JScrollPanel don't show the scroll

Question 1

Scrollpane and its scrollbars entirely rely on the size of the component in the viewport, which, by default, depends of the preferred size of that component.

Check this code which shows you a basic example of how this all works:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class TestScrollPane {

    public static class CustomComponent extends JPanel {

        private static final int RADIUS = 20;
        private int x = 0;
        private int y = 0;

        private double speed = 18;
        private double dx;
        private double dy;

        public CustomComponent() {
            dx = speed;
            dy = speed;
            Timer t = new Timer(20, new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {
                    x += dx;
                    y += dy;
                    if (x + RADIUS > getWidth()) {
                        x = getWidth() - RADIUS;
                        dx = -speed;
                    } else if (x < 0) {
                        x = 0;
                        dx = speed;
                    }
                    if (y + RADIUS > getHeight()) {
                        y = getHeight() - RADIUS;
                        dy = -speed;
                    } else if (y < 0) {
                        y = 0;
                        dy = speed;
                    }
                    repaint();
                }
            });
            t.start();
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.fillOval(x, y, RADIUS, RADIUS);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(600, 600);
        }
    }

    protected void initUI() {
        JFrame window = new JFrame(TestScrollPane.class.getSimpleName());
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JScrollPane scroll = new JScrollPane(new CustomComponent(), JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        window.add(scroll);
        window.setSize(600, 500);
        window.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TestScrollPane().initUI();
            }
        });
    }
}

Question 2

Actually your JScrollPane is 1000x1000px, so if there are scroll bars, you won't see them, because your frame is 500x500. Note that the JScrollPane acts on its content, that means that it shows scrollbars if the panel you are adding to it is bigger than the JScrollPane itself, but doesn't add scrollbars if the container is smaller.

Question 3

The viewable area/space is defined (in most cases) by the view's preferred size. This suggests that your problem lies with your scroll panes view and not the scroll pane or anything else you've provided us

enter image description here

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestScrollPane02 {

    public static void main(String[] args) {
        new TestScrollPane02();
    }

    public TestScrollPane02() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(new LargePane()));
                frame.setSize(200, 200);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class LargePane extends JPanel {

        public LargePane() {
            setLayout(new GridBagLayout());
            add(new JLabel("I'm a large panel"));
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.drawLine(0, 0, getWidth(), getHeight());
            g.drawLine(getWidth(), 0, 0, getHeight());
        }

    }

}

You can also have a look the Scrollable interface which provides additional hints back to the scroll pane...