Problem with Jcheckbox

Hi friends;
I need a small help. I want to change the property of a button based on the checkbox selected or deselected value.
My problem is :
if checkbox is selected then disable the button else
if checkbox is deselected then enable the button.
if(createLoginCKB.setEnabled(true)
button1.setEnabled(false)
else
button1.setEnabled(true)
But i am getting an error in the first line saying cannot convert void to boolean.
Please help
thanks
Ad

Use the isSelected() method to check if your checkbox is selected:
if( createLoginCKB.isSelected() )
...."How to Use Check Boxes":
http://java.sun.com/docs/books/tutorial/uiswing/components/button.html#checkbox

Similar Messages

Problem with JCheckBox in a JTable

Hello,
I have a JTable with JCheckBox as Editor for boolean values.
I added a ListSelectionListener on that JTable.
My problem is :
when I click on a cell which have a JCheckBoxEditor, there is only one event generated : the one which unselect the row previously selected.
So i can't answer the selection.
what could have append ?
thanks a lot.
fleur.

hi,
I have no custom editor for this table.
here is my code :
public VDEComposant(Locale langue,InterfaceModeleur listener,Composant composant,int largeur) {
super(langue,listener,largeur);
this.setLayout(new BorderLayout());
_modele=listener.getModele();
_composantCourant=composant;
this.addComposantsListener((ComposantsListener)listener.getGestionnaire());
construitBarreOutils();
setNbLigne1(this.listeComposant(composant).size());
int m=0;
if (composant==Composant.COMPOSANT){
_donCompPereApTM=this.creeModeleDonnee1(composant);
_donCompPereApTM.addTableModelListener(this);
setTableau1(new JTable(_donCompPereApTM));
m=1;
else{
if (composant.getPere()==Composant.COMPOSANT){
_donCompApTM=creeModeleDonnee1(composant);
_donCompApTM.addTableModelListener(this);
setTableau1(new JTable(_donCompApTM));
else {
_donCompUtTM=creeModeleDonnee1(composant);
_donCompUtTM.addTableModelListener(this);
setTableau1(new JTable(_donCompUtTM));
getTableau1().addMouseListener(((OngletDonnees)((OngletDonnees)getIHM().getOngletDonnees())).getOngletComposants());
MultipleComboBoxCellEditor editor = new MultipleComboBoxCellEditor(new JComboBox());
getTableau1().getColumnModel().getColumn(4+m).setCellEditor(editor) ;
getTableau1().setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
getTableau1().getSelectionModel().addListSelectionListener(this);
Dimension d1 = new Dimension(_largeur, getNbLigne1()*16);
JScrollPane sc1 = new JScrollPane(getTableau1());
sc1.setViewportView(getTableau1());
if((composant.getPere()!=null)&&(composant.getPere()!=Composant.COMPOSANT)){
this.add(_outils,BorderLayout.NORTH);
String s="";
if((composant.getPere()==null)||(composant.getPere()==Composant.COMPOSANT)){
String sc="";
if(composant==Composant.COMPOSANT_IMAGE){
sc=" "+_ressources.getString("images");
if(composant==Composant.COMPOSANT_LINEAIRE){
sc=" "+_ressources.getString("lineaires");
if(composant==Composant.COMPOSANT_METAD){
sc=" "+_ressources.getString("lotdonnees");
if(composant==Composant.COMPOSANT_NGS){
sc=" "+_ressources.getString("nongraphiques");
if(composant==Composant.COMPOSANT_SURFACIQUE){
sc=" "+_ressources.getString("surfaciques");
if(composant==Composant.COMPOSANT_SYMBOLIQUE){
sc=" "+_ressources.getString("symboliques");
s=_ressources.getString("liste_composant")+sc;
else{
s=_ressources.getString("description_composant");
JLabel lab = new JLabel(s,JLabel.CENTER);
JPanel inter = new JPanel(new GridLayout(1,1));
inter.add(lab);
inter.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createRaisedBevelBorder(),BorderFactory.createEtchedBorder()));
Box boite1 = Box.createVerticalBox();
boite1.add(inter);
boite1.add(sc1);
_inter.add(boite1);
//ajout du deuxieme tableau
_donAttCompTM=this.creeModeleDonnee2(composant);
_donAttCompTM.addTableModelListener(this);
setTableau2(new JTable(_donAttCompTM));
getTableau2().setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
getTableau2().getSelectionModel().addListSelectionListener(this);
getTableau2().addMouseListener(((OngletDonnees)((OngletDonnees)getIHM().getOngletDonnees())).getOngletComposants());
//ComboBox pour saisir le type de l'attribut
_typeA = new JComboBox();
_typeA.addItem(TypeEtendu.DATE.getNom());
_typeA.addItem(TypeEtendu.DOMAINE.getNom());
_typeA.addItem(TypePrimitif.ENTIER.getNom());
_typeA.addItem(TypePrimitif.LOGIQUE.getNom());
_typeA.addItem(TypePrimitif.REEL.getNom());
_typeA.addItem(TypePrimitif.TEXTE.getNom());
(getTableau2().getColumnModel().getColumn(3)).setCellEditor(new DefaultCellEditor(_typeA));;
//renderer pour la colonne des nom qui indique en gras l'attribut identifiant
getTableau2().getColumnModel().getColumn(1).setCellRenderer(new AttributTableCellRenderer(_composantCourant));
Dimension d2 = new Dimension(_largeur ,(getNbLigne2()*16));
JScrollPane sc2 = new JScrollPane(getTableau2());
sc2.setViewportView(getTableau2());
_inter.createVerticalStrut(16);
inter = new JPanel(new GridLayout(1,1));
lab = new JLabel(_ressources.getString("attributs"),JLabel.CENTER);
inter.add(lab);
inter.setBorder(BorderFactory.createCompoundBorder(BorderFactory.createRaisedBevelBorder(),BorderFactory.createEtchedBorder()));
Box boite2=Box.createVerticalBox();
boite2.add(inter);
boite2.add(sc2);
_inter.add(boite2);
if((composant.getPere()!=null)&&(composant.getPere()!=Composant.COMPOSANT)){
this.add(_inter,BorderLayout.CENTER);
else{
this.add(_inter,BorderLayout.NORTH);
public void valueChanged(ListSelectionEvent e) {
if (e.getValueIsAdjusting()) return;
ListSelectionModel lsm =(ListSelectionModel)e.getSource();
if (lsm.isSelectionEmpty()) {
else {
int ligneSel = lsm.getMinSelectionIndex();
if(e.getSource()==getTableau2().getSelectionModel()){
String alias = (String) _donAttCompTM.getValueAt(ligneSel,1);
attribut = composantCourant.getAttribut(alias);
else if(e.getSource()==getTableau1().getSelectionModel()){
VectorTableModel vtm = null;
int i = 0;
if(_donCompApTM != null){
vtm = _donCompApTM;
if(_donCompPereApTM != null){
vtm = _donCompPereApTM;
i =1;
if(vtm != null){
String alias = (String) vtm.getValueAt(ligneSel,i);
composantSelectionne= modele.getComposant(alias);
else{
composantSelectionne=composantCourant;
I hope it make sens,
thanks.

Problem with Icon in JCheckBox

I have a problem with a JCheckBox, when I assign an Icon to it, the checkBox dissapears and the only thing I see is the Icon. Is there a way to have the CheckBox and the Icon?
Thanks
Alejandro

class MyCheckBox extends JPanel {
JCheckBox jcb = new JCheckBox();
JLabel jl;
public MyCheckBox(String s, Icon i) {
    add(jcb);
    jl = new JLabel(s,i, JLabel.LEFT);
    add(jl);
public boolean isSelected() { return jcb.isSelected(); }
public void setSelected(boolean b) { jcb.setSelected(b); }
public String getText() { return jl.getText(); }
public void setText(String s) { jl.setText(s); }
public Icon getIcon() { return jl.getIcon(); }
public void setIcon(Icon i) { jl.setIcon(i); }
}

Problem with JCheckBoxMenuItem/JCheckBox

Hi guys, basically, I have this JCheckBoxMenuItem to set if another frame is always on top or not. But the problem is when I clicked that JCheckBoxMenuItem, the isSelected() method always returned false, even when it is selected. I think it might be I'm using the wrong event handler or there's some mechanism behind it that I'm not aware of. Or because the state is not updated instantly? I had the similar problem with my JCheckBox. Thanks very much for your help in advance!
    private void jCheckBoxMenuItem2ActionPerformed(java.awt.event.ActionEvent evt) {
        //set up if robot view is always on top
        if(jRadioButtonMenuItem2.isSelected()){
            rvf.setAlwaysOnTop(true);
            System.out.println("true");
        } else{
            rvf.setAlwaysOnTop(false);
            System.out.println("false");
    }    Cheers,
J
Edited by: J.T on Jan 30, 2008 3:10 AM

sorry guys i'm just being stupid hehe
if(jRadioButtonMenuItem2.isSelected()){this should be jCheckBoxMenuItem2............. i'm sorry for posting a stupid question.
thanks anyways.
j.

Focus Problem with JTree and Menus

Hi all,
I have a problem with focus when editing a JTree and selecting a menu. The problem occurs when the user single clicks on a node, invoking the countdown to edit. If the user quickly clicks on a menu item, the focus will go to the menu item, but then when the countdown finishes, the node now has keyboard focus.
Below is code to reproduce the problem. Click on the node, hover for a little bit, then quickly click on the menu item.
How would I go about fixing the problem? Thanks!
import java.awt.Container;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
public class MyTree extends JTree {
     public MyTree(DefaultTreeModel treemodel) {
          setModel(treemodel);
          setRootVisible(true);
     public static void main(String[] args) {
          JFrame frame = new JFrame();
          JMenuBar bar = new JMenuBar();
          JMenu menu = new JMenu("Test");
          JMenuItem item = new JMenuItem("Item");
          menu.add(item);
          bar.add(menu);
          frame.setJMenuBar(bar);
          Container contentPane = frame.getContentPane();
          contentPane.setLayout(new GridLayout(1, 2));
          DefaultMutableTreeNode root1 = new DefaultMutableTreeNode("Root");
          root1.add(new DefaultMutableTreeNode("Root2"));
          DefaultTreeModel model = new DefaultTreeModel(root1);
          MyTree tree1 = new MyTree(model);
          tree1.setEditable(true);
          tree1.setCellEditor(
               new ComponentTreeCellEditor(
                    tree1,
                    new ComponentTreeCellRenderer()));
          tree1.setRowHeight(0);
          contentPane.add(tree1);
          frame.pack();
          frame.show();
import java.awt.FlowLayout;
import java.util.EventObject;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.JTree;
import javax.swing.tree.DefaultTreeCellEditor;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeCellEditor;
import javax.swing.tree.TreeCellRenderer;
public class ComponentTreeCellEditor
     extends DefaultTreeCellEditor
     implements TreeCellEditor {
     private String m_oldValue;
     private TreeCellRenderer m_renderer = null;
     private DefaultTreeModel m_model = null;
     private JPanel m_display = null;
     private JTextField m_field = null;
     private JTree m_tree = null;
     public ComponentTreeCellEditor(
          JTree tree,
          DefaultTreeCellRenderer renderer) {
          super(tree, renderer);
          m_renderer = renderer;
          m_model = (DefaultTreeModel) tree.getModel();
          m_tree = tree;
          m_display = new JPanel(new FlowLayout(FlowLayout.LEFT));
          m_field = new JTextField();
          m_display.add(new JLabel("My Label "));
          m_display.add(m_field);
     public java.awt.Component getTreeCellEditorComponent(
          JTree tree,
          Object value,
          boolean isSelected,
          boolean expanded,
          boolean leaf,
          int row) {
          m_field.setText(value.toString());
          return m_display;
     public Object getCellEditorValue() {
          return m_field.getText();
      * The edited cell should always be selected.
      * @param anEvent the event that fired this function.
      * @return true, always.
     public boolean shouldSelectCell(EventObject anEvent) {
          return true;
      * Only edit immediately if the event is null.
      * @param event the event being studied
      * @return true if event is null, false otherwise.
     protected boolean canEditImmediately(EventObject event) {
          return (event == null);
}

You can provide a cell renderer to the JTree to paint the checkBox.
The following code checks or unchecks the box with each click also:
_tree.setCellRenderer(new DefaultTreeCellRenderer()
private JCheckBox checkBox = null;
public Component getTreeCellRendererComponent(JTree tree,
                                                Object value,
                                                boolean selected,
                                                boolean expanded,
                                                boolean leaf,
                                                int row,
                                                boolean hasFocus)
    // Each node will be drawn as a check box
    if (checkBox == null)
      checkBox = new JCheckBox();
      checkBox .setBackground(tree.getBackground());
    DefaultMutableTreeNode node = (DefaultMutableTreeNode)value;
    checkBox.setText(node.getUserObject().toString());
    checkBox.setSelected(selected);
    return checkBox;
});

Problem with Jtree and a checkbox

Hello,
I have a problem with my tree implementation.
I create a tree and i want to add a checkbox in each node.
this is my code :
DefaultMutableTreeNode root;
root = new DefaultMutableTreeNode(new JCheckBox());
DefaultTreeModel model = new DefaultTreeModel(root);
_tree = new JTree(model);
eastpane.add(tree);
THe problem is that my checkbox doesn't appear. And a message appears
instead of my checkbox.
But my tree appears.
Can anyone help me .
Thanks

You can provide a cell renderer to the JTree to paint the checkBox.
The following code checks or unchecks the box with each click also:
_tree.setCellRenderer(new DefaultTreeCellRenderer()
private JCheckBox checkBox = null;
public Component getTreeCellRendererComponent(JTree tree,
                                                Object value,
                                                boolean selected,
                                                boolean expanded,
                                                boolean leaf,
                                                int row,
                                                boolean hasFocus)
    // Each node will be drawn as a check box
    if (checkBox == null)
      checkBox = new JCheckBox();
      checkBox .setBackground(tree.getBackground());
    DefaultMutableTreeNode node = (DefaultMutableTreeNode)value;
    checkBox.setText(node.getUserObject().toString());
    checkBox.setSelected(selected);
    return checkBox;
});

Problem with CheckBox as table cell renderer

i m making a JTable having three columns.
i m also making a cellRenderer of my own MyRenderer
extending Jcheckbox and implementing TableCellRenderer
now i m setting MyRenderer as renderer for third column in my table and
DefaultCellEditor with jcheckbox as parameter as cell editor for this column
the code is like this--------------------
****making of JTable****
table= new JTable(3,3);
JScrollPane scrollPane = new JScrollPane(table);
TableColumn tableColumn = table.getColumn("Male"); // let us suppose that this gives third column
tableColumn.setCellRenderer(new MyRenderer ());
tableColumn.setCellEditor(new DefaultCellEditor(new JCheckBox()));
*****The classs implementing TableCellRenderer is given below******
class MyRenderer extends JCheckBox implements TableCellRenderer{
public MyRenderer(){
public Component getTableCellRendererComponent(JTable table, Object value,
boolean isSelected, boolean hasFocus,
int row, int column){
if(value != null){
Boolean booleanValue = (Boolean)value;
setSelected(booleanValue.booleanValue());
return this;
***********************************Problem****************************
The problem is that when we click on the cell of that column first time,
all the cells are selected.
I don't want to use getColumnClass() method for this problem .
If possible , please give some other solution.
what is the problem behind this,If anybody can help us.
Thanks in advance.

I think the problem is, when the value is null the checkbox return with the selected state, b'coz u r
returning the checkbox (as it is). so pl'z try with below code (ADDED).
public Component getTableCellRendererComponent(JTable table, Object value,
boolean isSelected, boolean hasFocus,
int row, int column){
if(value != null){
Boolean booleanValue = (Boolean)value;
setSelected(booleanValue.booleanValue());
else /// ADDED
setSelected(false);/// ADDED
return this;
Nediaph.

SwingUtilities.paintComponent - problems with painting childs of components

Maybe this question was mention already but i cant find any answer...
Thats what could be found in API about method paintComponent in SwingUtilities:
Paints a component c on an arbitrary graphics g in the specified rectangle, specifying the rectangle's upper left corner and size. The component is reparented to a private container (whose parent becomes p) which prevents c.validate() and c.repaint() calls from propagating up the tree. The intermediate container has no other effect.
The component should either descend from JComponent or be another kind of lightweight component. A lightweight component is one whose "lightweight" property (returned by the Component isLightweight method) is true. If the Component is not lightweight, bad things map happen: crashes, exceptions, painting problems...
So this method perfectly works for simple Java components like JButton / JCheckbox e.t.c.
But there are problems with painting JScrollBar / JScrollPane (only background of this component appears).
I tried to understand why this happens and i think the answer is that it has child components that does not draw at all using SwingUtilities.paintComponent()
(JScrollBar got at least 2 childs - 2 buttons on its both sides for scroll)
Only parent component appears on graphics - and thats why i see only gray background of scrollbar
So is there any way to draw something like panel with a few components on it if i have some Graphics2D to paint on and component itself?
Simple example with JScrollPane:
JScrollPane pane = new JScrollPane(new JLabel("TEST"));
pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
pane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
SwingUtilities.paintComponent(g2d, pane, new JPanel(), 0, 0, 200, 200);Edited by: mgarin on Aug 11, 2008 7:48 AM

Well the thing you advised could work... but this wont be effective, because i call repaint of the area, where Components painted, very often..
So it will lag like hell when i make 10-20 repaints in a second... (for e.g. when i drag anything i need mass repainting of the area)
Isnt there any more optimal way to do painting of the sub-components?
As i understand when any component (even complicated with childs) paints in swing - its paint method calls its child components paint() to show them... can this thing be reproduced to paint such components as JScrollPane?

Problem with ImageIO.read()

I have a problem with loading picture from file to variable Image img. Function ImageIO.read(fileIn) return always null pointer (whereas fileIn!=null). I'm using j2sdk-1_4_2_0. The same problem problem is in WindowsXP SP2 and Fedora 3 64bit.
Here is code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.net.*;
import java.awt.image.*;
import javax.imageio.*;
import java.net.URL;
import javax.imageio.ImageIO;
import java.io.*;
public class Converter extends JPanel implements ActionListener {
JPanel mainPanel, info1Panel,info2Panel,convertionPanel, fSizePanel,displayPanel;
JCheckBox enableConvertion;
JButton selectFile,doIt,close;
JRadioButton size1,size2;
ButtonGroup sizeGroup;
ImageIcon imagePrev;
JRadioButton[] convertion = new JRadioButton[2];
Image img;
JLabel previewLabel;
JFileChooser fc;
File fileIn = new File("10.jpg");
File fileOut;
public Converter() {
// Tworzenie paneli
mainPanel=new JPanel();
mainPanel.setLayout(null);
info1Panel=new JPanel();
info2Panel=new JPanel();
convertionPanel=new JPanel(new BorderLayout());
fSizePanel=new JPanel();
displayPanel= new JPanel();
//Tworzenie pozostalych elementow
enableConvertion = new JCheckBox("Enable JPG <-> PNG");
selectFile = new JButton("Select File");
doIt = new JButton("Do it!");
close= new JButton("Close");
fc = new JFileChooser();
size1 = new JRadioButton("The same resolution");
size2= new JRadioButton("Resize image to target size of file");
JLabel previewLabel = new JLabel();
ButtonGroup sizeGroup = new ButtonGroup();
imagePrev= new ImageIcon();
// proba ulozenia elementow na ramce
Insets insets = mainPanel.getInsets();
Dimension size = selectFile.getPreferredSize();
selectFile.setBounds(15 + insets.left, 15 + insets.top,size.width, size.height);
doIt.setBounds(15 + insets.left,15+5+ insets.top+size.height,size.width, size.height);
close.setBounds(15+insets.left,15+2*(5+size.height)+insets.top,size.width,size.height);
convertionPanel.setBounds(10,150,250,90);
convertionPanel.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Convertion"),
BorderFactory.createEmptyBorder(0,5,5,5)));
info1Panel.setBounds(150,10,200,140);
info1Panel.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Source File Information"),
BorderFactory.createEmptyBorder(0,5,5,5)));
info2Panel.setBounds(360,10,200,140);
info2Panel.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Target File Information"),
BorderFactory.createEmptyBorder(0,5,5,5)));
fSizePanel.setBounds(10, 250, 250, 90);
fSizePanel.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("File size"),
BorderFactory.createEmptyBorder(0,5,5,5)));
fSizePanel.setLayout(new GridLayout(2,0));
displayPanel.setBounds(270,150,290,190);
displayPanel.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Display"),
BorderFactory.createEmptyBorder(0,5,5,5)));
previewLabel.setHorizontalAlignment(JLabel.CENTER);
previewLabel.setVerticalAlignment(JLabel.CENTER);
previewLabel.setVerticalTextPosition(JLabel.CENTER);
previewLabel.setHorizontalTextPosition(JLabel.CENTER);
previewLabel.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createLoweredBevelBorder(),
BorderFactory.createEmptyBorder(5,5,5,5)));
previewLabel.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createEmptyBorder(0,0,10,0),
previewLabel.getBorder()));
size1.setSelected(true);
mainPanel.add(info1Panel);
mainPanel.add(info2Panel);
mainPanel.add(convertionPanel);
mainPanel.add(fSizePanel);
mainPanel.add(displayPanel);
//osadzamy w odpowiednich panelach elementy
mainPanel.add(selectFile);
mainPanel.add(doIt);
mainPanel.add(close);
sizeGroup.add(size1);
sizeGroup.add(size2);
fSizePanel.add(size1);
fSizePanel.add(size2);
displayPanel.add(previewLabel);
convertionPanel.add(enableConvertion);
selectFile.addActionListener(this);
public void actionPerformed(ActionEvent e) {
int returnVal = fc.showOpenDialog(Converter.this);
if (returnVal == JFileChooser.APPROVE_OPTION)
File fileIn = fc.getSelectedFile();
JFrame frame1=new JFrame();
JOptionPane.showMessageDialog(frame1, fileIn.getName());
if(fileIn==null)
JFrame frame2 = new JFrame();
JOptionPane.showMessageDialog(frame2,"FileIN==NULL");
//############## PROBLEM IS HERE ###########################
try
Image img=ImageIO.read(fileIn); // HERE IS THE PROBLEM: img==NULL
// WHERAS fileIn!=NULL
}catch (IOException event){}
if (img==null)
JFrame frame2 = new JFrame();
JOptionPane.showMessageDialog(frame2,"img==NULL");
private static void createAndShowGUI() {
//Make sure we have nice window decorations.
JFrame.setDefaultLookAndFeelDecorated(true);
//Create a new instance of LunarPhases.
Converter conv = new Converter();
//Create and set up the window.
JFrame convFrame = new JFrame("Conversion JPG <-> PNG");
convFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
convFrame.setContentPane(conv.mainPanel);
Insets insets = convFrame.getInsets();
convFrame.setSize(600 + insets.left + insets.right,400+insets.top + insets.bottom);
convFrame.setVisible(true);
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}

//############## PROBLEM IS HERE ###########################
try {
Image img=ImageIO.read(fileIn); // HERE IS THE PROBLEM: img==NULL
// WHERAS fileIn!=NULL
} catch (IOException event){}
if (img==null) {
    JFrame frame2 = new JFrame();
    JOptionPane.showMessageDialog(frame2,"img==NULL");
}1. Please use [code] tags when posting code -- it makes the code more readable.
2. When posting code, post a minimal example program. You could have filtered
out all the extraneous GUI code, for example. Remember: the shorter the code, the
more likely it is a forum member will read it! Posting long runs of code only
hurts yourself.
3. All that being said, your problem is a simple oversight: notice that the
variable "img" in your try block is a local variable, not the field named "img"
than you test after the try block.
You should have written:
try {
    img=ImageIO.read(fileIn);
} catch (IOException event){
    e.printStackTrace();
}

Problems with actionListeners on CardLayout...Help Please

I'm having a problem with my clear button on card2 in my code. When pressed it will not clear the data, and I don't see anything wrong with the code. Am I overlooking something? Please take a look at the long code I have posted and let me know what is going on with this if you could.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
public class BankGUI implements ItemListener
     JPanel cards;
     final String main = "Main menu";
     final String addCust = "Add a new customer";
     final String upCust = "Change a current customer's information";
     final String addAcct = "Add a new account";
     final String withdrawl = "Withdrawl monies from an account";
     final String deposit = "Deposit monies into an account";
     final String report = "Run report to show all accounts";
     JComboBox cb;
     JRadioButton savings, checking;
     JCheckBox yes, no;
     JLabel firstNameLabel, lastNameLabel, addressLabel, cityLabel, stateLabel,
          phoneLabel, customerNumbLabel, accountNumbLabel, depositLabel,
          accountTypeLabel, savingsProLabel, balanceLabel, withdrawlLabel;
     JTextField firstNameField, lastNameField, addressField, cityField,
          stateField, phoneField, customerNumbField, accountNumbField,
          depositField, accountTypeField, balanceField, withdrawlField;
     JButton submit1, submit3, submit4, submit5, submit6, clear, logoff, run, find,
           delete, update, runReport;
     JFrame f;
     String firstName;
     String lastName;
     String address;
     String city;
     String state;
     String phoneNumber;
     String customerNumber;
     Controller cont;
     Customer cust;
     public void addComponent(Container pane)
          JPanel comboBoxPane = new JPanel();
          String comboBoxItems[] = {main, addCust, upCust, addAcct,
               withdrawl, deposit, report};
          JComboBox cb = new JComboBox(comboBoxItems);
          cb.setEditable(false);
          cb.addItemListener(this);
          comboBoxPane.add(cb);
          JPanel card1 = new JPanel(); //main menu
          logoff = new JButton("Logoff");
          logoff.addActionListener(new ActionListener()
               public void actionPerformed(ActionEvent l)
                    cont = new Controller();
                    cont.wrapUp();
          card1.add(logoff); //end main menu
          JPanel card2 = new JPanel(new GridLayout(0,4,1,1)); //add customer
          firstNameLabel = new JLabel("First Name:", SwingConstants.RIGHT);
          card2.add(firstNameLabel);
          firstNameField = new JTextField("", 10);
          card2.add(firstNameField);
          lastNameLabel = new JLabel("Last Name:", SwingConstants.RIGHT);
          card2.add(lastNameLabel);
          lastNameField = new JTextField("", 10);
          card2.add(lastNameField);
          addressLabel = new JLabel("Address:", SwingConstants.RIGHT);
          card2.add(addressLabel);
          addressField = new JTextField("", 10);
          card2.add(addressField);
          cityLabel = new JLabel("City:", SwingConstants.RIGHT);
          card2.add(cityLabel);
          cityField = new JTextField("", 10);
          card2.add(cityField);
          stateLabel = new JLabel("State:", SwingConstants.RIGHT);
          card2.add(stateLabel);
          stateField = new JTextField("", 10);
          card2.add(stateField);
          phoneLabel = new JLabel("Phone Number:", SwingConstants.RIGHT);
          card2.add(phoneLabel);
          phoneField = new JTextField("", 10);
          card2.add(phoneField);
          customerNumbLabel = new JLabel("Customer Number (SSN):", SwingConstants.RIGHT);
          card2.add(customerNumbLabel);
          customerNumbField = new JTextField("", 10);
          card2.add(customerNumbField);
          card2.add(new JLabel(""));
          card2.add(new JLabel(""));
          card2.add(new JLabel(""));
          submit1 = new JButton("Submit");
          /*submit1.addActionListener(new ActionListener()
               public void actionPerformed(ActionEvent s1)
                    firstName = firstNameField.getText();
                    lastName = lastNameField.getText();
                    address = addressField.getText();
                    city = cityField.getText();
                    state = stateField.getText();
                    phoneNumber = phoneField.getText();
                    customerNumber = customerNumbField.getText();
                    Customer cust = new Customer(firstName, lastName, address, city, state, phoneNumber, customerNumber);
                    System.out.println(cust.getFirstName());
          card2.add(submit1);
          clear = new JButton("Clear");
          clear.addActionListener(new ActionListener()
               public void actionPerformed(ActionEvent c)
                    firstNameField.setText("");
                    lastNameField.setText("");
                    addressField.setText("");
                    cityField.setText("");
                    stateField.setText("");
                    phoneField.setText("");
                    customerNumbField.setText("");
                    firstNameField.requestFocus();
          card2.add(clear); //end add customer
          JPanel card3 = new JPanel(new GridLayout(0,4,1,1)); //update customer
          card3.add(new JLabel(""));
          customerNumbLabel = new JLabel("Customer Number (SSN):", SwingConstants.RIGHT);
          card3.add(customerNumbLabel);
          customerNumbField = new JTextField("", 10);
          card3.add(customerNumbField);
          card3.add(new JLabel(""));
          card3.add(new JLabel(""));
          card3.add(new JLabel(""));
          find = new JButton("Find");
          card3.add(find);
          card3.add(new JLabel(""));
          card3.add(new JLabel(""));
          card3.add(new JLabel(""));
          card3.add(new JLabel(""));
          card3.add(new JLabel(""));
          firstNameLabel = new JLabel("First Name:", SwingConstants.RIGHT);
          card3.add(firstNameLabel);
          firstNameField = new JTextField("", 10);
          card3.add(firstNameField);
          lastNameLabel = new JLabel("Last Name:", SwingConstants.RIGHT);
          card3.add(lastNameLabel);
          lastNameField = new JTextField("", 10);
          card3.add(lastNameField);
          addressLabel = new JLabel("Address:", SwingConstants.RIGHT);
          card3.add(addressLabel);
          addressField = new JTextField("", 10);
          card3.add(addressField);
          cityLabel = new JLabel("City:", SwingConstants.RIGHT);
          card3.add(cityLabel);
          cityField = new JTextField("", 10);
          card3.add(cityField);
          stateLabel = new JLabel("State:", SwingConstants.RIGHT);
          card3.add(stateLabel);
          stateField = new JTextField("", 10);
          card3.add(stateField);
          phoneLabel = new JLabel("Phone Number:", SwingConstants.RIGHT);
          card3.add(phoneLabel);
          phoneField = new JTextField("", 10);
          card3.add(phoneField);
          card3.add(new JLabel(""));
          submit3 = new JButton("Save Changes");
          card3.add(submit3); //end update customer
          JPanel card4 = new JPanel(new GridLayout(0,4,1,1)); //add account
          customerNumbLabel = new JLabel("Customer Number (SSN):", SwingConstants.RIGHT);
          card4.add(customerNumbLabel);
          customerNumbField = new JTextField("", 10);
          card4.add(customerNumbField);
          card4.add(new JLabel(""));
          card4.add(new JLabel(""));
          accountNumbLabel = new JLabel("Account Number:", SwingConstants.RIGHT);
          card4.add(accountNumbLabel);
          accountNumbField = new JTextField("", 10);
          card4.add(accountNumbField);
          card4.add(new JLabel(""));
          card4.add(new JLabel(""));
          accountTypeLabel = new JLabel("Account Type:", SwingConstants.RIGHT);
          card4.add(accountTypeLabel);
          savings = new JRadioButton("Savings");
          card4.add(savings);
          checking = new JRadioButton("Checking");
          card4.add(checking);
          card4.add(new JLabel(""));
          depositLabel = new JLabel("Deposit Amount:", SwingConstants.RIGHT);
          card4.add(depositLabel);
          depositField = new JTextField("", 10);
          card4.add(depositField);
          card4.add(new JLabel(""));
          card4.add(new JLabel(""));
          submit4 = new JButton("Submit");
          card4.add(submit4);//end add account
          JPanel card5 = new JPanel(new GridLayout(0,4,1,1)); //withdrawl
          accountNumbLabel = new JLabel("Account Number:", SwingConstants.RIGHT);
          card5.add(accountNumbLabel);
          accountNumbField = new JTextField("", 10);
          card5.add(accountNumbField);
          card5.add(new JLabel(""));
          card5.add(new JLabel(""));
          withdrawlLabel = new JLabel("Withdrawl Amount:", SwingConstants.RIGHT);
          card5.add(withdrawlLabel);
          withdrawlField = new JTextField("", 10);
          card5.add(withdrawlField);
          card5.add(new JLabel(""));
          card5.add(new JLabel(""));
          submit5 = new JButton("Submit");
          card5.add(submit5);//end withdrawl
          JPanel card6 = new JPanel(new GridLayout(0,4,1,1)); //deposit
          accountNumbLabel = new JLabel("Account Number:", SwingConstants.RIGHT);
          card6.add(accountNumbLabel);
          accountNumbField = new JTextField("", 10);
          card6.add(accountNumbField);
          card6.add(new JLabel(""));
          card6.add(new JLabel(""));
          depositLabel = new JLabel("Deposit Amount:", SwingConstants.RIGHT);
          card6.add(depositLabel);
          depositField = new JTextField("", 10);
          card6.add(depositField);
          card6.add(new JLabel(""));
          card6.add(new JLabel(""));
          submit6 = new JButton("Submit");
          card6.add(submit6);//end deposit
          JPanel card7 = new JPanel(); //run report
          card7.add(new JLabel(""));
          runReport = new JButton("Run Report");
          card7.add(runReport);//end report
          cards = new JPanel(new CardLayout());
          cards.add(card1, main);
          cards.add(card2, addCust);
          cards.add(card3, upCust);
          cards.add(card4, addAcct);
          cards.add(card5, withdrawl);
          cards.add(card6, deposit);
          cards.add(card7, report);
          pane.add(comboBoxPane, BorderLayout.PAGE_START);
          pane.add(cards);
     public void itemStateChanged(ItemEvent evt)
          CardLayout cl = (CardLayout)(cards.getLayout());
          cl.show(cards, (String)evt.getItem());
     public void createGUI()
          f = new JFrame("Bank of Sean");
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          BankGUI bankGUI = new BankGUI();
          bankGUI.addComponent(f.getContentPane());
          f.pack();
          f.setVisible(true);
     public static void main(String[] args)
          javax.swing.SwingUtilities.invokeLater(new Runnable()
               public void run()
                    BankGUI bankGUI = new BankGUI();
                    bankGUI.createGUI();
}

You have a generic problem that is illustrated by looking at your 'firstNameField'. You define just one 'firstNameField' variable and then allocated a value several times so that the content of 'firstNameField' add to card2 using
card2.add(firstNameField);
does not refer to the same object as is used in your action listener
firstNameField.setText("");
because in your card3 section you overwrite the original content ot the reference.
You can fix this by sharing a Document e.g.
Document doc = firstNameField.getDocument();
firstNameField = new JTextField(doc, "", 10);
card3.add(firstNameField);
for each time a new field is reqired.

Actionlistener for JCombobox with JCheckbox

Hi!
I have written a JComboBox item which holds a checkbox :
public class CheckComboItem extends JCheckBox{
    private static final long serialVersionUID = 1677961185556377734L;
    public Integer id = 0;
    public CheckComboItem(Integer id, String text, Boolean state) {
        super(text, state);
        this.id = id;
}This works fine; However i have problems with my action listener, which should change the checkbox' selection state.
Unfortunately this only works sometimes (randomly) :-(
public class CheckComboListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        JComboBox cb = (JComboBox) e.getSource();
        CheckComboItem store = (CheckComboItem) cb.getSelectedItem();
        store.setSelected((!store.isSelected()));
}Can you please tell me what i am doing wrong/ how this needs to be improved ?
Thank you very much!

You managed to find the Swing forum the last time you posted a Swing question.
Why didn't you search the Swing forum this time before you posted a question?
Maybe a JCheckBoxMenuItem will work better.
If you need further help then you need to create a [Short, Self Contained, Compilable and Executable, Example Program (SSCCE)|http://homepage1.nifty.com/algafield/sscce.html], that demonstrates the incorrect behaviour.

A problem with threads

I am trying to implement some kind of a server listening for requests. The listener part of the app, is a daemon thread that listens for connections and instantiates a handling daemon thread once it gets some. However, my problem is that i must be able to kill the listening thread at the user's will (say via a sto button). I have done this via the Sun's proposed way, by testing a boolean flag in the loop, which is set to false when i wish to kill the thread. The problem with this thing is the following...
Once the thread starts excecuting, it will test the flag, find it true and enter the loop. At some point it will LOCK on the server socket waiting for connection. Unless some client actually connects, it will keep on listening indefinatelly whithought ever bothering to check for the flag again (no matter how many times you set the damn thing to false).
My question is this: Is there any real, non-theoretical, applied way to stop thread in java safely?
Thank you in advance,
Lefty

This was one solution from the socket programming forum, have you tried this??
public Thread MyThread extends Thread{
     boolean active = true;
     public void run(){
          ss.setSoTimeout(90);
          while (active){
               try{
                    serverSocket = ss.accept();
               catch (SocketTimeoutException ste){
               // do nothing
     // interrupt thread
     public void deactivate(){
          active = false;
          // you gotta sleep for a time longer than the
          // accept() timeout to make sure that timeout is finished.
          try{
               sleep(91);
          }catch (InterruptedException ie){
          interrupt();
}

Problem with Threads and a static variable

I have a problem with the code below. I am yet to make sure that I understand the problem. Correct me if I am wrong please.
Code functionality:
A timer calls SetState every second. It sets the state and sets boolean variable "changed" to true. Then notifies a main process thread to check if the state changed to send a message.
The problem as far I understand is:
Assume the timer Thread calls SetState twice before the main process Thread runs. As a result, "changed" is set to true twice. However, since the main process is blocked twice during the two calls to SetState, when it runs it would have the two SetState timer threads blocked on its synchronized body. It will pass the first one, send the message and set "changed" to false since it was true. Now, it will pass the second thread, but here is the problem, "changed" is already set to false. As a result, it won't send the message even though it is supposed to.
Would you please let me know if my understanding is correct? If so, what would you propose to resolve the problem? Should I call wait some other or should I notify in a different way?
Thanks,
B.D.
Code:
private static volatile boolean bChanged = false;
private static Thread objMainProcess;
   protected static void Init(){
        objMainProcess = new Thread() {
            public void run() {
                while( objMainProcess == Thread.currentThread() ) {
                   GetState();
        objMainProcess.setDaemon( true );
        objMainProcess.start();
    public static void initStatusTimer(){
        if(objTimer == null)
             objTimer = new javax.swing.Timer( 1000, new java.awt.event.ActionListener(){
                public void actionPerformed( java.awt.event.ActionEvent evt){
                          SetState();
    private static void SetState(){
        if( objMainProcess == null ) return;
        synchronized( objMainProcess ) {
            bChanged = true;
            try{
                objMainProcess.notify();
            }catch( IllegalMonitorStateException e ) {}
    private static boolean GetState() {
        if( objMainProcess == null ) return false;
        synchronized( objMainProcess ) {
            if( bChanged) {
                SendMessage();
                bChanged = false;
                return true;
            try {
                objMainProcess.wait();
            }catch( InterruptedException e ) {}
            return false;
    }

Thanks DrClap for your reply. Everything you said is right. It is not easy to make them alternate since SetState() could be called from different places where the state could be anything else but a status message. Like a GREETING message for example. It is a handshaking message but not a status message.
Again as you said, There is a reason I can't call sendMessage() inside setState().
The only way I was able to do it is by having a counter of the number of notifies that have been called. Every time notify() is called a counter is incremented. Now instead of just checking if "changed" flag is true, I also check if notify counter is greater than zero. If both true, I send the message. If "changed" flag is false, I check again if the notify counter is greater than zero, I send the message. This way it works, but it is kind of a patch than a good design fix. I am yet to find a good solution.
Thanks,
B.D.

Problem with threads running javaw

Hi,
Having a problem with multi thread programming using client server sockets. The program works find when starting the the application in a console using java muti.java , but when using javaw multi.java the program doesnt die and have to kill it in the task manager. The program doesnt display any of my gui error messages either when the server disconnect the client. all works find in a console. any advice on this as I havent been able to understand why this is happening? any comment would be appreciated.
troy.

troy,
Try and post a minimum code sample of your app which
does not work.
When using javaw, make sure you redirect the standard
error and standard output streams to file.
Graeme.Hi Graeme,
I dont understand what you mean by redirection to file? some of my code below.
The code works fine under a console, code is supposed to exit when the client (the other server )disconnects. the problem is that but the clientworker side of the code still works. which under console it doesnt.
public class Server{
ServerSocket aServerSocket;
Socket dianosticsSocket;
Socket nPortExpress;
ClientListener aClientListener;
LinkedList queue = new LinkedList();
int port = 0;
int clientPort = 0;
String clientName = null;
boolean serverAlive = true;
* Server constructor generates a server
* Socket and then starts a client threads.
* @param aPort      socket port of local machine.
public Server(int aPort, String aClientName, int aClientPort){
port = aPort;
clientName = aClientName;
clientPort = aClientPort;
try{
// create a new thread
aServerSocket = new ServerSocket(port) ;
// connect to the nPortExpress
aClientListener = new ClientListener(InetAddress.getByName(clientName), clientPort, queue,this);
// aClientListener.setDaemon(true);
aClientListener.start();
// start a dianostic port
DiagnosticsServer aDiagnosticsServer = new DiagnosticsServer(port,queue,aClientListener);
// System.out.println("Server is running on port " + port + "...");
// System.out.println("Connect to nPort");
catch(Exception e)
// System.out.println("ERROR: Server port " + port + " not available");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Server port " + port + " not available", JOptionPane.ERROR_MESSAGE);
serverAlive = false;
System.exit(1);
while(serverAlive&&aClientListener.hostSocket.isConnected()){
try{
// connect the client
Socket aClient = aServerSocket.accept();
//System.out.println("open client connection");
//System.out.println("client local: "+ aClient.getLocalAddress().toString());
// System.out.println("client localport: "+ aClient.getLocalPort());
// System.out.println("client : "+ aClient.getInetAddress().toString());
// System.out.println("client port: "+ aClient.getLocalPort());
// make a new client thread
ClientWorker clientThread = new ClientWorker(aClient, queue, aClientListener, false);
// start thread
clientThread.start();
catch(Exception e)
//System.out.println("ERROR: Client connection failure");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Client connection failure", JOptionPane.ERROR_MESSAGE);
}// end while
} // end constructor Server
void serverExit(){
     JOptionPane.showMessageDialog(null, "Server ","ERROR: nPort Failure", JOptionPane.ERROR_MESSAGE);
     System.exit(1);
}// end class Server
*** connect to another server
public class ClientListener extends Thread{
InetAddress hostName;
int hostPort;
Socket hostSocket;
BufferedReader in;
PrintWriter out;
boolean loggedIn;
LinkedList queue;      // reference to Server queue
Server serverRef; // reference to main server
* ClientListener connects to the host server.
* @param aHostName is the name of the host eg server name or IP address.
* @param aHostPort is a port number of the host.
* @param aLoginName is the users login name.
public ClientListener(InetAddress aHostName, int aHostPort,LinkedList aQueue,Server aServer)      // reference to Server queue)
hostName = aHostName;
hostPort = aHostPort;
queue = aQueue;
serverRef = aServer;
// connect to the server
try{
hostSocket = new Socket(hostName, hostPort);
catch(IOException e){
//System.out.println("ERROR: Connection Host Failed");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Connection to nPort Failed", JOptionPane.ERROR_MESSAGE);
System.exit(0);
} // end constructor ClientListener
** multi client connection server
ClientWorker(Socket aSocket,LinkedList aQueue, ClientListener aClientListener, boolean diagnostics){
queue = aQueue;
addToQueue(this);
client = aSocket;
clientRef = aClientListener;
aDiagnostic = diagnostics;
} // end constructor ClientWorker
* run method is the main loop of the server program
* in change of handle new client connection as well
* as handle all messages and errors.
public void run(){
boolean alive = true;
String aSubString = "";
in = null;
out = null;
loginName = "";
loggedIn = false;
while (alive && client.isConnected()&& clientRef.hostSocket.isConnected()){
try{
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(client.getOutputStream()));
if(aDiagnostic){
out.println("WELCOME to diagnostics");
broadCastDia("Connect : diagnostics "+client.getInetAddress().toString());
out.flush();
else {
out.println("WELCOME to Troy's Server");
broadCastDia("Connect : client "+client.getInetAddress().toString());
     out.flush();
String line;
while(((line = in.readLine())!= null)){
StringTokenizer aStringToken = new StringTokenizer(line, " ");
if(!aDiagnostic){
broadCastDia(line);
clientRef.sendMessage(line); // send mesage out to netExpress
out.println(line);
out.flush();
else{
if(line.equals("GETIPS"))
getIPs();
else{
clientRef.sendMessage(line); // send mesage out to netExpress
out.println(line);
out.flush();
} // end while
catch(Exception e){
// System.out.println("ERROR:Client Connection reset");
                         JOptionPane.showMessageDialog(null, (e.toString()),"ERROR:Client Connection reset", JOptionPane.ERROR_MESSAGE);
try{
if(aDiagnostic){
broadCastDia("Disconnect : diagnostics "+client.getInetAddress().toString());
out.flush();
else {
broadCastDia("Disconnect : client "+client.getInetAddress().toString());
     out.flush();
// close the buffers and connection;
in.close();
out.close();
client.close();
// System.out.println("out");
// remove from list
removeThreadQueue(this);
alive = false;
catch(Exception e){
// System.out.println("ERROR: Client Connection reset failure");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Client Connection reset failure", JOptionPane.ERROR_MESSAGE);
}// end while
} // end method run
* method run - Generates io stream for communicating with the server and
* starts the client gui. Run also parses the input commands from the server.
public void run(){
boolean alive = true;
try{
// begin to life the gui
// aGuiClient = new ClientGui(hostName.getHostName(), hostPort, loginName, this);
// aGuiClient.show();
in = new BufferedReader(new InputStreamReader(hostSocket.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(hostSocket.getOutputStream()));
while (alive && hostSocket.isConnected()){
String line;
while(((line = in.readLine())!= null)){
System.out.println(line);
broadCast(line);
} // end while
} // end while
catch(Exception e){
//     System.out.println("ERRORa Connection to host reset");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Connection to nPort reset", JOptionPane.ERROR_MESSAGE);
try{
hostSocket.close();
     }catch(Exception a){
     JOptionPane.showMessageDialog(null, (a.toString()),"ERROR: Exception", JOptionPane.ERROR_MESSAGE);
alive = false;
System.exit(1);
} // end method run

Problem with threads and camera.

Hi everybody!
I've a problem with taking snapshot.
I would like to display a loading screen after it take snapshot ( sometimes i
have to wait few seconds after i took snapshot. Propably photo is being taken in time where i have to wait).
I was trying to use threads but i didn't succeed.
I made this code:
display.setCurrent(perform);
        new Thread(new Runnable(){
            public void run() {
                while((!performing.isShown()) && (backgroundCamera.isShown())){
                    Thread.yield();
                notifyAll();
        }).start();
        new Thread(new Runnable(){
            public void run() {
                try {
                    this.wait();
                } catch(Exception e) {
                    exceptionHandler(e);
                photo = camera.snapshot();
                display.setCurrent(displayPhoto);
        }).start();This code is sometimes showing performing screen but sometimes no.
I don't know why. In my opinion performing.isShown() method isn't working correctly.
Does anyone have some idea how to use threads here?

Hi,
I've finally managed to work this fine.
The code:
       Object o = new Object();
       display.setCurrent(perform);
        new Thread(new Runnable(){
            public void run() {
                while(!performing.isShown()){
                    Thread.yield();
               synchronized(o) {
                  o.notify();
        }).start();
        new Thread(new Runnable(){
            public void run() {
                try {
                    synchronized(o) {
                       o.wait(1);
                } catch(Exception e) {
                    exceptionHandler(e);
                photo = camera.snapshot();
                display.setCurrent(displayPhoto);
        }).start();

Problem with Jcheckbox

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