We Keep Coding

Can I use actionListeners on JPanels?

I am trying to add and actionListener to a JPanel it's self but keep getting the error"cannot find symbol". I was just wondering if it is possible to do this as I want to be able to click on the panel and make the colour change. Any help would be appreciated.
Here is what i have so far.
import java.awt.*;
import javax.swing.*;
import javax.swing.JPanel.*;
import java.awt.Color.*;
import java.awt.event.*;
/**
* Write a description of class SimpleFrame here.
*
* #author OFJ2
* #version
*/
public class Game extends JFrame
implements ActionListener
{
private final int ROWS = 5;
private final int COLUMS = 2;
private final int GAP = 2;
private final int SIZE = ROWS * COLUMS;
private int x;
private JPanel leftPanel = new JPanel(new GridLayout(ROWS,COLUMS, GAP,GAP));
private JPanel [] gridPanel = new JPanel[SIZE];
private JPanel middlePanel = new JPanel();
private JPanel rightPanel = new JPanel();
private Color col1 = Color.GREEN;
private Color col2 = Color.YELLOW;
private Color tempColor;
public Game()
{
super("Chasing Bombs OFJ2");
setSize(200,200);
setVisible(true);
makeFrame();
}
public void makeFrame()
{
Container contentPane = getContentPane();
contentPane.setLayout(new GridLayout());
leftPanel.setLayout(new GridLayout(ROWS, COLUMS));
//JLabel label2 = new JLabel("Pocahontas");
JButton playButton = new JButton("Play Game");
JButton exitButton = new JButton("Exit");
JButton easyButton = new JButton("Easy");
JButton mediumButton = new JButton("Medium");
JButton hardButton = new JButton("Hard");
add(leftPanel);
add(middlePanel, new FlowLayout());
add(rightPanel);
setGrid();
middlePanel.add(playButton);
middlePanel.add(exitButton);
rightPanel.add(easyButton);
rightPanel.add(mediumButton);
rightPanel.add(hardButton);
leftPanel.setBackground(Color.PINK);
middlePanel.setBackground(Color.RED);
easyButton.addActionListener(this);
mediumButton.addActionListener(this);
hardButton.addActionListener(this);
playButton.addActionListener(this);
exitButton.addActionListener(this);
}
public void setGrid()
{
for(int x = 0; x < SIZE; x++) {
gridPanel[x] = new JPanel();
gridPanel[x].setBorder(BorderFactory.createLineBorder(Color.BLACK));
leftPanel.add(gridPanel[x]);
gridPanel[x].setBackground(Color.GREEN);
gridPanel[x].addActionListener(this);
}
}
#Override
public void actionPerformed(ActionEvent e)
{
Object source = e.getSource();
if (source == gridPanel[0]){
gridPanel[x].setBackground(Color.BLACK);
}
}
}
I have tried to find if there is any other method that is needed to do this but cant find anything. Is it possible that I will have to add a button to fill each of the panels to make this work?
Thanks!

It defaults to no addActionListener, and the code below is a reference suggestion.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
class GPanel extends JPanel {
private List<ActionListener> listenerList = new ArrayList<>();
public GPanel() {
addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
var event = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "GPanel");
for (var i : listenerList) {
i.actionPerformed(event);
}
}
});
}
public void addActionListener(ActionListener listener) {
listenerList.add(listener);
}
}
public class ActionListenerTest extends JFrame {
public static void main(String[] args) {
new ActionListenerTest();
}
public ActionListenerTest() {
GPanel test = new GPanel();
test.setBackground(Color.BLUE);
add(test);
test.addActionListener(e-> {
System.out.println("Click: " + e.getActionCommand());
});
pack();
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
}

dispose method only works once then fails to function

I'm having trouble with the functionality of dispose for my checkerboard (called Checkers) . For each checkerboard that I have, i want to be able to remove it by using dispose before calling another instance of my interface. Here is my progress so far:
Checkers class:
import java.awt.*;
import javax.swing.*;
import java.awt.Color.*;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import java.util.Random;
public class Checkers extends JFrame
{
Random random = new Random();
private final int ROWS = 2;
private final int COLS = 5;
private final int GAP = 2;
private final int NUM = ROWS * COLS;
private int i;
public int score;
private JPanel pane = new JPanel(new GridLayout(ROWS,COLS, GAP,GAP));
private JPanel pane2 = new JPanel();
private JPanel pane3 = new JPanel();
private JButton btn1 = new JButton("Play A Game");
private JButton btn2 = new JButton("Exit");
private JButton btn3 = new JButton("Easy");
private JButton btn4 = new JButton("Intermediate");
private JButton btn5 = new JButton("Difficult");
private JLabel lbl1 = new JLabel ("score: " + score);
private JLabel gameLost = new JLabel("You lose! You got: " + score + " points");
private MyPanel [] panel = new MyPanel[NUM];
private Color col1 = Color.RED;
private Color col2 = Color.WHITE;
private Color col3 = Color.GREEN;
private Color tempColor;
public Checkers()
{
super("Checkers");
setSize(600,600);
setVisible(true);
setBackground(Color.BLACK);
setBoard();
}
public void setBoard()
// roates colors on the checkbaord
{
for (int i = 0; i < panel.length; i++) {
panel[i] = new MyPanel(this);
pane.add(panel[i]);
if (i % COLS == 0) {
tempColor = col1;
col1 = col2;
col2 = tempColor;}
if (i % 2 == 0) {
panel[i].setBackground(col1);}
else {
panel[i].setBackground(col2);}
}
//pane background colour and the size of this pane.
pane.setBackground(Color.BLACK);
pane.setPreferredSize(new Dimension(300,300));
//pane background colour and size of this pane.
pane2.setBackground(Color.white);
pane2.setPreferredSize(new Dimension(300,300));
//directions on the board where these panes appear.
add(pane, BorderLayout.WEST);
add(pane2, BorderLayout.EAST);
pane2.add(lbl1);
pane2.setLayout(new BoxLayout(pane2, BoxLayout.PAGE_AXIS));
}
public void incrementScore(){
score++;
lbl1.setText("Score: " + Integer.toString(score));
}
//This is the method for resetting via dispose - only works once.
public void restartBoard(){
this.dispose();
new Checkers();
}
}
And also the MyPanel class
public class MyPanel extends JPanel implements MouseListener {
private final Checkers checkers;
public MyPanel(Checkers checkers) {
this.checkers = checkers;
addMouseListener(this);
}
#Override
public void mouseClicked(MouseEvent e) {
setBackground(Color.BLACK);
checkers.incrementScore();
}
#Override
public void mousePressed(MouseEvent e) {
}
#Override
public void mouseReleased(MouseEvent e) {
}
#Override
public void mouseEntered(MouseEvent e) {
}
#Override
public void mouseExited(MouseEvent e) {
}
}
EXPECTED RESULT - What i'd like to do is be able to close the current version of interface by using the dispose method, and then opening a new instance of said interface.
ACTUAL RESULT - When opening an interface, then calling dispose method, it will work once. once you try to remove the 2nd interface when creating a 3rd interface, dispose will not function, and I cant see why this is.
Any help is welcome.

For what it's worth, this is an MCVE that shows your likely problem:
import java.awt.Dimension;
import javax.swing.*;
public class CheckersTest {
private static void createAndShowGui() {
Checkers checkers = new Checkers();
JButton restartButton = new JButton("Restart");
restartButton.addActionListener(event -> checkers.restartBoard());
JPanel restartPanel = new JPanel();
restartPanel.setPreferredSize(new Dimension(400, 400));
restartPanel.add(restartButton);
JFrame frame = new JFrame("Checkers Test");
frame.add(restartPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
class Checkers extends JFrame {
public Checkers() {
setPreferredSize(new Dimension(200, 200));
pack();
setLocationByPlatform(true);
setVisible(true);
}
public void restartBoard(){
this.dispose();
new Checkers();
}
}
The restart button refers to the original Checkers instance and so will not close any new instances created. The solution would be to get the restart method out of Checkers, create a Checkers field, and make sure the restart method refers to the visible Checkers instance:
import java.awt.Dimension;
import javax.swing.*;
public class CheckersTest {
private static Checkers checkers = new Checkers(); // holds reference
private static void restartBoard() {
if (checkers != null) {
checkers.dispose();
checkers = new Checkers(); // assign to reference field
}
}
private static void createAndShowGui() {
// !! Checkers checkers = new Checkers();
JButton restartButton = new JButton("Restart");
// !! restartButton.addActionListener(event -> checkers.restartBoard());
restartButton.addActionListener(event -> restartBoard());
JPanel restartPanel = new JPanel();
restartPanel.setPreferredSize(new Dimension(400, 400));
restartPanel.add(restartButton);
JFrame frame = new JFrame("Checkers Test");
frame.add(restartPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
class Checkers extends JFrame {
public Checkers() {
setPreferredSize(new Dimension(200, 200));
pack();
setLocationByPlatform(true);
setVisible(true);
}
}
Notes:
Again a much better design is not to swap JFrames but rather JPanel views
Note that the MCVE has code that reproduces the problem but avoids code not related to the problem. So it shows the restartBoard method, it compiles, but avoids game code since this is not relevant to the problem.

Spacing errors while printing vector to JTextArea

So I'm working on making a database system built on top of a Java Swing GUI... I have one button that works to add a person/thing to a vector (in this case the database):
// Database
Vector<String> db = new Vector<String>();
Here is the button's actionlistener to add:
new ActionListener() {
public void actionPerformed(ActionEvent e) {
String newStudent = student.getText();
db.addElement(newStudent);
This part all seems to be working fine, however, when I go to print out the vector on a JTextArea using a string buffer, there are odd spacing issues in the text on the JTextArea
Here is the StringBuffer and section where I print the vector onto the JTextArea:
StringBuffer dbb = new StringBuffer();
for (int i = 0; i < db.size(); i++) {
dbb.append(db.get(i) + '\n');
}
// printDB is the JTextArea
printDB.setText(dbb.toString());
add(printDB);
Screenshot of spacing issues:
Screenshot
Any Ideas on what might be causing this? The spacing seems to be linear as well (1space, 2spaces, 3spaces...)
Link to full project if needed (Sorry for bad code in general lol i'm just beginning): Full Code
Sorry if linear isn't the right word btw I couldn't think of another way to describe it
Code:
import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import java.util.*;
import java.util.Vector.*;
import javax.swing.*;
public class Database extends JFrame implements ActionListener, EventListener {
// Database
Vector<String> db = new Vector<String>();
// Main Menu Buttons:
JButton addStudent = new JButton("Add Student");
JButton deleteStudent = new JButton("Delete Button");
JButton deleteAll = new JButton("Delete All Students");
JButton printAll = new JButton("Print Database");
JTextArea welcome = new JTextArea("Welcome!");
// Add Student Menu:
JTextField student = new JTextField();
JButton submit = new JButton("Add Student");
// Print Students
JTextArea printDB = new JTextArea();
JButton returnMenu = new JButton("Return to Menu");
public Database() {
super("DatabaseGUI");
setSize(800, 600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(null);
setResizable(false);
welcome.setBackground(this.getForeground());
add(welcome);
welcome.setSize(60, 15);
welcome.setLocation(386, 300);
add(addStudent);
addStudent.setSize(150, 50);
addStudent.setLocation(25, 100);
add(deleteStudent);
deleteStudent.setSize(150, 50);
deleteStudent.setLocation(625, 100);
add(deleteAll);
deleteAll.setLocation(225, 100);
deleteAll.setSize(150, 50);
add(printAll);
printAll.setLocation(425, 100);
printAll.setSize(150, 50);
addStudent.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
welcome.setVisible(false);
addStudent.setVisible(false);
deleteStudent.setVisible(false);
deleteAll.setVisible(false);
printAll.setVisible(false);
add(student);
add(submit);
submit.setVisible(true);
submit.setSize(150, 30);
submit.setLocation(425, 250);
student.setVisible(true);
student.setSize(150, 30);
student.setLocation(275, 250);
submit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String newStudent = student.getText();
db.addElement(newStudent);
student.setText(null);
student.setVisible(false);
submit.setVisible(false);
welcome.setVisible(true);
addStudent.setVisible(true);
deleteStudent.setVisible(true);
deleteAll.setVisible(true);
printAll.setVisible(true);
}
});
}
});
printAll.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
welcome.setVisible(false);
addStudent.setVisible(false);
deleteStudent.setVisible(false);
deleteAll.setVisible(false);
printAll.setVisible(false);
StringBuffer dbb = new StringBuffer();
for (int i = 0; i < db.size(); i++) {
dbb.append(db.get(i) + '\n');
}
printDB.setText(dbb.toString());
add(printDB);
printDB.setSize(300, 400);
printDB.setEditable(false);
printDB.setLocation(100, 100);
printDB.setVisible(true);
add(returnMenu);
returnMenu.setVisible(true);
returnMenu.setSize(200, 30);
returnMenu.setLocation(500, 400);
returnMenu.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
returnMenu.setVisible(false);
printDB.setVisible(false);
welcome.setVisible(true);
addStudent.setVisible(true);
deleteStudent.setVisible(true);
deleteAll.setVisible(true);
printAll.setVisible(true);
}
});
}
});
setVisible(true);
}
public static void main(String[] args) {
Database student = new Database();
}
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
}

You're adding an ActionListener to the submit button repeatedly within the addStudent ActionListener, meaning as addStudent is pressed, more and more ActionListeners will be added to submit and this is not what you want.
Suggestions:
Add an ActionListener just once to your JButtons and not within other event listeners which may be called multiple times. Consider adding all ActionListeners within your class constructor.
Side recs:
Don't use absolute positioning and null layouts. While null layouts and setBounds() might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.
Learn how to use and then use CardLayout to allow you to cleanly and easily swap your views.
For example,
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
#SuppressWarnings("serial")
public class Database2 extends JPanel {
// constants for the cards
public static final String WELCOME = "welcome";
public static final String ADD_STUDENT = "add student";
public static final String DISPLAY_DATA = "display data";
private JTextArea displayTextArea = new JTextArea(15, 20);
private JTextField addStudentField = new JTextField(10);
private CardLayout cardLayout = new CardLayout();
private List<String> db = new ArrayList<>();
public Database2() {
// prepare JTextArea
displayTextArea.setWrapStyleWord(true);
displayTextArea.setLineWrap(true);
displayTextArea.setFocusable(false);
// set layout as CardLayout and add all JPanels with constants
setLayout(cardLayout);
add(createWelcomePanel(), WELCOME);
add(createAddStudentPanel(), ADD_STUDENT);
add(createDisplayDataPanel(), DISPLAY_DATA);
}
private JPanel createWelcomePanel() {
ShowStudentPanelAction showStudentAction = new ShowStudentPanelAction("Add Student");
DisplayDataAction displayDataAction = new DisplayDataAction("Display Data");
JButton addStudentButton = new JButton(showStudentAction);
JButton displayDataButton = new JButton(displayDataAction);
JPanel topPanel = new JPanel(new GridLayout(1, 0, 5, 0));
topPanel.add(addStudentButton);
topPanel.add(displayDataButton);
topPanel.add(new JButton(new ExitAction("Exit", KeyEvent.VK_X)));
JLabel welcomeLabel = new JLabel("Welcome", SwingConstants.CENTER);
// make JLabel text bigger
welcomeLabel.setFont(welcomeLabel.getFont().deriveFont(Font.BOLD, 42f));
// and give it a border 30 points wide
int ebGap = 30;
welcomeLabel.setBorder(BorderFactory.createEmptyBorder(ebGap, ebGap,
ebGap, ebGap));
JPanel welcomePanel = new JPanel(new BorderLayout());
ebGap = 4;
welcomePanel.setBorder(BorderFactory.createEmptyBorder(ebGap, ebGap, ebGap, ebGap));
welcomePanel.add(topPanel, BorderLayout.PAGE_START);
welcomePanel.add(welcomeLabel, BorderLayout.CENTER);
return welcomePanel;
}
private JPanel createAddStudentPanel() {
AddStudentAction addStudentAction = new AddStudentAction("Add Student");
addStudentField.setAction(addStudentAction);
JPanel addStudentPanel = new JPanel();
addStudentPanel.add(addStudentField);
addStudentPanel.add(new JButton(addStudentAction));
return addStudentPanel;
}
private JPanel createDisplayDataPanel() {
JPanel displayDataPanel = new JPanel();
JScrollPane scrollPane = new JScrollPane(displayTextArea);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
displayDataPanel.add(scrollPane);
displayDataPanel.add(new JButton(new ReturnToWelcomeAction("Return")));
return displayDataPanel;
}
private class ShowStudentPanelAction extends AbstractAction {
public ShowStudentPanelAction(String name) {
super(name);
int mnemonic = (int) name.charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
cardLayout.show(Database2.this, ADD_STUDENT);
addStudentField.requestFocusInWindow();
addStudentField.selectAll();
}
}
private class DisplayDataAction extends AbstractAction {
public DisplayDataAction(String name) {
super(name);
int mnemonic = (int) name.charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
StringBuilder sb = new StringBuilder();
for (String studentName : db) {
sb.append(studentName + "\n");
}
displayTextArea.setText(sb.toString());
cardLayout.show(Database2.this, DISPLAY_DATA);
}
}
private class AddStudentAction extends AbstractAction {
public AddStudentAction(String name) {
super(name);
int mnemonic = (int) name.charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
String studentText = addStudentField.getText();
db.add(studentText);
cardLayout.show(Database2.this, WELCOME);
}
}
private class ReturnToWelcomeAction extends AbstractAction {
public ReturnToWelcomeAction(String name) {
super(name);
int mnemonic = (int) name.charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
cardLayout.show(Database2.this, WELCOME);
}
}
private class ExitAction extends AbstractAction {
public ExitAction(String name, int mnemonic) {
super(name);
putValue(MNEMONIC_KEY, mnemonic);
}
#Override
public void actionPerformed(ActionEvent e) {
Window window = SwingUtilities.getWindowAncestor(Database2.this);
if (window != null) {
window.dispose();
}
}
}
private static void createAndShowGui() {
Database2 mainPanel = new Database2();
JFrame frame = new JFrame("Database2");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

Resize JOptionPane Dialog and lines in a dialogs

My program is supposed to have the basic code examples in java and to do that I need help to have the dialogues where I can write have the code preloaded but I can't add spaces in the dialogues and resize them. Please help!
Main Class:
public class JavaHelperTester{
public static void main(String[] args){
JavaWindow display = new JavaWindow();
JavaHelper j = new JavaHelper();
display.addPanel(j);
display.showFrame();
}
}
Method Class:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class JavaHelper extends JPanel implements ActionListener{
JButton print = new JButton("Print Statements");
JButton classes = new JButton("Classes");
JButton varibles = new JButton("Assiging variables");
JButton signs = new JButton("Sign meanings");
JButton typesv = new JButton("Different Types of variables");
JButton scanners = new JButton("Scanner");
JButton loops = new JButton("Loops");
JButton ifstatements = new JButton("If statements");
JButton graphics = new JButton("Graphics");
JButton objects = new JButton("Making an oject");
JButton importstatments = new JButton("Import Statements");
JButton integers = new JButton("Different types of integers");
JButton methods = new JButton("Scanner methods");
JButton math = new JButton("Math in java");
JButton creation = new JButton("Method creation");
JButton arrays = new JButton("Arrays");
JButton jframe = new JButton("JFrame");
JButton stringtokenizer = new JButton("String Tokenizer");
JButton extending = new JButton("Class extending");
JButton fileio = new JButton("File I.O.");
JButton quit = new JButton("Quit");
public JavaHelper(){
setPreferredSize(new Dimension(500,350));
setBackground(Color.gray);
this.add(print);
print.addActionListener(this);
this.add(classes);
classes.addActionListener(this);
this.add(varibles);
varibles.addActionListener(this);
this.add(signs);
signs.addActionListener(this);
this.add(typesv);
typesv.addActionListener(this);
this.add(scanners);
scanners.addActionListener(this);
this.add(loops);
loops.addActionListener(this);
this.add(ifstatements);
ifstatements.addActionListener(this);
this.add(graphics);
graphics.addActionListener(this);
this.add(objects);
objects.addActionListener(this);
this.add(importstatments);
importstatments.addActionListener(this);
this.add(integers);
integers.addActionListener(this);
this.add(methods);
methods.addActionListener(this);
this.add(math);
math.addActionListener(this);
this.add(creation);
creation.addActionListener(this);
this.add(arrays);
arrays.addActionListener(this);
this.add(jframe);
jframe.addActionListener(this);
this.add(stringtokenizer);
stringtokenizer.addActionListener(this);
this.add(fileio);
fileio.addActionListener(this);
this.add(quit);
quit.addActionListener(this);
}
public void paintComponent(Graphics g){
super.paintComponent(g);
}
public void actionPerformed(ActionEvent e){
if(e.getSource() == print){
JOptionPane.showMessageDialog (null, "System.out.println(); and System.out.print();", "Print Statements", JOptionPane.INFORMATION_MESSAGE);
}
if(e.getSource() == classes){
JOptionPane.showMessageDialog (null, "Main class : public class ClassNameTester{ // public static void main(String[] args){, Other Classes : public class ClassName", "Classes", JOptionPane.INFORMATION_MESSAGE);
}
if(e.getSource() == quit){
System.exit(0);
}
}
private void dialogSize(){
}
}
JavaWindow:
import java.awt.*;
import javax.swing.*;
public class JavaWindow extends JFrame{
private Container c;
public JavaWindow(){
super("Java Helper");
c = this.getContentPane();
}
public void addPanel(JPanel p){
c.add(p);
}
public void showFrame(){
this.pack();
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

I made changes to clean up the Java Helper GUI and to allow you to format the information on the JOptionPane dialogs.
Here's the Java Helper GUI.
And here's the Classes JOptionPane.
I modified your JavaHelperTester class to include a call to the SwingUtilities invokeLater method. This method puts the creation and use of your Swing components on the Event Dispatch thread (EDT). A Swing GUI must start with a call to the SwingUtilities invokeLater method.
I also formatted all of your code and resolved the imports.
package com.ggl.java.helper;
import javax.swing.SwingUtilities;
public class JavaHelperTester {
public static void main(String[] args) {
Runnable runnable = new Runnable() {
#Override
public void run() {
JavaWindow display = new JavaWindow();
JavaHelper j = new JavaHelper();
display.addPanel(j);
display.showFrame();
}
};
SwingUtilities.invokeLater(runnable);
}
}
Here's your JavaWindow class.
package com.ggl.java.helper;
import java.awt.Container;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class JavaWindow extends JFrame {
private static final long serialVersionUID = 6535974227396542181L;
private Container c;
public JavaWindow() {
super("Java Helper");
c = this.getContentPane();
}
public void addPanel(JPanel p) {
c.add(p);
}
public void showFrame() {
this.pack();
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
And here's your JavaHelper class. I made the changes to your action listener to allow you to define the text as an HTML string. You may only use HTML 3.2 commands.
I also changed your button panel to use the GridLayout. The grid layout makes your buttons look neater and makes it easier for the user to select a JButton.
package com.ggl.java.helper;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class JavaHelper extends JPanel implements ActionListener {
private static final long serialVersionUID = -3150356430465932424L;
JButton print = new JButton("Print Statements");
JButton classes = new JButton("Classes");
JButton varibles = new JButton("Assiging variables");
JButton signs = new JButton("Sign meanings");
JButton typesv = new JButton("Different Types of variables");
JButton scanners = new JButton("Scanner");
JButton loops = new JButton("Loops");
JButton ifstatements = new JButton("If statements");
JButton graphics = new JButton("Graphics");
JButton objects = new JButton("Making an oject");
JButton importstatments = new JButton("Import Statements");
JButton integers = new JButton("Different types of integers");
JButton methods = new JButton("Scanner methods");
JButton math = new JButton("Math in java");
JButton creation = new JButton("Method creation");
JButton arrays = new JButton("Arrays");
JButton jframe = new JButton("JFrame");
JButton stringtokenizer = new JButton("String Tokenizer");
JButton extending = new JButton("Class extending");
JButton fileio = new JButton("File I.O.");
JButton quit = new JButton("Quit");
public JavaHelper() {
this.setLayout(new GridLayout(0, 2));
setBackground(Color.gray);
this.add(print);
print.addActionListener(this);
this.add(classes);
classes.addActionListener(this);
this.add(varibles);
varibles.addActionListener(this);
this.add(signs);
signs.addActionListener(this);
this.add(typesv);
typesv.addActionListener(this);
this.add(scanners);
scanners.addActionListener(this);
this.add(loops);
loops.addActionListener(this);
this.add(ifstatements);
ifstatements.addActionListener(this);
this.add(graphics);
graphics.addActionListener(this);
this.add(objects);
objects.addActionListener(this);
this.add(importstatments);
importstatments.addActionListener(this);
this.add(integers);
integers.addActionListener(this);
this.add(methods);
methods.addActionListener(this);
this.add(math);
math.addActionListener(this);
this.add(creation);
creation.addActionListener(this);
this.add(arrays);
arrays.addActionListener(this);
this.add(jframe);
jframe.addActionListener(this);
this.add(stringtokenizer);
stringtokenizer.addActionListener(this);
this.add(fileio);
fileio.addActionListener(this);
this.add(quit);
quit.addActionListener(this);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == print) {
String title = ((JButton) e.getSource()).getText();
JLabel label = new JLabel(createPrintText());
JOptionPane.showMessageDialog(this, label, title,
JOptionPane.INFORMATION_MESSAGE);
}
if (e.getSource() == classes) {
String title = ((JButton) e.getSource()).getText();
JLabel label = new JLabel(createClassesText());
JOptionPane.showMessageDialog(this, label, title,
JOptionPane.INFORMATION_MESSAGE);
}
if (e.getSource() == quit) {
System.exit(0);
}
}
private String createPrintText() {
StringBuilder builder = new StringBuilder();
builder.append("<html><pre><code>");
builder.append("System.out.print()");
builder.append("<br>");
builder.append("System.out.println()");
builder.append("</code></pre>");
return builder.toString();
}
private String createClassesText() {
StringBuilder builder = new StringBuilder();
builder.append("<html><pre><code>");
builder.append("Main class : public class ClassNameTester { <br>");
builder.append(" public static void main(String[] args) { <br>");
builder.append(" } <br>");
builder.append("} <br><br>");
builder.append("Other Classes : public class ClassName { <br>");
builder.append("}");
builder.append("</code></pre>");
return builder.toString();
}
}

Get the selected component from a JPanel

I am dynamically adding items to my JPanel through an ArrayList<Items>. Basically the items object looks like that:
public class Item {
private JComponent component;
private String functionality;
public Item(JComponent component, String functionality) {
super();
this.component = component;
this.functionality = functionality;
}
public JComponent getComponent() {
return component;
}
public void setComponent(JComponent component) {
this.component = component;
}
public String getFunctionality() {
return functionality;
}
public void setFunctionality(String functionality) {
this.functionality = functionality;
}
}
Here I am adding my buttons dynamically: (try the example out if you want)
public class minimumExample extends JFrame {
private JButton addItem;
private JComboBox itemBox;
private String[] itemSelect = { "test1", "test2" };
private JPanel addUpperPane;
private JPanel addLowerPane;
private ArrayList<Item> displayedItems = new ArrayList<Item>();
private JButton upButton;
private JButton downButton;
private JButton deleteButton;
public void createControlPane() {
addUpperPane = new JPanel();
addLowerPane = new JPanel(new GridLayout(0, 1));
addItem = new JButton("Add item");
upButton = new JButton("Up");
downButton = new JButton("Down");
deleteButton = new JButton("Delete");
itemBox = new JComboBox(itemSelect);
addItem.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if(itemBox.getSelectedItem().toString().equals("test1")) {
displayedItems.add(new Item( new ButtonComp().butt(), "test1"));
validate();
repaint();
}
if(itemBox.getSelectedItem().toString().equals("test2")) {
displayedItems.add(new Item( new LabelComp().label(), "test2"));
validate();
repaint();
}
for (int i = 0; i < displayedItems.size(); i++) {
addLowerPane.add(displayedItems.get(i).getComponent());
validate();
repaint();
}
}
});
addUpperPane.add(itemBox, BorderLayout.EAST);
addUpperPane.add(addItem, BorderLayout.WEST);
addUpperPane.add(new JLabel(" | "), BorderLayout.WEST);
addUpperPane.add(upButton, BorderLayout.WEST);
addUpperPane.add(downButton, BorderLayout.WEST);
addUpperPane.add(deleteButton, BorderLayout.WEST);
addUpperPane.add(new JSeparator(JSeparator.HORIZONTAL));
//put everything together
add(addUpperPane, BorderLayout.NORTH);
add(addLowerPane, BorderLayout.SOUTH);
repaint();
}
private void makeLayout() {
setTitle("Test App");
setLayout(new BorderLayout());
setPreferredSize(new Dimension(1000, 500));
createControlPane();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setVisible(true);
}
/**
* starts the GUI
*/
public void start() {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
makeLayout();
}
});
}
public static void main(String[] args) throws IOException {
minimumExample ex = new minimumExample();
ex.start();
}
public class ButtonComp extends Component {
public JPanel butt() {
JPanel panel = new JPanel();
JButton button = new JButton("Test1");
JCheckBox check = new JCheckBox();
panel.add(button);
panel.add(check);
return panel;
}
}
public class LabelComp extends Component {
public JPanel label() {
JPanel panel = new JPanel();
JLabel label = new JLabel("Test2");
JCheckBox check = new JCheckBox();
panel.add(label);
panel.add(check);
return panel;
}
}
}
The program basically looks like that:
My problem is that the buttons Up, Down and Delete do not work, because I do not know how to get the selected element from the pane to delete it from the list where all components are in. Any recommendations on how to make this work?
I really appreciate your answer!
UPDATE
I changed my code your specifications #cghislai but it does not work. Try it out yourself:
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSeparator;
public class minimumExample extends JFrame {
private JButton addItem;
private JComboBox itemBox;
private String[] itemSelect = { "test1", "test2" };
private JPanel addUpperPane;
private JPanel addLowerPane;
private List<CheckableItem> displayedItems = new ArrayList<CheckableItem>();
private JButton upButton;
private JButton downButton;
private JButton deleteButton;
public void createControlPane() {
addUpperPane = new JPanel();
addLowerPane = new JPanel(new GridLayout(0, 1));
addItem = new JButton("Add item");
upButton = new JButton("Up");
downButton = new JButton("Down");
deleteButton = new JButton("Delete");
itemBox = new JComboBox(itemSelect);
addItem.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if(itemBox.getSelectedItem().toString().equals("test1")) {
ButtonComp butt = new ButtonComp();
butt.init();
displayedItems.add(butt);
validate();
repaint();
}
if(itemBox.getSelectedItem().toString().equals("test2")) {
// displayedItems.add(new CopyOfItem( new LabelComp(), "test2"));
validate();
repaint();
}
for (int i = 0; i < displayedItems.size(); i++) {
addLowerPane.add(displayedItems.get(i).getComponent());
validate();
repaint();
}
}
});
deleteButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
Iterator<CheckableItem> it = displayedItems.iterator();
while (it.hasNext()) {
CheckableItem next = it.next();
if (next.isSelected()) {
addLowerPane.remove(next.getComponent());
it.remove();
continue;
}
}
}
});
addUpperPane.add(itemBox, BorderLayout.EAST);
addUpperPane.add(addItem, BorderLayout.WEST);
addUpperPane.add(new JLabel(" | "), BorderLayout.WEST);
addUpperPane.add(upButton, BorderLayout.WEST);
addUpperPane.add(downButton, BorderLayout.WEST);
addUpperPane.add(deleteButton, BorderLayout.WEST);
addUpperPane.add(new JSeparator(JSeparator.HORIZONTAL));
//put everything together
add(addUpperPane, BorderLayout.NORTH);
add(addLowerPane, BorderLayout.SOUTH);
repaint();
}
private void makeLayout() {
setTitle("Test App");
setLayout(new BorderLayout());
setPreferredSize(new Dimension(1000, 500));
createControlPane();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setVisible(true);
}
/**
* starts the GUI
*/
public void start() {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
makeLayout();
}
});
}
public static void main(String[] args) throws IOException {
minimumExample ex = new minimumExample();
ex.start();
}
public abstract class CheckableItem {
protected JCheckBox check;
public boolean isSelected() {
return check.isSelected();
}
public abstract Component getComponent();
}
public class ButtonComp extends CheckableItem {
JPanel panel = new JPanel();
public void init() {
JButton button = new JButton("Test1");
check = new JCheckBox();
panel.add(button);
panel.add(check);
}
#Override
public Component getComponent() {
return panel;
}
}
public class LabelComp extends JPanel {
public void label() {
// JPanel panel = new JPanel();
JLabel label = new JLabel("Test2");
JCheckBox check = new JCheckBox();
add(label);
add(check);
}
}
}

You need to traverse all your items, check if the item checkbox is selected, if this is the case, remove your item from the panel. I would make an abstract CheckableItem class with a getter to the JCheckbox and the Component. Then, for each of you item, if the checkbox is selected, remove the component from the parent.
public abstract class CheckableItem {
protected JCheckbox checkbox;
public boolean isSelected() {
return checkbox.isSelected();
}
public abstract Component getComponent();
}
public class ButtonComp extends CheckableItem {
private Panel panel;
public void init() {
checkbox = new JCheckbox;
panel = new JPanel();
panel.add(new JButton());
panel.add(checkbox);
}
public Component getComponent() {
return panel;
}
}
Then to keep track of your items:
private List<CheckableItem> items = new ArrayList<>();
// ...
ButtonComp comp = new ButtonComp();
comp.init();
items.add(comp);
Then to remove all checked:
Iterator<CheckbleItem> it = items.iterator();
while (it.hasNext()) {
CheckableItem next = it.next();
if (next.isSelected()) {
mainPanel.remove(next.getComponent());
it.remove();
continue;
}
}

Why don't you just have your ButtomComp and LabelComp extend from JPanel? This would solve a lot of your problems I think. For example :
public class ButtonComp extends JPanel {
JButton button;
JCheckBox check = new JCheckBox();
public ButtonComp() {
button = new JButton("Test1");
this.add(button);
this.add(check);
}
}
Then all you would need to do is iterate over your items and look at the checkbox in the components :
for (int i = 0; i < displayedItems.size(); i++) {
if (displayedItems.get(i).check.isSelected()) {
displayedItems.remove(i);
}
}
Note: haven't tested this code. But you should get the idea.