[] s)
{
Example l = new Example();
l.pack();
l.setVisible(true);
}
}
So right here:
list.addListSelectionListener(new ListSelectionListener()
{
public void valueChanged(ListSelectionEvent evt)
{
// To avoid double value selected
if (evt.getValueIsAdjusting())
return;
System.out.println("Selected: " + list.getSelectedValue());
}
});
So what you are actually doing is to "plug" a ListSelectionListener to your JList so that can be notified for any events that occur to the JList. Within the valueChanged you add the code need to be executed when the user select something in the JList.

There is this wonderful resource with the JList JavaDoc.

Find selected item of a JList and display it in real time

I have a JList, where i am displaying some ID's. I want to capture the ID the user clicked and dis play it on a JLabel.
String selected = jlist.getSelectedItem().toString();
The above code gives me the selected JList value. But this code has to be placed inside a button event, where when i click the button it will get the JList value an assign it to the JLabel.
But, what i want to do is, as soon as the user clicks an item of the JList to update the JLabel in real time. (without having to click buttons to fire an action)

A simple example would be like below using listselectionlistener
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
public class JListDemo extends JFrame {
public JListDemo() {
setSize(new Dimension(300, 300));
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new FlowLayout());
final JLabel label = new JLabel("Update");
String[] data = { "one", "two", "three", "four" };
final JList dataList = new JList(data);
dataList.addListSelectionListener(new ListSelectionListener() {
#Override
public void valueChanged(ListSelectionEvent arg0) {
if (!arg0.getValueIsAdjusting()) {
label.setText(dataList.getSelectedValue().toString());
}
}
});
add(dataList);
add(label);
setVisible(true);
}
public static void main(String args[]) {
new JListDemo();
}
}

Why don't you put a ListSelectionListener on your JList, and add your above code in to it.
I'm assuming you already know how to create listeners on JButtons, based on your question, so you just need to tweak it to create a ListSelectionListener instead, then assign the listener to your JList using jlist.addListSelectionListener(myListener);
There is a nice tutorial here that should get you started, or refer to the documentation
You should be aiming for something like this...
jlist.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent event) {
if (!event.getValueIsAdjusting()){
JList source = (JList)event.getSource();
String selected = source.getSelectedValue().toString();
}
}
});

Use a ListSelectionListener:
JList list = new JList(...);
list.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent evt) {
if (!evt.getValueIsAdjusting()) {
// code here
}
}
});