Exception on thread "AWT-EventQueue-0" java.lang.ClassCastException in my JFrame class
I am doing a simulation of life, I have a wolf that eats sheep, sheep eat grass. It's simple, but I'm not an expert in materials JFrame
and JPanel
. This is my code JFrame
:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
public class InterfaceGraphique extends JFrame{
private Case[][] caseMemoire = new Case[16][16];
public InterfaceGraphique(){
setSize(800, 825);
setTitle("Evolution");
setLocationRelativeTo(null);
Container c = getContentPane();
c.setLayout(null);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
for(int i = 0; i<16; i++){
for(int j = 0; j<16; j++){
Case ca = new Case(i*50, j*50);
caseMemoire[i][j] = ca;
add(ca);
}
}
setVisible(true);
}
public Case getCase(int i, int j){
return caseMemoire[i][j];
}
public class Case extends JPanel{
private int coordX;
private int coordY;
private JLabel image;
public Case(int x, int y){
coordX = x;
coordY = y;
setBounds(coordX, coordY, 55, 55);
image = new JLabel(new ImageIcon("../images/Grass.png"));
this.setLayout(new BorderLayout());
this.add(image);
}
public void setImg(int i){
switch(i){
case 0:
this.remove(image);
image = new JLabel( new ImageIcon("../images/Grass.png"));
this.setLayout(new BorderLayout());
this.add(image);
break;
case 1:
this.remove(image);
break;
case 2:
this.remove(image);
image = new JLabel( new ImageIcon("../images/Wolf.png"));
this.setLayout(new BorderLayout());
this.add(image);
break;
case 3:
this.remove(image);
image = new JLabel( new ImageIcon("../images/Sheep.png"));
this.setLayout(new BorderLayout());
this.add(image);
break;
}
}
public JLabel getImage(){
return image;
}
}
public void afficheUniv(Univers u){
for (int i=0; i < u.getLignes(); i++){
for (int j=0; j < u.getColones(); j++) {
if(u.getCellule(i, j).isLoup())
caseMemoire[i][j].setImg(2);
else if(u.getCellule(i, j).isMouton())
caseMemoire[i][j].setImg(3);
else if(u.getCellule(i, j).isHerbe())
caseMemoire[i][j].setImg(0);
else if(u.getCellule(i, j).isSels())
caseMemoire[i][j].setImg(1);
else
caseMemoire[i][j].setImg(1);
}
}
}
public static void main(String[] args){
Univers u = new Univers (16, 16, 5, 5);
InterfaceGraphique evolution = new InterfaceGraphique();
while(u.getNbMoutons()+u.getNbLoups() > 0){
u.simulation();
evolution.afficheUniv(u);
evolution.setVisible(true);
}
JOptionPane.showMessageDialog(null,
"Il n'y a plus d'animaux en vie !",
"Fin",
JOptionPane.PLAIN_MESSAGE);
}
}
Compilation javac Interfacegraphique.java
works fine. But when I run my program ( java InterfaceGraphique
) I have an error:
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException
at javax.swing.LayoutComparator.compare(LayoutComparator.java:75)
at javax.swing.LayoutComparator.compare(LayoutComparator.java:42)
at java.util.TimSort.countRunAndMakeAscending(TimSort.java:356)
at java.util.TimSort.sort(TimSort.java:230)
at java.util.Arrays.sort(Arrays.java:1512)
at java.util.ArrayList.sort(ArrayList.java:1454)
at java.util.Collections.sort(Collections.java:175)
at javax.swing.SortingFocusTraversalPolicy.enumerateAndSortCycle(SortingFocusTraversalPolicy.java:136)
at javax.swing.SortingFocusTraversalPolicy.getFocusTraversalCycle(SortingFocusTraversalPolicy.java:110)
at javax.swing.SortingFocusTraversalPolicy.getFirstComponent(SortingFocusTraversalPolicy.java:445)
at javax.swing.LayoutFocusTraversalPolicy.getFirstComponent(LayoutFocusTraversalPolicy.java:166)
at javax.swing.SortingFocusTraversalPolicy.getDefaultComponent(SortingFocusTraversalPolicy.java:535)
at java.awt.FocusTraversalPolicy.getInitialComponent(FocusTraversalPolicy.java:169)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:420)
at java.awt.Component.dispatchEventImpl(Component.java:4752)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:719)
at java.awt.EventQueue$4.run(EventQueue.java:717)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Can you help me find my problem, I don't know where mine is ClassCastException
.
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OK, so the problem is rather obscure, but a typical problem in Swing applications: you can only perform GUI operations on the Dispatch Event thread.
This means that you cannot change your frame (like add / remove panels) to your "main thread" and go through the method SwingUtilities.invokeAndWait
. If you don't, all sorts of weird things can happen, such as NullPointerException
, ConcurrentModificationException
and presumably what you had.
If you change your method main()
like this, it works without exception:
public static void main(String[] args) throws InvocationTargetException, InterruptedException {
final Univers u = new Univers(16, 16, 5, 5);
final InterfaceGraphique evolution = new InterfaceGraphique();
while (u.getNbMoutons() + u.getNbLoups() > 0) {
u.simulation();
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
evolution.afficheUniv(u);
evolution.setVisible(true);
}
});
}
JOptionPane.showMessageDialog(null, "Il n'y a plus d'animaux en vie !", "Fin",
JOptionPane.PLAIN_MESSAGE);
}
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