Manish Basdeo
Manish Basdeo

Reputation: 6269

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                   

}

Upvotes: 1

Views: 4312

Answers (2)

trashgod
trashgod

Reputation: 205885

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:

SO Logo

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();
            }
        }
    }
}

Upvotes: 15

Sam Barnum
Sam Barnum

Reputation: 10744

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);
}

Upvotes: 3

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