JButton setIcon Updation error

Question

Currently i m making a java program using netbeans based on changing image in a button....

Actually my requirement is to change the Image icon of a button as i click another button (Say A).....

i came out with the following program........

       // Following function is included inside the button's (Here A) ActionListener........
       public void change_image()
       {
             if(sex==0)
             {
                   ic=new ImageIcon("E:\\java_images\\female_profile.jpg");
                   sex=1;
             }
             else if(sex==1)
             {
                   ic = new ImageIcon("E:\\java_images\\male_profile.png");
                   sex=0;
             }

              // To resize the image into the size of the button... 
               labelicon.setImage(ic.getImage().getScaledInstance(image_btn.getWidth(),image_btn.getHeight(), Image.SCALE_DEFAULT));

             img_btn.setIcon(labelicon);

         }

The Variables i've included are

           private int sex;    // 0  - female, 1 - male

           private ImageIcon ic,labelicon;  // variables meant for storing ImageIcons.....
           private JButton img_btn;  // the button at which the image is to  be displayed....

Now the Weird Behaviour i observed is.......

The image gets displayed on the button click, only when i click the minimize button. i.e when the i click the button A, the code specified in the ActionListener is getting executed. But the effect of the image change appears only when i minimize the window and again make it appear on the screen.... Can anyone tell why this is occuring and how can i remove the problem ??

All i want is to change the image the moment i click the A Button..... Well..i haven't included for the code for creating button since they are easily done by netbeans swing GUI builder......

Answer 1

1. load Icon / ImageIcon as local variable once time, there no reason to re_loading image from ActionListener

2. in the API is description that Image#ScaledInstance is pretty asynchronous

3. otherwise you have to call

.

labelicon.getImage().flush();
img_btn.setIcon(labelicon);

EDIT

@akp wrote but..how would you resize the icon image..??

there are two or three another ways how to put Icon /ImageIcon and will be resiziable with its parent, JLabelcould be easiest of ways

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.swing.*;

public class JButtonAndIcon {

    private static JLabel label = new JLabel();
    private static Random random = new Random();
    private static ImageIcon image1; // returns null don't worry about 
    private static ImageIcon image2; // returns null don't worry about 
    private static Timer backTtimer;
    private static int HEIGHT = 300, WEIGHT = 200;

    public static void main(String[] args) throws IOException {
        label.setPreferredSize(new Dimension(HEIGHT, WEIGHT));
        final JButton button = new JButton("Push");
        button.setBorderPainted(false);
        button.setBorder(null);
        button.setFocusable(false);
        button.setMargin(new Insets(0, 0, 0, 0));
        button.setContentAreaFilled(false);
        button.setLayout(new BorderLayout());
        button.add(label);
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                if (button.getIcon() == image1) {
                    label.setIcon(image2);
                } else {
                    label.setIcon(image1);
                }
            }
        });
        JFrame frame = new JFrame("Test");
        frame.add(button);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        startBackground();
        frame.setVisible(true);
    }

    private static void startBackground() {
        backTtimer = new javax.swing.Timer(750, updateBackground());
        backTtimer.start();
        backTtimer.setRepeats(true);
    }

    private static Action updateBackground() {
        return new AbstractAction("Background action") {

            private static final long serialVersionUID = 1L;

            @Override
            public void actionPerformed(ActionEvent e) {
                label.setIcon(new ImageIcon(getImage()));
            }
        };
    }

    public static BufferedImage getImage() {
        int w = label.getWidth();
        int h = label.getHeight();
        GradientPaint gp = new GradientPaint(0f, 0f, new Color(
                127 + random.nextInt(128),
                127 + random.nextInt(128),
                127 + random.nextInt(128)),
                w, w,
                new Color(random.nextInt(128), random.nextInt(128), random.nextInt(128)));
        BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = bi.createGraphics();
        g2d.setPaint(gp);
        g2d.fillRect(0, 0, w, h);
        g2d.setColor(Color.BLACK);
        return bi;
    }
}

Answer 2

The problem here is that you are updating the internals of an Icon. The setIcon method will think that it's the same icon that the button already has. I would recommend you to do two different Icon objects that to use to update the icon with. That will fix the problems.

---

Example (with two different icons):

public static void main(String[] args) throws IOException {

    final ImageIcon redIcon = createImageIcon(10, 10, Color.RED);
    final ImageIcon blueIcon = createImageIcon(10, 10, Color.BLUE);

    final JButton button = new JButton("Push", blueIcon);
    button.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (button.getIcon() == redIcon)
                button.setIcon(blueIcon);
            else
                button.setIcon(redIcon);
        }
    });

    JFrame frame = new JFrame("Test");
    frame.add(button);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
}

private static ImageIcon createImageIcon(int w, int h, Color color) {
    Image image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
    Graphics g = image.getGraphics(); 
    g.setColor(color); 
    g.fillRect(0, 0, w, h); 
    g.dispose();
    return new ImageIcon(image);
}

---

Background:

Looking at the source of AbstractButton.setIcon, you can see that it won't know about the update if the reference "isn't updated":

    .....
    if (defaultIcon != oldValue) {
        if (defaultIcon == null || oldValue == null ||
            defaultIcon.getIconWidth() != oldValue.getIconWidth() ||
            defaultIcon.getIconHeight() != oldValue.getIconHeight()) {
            revalidate();
        } 
        repaint();
    }

---

Note to @HarryJoy, you actually had a point even though you didn't know why... :) Sorry! +1 again!

Answer 3

//Call img_btn.revalidate() and img_btn.repaint()

Correction, setIcon should already do this. I use the hacky way of img_btn.setText("<HTML><BODY><IMG SRC=\"/path/to/img.jpg\"/></BODY</HTML>"); personally.