Develop Reference

Trying to start program on JButton press

I am trying to make a simple program that will ask the user a question and then compare their answer with a stored correct answer. The problem seems to be that the main loop of the program is not running when I click the Ready JButton.
I tried changing the main method to another non-default name and adding a call to it in the actionPerformed() method, and it did seem to execute the loop at least once, but then led to not being able to close the applet without the task manager once I clicked the button. I don't know if that means it hit an endless loop or what.
I'm sure there is more to fix in this code besides this issue, but I cannot make any progress on that without clearing this up first. If there is a problem with the way I went about creating the GUI please let me know. I tried to base it off of an assignment I did that worked just fine, so I don't know whether or not that is the issue.
Any help provided is appreciated.
Here is the code:
import java.awt.*;
import javax.swing.*;
public class Langarden_App extends JApplet{
private int width = 800, height = 600;
private LangardenPanel langPanel;
public void init(){
langPanel = new LangardenPanel();
getContentPane().add(langPanel);
setSize(width, height);
}
}
And the class with the logic
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import java.util.*;
public class LangardenPanel extends JPanel{
private static JButton submit;
private static JButton ready = new JButton("Ready");
private static JLabel instruct;
private JTextField input = new JTextField(100);
private static String inString;
private static ArrayList<String> questions;
private static ArrayList<String> answers;
private static Random rand = new Random();
public LangardenPanel(){
questions = new ArrayList<String> (Arrays.asList("¿Qué es la palabra para 'inveirno' en ingles?", "¿Qué es la forma de 'yo' del verbo 'venir'?"));
answers = new ArrayList<String> (Arrays.asList("winter", "voy"));
instruct = new JLabel("Welcome to Langarden! Press Submit to begin. You have one minute and three attempts for each question.");
submit = new JButton("Submit");
this.setLayout(new BorderLayout());
add(BorderLayout.SOUTH, ready);
add(BorderLayout.NORTH, instruct);
add(BorderLayout.CENTER, input);
ready.addActionListener(new SubListener());
}
public static void main(String[] args){
try{
TimeUnit.SECONDS.sleep(3);
} catch (InterruptedException e){
}
System.out.println("Setting text");
instruct.setText("Alright! Let's Go!");
try{
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e){
}
do{
System.out.println("Running loop");
int qnum = rand.nextInt(questions.size());
instruct.setText(questions.get(qnum));
for (int i=0; i<3; i++){
try {
TimeUnit.SECONDS.sleep(60);
} catch (InterruptedException e) {
}
if(checkAnswer(qnum, inString)){
instruct.setText("Correct!");
break;
} else {
instruct.setText("Try again...\n" + questions.get(qnum));
}
}
instruct.setText("The correct answer was " + answers.get(qnum));
try{
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e){
}
questions.remove(qnum);
answers.remove(qnum);
instruct.setText("Would you like to continue? Enter No and click Submit to exit.");
} while (!inString.equalsIgnoreCase("No") && questions.size() != 0);
instruct.setText("Congratulations, you have completed this module!");
}
private static boolean checkAnswer(int qnum, String inString) {
if (answers.get(qnum).equalsIgnoreCase(inString))
return true;
return false;
}
private class SubListener implements ActionListener{
public void actionPerformed(ActionEvent e){
System.out.println("Button Pressed!");
if(e.getSource() == ready){
add(BorderLayout.SOUTH, submit);
submit.addActionListener(new SubListener());
} else {
inString = input.getText();
}
}
}
}

Get rid of the main method. If this is running as an applet, then the program has no business having a main method.
Make all fields non-static. Yes all.
Get rid of the while-true loop. If this runs, this will squelch your Swing event thread rendering your GUI frozen and helpless. Use a Swing Timer instead as a "pseudo" loop. Please check out the Swing Timer Tutorial for more on this.
Any time you add a component to a container, you should call revalidate() and repaint() on that same container so that the container's layout managers can layout the new component, and so that the OS can repaint over any "dirty" pixels.
Rather than add a new JButton as you're doing, much better is to swap components using a CardLayout. The tutorial can be found here: CardLayout tutorial.

JTextArea.append not displaying

I'm trying to write the contents of an array to a JTextArea. I've tried everything I can think of, and I can't understand what isn't working here. I've stripped the unnecessary stuff out of my code, here's the two relevant classfiles:
Main class:
package irclogtest;
public class BriBotMain {
public static void main(String args[]) throws Exception {
boolean startup = true;
//frame test launch
BriDisplayGUI data = new BriDisplayGUI(startup);
data.irclog.append("BriBot Startup Successful!" + "\n");
//example access through function when startup is false (only in main class for sample code to demonstrate issue)
try {
BriDisplayGUI data2 = new BriDisplayGUI(false); //tells us which class we're accessing
String[] textForGUI = new String[2]; //tells us the array has 2 lines
textForGUI[0] = "this is the first line"; //set the first line of the array to this text
textForGUI[1] = "this is the second";
data2.arrayToDisplay(textForGUI); //appends contents of array to text window
}
catch(Exception e) {
System.out.println(e);
}
}
}
GUI display class:
package irclogtest;
import java.awt.event.*;
import java.io.IOException;
import javax.swing.*;
public class BriDisplayGUI extends JFrame implements ActionListener {
private static final long serialVersionUID = -7811223081379421773L;
String file_name = "C:/Bribot/logfile.txt";
//these lines create the objects we use
JFrame frame = new JFrame();
JPanel pane = new JPanel();
JButton pressme = new JButton("Click here");
JButton pressme2 = new JButton("Also here");
JTextArea irclog = new JTextArea( 20, 70);
JScrollPane scrollirc = new JScrollPane(irclog);
public BriDisplayGUI(boolean startup) { //startup function, opens and sets up the window
if(startup == true){
frame.setTitle("Bribot Test Frame"); frame.setBounds(100,100,840,420); //sets title of window, sets position and size of window
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //tells program to end on window close
frame.add(pane); //adds the main display pane to the window
//panel customization goes here
pressme.addActionListener(this);
pane.add(pressme);
pressme2.addActionListener(this);
pane.add(pressme2);
pressme.requestFocusInWindow();
irclog.setEditable(false);
scrollirc.setVerticalScrollBarPolicy( JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
pane.add(scrollirc);
irclog.setLineWrap(true);
irclog.setWrapStyleWord(true);
//pane.add(inputthing);
frame.setVisible(true);
} else {
System.out.println("Display Class Called");
}
}
public void arrayToDisplay(String[] text) throws IOException {
int i;
for ( i=0; i < text.length; i++) {
irclog.append( text[i] + "\n");
System.out.println( i + ": " + text[i]);
}
}
public void singleToDisplay(String text) throws IOException {
irclog.append(text + "\n");
System.out.println(text);
}
//basic event handler
public void actionPerformed(ActionEvent event) {
Object source = event.getSource();
if (source == pressme) {
} else if(source == pressme2) {
}
}
}
The first append works fine, but the second doesn't, and I can't figure out why (although the for loop does, as the contents of the array get written to console). I've searched quite a bit and nothing I've tried works. Can anyone point out the inevitable obvious oversight here? I'm the definition of a novice, so any advice is appreciated.
Thanks!

The default constructor doesn't do anything, meaning it doesn't construct any kind of UI or display, what would be, an empty frame.
You seem to be thinking the text will appear in data when you are appending it to data1
Try calling this(false) within the default constructor
A better solution would be to construct the core UI from the default constructor and from the "startup" constructor call this() and then modify the UI in what ever way this constructor needs

It seems like you write a new program. Why do you use Swing? Did you take a look at JavaFX?
I am not sure if that is going to fix your problem but you could try a foreach
for(String s : text){
irclog.append(s+"\n");
}

Multiple JLabel doesn't print on screen

I want to print multiple label according to the number(no string allowed) you wrote in a text field first. I want it to be dynamical. I want it to change every time you type something in the text field.
So far it can read if it's a number or a string and throw exception if the text doesn't match the requirement.
I've try multiple thing to print multiple Jlabel on the screen, but it didn't work so far.
Here's the code: can you help me?
The main window class
public class MainWindow extends JFrame {
private MainPanel mp = new MainPanel();
public MainWindow()
{
this.setVisible(true);
this.setTitle("Calculateur sur 100");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(200, 400);
this.setLocationRelativeTo(null);
this.setContentPane(mp);
}}
The mainPanel class
public class MainPanel extends JPanel implements ActionListener, MouseListener, KeyListener {
private JTextField tI = new JTextField("Pourcentage");
private JOptionPane jop3 = new JOptionPane();
public MainPanel()
{
this.add(tI);
tI.addKeyListener(this);
tI.addMouseListener(this);
}
//Mathematic calculation
private double onHundred(int tot, int now)
{
return (tot / 100) * now;
}
public void keyReleased(KeyEvent e)
{
boolean ok = true;
try
{
int numbs = Integer.parseInt(tI.getText());
}
catch(Exception s)
{
tI.setText("");
jop3.showMessageDialog(null, "Veuillez entrer seulement des chiffres", "Erreur", JOptionPane.ERROR_MESSAGE);
ok = false;
}
if(ok)
{
System.out.print("Supposed to print");
JLabel[] label = new JLabel[Integer.parseInt(tI.getText())];
for(int i = Integer.parseInt(tI.getText()); i <= 0; i--)
{
label[i] = new JLabel(i + " = " + Math.ceil(onHundred(Integer.parseInt(tI.getText()), i)));
label[i].setVisible(true);
this.add(label[i]);
}
}
}

You MainWindow class should look something like this:
public class MainWindow extends JFrame {
private MainPanel mp = new MainPanel();
public static void main(String[] args) {
new MainWindow();
}
public MainWindow() {
setContentPane(mp);
setTitle("Calculateur sur 100");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setLocationRelativeTo(null);
setVisible(true);
}
}
Note the order: setContentPane then pack then setVisible. pack replaces setSize as it determines the preferred size of the window based on its components.
I modified your MainPanel class:
public class MainPanel extends JPanel {
private JTextField tI = new JTextField("Pourcentage");
JPanel labelPanel = new JPanel();
public MainPanel() {
setLayout(new BorderLayout());
tI.getDocument().addDocumentListener(new MyDocumentListener());
add(tI, BorderLayout.PAGE_START);
add(labelPanel);
}
private int check() {
int numL;
try {
numL = Integer.parseInt(tI.getText());
} catch (NumberFormatException exc) {
return 0;
}
return numL > 100? 100 : numL;
}
private void update(int numL) {
labelPanel.removeAll();
for (int i = 0; i < numL; i++)
labelPanel.add(new JLabel(String.valueOf(i+1)));
JFrame mainWindow = ((JFrame) SwingUtilities.getWindowAncestor(this));
mainWindow.pack();
mainWindow.repaint();
}
class MyDocumentListener implements DocumentListener {
#Override
public void insertUpdate(DocumentEvent e) {
update(check());
}
#Override
public void removeUpdate(DocumentEvent e) {
update(check());
}
#Override
public void changedUpdate(DocumentEvent e) {
}
}
}
Explanation:
The main panel has the text field separately from another panel which updates dynamically to contain the labels.
The text field uses a DocumentListener instead of a KeyListener to listen to changes in its contents. This is the correct approach for many reasons I will not get into here unless really necessary.
Whenever the text changes, a check method verifies that the input is a number. If it's not it returns 0. If it's more than 100 it returns 100. You can change this behavior as you need.
The value from check is passed to update which clears all the previous labels and reconstructs them. (You can do a bit of optimization here if you want by keeping labels in memory but not displaying them. If the cap is 100 as in my example this won't be noticeable.). The main frame then recalculates the space it needs for all the labels and then repaints.
The labels appear next to each other because the default layout for JPanel is FlowLayout. You can change this as needed.

First - you have Integer.parseInt(tI.getText()) a number of times within the same keyReleased function. When you have done the first check to assign it to int numbs, then use numbs from then on, instead of referring back to tI.getText(). Theoretically the user input can change while you are processing your array, which will cause runtime exceptions or undesired results. Hint - declare numbs directly under ok.
Second - after you add controls programmatically, you need to invalidate the control on to which you are adding them, ie your MainPanel. The invalidate directive tells the control that it is not drawn correctly and needs to be repainted (do this at the completion of your loop). Look through the documentation for JPanel for invalidate and paint.

JFrame.setVisible(true) keeps iterating it's parent method until a stackOverflowError occurs

I've got a JFrame subclass which waits for a specific console input before displaying a JFrame and its contained widgets using the setVisible(true) method. The widgets (which are a subclass of JPanels) are added to the parent JFrame from a LinkedList using an iterator, and are added to the LinkedList via another method in the class.
When I run the program, it keeps repeating the method which contains this.setVisible(true), and doesn't display anything. Any help would be greatly appreciated. I've pasted the code below.
public class GUI extends JFrame{
class KPanel extends JPanel{ //virtual class for Panels that displayed variable name in titled border
public KPanel(String varName){
TitledBorder varTitle = new TitledBorder(varName +":");
this.setBorder(varTitle);
}
}
private LinkedList<KPanel> buffer; //list containing components to be added to GUI
public GUI(String title){
setTitle(title);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(300,300);
buffer = new LinkedList<KPanel>(); //initializes linkedlist buffer
}
public void addBox(String var, String val){
//creates a panel containing a string, adds it to the buffer
KPanel temp = new KPanel(var);
JLabel valLabel = new JLabel(val);
temp.add(valLabel);
buffer.add(temp);
}
public void show(){
int i=0;
int wid_height;
int x = 0;
if ((x = buffer.size()) != 0)
wid_height = this.getHeight()/x; //calculates widget heights for even distribution along frame
else{
System.out.println("No variables set!");
return;
}
System.out.println("buffer: " + buffer.size() + "\nheights: " + wid_height);
Iterator<KPanel> iter = buffer.iterator();
KPanel temp = new KPanel("");
while(iter.hasNext()){
temp = iter.next();
temp.setSize(this.getWidth(), wid_height);
temp.setLocation(0, wid_height*i);
this.add(temp);
i++;
}
this.setVisible(true);
return;
}
}

Your show() method is overriding an existing method in JFrame. Use a different name, or, better yet, don't extend JFrame unless you really need to change how a frame behaves.

The problem is that your show() method is overriding the show() method in JFrame. What leads to the StackOverflowError is that it's calling setVisible(true). This method is inherited from Component, and it is simple. Here's the code:
public void setVisible(boolean b) {
show(b);
}
and show(b) calls show():
public void show(boolean b) {
if (b) {
show();
} else {
hide();
}
}
So, your show calls setVisible, which calls your show, with nothing to break the cycle. I would use a different name for your show method to prevent this infinite loop.

Simple memory game with replay button

I want to build a simple memory game. I want to put a replay button, which is play again the memory game.
I have built a class named MemoryGame and a main class.
Here is the part of the ButtonListener code.
public void actionPerformed(ActionEvent e) {
if (exitButton == e.getSource()) {
System.exit(0);
}
else if (replayButton == e.getSource()) {
//How can I declare it?
}
}
If I declare the replay button as :
new MemoryGame();
It's work fine, but it pops up another windows.
I want to clear the current display and return to the beginning, without a new windows. How can I do that?
EDIT :
I think I need to rewrite the code of my program, because my program does not have the init() method as suggested which is the initial state of the program.
My Java knowledge is very limited and usually I create less method and dump most into a method.
I will try to redo my program.
Thanks for the suggestions.

Show us what is inside the MemoryGame how you create its initial state. Effectively what folks are suggesting here is for you is to have an initial method which will set-up the game state which the MemeoryGame constructor will call. Then on replay-button of the game you call this method.
Something along these lines:
void init(){
this.x = 10;
this.y = 10;
}
public MemoryGame(){
init();
}
public void actionPerformed(ActionEvent e) {
if (exitButton == e.getSource()) {
System.exit(0);
}
else if (replayButton == e.getSource()) {
init();
}
}

one way you can do it although it might be dirty, is to grab your MemoryGame constructor, and put the stuff inside it inside another method, and call that method in your constructor and inside the button event.
as an example i have made the following class and it resets itself with the use of the previous technique:
public class App extends JFrame{
public static void main(String[] args){
new App();
}
public App(){
init();
}
private JButton changeColorButton;
private JButton resetAppButton;
private JPanel panel;
private void init() {
changeColorButton=null;
resetAppButton=null;
panel=null;
this.setSize(200,400);
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel = new JPanel();
panel.setBackground(Color.white);
panel.setPreferredSize(new Dimension(200,400));
changeColorButton = new JButton("Change");
changeColorButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
panel.setBackground(Color.black);
panel.repaint();
}
});
changeColorButton.setPreferredSize(new Dimension(100,100));
resetAppButton = new JButton("Reset");
resetAppButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
init();
}
});
resetAppButton.setPreferredSize(new Dimension(100,100));
panel.add(changeColorButton);
panel.add(resetAppButton);
this.add(panel);
this.validate();
}
}
what this app does is it has two buttons. one changes the color and the other resets the app itself.

You should think about re-factoring your code so that the MemoryGame class does not create the GUI, then you wont be recreating it whenever you initialise a new Game.
It's a good idea to keep program logic separate to UI code.

What you could do is you could call dispose() on your JFrame. This will get rid of it and go to your title screen like this:
Here's the button code
public void actionPerformed(ActionEvent event)
{
if (closeButton = event.getSource())
{
System.exit(0);
}
if (playAgainButton = event.getSource())
{
Game.frame.dispose(); // Your class name, then the JFrame variable and call dispose
}
}
This will work but you may have a few problems reseting your program. If so then create a reset method where you can reset all your variables and call when playAgainButton is clicked. For example:
public void reset()
{
// Right here you'd reset all your variables
// Perhaps you have a gameOver variable to see if it's game over or not reset it
gameOver = false;
}