Load and display all files with .jpg, .png and .gif from directory path

[men8]

Hello, i'm doing this task for my university java class and I've got a big problem with displaying pictures. I'm sucesfully load and recognize the extensions, but when they load I've got only frames with bugged diagonals (first is ok and adapts to the size of the frame, but next ones are broken and I don't know how to fix it) please help.
This is Main class

package cw6_zad2;
//C:\Users\MEN8\Desktop\ZDJECIA\test
 
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.concurrent.TimeUnit;
 
import javax.imageio.ImageIO;
import javax.swing.JFrame;
 
public class Main extends JFrame {
 
        private static final long serialVersionUID = -1906466112293567427L;
        private static String path;
        private int time;
        private static int fSize;
          // array of supported extensions (use a List if you prefer)
    final static String[] EXTENSIONS = new String[]{
        "gif", "png", "jpg" // and other formats you need
    };
    // filter to identify images based on their extensions
    final static FilenameFilter IMAGE_FILTER = new FilenameFilter() {
 
        @Override
        public boolean accept(final File dir, final String name) {
            for (final String ext : EXTENSIONS) {
                if (name.endsWith("." + ext)) {
                    return (true);
                }
            }
            return (false);
        }
    };
    public void readParams()
        {
                String arg = javax.swing.JOptionPane.showInputDialog("Prosze podac adres folderu oraz czas wyswietlania");
                String[] tab =arg.split(" ");
                path = tab[0];
                time = Integer.parseInt(tab[1]);
                fSize = Integer.parseInt(tab[2]);
                final File dir = new File(path);
                if (dir.isDirectory()) {
                        for (final File f : dir.listFiles(IMAGE_FILTER)) {
                                try {
                                        repaint();
                                        BufferedImage img = ImageIO.read(f);
                                        ImagePanel p = new ImagePanel(f.getName());
                                        add(p);
                                        pack();
                                    setTitle(f.getName());
                                    setLocationRelativeTo(null);
                                    setVisible(true);
                                    try {
                                        TimeUnit.SECONDS.sleep(this.time);
                                        if(f.getName() != "")
                                        {
                                               
                                                dispose();
                                                repaint();
                                        }else
                                        {
                                                repaint();
                                                setTitle("Przekatne");
                                            add(new  ImageField(img.getWidth(), img.getHeight()));
                                            setDefaultCloseOperation(EXIT_ON_CLOSE);  
                                            pack();
                                            setLocationRelativeTo(null);
                                            setVisible(true);
                                        }
                                    } catch (Exception e) {}
                                        System.out.println("image: " + f.getName());
                                        System.out.println(" width : " + img.getWidth());
                                        System.out.println(" height: " + img.getHeight());
                                        System.out.println(" size  : " + f.length());  
                                }catch (final IOException e) {
                                        // handle errors here
                                }
                        }
                }
               
        }
       
       
 
        public static void main(String[] args)
        {
                Main m = new Main();
                m.readParams();
               
        }
}

ImagePanel class

package cw6_zad2;
 
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Toolkit;
 
import javax.swing.JPanel;
 
public class ImagePanel extends JPanel {
 
        private static final long serialVersionUID = -8023867670007487938L;
       
        Image img;
        boolean loaded = false;
        int w, h;
        MediaTracker mt;
 
          public ImagePanel(String imgFileName) {
            loadImage(imgFileName);
          }
 
          public void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (this.img != null && this.loaded)
              g.drawImage(this.img, 0, 0, getWidth(), getHeight(), this);
            else
            {
                super.paintComponent(g);
                    this.w = getWidth();
                    this.h = getHeight();
                    g.setColor(Color.blue);
                   
                    g.drawLine(0, 0, this.w, this.h);
                    g.drawLine(0, this.h, this.w, 0);
               
            }
          }
 
          private void loadImage(String imgFileName) {
                this.img = Toolkit.getDefaultToolkit().getImage(imgFileName);
            this.mt = new MediaTracker(this);
            this.mt.addImage(this.img, 1);
            try {
                this.mt.waitForID(1);
            } catch (InterruptedException exc) {
            }
            this.w = this.img.getWidth(this);
            this.h = this.img.getHeight(this);
            if (this.w != -1 && this.w != 0 && this.h != -1 && this.h != 0) {
                this.loaded = true;
              setPreferredSize(new Dimension(this.w, this.h));
            } else
              setPreferredSize(new Dimension(200, 200));
          }
 
        }

and ImageField class

package cw6_zad2;
 
import java.awt.Dimension;
 
import javax.swing.JComponent;
 
public class ImageField extends JComponent
{
        private static final long serialVersionUID = -6546532428097591931L;
        Dimension d;
        public ImageField(int w, int h)
          {
            this.d = new Dimension(w, h);
            setMinimumSize(d);
            setPreferredSize(new Dimension(d));
            setMaximumSize(d);
          }
}

Sorry for my english, if something is not clear or not incomprehensible I will try to explain.