Develop Reference

Return value from custom JDialog

I see this has been asked multiple times and apologize in advance if I'm just missing something simple...
I've created a custom JDialog with the examples provided in the Java docs here and from a similar question asked here.
My main application is a JFrame that contains a JPanel with an array of JButtons that display various employee names. I've added a custom ActionListener to each JButton that calls the mentioned JDialog:
//inner class for handling user button pushes
private class UserButtonHandler implements ActionListener
{
//handle button event
#Override
public void actionPerformed(ActionEvent event)
{
statusDialog = new ChangeDialog(statusWindow);
statusDialog.setVisible(true);
statusDialog.setLocationRelativeTo(null);
//set title for dialog box
String dialogTitle = "Status change for " + event.getActionCommand();
statusDialog.setTitle(dialogTitle);
statNum = ((ChangeDialog) statusDialog).getInputStatus();
System.out.println("Current num is: " + statNum);
//statNum = statusDialog.getInputStatus();
}
}
Here is the class for the custom JDialog (ChangeDialog):
class ChangeDialog extends JDialog implements ActionListener, PropertyChangeListener
{
//create panel where users can modify their status
private final ChangePanel empStatusChangePanel;
//text of buttons in dialog
private String btnString1 = "OK";
private String btnString2 = "Cancel";
private String btnString3 = "Clear Time-Off";
private JOptionPane statusPane;
//determines message to return for user input
private int inputStatus;
public ChangeDialog(JFrame statusFrame)
{
empStatusChangePanel = new ChangePanel();
//create an array specifying the number
//of dialog buttons and their text
Object[] options = {btnString1, btnString2, btnString3};
//create the JOptionPane
statusPane = new JOptionPane(empStatusChangePanel,
JOptionPane.PLAIN_MESSAGE,
JOptionPane.YES_NO_CANCEL_OPTION,
null,
options,
options[0]);
//set contents of dialog
setContentPane(statusPane);
//handle window closing
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
//register event handler for changes in status pane state
statusPane.addPropertyChangeListener(this);
pack();
}
#Override
public void actionPerformed(ActionEvent e)
{
statusPane.setValue(btnString1);
}
#Override
public void propertyChange(PropertyChangeEvent e)
{
String prop = e.getPropertyName();
if (isVisible()
&& (e.getSource() == statusPane)
&& (JOptionPane.VALUE_PROPERTY.equals(prop)))
{
Object value = statusPane.getValue();
if (value == JOptionPane.UNINITIALIZED_VALUE)
{
//ignore reset
return;
}
//Reset the JOptionPane's value. If this is not done,
//then if the user presses the same button next time,
//no property change event will be fired
statusPane.setValue(JOptionPane.UNINITIALIZED_VALUE);
if(value.equals(btnString1)) //user clicked "OK"
{
//validation of user input
inputStatus = empStatusChangePanel.validateUserInput();
//handle validation results
switch (inputStatus)
{
case 0: //user input is good
JOptionPane.showMessageDialog(this, "Good input given");
dispose();
break;
case 1: //one (or both) of the date pickers are empty
JOptionPane.showMessageDialog(this, "PTO pickers can't be empty.",
"ERROR", JOptionPane.ERROR_MESSAGE);
break;
case 2:
case 3: //bad date range (start before end or visa-versa)
JOptionPane.showMessageDialog(this, "Bad date range.",
"ERROR", JOptionPane.ERROR_MESSAGE);
break;
case 99: //dates are equal
JOptionPane.showMessageDialog(this, "Single-day PTO");
dispose();
break;
}
}
else if(value.equals(btnString3)) //user clicked "Clear Input"
{
JOptionPane.showMessageDialog(this, "User clicked 'clear input");
//more processing should be done here
empStatusChangePanel.recycle();
//dispose();
}
else //user clicked "Cancel" or closed dialog
{
JOptionPane.showMessageDialog(this, "User closed status window");
dispose();
}
}
}
//returns value from user validation
public int getInputStatus()
{
return inputStatus;
}
}
I need to access the method getInputStatus from the custom dialog but each attempt I've tried comes back stating that:
getInputStatus is undefined for the type JDialog
I have looked at several other similar posts but feel that I'm missing something fundamental in trying to solve this problem (or I've been looking at the code too long).
Another thing that has me stumped (and why I left it in the first snippet) is that if I cast the method to the type ChangeDialog
statNum = ((ChangeDialog) statusDialog).getInputStatus();
It suddenly has access (this was a suggestion from Eclipse and doesn't make sense to me). Thanks again for any and all help.

That is how inheritance works, you have defined statusDialog as a JDialog reference and JDialog doesn't have a getInputStatus method.
To access the members of ChangeDialog, you have to define statusDialog as variable of ChangeDialog.

JLabel.setText() is only setting text for last element in a loop

First of all, apologies for how long winded this is.
I'm trying to make a simple roulette game that allows a user to add players, place bets for these players, and spin the roulette wheel, which is represented as a simple JLabel that updates it's text with each number it passes.
However, I've run into a bug that I'm having a lot of trouble with: the JLabel only updates the text for the last element in my loop.
Basically, my solution works like this:
When a user presses a button labelled "Spin" (given that users have been added to the game), I call a method from a class called SpinWheelService, which is an Observable singleton which in turn calls the notifyObservers() method:
public void actionPerformed(ActionEvent e) {
String cmd = e.getActionCommand();
String description = null;
if (ADD_PLAYER.equals(cmd)) {
addDialog();
} else if (PLACE_BET.equals(cmd)) {
betDialog();
} else if (SPIN.equals(cmd)) {
SpinWheelService.sws.setSpinWheelService();
} else if (DISPLAY.equals(cmd)) {
System.out.println("Display selected!");
}
}
Here is my SpinWheelService class:
package model;
import java.util.*;
public class SpinWheelService extends Observable {
public static SpinWheelService sws = new SpinWheelService();
public void setSpinWheelService() {
setChanged();
notifyObservers();
}
}
The only listener registered for SpinWheelService is this class, where GameEngine is my game engine that handles internal game logic, WheelCallbackImpl is a class that updates the View:
class SpinWheelObserver implements Observer {
GameEngine gameEngine;
ArrayList<SimplePlayer> players;
WheelCallbackImpl wheelCall;
int n;
public SpinWheelObserver(GameEngine engine, WheelCallbackImpl wheel, ArrayList<SimplePlayer> playerList) {
players = playerList;
gameEngine = engine;
wheelCall = wheel;
}
public void update(Observable sender, Object arg) {
// check if any players are present
if (players.size() == 0) {
System.out.println("Empty player array!");
return;
}
do {
gameEngine.spin(40, 1, 300, 30, wheelCall);
n = wheelCall.playback();
} while (n== 0);
}
}
The main point of note here is my gameEngine.spin() method, which is this:
public class GameEngineImpl implements GameEngine {
private List<Player> playerList = new ArrayList<Player>();
// method handles the slowing down of the roulette wheel, printing numbers at an incremental delay
public void delay(int millis) {
try {
Thread.sleep(millis);
} catch (InterruptedException e) {
System.out.println("Sleep method failed.");
}
}
public void spin(int wheelSize, int initialDelay, int finalDelay,
int delayIncrement, WheelCallback callback) {
Random rand = new Random();
int curNo = rand.nextInt(wheelSize) + 1;
int finalNo = 0;
assert (curNo >= 1);
// while loop handles how long the wheel will spin for
while (initialDelay <= finalDelay) {
delay(initialDelay);
initialDelay += delayIncrement;
// handles rotating nature of the wheel, ensures that if it reaches wheel size, reverts to 1
if (curNo > wheelSize) {
curNo = 1;
callback.nextNumber(curNo, this);
curNo++;
}
assert (curNo <= wheelSize);
callback.nextNumber(curNo, this);
curNo++;
finalNo = curNo - 1;
}
calculateResult(finalNo);
callback.result(finalNo, this);
}
The method callback.nextNumber(curNo, this):
public void nextNumber(int nextNumber, GameEngine engine) {
String strNo = Integer.toString(nextNumber);
assert (nextNumber >= 1);
System.out.println(nextNumber);
wcWheel.setCounter(strNo);
}
Where in, wcWheel is my singleton instance of my View, which contains the method setCounter():
public void setCounter(String value) {
label.setText(value);
}
Sorry for how convoluted my explanation is, but basically what it boils down to is that setCounter() is definitely being called, but seems to only call the setText() method on the final number. So what I'm left with is an empty label that doesn't present the number until the entire roulette has finished spinning.
I've determined that setCounter() runs on the event dispatch thread, and I suspect this is a concurrency issue but I have no idea how to correct it.
I've tried to include all relevant code, but if I'm missing anything, please mention it and I'll post it up as well.
I'm at my wits end here, so if anyone would be kind of enough to help, that would be so great.
Thank you!

Your while loop along Thread.sleep() will block and repainting or changing of the UI until the loop is finished.
Instead you'll want to implement a javax.swing.Timer for the delay, and keep a counter for the number of ticks, to stop it. You can see more at How to Use Swing Timers
The basic construct is
Timer ( int delayInMillis, ActionListener listener )
where delayInMillis is the millisecond delay between firing of an ActionEvent. This event is listened for by the listener. So every time the event is fired, the actionPerfomed of the listener is called. So you might do something like this:
Timer timer = new Timer(delay, new ActionListener()(
#Override
public void actionPerformed(ActionEvent e) {
if (count == 0) {
((Timer)e.getSource()).stop();
} else {
//make a change to your label
count--;
}
}
));
You can call timer.start() to start the timer. Every delay milliseconds, the label will change to what you need it to, until some arbitrary count reaches 0, then timer stops. You can then set the count variable to whatever you need to, if you want to to be random, say depending on how hard the wheel is spun :D

I think you didn't post all the relevant code that is required to know exactly the problem.
But most likely the problem is due to you run your loop and JLabel.setText() in the EDT (Event Dispatching Thread).
Note that updating the UI components (e.g. the text of a JLabel) also happens in the EDT, so while your loop runs in the EDT, the text will not be updated, only after your loop ended and you return from your event listener. Then since you modified the text of the JLabel it will be refreshed / repainted and you will see the last value you set to it.
Example to demonstrate this. In the following example a loop in the event listener loops from 0 to 9 and sets the text of the label, but you will only see the final 9 be set:
JPanel p = new JPanel();
final JLabel l = new JLabel("-1");
p.add(l);
JButton b = new JButton("Loop");
p.add(b);
b.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
for ( int i = 0; i < 10; i++ ) {
l.setText( "" + i );
try { Thread.sleep( 200 ); } catch ( InterruptedException e1 ) {}
}
}
} );
A proposed solution: Use javax.swing.Timer to do the loop's work. Swing's timer calls its listeners in the EDT so it's safe to update swing components in it, and once the listener returns, a component UI update can happen immediately:
JPanel p = new JPanel();
final JLabel l = new JLabel("-1");
p.add(l);
JButton b = new JButton("Loop");
p.add(b);
b.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
new Timer(200, new ActionListener() {
int i = 0;
#Override
public void actionPerformed(ActionEvent e2) {
l.setText("" + i);
if ( ++i == 10 )
((Timer)e2.getSource()).stop();
}
}).start();
}
} );
In this solution you will see the label's text counting from 0 up to 9 nicely.

It's appears to me that your entire game must block in the action handler until the while loop has finished? So the text of the label will be getting updated but only the last update will be visible once the AWT thread is running again.

JoptionPane ShowConfirmDialog

I have a Java program. When I run the program, it will give me a GUI which as I attached.
When I want to close it, it will prompt out a confirm dialog. If I press the Yes button, it will quit the program using System.exit().
public static void main(String args[])
{
ButtonTest app = new ButtonTest( );
app.addWindowListener(
new WindowAdapter( )
{
public void windowClosing (WindowEvent e)
{
String message = " Really Quit ? ";
String title = "Quit";
int reply = JOptionPane.showConfirmDialog(null, message, title, JOptionPane.YES_NO_OPTION);
if (reply == JOptionPane.YES_OPTION)
{
System.exit(0);
}
}
}
);
}
If I don't want to quit the program, what can I do? System.continued() ?

You Don't need the else in this case

Try setting this,
app.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE)
[Edited]
So, your code will become something like this,
public static void main(String args[]) {
ButtonTest app = new ButtonTest();
app.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
int reply = JOptionPane.showConfirmDialog(null,
"Really Quit ?", "Quit", JOptionPane.YES_NO_OPTION);
if (reply == JOptionPane.YES_OPTION)
System.exit(0);
}
});
app.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
app.setSize(640, 480);
app.setVisible(true);
}
[Explanation]
You might be thinking that why it is like that. The behaviour of windows close button for JFrame, unlike Frame,is to hide the window. Therefore, it will hide/close the window anyway. But when you specify that it must also exit the program, when the user click yes. Then, besides closing the window, it also exits the program. And when user clicks no, it does nothing but closes the window anyway. Hence, you must tell it explicitly that DO_NOTHING_ON_CLOSE.
[Docs]
Unlike a Frame, a JFrame has some notion of how to respond when the
user attempts to close the window. The default behavior is to simply
hide the JFrame when the user closes the window. To change the default
behavior, you invoke the method setDefaultCloseOperation(int). To make
the JFrame behave the same as a Frame instance, use
setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE).
Ref: JFrame docs

If you will ask me, I will go with, on YES SELECTION instead of abruptly closing my Application with System.exit(0), I will choose the gracious way of closing my Application, by using frameObject.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) and on NO SELECTION , I will go for frameObject.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE). Here is one sample program for your help :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ApplicationCloseExample
{
private void displayGUI()
{
final JFrame frame = new JFrame("Application Close Example");
frame.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent we)
{
int result = JOptionPane.showConfirmDialog(
frame, "Do you want to Exit ?"
, "Exit Confirmation : ", JOptionPane.YES_NO_OPTION);
if (result == JOptionPane.YES_OPTION)
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
else if (result == JOptionPane.NO_OPTION)
frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
}
});
frame.setSize(300, 300);
frame.setVisible(true);
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new ApplicationCloseExample().displayGUI();
}
});
}
}

If you want the program to continue when you press NO, place the rest of your code in else block or call the function where you have placed the rest of your code.
Removing else block is also an option if you don't want to place any action on the NO button because the JOptionPane.showConfirmDialog() will close anyways. You can continue with rest of your code after the if statement.
FYI- There is no System.continue(). The program pretty much does that on it's own.

You can add an else block. if you want to run the main method again (which I assume you do) it should look like this. You should have some method which you run if the user chooses no, whether it is the main method main(null) or another method.
public static void main(String args[])
{
ButtonTest app = new ButtonTest( );
app.addWindowListener(
new WindowAdapter( )
{
public void windowClosing (WindowEvent e)
{
String message = " Really Quit ? ";
String title = "Quit";
int reply = JOptionPane.showConfirmDialog(null, message, title, JOptionPane.YES_NO_OPTION);
if (reply == JOptionPane.YES_OPTION)
{
System.exit(0);
}
else
{
//whatever you plan on running instead here, instead of quitting,
//main(null) to run the main method, or put another method if you want
}
}
}
);
}

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;
}

Java: turn-based battle system (with gui)

EDIT (4/3/2017): Sorry, I was a noob back then.
I'm trying to make a turn-based battle system where the player clicks buttons on his turn. But I can't seem to find out how to code it. Below is the code on what I did.
What should happen here is that when I click the attack button(for example) the next turn will be the monster's turn but the playerTurn variable doesn't change when I click the button. playerTurn is always true. Can you help me correct this? It is a turn-based battle system.
public class BattleFrame extends JFrame implements ActionListener, Runnable {
private JButton atkButton = new JButton("Attack");
private JButton runButton = new JButton("Run");
private JButton itemButton = new JButton("Item");
private JButton magicButton = new JButton("Magic");
private JPanel panelButtons = new JPanel();
private Random rand = new Random();
private Boolean playerTurn;
private Thread t;
public BattleFrame() {
setSize(480, 390);
setLayout(null);
// I have not included the code with the setting of the JButtons
initPanel(); // initialize the panel with buttons
setResizable(false);
setVisible(true);
playerTurn = true;
t = new Thread(this);
t.start();
}
// I'm not so familiar with 'synchronized' but I tried it here but it doesn't change anything
public void actionPerformed(ActionEvent e) {
Object src = e.getSource();
if(src.equals(atkButton) && playerTurn) {
System.out.println("Attack!");
playerTurn = false;
}
else if(src.equals(runButton) && playerTurn) {
System.out.println("Run!");
playerTurn = false;
}
else if(src.equals(itemButton) && playerTurn) {
System.out.println("Item");
playerTurn = false;
}
else if(src.equals(magicButton) && playerTurn) {
System.out.println("Magic");
playerTurn = false;
}
}
public void run() {
while(true) {
if(playerTurn == false) {
System.out.println("Monster's turn!"); // just printing whose turn it is
playerTurn = true;
}
else System.out.println("player's turn!");
}
}
public static void main(String[] args) {
new BattleFrame();
}
}

A Boolean is an object, so gets compared by identity, not value.
assert new Boolean (true) == new Boolean(true);
The above will fail, as the two different Boolean objects are not the same object.
For general use, use the primitive type boolean, not the standard library class Boolean. Cases where you should use Boolean are pretty rare: it's one of those things that exists more for symmetry than any real practical reason. If you do use it, you need to use a.equals(b) not a == b.
For more details, see:
http://www.java-samples.com/showtutorial.php?tutorialid=221