image doesnt shows on JLabel when click on next button, using java Swing

Question

I am trying to make small program that shows pic on JLabel when user click on Next Button.The Problem is when i click on next button it shows nothing.but if i resize frame it shows all pics from directory. instead of one picture at a time. Please excuse my English. here is my code.

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.imageio.ImageIO;
import java.io.*;
import java.awt.image.BufferedImage;

class test {
    public static void main(String args[]) {
        frame f = new frame();
        f.gui();
        f.actions();
    }
}

class frame {

    BufferedImage file;
    File img;
    ImageIcon icon;

    JLabel image;
    JFrame frame;
    JPanel panel;
    String[] path = { "juice.jpg", "gal.jpg", "truck.jpg", "Drive.jpg" };

    JButton next = new JButton("NEXT");
    JButton pre = new JButton("PREVOIUS");
    JTextField field = new JTextField(10);

    static int num = 0;

    public void gui() {

        frame = new JFrame("pic gallery");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        FlowLayout flow = new FlowLayout();
        frame.setLayout(flow);
        panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.LINE_AXIS));
        panel.add(next);
        panel.add(pre);
        panel.add(field);

        JLabel piclabel = new JLabel();

        frame.getContentPane().add(panel);
    }

    void actions() {

        next.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                img = new File(path[num]);
                System.out.println(num);
                try {
                    file = ImageIO.read(img);
                    icon = new ImageIcon(file);
                    image = new JLabel("", icon, JLabel.CENTER);

                    image.setVisible(true);
                    frame.getContentPane().add(image);

                } catch (IOException g) {

                }
                if (num < path.length - 1) {
                    num++;
                    field.setText(num + "");

                } else {
                    num = 0;

                }
            }
        });
    }
}

Answer 1

Add frame.revalidate() and frame.repaint() after frame.getContentPane().add(image);

Swing is lazy when it comes to performing updates to the layout hierarchy, which is good thing, imagine adding a few dozen components and having the entire component hierarchy been updated for each one.

So, instead, you need to update the container manually when you've made changes

added as you suggested . now it shows next image on frame along with prevous image. but i wants 1 image at a time

Then remove the first image, or better yet, instead of creating a new JLabel each time, create a single JLabel and simply change it's icon property, which should invalidate the container automatically

Answer 2

In your ActionListener for next you need to remove the previous Label then add the new Label

try
{
     file = ImageIO.read(img);
     icon = new ImageIcon(file);
     if(image != null) frame.remove(image);
     image = new JLabel("", icon, SwingConstants.CENTER);

     image.setVisible(true);
     frame.getContentPane().add(image);
     frame.revalidate();
     frame.repaint();
}
catch (IOException g)
{
}