Develop Reference

How to download and display an image with SwingWorker [duplicate]

I want to display an image from the web to a panel in another JFrame at the click of a button. Whenever I click the button, first the image loads; and during this time, the current form potentially freezes. Once the image has loaded, the form is displayed with the image. How can I avoid the situation where my form freezes since it is very irritating. Among my codes:
My current class:
private void btn_TrackbusActionPerformed(java.awt.event.ActionEvent evt) {
try {
sendMessage("Query,map,$,start,211,Arsenal,!");
System.out.println(receiveMessage());
} catch (UnknownHostException ex) {
Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex);
}
catch (Exception ex) {
Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex);
}
client_trackedbus nextform=new client_trackedbus(planform,connection,packet_receive,packet_send);
this.setVisible(false);
this.dispose();
nextform.setVisible(true);
// TODO add your handling code here:
}
My next class that displays the image:
public class client_trackedbus extends javax.swing.JFrame {
client_planform planform=null;
DatagramSocket connection=null;
DatagramPacket packet_receive=null;
DatagramPacket packet_send=null;
JLabel label=null;
/** Creates new form client_trackedbus */
public client_trackedbus(client_planform planform,DatagramSocket connection,DatagramPacket packet_receive,DatagramPacket packet_send) {
initComponents();
this.planform=planform;
this.connection=connection;
this.packet_receive=packet_receive;
this.packet_send=packet_send;
try {
displayMap("http://www.huddletogether.com/projects/lightbox2/images/image-2.jpg", jPanel1, new JLabel());
} catch (MalformedURLException ex) {
Logger.getLogger(client_trackedbus.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void displayMap(String url,JPanel panel,JLabel label) throws MalformedURLException{
URL imageurl=new URL(url);
Image image=(Toolkit.getDefaultToolkit().createImage(imageurl));
ImageIcon icon = new ImageIcon(image);
label.setIcon(icon);
panel.add(label);
// System.out.println(panel.getSize().width);
this.getContentPane().add(panel);
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jLabel1 = new javax.swing.JLabel();
btn_Exit = new javax.swing.JButton();
btn_Plan = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("Public Transport Journey Planner");
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 368, Short.MAX_VALUE)
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 172, Short.MAX_VALUE)
);
jLabel1.setFont(new java.awt.Font("Arial", 1, 18));
jLabel1.setText("Your tracked bus");
btn_Exit.setText("Exit");
btn_Exit.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
btn_ExitActionPerformed(evt);
}
});
btn_Plan.setText("Plan journey");
btn_Plan.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
btn_PlanActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(104, 104, 104)
.addComponent(jLabel1))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(65, 65, 65)
.addComponent(btn_Plan)
.addGap(65, 65, 65)
.addComponent(btn_Exit, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addContainerGap(20, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(35, 35, 35)
.addComponent(jLabel1)
.addGap(18, 18, 18)
.addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(btn_Exit)
.addComponent(btn_Plan))
.addContainerGap(12, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void btn_ExitActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
Exitform();
}
private void btn_PlanActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
this.setVisible(false);
this.dispose();
this.planform.setVisible(true);
}
private void Exitform(){
this.setVisible(false);
this.dispose();
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
// new client_trackedbus().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton btn_Exit;
private javax.swing.JButton btn_Plan;
private javax.swing.JLabel jLabel1;
private javax.swing.JPanel jPanel1;
// End of variables declaration
}

As suggested in the article Concurrency in Swing, your button handler's query may be blocking the event dispatch thread. Using javax.swing.SwingWorker is one approach to loading images in the background, while displaying progress and keeping the GUI thread alive.
Addendum: Here's a sscce that loads the SO logo; it's been updated to handle exceptions and resize the enclosing container to fit the loaded image:
import java.awt.*;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.ExecutionException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.*;
/**
* #see http://stackoverflow.com/questions/4530659
*/
public final class WorkerTest extends JFrame {
private final JLabel label = new JLabel("Loading...");
public WorkerTest() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
label.setHorizontalTextPosition(JLabel.CENTER);
label.setVerticalTextPosition(JLabel.BOTTOM);
this.add(label);
this.pack();
this.setLocationRelativeTo(null);
}
private void start() {
new ImageWorker().execute();
}
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
WorkerTest wt = new WorkerTest();
wt.setVisible(true);
wt.start();
}
});
}
class ImageWorker extends SwingWorker<Image, Void> {
private static final String TEST
= "http://cdn.sstatic.net/stackexchange/img/logos/so/so-logo.png";
#Override
protected Image doInBackground() throws IOException {
Image image = ImageIO.read(new URL(TEST));
return image.getScaledInstance(640, -1, Image.SCALE_SMOOTH);
}
#Override
protected void done() {
try {
ImageIcon icon = new ImageIcon(get());
label.setIcon(icon);
label.setText("Done");
WorkerTest.this.pack();
WorkerTest.this.setLocationRelativeTo(null);
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
}
}

public class SSBTest extends javax.swing.JFrame {
/** Creates new form worker1 */
public SSBTest() {
initComponents();
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
jPanel1 = new javax.swing.JPanel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setText("jLabel1");
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGap(0, 348, Short.MAX_VALUE));
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGap(0, 210, Short.MAX_VALUE));
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(layout.createSequentialGroup().addContainerGap(196, Short.MAX_VALUE).addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 182, javax.swing.GroupLayout.PREFERRED_SIZE).addGap(178, 178, 178)).addGroup(layout.createSequentialGroup().addGap(86, 86, 86).addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE).addContainerGap(122, Short.MAX_VALUE)));
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup().addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 40, Short.MAX_VALUE).addComponent(jLabel1).addGap(36, 36, 36)));
pack();
}// </editor-fold>
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
final SSBTest ssbTest = new SSBTest();
ssbTest.setVisible(true);
ssbTest.execute();
}
});
}
private void execute() {
(new MeaningOfLifeFinder(jLabel1, jPanel1)).execute();
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JPanel jPanel1;
// End of variables declaration
}
class MeaningOfLifeFinder extends SwingWorker<Icon, Object> {
JLabel label = null;
JPanel panel;
MeaningOfLifeFinder(JLabel label, JPanel jpanel) {
this.label = label;
this.panel = jpanel;
}
protected Icon doInBackground() throws IOException {
URL imageurl;
Image image = null;
System.out.println("image loading");
imageurl = new URL("http://maps.google.com/maps/api/staticmap"
+ "?zoom=14&size=512x512&maptype=roadmap"
+ "&markers=color:green|label:21|-15.0,-150.0&sensor=false");
//image = (Toolkit.getDefaultToolkit().createImage(imageurl));
image = ImageIO.read(imageurl);
ImageIcon icon = new ImageIcon(image);
System.out.println("image loaded...");
return icon;
}
#Override
protected void done() {
try {
System.out.println("image adding to label...");
label.setIcon(get());
//panel.add(label);
System.out.println("image loaded to label...");
} catch (Exception ignore) {
}
}
// System.out.println(panel.getSize().width);
}

Java Get Selected Combobox from Another JFrame

I am a newbie here. Sorry for any bad post or any other bad things.
This question is the continuation of this stackoverflow question. And I already know about the JFrame problem JFrame Bad Practice. The problem is I'm a newbie using Netbeans to code Java. All I know is how to make program with JFrame. Below is the code that I have made. Please help me correct it so the purpose of my code (set Answer class text from TheCombo class selected combobox) can be done.
Please correct this codes (I have 3 classes). I want to get the ComboBox selected Item to be used in the answer class.
Main Class:
package testing;
public class Testing {
public static void main(String[] args) {
new TheCombo().setVisible(true);
}
}
Combo Class:
package testing;
public class TheCombo extends javax.swing.JFrame {
public TheCombo() {
initComponents();
}
public String getItem()
{
String theItem = jComboBox1.getSelectedItem().toString();
return theItem;
}
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jComboBox1 = new javax.swing.JComboBox();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
jButton1.setText("Go");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jButton1)
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton1))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
new Answer().setVisible(true);
this.dispose();
}
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(TheCombo.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new TheCombo().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JComboBox jComboBox1;
// End of variables declaration
}
The Other Class (I want to set text the JTextField1 with selected item from the ComboBox at Combo Class):
package testing;
public class Answer extends javax.swing.JFrame {
TheCombo tc = new TheCombo();
public Answer() {
initComponents();
jTextField1.setText(tc.getItem());
}
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jTextField1 = new javax.swing.JTextField();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jTextField1.setHorizontalAlignment(javax.swing.JTextField.CENTER);
jTextField1.setEnabled(false);
jButton1.setText("Back");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(jButton1)
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton1))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
new TheCombo().setVisible(true);
this.dispose();
}
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Answer.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Answer().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JTextField jTextField1;
// End of variables declaration
}

There are a number of ways you might be able to achieve this, but based on the structure of your code, you seem to be wanting to ask the user a question and then based on the response, do something.
This just screams modal dialog. See How to Make Dialogs for more details
And for example...
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new QuestionPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class FruitPane extends JPanel {
private JComboBox<String> cb;
public FruitPane() {
add(new JLabel("Fruit: "));
cb = new JComboBox<String>(new String[]{"Bananas", "Apples", "Pears"});
add(cb);
}
public String getSelectedFruit() {
return (String) cb.getSelectedItem();
}
}
public class QuestionPane extends JPanel {
private JTextField field;
public QuestionPane() {
add(new JLabel("Your fruit selection"));
field = new JTextField(10);
field.setEditable(false);
add(field);
JButton btn = new JButton("Pick");
add(btn);
btn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
FruitPane pane = new FruitPane();
pane.setBorder(new EmptyBorder(10, 10, 10, 10));
int option = JOptionPane.showConfirmDialog(QuestionPane.this, pane, "Fruit", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
if (option == JOptionPane.OK_OPTION) {
String fruit = pane.getSelectedFruit();
field.setText(fruit);
}
}
});
}
}
}

send a input String from JPanel 1 to JPanel2 [duplicate]

How do I wire output to paneWithList?
PaneWithList has a listener on its JList so that the selected row is output to the console. How can I direct that output to the JTextPane on output?
Could PaneWithList fire an event which Main picks up? Would PropertyChangeSupport suffice?
Main.java:
package dur.bounceme.net;
import javax.swing.JTabbedPane;
public class Main {
private static JTabbedPane tabs;
private static PaneWithList paneWithList;
private static PaneWithTable paneWithTable;
private static Output output;
public static void main(String[] args) {
tabs = new javax.swing.JTabbedPane();
paneWithList = new PaneWithList();
paneWithTable = new PaneWithTable();
tabs.addTab("list", paneWithList);
tabs.addTab("table", paneWithTable);
tabs.addTab("output", output);
}
}

Here's an example using the observer pattern, also seen here, here and here. Note that it would also be possible to listen to the combo's model.
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.*;
/**
* #see http://en.wikipedia.org/wiki/Observer_pattern
* #see https://stackoverflow.com/a/10523401/230513
*/
public class PropertyChangeDemo {
public PropertyChangeDemo() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setResizable(false);
f.add(new ObserverPanel());
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
PropertyChangeDemo example = new PropertyChangeDemo();
}
});
}
}
class ObserverPanel extends JPanel {
private JLabel title = new JLabel("Value received: ");
private JLabel label = new JLabel("null", JLabel.CENTER);
public ObserverPanel() {
this.setBorder(BorderFactory.createTitledBorder("ObserverPanel"));
JPanel panel = new JPanel(new GridLayout(0, 1));
panel.add(title);
panel.add(label);
this.add(panel);
ObservedPanel observed = new ObservedPanel();
observed.addPropertyChangeListener(new PropertyChangeListener() {
#Override
public void propertyChange(PropertyChangeEvent e) {
if (e.getPropertyName().equals(ObservedPanel.PHYSICIST)) {
String value = e.getNewValue().toString();
label.setText(value);
}
}
});
this.add(observed);
}
}
class ObservedPanel extends JPanel {
public static final String PHYSICIST = "Physicist";
private static final String[] items = new String[]{
"Alpher", "Bethe", "Gamow", "Dirac", "Einstein"
};
private JComboBox combo = new JComboBox(items);
private String oldValue;
public ObservedPanel() {
this.setBorder(BorderFactory.createTitledBorder("ObservedPanel"));
combo.addActionListener(new ComboBoxListener());
this.add(combo);
}
private class ComboBoxListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent ae) {
String newValue = (String) combo.getSelectedItem();
firePropertyChange(PHYSICIST, oldValue, newValue);
oldValue = newValue;
}
}
}

I'd be use JMenu with JMenuItems with contents layed by using CardLayout rather than very complicated JTabbedPane(s)

For my own reference, and for anyone using the Netbeans GUI builder, this works so far as it goes:
The PanelWithList class:
package dur.bounceme.net;
public class PanelWithList extends javax.swing.JPanel {
public PanelWithList() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jScrollPane1 = new javax.swing.JScrollPane();
jList1 = new javax.swing.JList();
jScrollPane2 = new javax.swing.JScrollPane();
jTextArea1 = new javax.swing.JTextArea();
jList1.setModel(new javax.swing.AbstractListModel() {
String[] strings = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" };
public int getSize() { return strings.length; }
public Object getElementAt(int i) { return strings[i]; }
});
jList1.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
jList1.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jList1MouseClicked(evt);
}
});
jList1.addKeyListener(new java.awt.event.KeyAdapter() {
public void keyReleased(java.awt.event.KeyEvent evt) {
jList1KeyReleased(evt);
}
});
jScrollPane1.setViewportView(jList1);
jTextArea1.setColumns(20);
jTextArea1.setRows(5);
jScrollPane2.setViewportView(jTextArea1);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
this.setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(54, 54, 54)
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 247, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 308, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(167, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(35, 35, 35)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jScrollPane2)
.addComponent(jScrollPane1))
.addContainerGap(166, Short.MAX_VALUE))
);
}// </editor-fold>
private void jList1MouseClicked(java.awt.event.MouseEvent evt) {
row();
}
private void jList1KeyReleased(java.awt.event.KeyEvent evt) {
row();
}
// Variables declaration - do not modify
private javax.swing.JList jList1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JScrollPane jScrollPane2;
private javax.swing.JTextArea jTextArea1;
// End of variables declaration
private void row() {
Object o = jList1.getSelectedValue();
String s = (String)o;
jTextArea1.setText(s);
this.firePropertyChange("list", -1, 1);
}
}
and Frame.java as a driver:
package dur.bounceme.net;
public class Frame extends javax.swing.JFrame {
public Frame() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jTabbedPane1 = new javax.swing.JTabbedPane();
panelWithList1 = new dur.bounceme.net.PanelWithList();
panelWithTable1 = new dur.bounceme.net.PanelWithTable();
newJPanel1 = new dur.bounceme.net.PanelWithCombo();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
panelWithList1.addPropertyChangeListener(new java.beans.PropertyChangeListener() {
public void propertyChange(java.beans.PropertyChangeEvent evt) {
panelWithList1PropertyChange(evt);
}
});
jTabbedPane1.addTab("tab1", panelWithList1);
jTabbedPane1.addTab("tab2", panelWithTable1);
jTabbedPane1.addTab("tab3", newJPanel1);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 937, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jTabbedPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 913, Short.MAX_VALUE)
.addContainerGap()))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 555, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jTabbedPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 521, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(22, Short.MAX_VALUE)))
);
pack();
}// </editor-fold>
private void panelWithList1PropertyChange(java.beans.PropertyChangeEvent evt) {
System.out.println("panelWithList1PropertyChange ");
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/*
* Set the Nimbus look and feel
*/
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/*
* If Nimbus (introduced in Java SE 6) is not available, stay with the
* default look and feel. For details see
* http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Frame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Frame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Frame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Frame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/*
* Create and display the form
*/
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Frame().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JTabbedPane jTabbedPane1;
private dur.bounceme.net.PanelWithCombo newJPanel1;
private dur.bounceme.net.PanelWithList panelWithList1;
private dur.bounceme.net.PanelWithTable panelWithTable1;
// End of variables declaration
}
The key being that panelWithList1PropertyChange is the listener on 'panelWithList' itself.
Because PanelWithList.firePropertyChange("list", -1, 1); cannot send Object nor String that I see, I'm not exactly sure how to get the value selected all the way from the JList up to the JFrame.
Hmm, well the API says yes it can send Objects. Have to check that out.
I think it's necessary to get some info about the model which the JList is using up to the JFrame. However, doesn't that break MVC? Or maybe that's the wrong approach.

Java refreshing second form

I have two forms. First one is to decide numbers of button by using jslider. Second form is to display jbuttons according to jslider value. When i click jbutton2, the second form shows and display buttons. It is working perfectly. However, I want to create jbutton on the second form without clicking jbutton2 in the first form.
Instead, when I change jslider, it should create jbuttons on the second form at the run time and once i change jslider it should create that amount of button again on the second form and refreshing the second form button numbers according to jslider value.
I have tried revalidate();, repaint(); but they do not work, they dont refresh the second form.
So, How can I refresh second form when the jslider ,that is on the first form, changes ? Please help.....
Edit:I am using default Jframe of netbeans....
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
public class NewJFrame7 extends javax.swing.JFrame {
/**
* Creates new form NewJFrame7
*/
public NewJFrame7() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jSlider1 = new javax.swing.JSlider();
jButton2 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jSlider1.setMajorTickSpacing(2);
jSlider1.setMaximum(20);
jSlider1.setMinimum(1);
jSlider1.setPaintLabels(true);
jSlider1.setPaintTicks(true);
jSlider1.setToolTipText("");
jSlider1.addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(javax.swing.event.ChangeEvent evt) {
jSlider1StateChanged(evt);
}
});
jButton2.setText("jButton2");
jButton2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton2ActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(29, 29, 29)
.addComponent(jSlider1, javax.swing.GroupLayout.PREFERRED_SIZE, 295, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(273, Short.MAX_VALUE))
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(262, 262, 262)
.addComponent(jButton2)
.addContainerGap(262, Short.MAX_VALUE)))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(87, 87, 87)
.addComponent(jSlider1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(168, Short.MAX_VALUE))
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(138, 138, 138)
.addComponent(jButton2)
.addContainerGap(139, Short.MAX_VALUE)))
);
pack();
}// </editor-fold>
private void jSlider1StateChanged(javax.swing.event.ChangeEvent evt) {
// TODO add your handling code here:
}
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
form2 = true;
new NewJFrame8().setVisible(true);
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/*
* Set the Nimbus look and feel
*/
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/*
* If Nimbus (introduced in Java SE 6) is not available, stay with the
* default look and feel. For details see
* http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewJFrame7.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame7.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame7.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame7.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/*
* Create and display the form
*/
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NewJFrame7().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton2;
private javax.swing.JSlider jSlider1;
// End of variables declaration
}
2.form
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
public class NewJFrame8 extends javax.swing.JFrame {
/**
* Creates new form NewJFrame8
*/
public NewJFrame8() {
initComponents();
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(371, Short.MAX_VALUE)
.addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(19, 19, 19))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(48, 48, 48)
.addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(242, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/*
* Set the Nimbus look and feel
*/
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/*
* If Nimbus (introduced in Java SE 6) is not available, stay with the
* default look and feel. For details see
* http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewJFrame8.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame8.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame8.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame8.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/*
* Create and display the form
*/
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NewJFrame8().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JPanel jPanel1;
// End of variables declaration
}

One layout constraint (BorderLayout.CENTER) to place them, and one component to appear therein. (With apologies to Tolkien.)

Do check this sample Program, is this what you need. revalidate() and repaint() is what works here for this.
import java.awt.*;
import javax.swing.event.*;
import javax.swing.*;
public class SliderExample
{
private JSlider slider;
private static final int MIN_BUTTONS = 2;
private static final int SOME_BUTTONS = 4;
private static final int MAX_BUTTONS = 6;
private void createAndDisplayGUI()
{
ButtonPanel bp = new ButtonPanel();
JFrame frame = new JFrame("JSlider Example : ");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationByPlatform(true);
JPanel contentPane = new JPanel();
slider = new JSlider(JSlider.HORIZONTAL, MIN_BUTTONS, MAX_BUTTONS
, SOME_BUTTONS);
slider.addChangeListener(new ChangeListener()
{
public void stateChanged(ChangeEvent ce)
{
int value = (int) slider.getValue();
ButtonPanel.panel.removeAll();
for (int i = 0; i < value; i++)
{
ButtonPanel.panel.add(new JButton("JButton " + i));
}
ButtonPanel.panel.revalidate();
ButtonPanel.panel.repaint();
}
});
contentPane.add(slider);
frame.getContentPane().add(contentPane);
frame.pack();
frame.setVisible(true);
frame.requestFocusInWindow();
}
public static void main(String... args)
{
Runnable runnable = new Runnable()
{
public void run()
{
new SliderExample().createAndDisplayGUI();
}
};
SwingUtilities.invokeLater(runnable);
}
}
class ButtonPanel extends JFrame
{
public static JPanel panel;
public ButtonPanel()
{
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationByPlatform(true);
panel = new JPanel();
panel.setLayout(new GridLayout(0, 2));
getContentPane().add(panel);
setSize(300, 300);
setVisible(true);
}
}

import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.*;
public class SliderExample
{
private JSlider slider;
private static final int MIN_BUTTONS = 2;
private static final int SOME_BUTTONS = 4;
private static final int MAX_BUTTONS = 6;
private JButton[] buttonArray;
private ActionListener actionButton = new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
JButton button = (JButton) ae.getSource();
System.out.println(button.getText());
}
};
private void createAndDisplayGUI()
{
ButtonPanel bp = new ButtonPanel();
JFrame frame = new JFrame("JSlider Example : ");
frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
frame.setLocationByPlatform(true);
JPanel contentPane = new JPanel();
slider = new JSlider(JSlider.HORIZONTAL, MIN_BUTTONS, MAX_BUTTONS
, SOME_BUTTONS);
slider.addChangeListener(new ChangeListener()
{
public void stateChanged(ChangeEvent ce)
{
int value = (int) slider.getValue();
ButtonPanel.panel.removeAll();
buttonArray = new JButton[value];
for (int i = 0; i < value; i++)
{
buttonArray[i] = new JButton(String.valueOf(i));
buttonArray[i].addActionListener(actionButton);
ButtonPanel.panel.add(buttonArray[i]);
}
ButtonPanel.panel.revalidate();
ButtonPanel.panel.repaint();
}
});
contentPane.add(slider);
frame.getContentPane().add(contentPane);
frame.pack();
frame.setVisible(true);
frame.requestFocusInWindow();
}
public static void main(String... args)
{
Runnable runnable = new Runnable()
{
public void run()
{
new SliderExample().createAndDisplayGUI();
}
};
SwingUtilities.invokeLater(runnable);
}
}
class ButtonPanel extends JFrame
{
public static JPanel panel;
public ButtonPanel()
{
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationByPlatform(true);
panel = new JPanel();
panel.setLayout(new GridLayout(0, 2));
getContentPane().add(panel);
setSize(300, 300);
setVisible(true);
}
}
For your statement this.buttonArray[i].addActionListener(this);, the reason as to why this is not working, is because, you are inside the object of anonymous class new ChangeListener(), which doesn't have anything named buttonArray[i] inside itself, it's the Instance Variable of SliderExample class, so either place an object of SliderExample class or if you are referring to your code, then use the Object of the class which initializes the array like inside inside NewFrame8 you had written JButton[] buttonArray = new JButton[120];, so use NewFrame8's object instead of this to refer to the buttonArray[i] thingy.

To display an image

I want to display an image from the web to a panel in another JFrame at the click of a button. Whenever I click the button, first the image loads; and during this time, the current form potentially freezes. Once the image has loaded, the form is displayed with the image. How can I avoid the situation where my form freezes since it is very irritating. Among my codes:
My current class:
private void btn_TrackbusActionPerformed(java.awt.event.ActionEvent evt) {
try {
sendMessage("Query,map,$,start,211,Arsenal,!");
System.out.println(receiveMessage());
} catch (UnknownHostException ex) {
Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex);
}
catch (Exception ex) {
Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex);
}
client_trackedbus nextform=new client_trackedbus(planform,connection,packet_receive,packet_send);
this.setVisible(false);
this.dispose();
nextform.setVisible(true);
// TODO add your handling code here:
}
My next class that displays the image:
public class client_trackedbus extends javax.swing.JFrame {
client_planform planform=null;
DatagramSocket connection=null;
DatagramPacket packet_receive=null;
DatagramPacket packet_send=null;
JLabel label=null;
/** Creates new form client_trackedbus */
public client_trackedbus(client_planform planform,DatagramSocket connection,DatagramPacket packet_receive,DatagramPacket packet_send) {
initComponents();
this.planform=planform;
this.connection=connection;
this.packet_receive=packet_receive;
this.packet_send=packet_send;
try {
displayMap("http://www.huddletogether.com/projects/lightbox2/images/image-2.jpg", jPanel1, new JLabel());
} catch (MalformedURLException ex) {
Logger.getLogger(client_trackedbus.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void displayMap(String url,JPanel panel,JLabel label) throws MalformedURLException{
URL imageurl=new URL(url);
Image image=(Toolkit.getDefaultToolkit().createImage(imageurl));
ImageIcon icon = new ImageIcon(image);
label.setIcon(icon);
panel.add(label);
// System.out.println(panel.getSize().width);
this.getContentPane().add(panel);
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jLabel1 = new javax.swing.JLabel();
btn_Exit = new javax.swing.JButton();
btn_Plan = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("Public Transport Journey Planner");
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 368, Short.MAX_VALUE)
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 172, Short.MAX_VALUE)
);
jLabel1.setFont(new java.awt.Font("Arial", 1, 18));
jLabel1.setText("Your tracked bus");
btn_Exit.setText("Exit");
btn_Exit.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
btn_ExitActionPerformed(evt);
}
});
btn_Plan.setText("Plan journey");
btn_Plan.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
btn_PlanActionPerformed(evt);
}
});
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(104, 104, 104)
.addComponent(jLabel1))
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addGap(65, 65, 65)
.addComponent(btn_Plan)
.addGap(65, 65, 65)
.addComponent(btn_Exit, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addContainerGap(20, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(35, 35, 35)
.addComponent(jLabel1)
.addGap(18, 18, 18)
.addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(btn_Exit)
.addComponent(btn_Plan))
.addContainerGap(12, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void btn_ExitActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
Exitform();
}
private void btn_PlanActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
this.setVisible(false);
this.dispose();
this.planform.setVisible(true);
}
private void Exitform(){
this.setVisible(false);
this.dispose();
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
// new client_trackedbus().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton btn_Exit;
private javax.swing.JButton btn_Plan;
private javax.swing.JLabel jLabel1;
private javax.swing.JPanel jPanel1;
// End of variables declaration
}

As suggested in the article Concurrency in Swing, your button handler's query may be blocking the event dispatch thread. Using javax.swing.SwingWorker is one approach to loading images in the background, while displaying progress and keeping the GUI thread alive.
Addendum: Here's a sscce that loads the SO logo; it's been updated to handle exceptions and resize the enclosing container to fit the loaded image:
import java.awt.*;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.ExecutionException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.*;
/**
* #see http://stackoverflow.com/questions/4530659
*/
public final class WorkerTest extends JFrame {
private final JLabel label = new JLabel("Loading...");
public WorkerTest() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
label.setHorizontalTextPosition(JLabel.CENTER);
label.setVerticalTextPosition(JLabel.BOTTOM);
this.add(label);
this.pack();
this.setLocationRelativeTo(null);
}
private void start() {
new ImageWorker().execute();
}
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
WorkerTest wt = new WorkerTest();
wt.setVisible(true);
wt.start();
}
});
}
class ImageWorker extends SwingWorker<Image, Void> {
private static final String TEST
= "http://cdn.sstatic.net/stackexchange/img/logos/so/so-logo.png";
#Override
protected Image doInBackground() throws IOException {
Image image = ImageIO.read(new URL(TEST));
return image.getScaledInstance(640, -1, Image.SCALE_SMOOTH);
}
#Override
protected void done() {
try {
ImageIcon icon = new ImageIcon(get());
label.setIcon(icon);
label.setText("Done");
WorkerTest.this.pack();
WorkerTest.this.setLocationRelativeTo(null);
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
}
}

public class SSBTest extends javax.swing.JFrame {
/** Creates new form worker1 */
public SSBTest() {
initComponents();
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
#SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
jPanel1 = new javax.swing.JPanel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setText("jLabel1");
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGap(0, 348, Short.MAX_VALUE));
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGap(0, 210, Short.MAX_VALUE));
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(layout.createSequentialGroup().addContainerGap(196, Short.MAX_VALUE).addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 182, javax.swing.GroupLayout.PREFERRED_SIZE).addGap(178, 178, 178)).addGroup(layout.createSequentialGroup().addGap(86, 86, 86).addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE).addContainerGap(122, Short.MAX_VALUE)));
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup().addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE).addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 40, Short.MAX_VALUE).addComponent(jLabel1).addGap(36, 36, 36)));
pack();
}// </editor-fold>
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
final SSBTest ssbTest = new SSBTest();
ssbTest.setVisible(true);
ssbTest.execute();
}
});
}
private void execute() {
(new MeaningOfLifeFinder(jLabel1, jPanel1)).execute();
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JPanel jPanel1;
// End of variables declaration
}
class MeaningOfLifeFinder extends SwingWorker<Icon, Object> {
JLabel label = null;
JPanel panel;
MeaningOfLifeFinder(JLabel label, JPanel jpanel) {
this.label = label;
this.panel = jpanel;
}
protected Icon doInBackground() throws IOException {
URL imageurl;
Image image = null;
System.out.println("image loading");
imageurl = new URL("http://maps.google.com/maps/api/staticmap"
+ "?zoom=14&size=512x512&maptype=roadmap"
+ "&markers=color:green|label:21|-15.0,-150.0&sensor=false");
//image = (Toolkit.getDefaultToolkit().createImage(imageurl));
image = ImageIO.read(imageurl);
ImageIcon icon = new ImageIcon(image);
System.out.println("image loaded...");
return icon;
}
#Override
protected void done() {
try {
System.out.println("image adding to label...");
label.setIcon(get());
//panel.add(label);
System.out.println("image loaded to label...");
} catch (Exception ignore) {
}
}
// System.out.println(panel.getSize().width);
}