display JLabels dynamically in JPanel/JFrame

Question

I am trying display images in sequential manner, but having difficulties in displaying(only last image is getting displayed on screen). I tried using CardLayout but as my number of JLabels(which contains ImageIcon) are high so it's giving me outofmemory exception. here's my code:

I have JFrame inside that I have JPanel in which I am trying to display JLabel one by one.

    public class ImageMain extends JFrame implements ActionListener{
    private static final long serialVersionUID = 2916361361443483318L;
    private JFileChooser fc = null;
    private JMenuItem item1,item2;
    private BufferedImage image = null;
    private JPanel panel = null;
    private int width = 0;
    private int height = 0;
    private BorderLayout card;
    private Container contentPane;

    public ImageMain() {
        JFrame frame = new JFrame("Image Extraction Tool");
        frame.setExtendedState(Frame.MAXIMIZED_BOTH);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        contentPane = frame.getContentPane();
        panel = new JPanel();
        card = new BorderLayout();
        panel.setLayout(card);
        panel.setBackground(Color.white);

        JMenuBar menuBar = new JMenuBar();
        JMenu menu = new JMenu("Menu");
        menuBar.add(menu);
        item1 = new JMenuItem("Browse an image");
        item2 = new JMenuItem("Exit");

        item1.addActionListener(this);
        item2.addActionListener(this);

        menu.add(item1);
        menu.add(item2);
        frame.setJMenuBar(menuBar);

        contentPane.add(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                ImageMain img = new ImageMain();
            }
        });
    }

    @Override
    public void actionPerformed(ActionEvent e) {

        if(e.getSource() == item1){
                if(fc == null)
                    fc = new JFileChooser();
                int retVal = fc.showOpenDialog(null);
                if(retVal == JFileChooser.APPROVE_OPTION){
                    File file = fc.getSelectedFile();
                    try {
                        image = ImageIO.read(file);
                        height = image.getHeight();
                        width = image.getWidth();

                        int[][] pixelData = new int[height * width][3];

                        int[] rgb;

                        int counter = 0;
                        for(int i = 0; i < height; i++){
                            for(int j = 0; j < width; j++){
                                rgb = getPixelData(image, i, j);

                                for(int k = 0; k < rgb.length; k++){
                                    pixelData[counter][k] = rgb[k];
                                }

                                counter++;
                            }
                        }

                        for(int m=pixelData.length-10; m < pixelData.length; m++){
                            System.out.println(m);
                            int[] pix = new int[width*height*3];

                            for(int i=0;i< width*height*3; i+=3){
                                pix[i] = pixelData[m][0];
                                pix[i+1] = pixelData[m][1];
                                pix[i+2] = pixelData[m][2];
                            }
                            JLabel createImageLabel = createImageLabel(pix);
                            panel.add(createImageLabel);
                           // panel.revalidate();panel.repaint();
                            contentPane.revalidate();contentPane.repaint();
                            Thread.sleep(2000);
                        }



                    } catch (IOException e1) {
                        System.out.println("IO::"+e1.getMessage());
                    }catch(Exception e1){
                        System.out.println("Exception::"+e1.getMessage());
                    }
                }
        }
        if(e.getSource() == item2){
            System.exit(0);
        }
    }


    private int[] getPixelData(BufferedImage image, int x, int y) {
        int argb = image.getRGB(y, x);

        int rgb[] = new int[] {
            (argb & 0x00ff0000) >> 16 , //red
            (argb & 0x0000ff00) >> 8, //green
             argb & 0x000000ff        //blue
        };

        return rgb;
    }

    private JLabel createImageLabel(int[] pixels){
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        WritableRaster raster = image.getRaster();
        raster.setPixels(0, 0, width, height, pixels);
        JLabel label = new JLabel(new ImageIcon(image));
        return label;
    }



}

please advice.

Thanks in advance.

Answer 1

Please check for similar questions and answers on this site about not calling Thread.sleep(...) inside of the Swing event thread. As they state, calling this will put your entire Swing GUI to sleep which is not your intention, I'm sure. Since your problem is no different from all the rest, the solution is the same as well: use a Swing Timer for intermittent actions, and use a background thread such as that generated by a SwingWorker for long-running background actions -- such as reading in images.

Also, if all you're doing is swapping images, then one JLabel should work fine. Just swap the ImageIcon that it displays in your Swing Timer.

---

Edit
You state:

I am not sure how to iterate my 2D array with swing Timer, every 2 sec I want to iterate my array and perform some action.

Suggestions:

• Give your timer a delay of 2000 (for milliseconds)
• Give the Timer's ActionListener one or two int counter fields that are initialized to 0.
• In the actionPerformed method, use the counter to get the item of interest, and then advance the counter(s).
• Read the Swing Timer Tutorial.