setting something disposed or invisible java

Question

changed the project since its working now. kinda. the image still isnt changing.

package icnon;

import javax.imageio.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class FrameIconExample extends JFrame implements ActionListener {

    JLabel j;
    JPanel p, l, k;
    JButton picOne, picTwo;
    Container cPane;

    public FrameIconExample() {
        JButton picOne = new JButton("picOne");
        JButton picTwo = new JButton("picTwo");
        picOne.setName("picOne");
        picTwo.setName("picTwo");

        picOne.addActionListener(this);
        picTwo.addActionListener(this);

        p = new JPanel(new GridLayout(2, 1));
        l = new JPanel(new FlowLayout());
        k = new JPanel(new FlowLayout());

        cPane = getContentPane();

        j = new JLabel(new ImageIcon(
            "../meet/src/images/beautiful-closeup-portrait-photography.jpg"));

        l.add(j);
        k.add(picOne);
        k.add(picTwo);
        p.add(l);
        p.add(k);

        add(p);
    }

    public static void main(String[] args) {
        FrameIconExample frame = new FrameIconExample();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.setSize(new Dimension(300, 800));
        frame.setTitle("Frame Icon Example");

        // Display the form
        frame.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        JButton temp = (JButton) e.getSource();
        String src = "../meet/src/images/Majken Kruse portrait - john.jpg";

        //System.out.println(src + " " + temp.getName());

        if (temp.getName().equalsIgnoreCase("picOne")) {
            try {

                l.hide();

                try {

                    src = "../meet/src/images/beautiful-closeup-portrait-photography.jpg";
                    System.out.println(src + " " + temp.getName());
                    Icon img;
                    j = new JLabel(new ImageIcon(src));

                    l.add(j);

                    System.out.println("1");
                } catch (Exception q) {
                    q.printStackTrace();
                }

                if (temp.getName().equalsIgnoreCase("picTwo")) {
                    src = "../icontest/images/Majken Kruse portrait - john.jpg";
                    System.out.println(src + " " + temp.getName());
                    Icon img;
                    j = new JLabel(new ImageIcon(src));
                    l.add(j);
                    System.out.println("2");
                }
            } catch (Exception x) {
                x.printStackTrace();
            }
        }
    }
}

excuse the bad indentation. im pretty sure the method l.add(j); is the reason the image doesnt change.

any ideas what it should be?

Answer 1

I assume you did not set the correct image location. Are you sure the images are in the exact location you specified? What IDE are you using? If you use Eclipse, a refresh of your project might help.

Answer 2

Note: this answer was made for the revisions 1 and 2 of the question.

It's not an Awt error, it's a NullPointerException.

Your field l is null, because on the moment you thought you created it, you actually masked it with a local variable.

JPanel p = new JPanel(new GridLayout(2, 1));
JPanel l = new JPanel(new FlowLayout());
JPanel k = new JPanel(new FlowLayout());

Should be:

p = new JPanel(new GridLayout(2, 1));
l = new JPanel(new FlowLayout());
k = new JPanel(new FlowLayout());

Read again the error, with the stack trace. It tells you which line is the problem, and the type of the error tells you what happened, in this case.

Answer 3

The problem you are having is that you declare a global JPanel named l, but then when you instantiate JPanels in your constructor, you declare and assign a local scope JPanel named l. When you try to add a component in your actionPerformed, you are attempting to add it to the null global var.