I'm having trouble getting JScrollPanes to actually display scroll bars

Question

I\'ve found some examples scattered around the internet involving getting an image or a textbox to display scroll bars, but they all involve a program that basically display

Answer 1

Better that you should use layout managers to your advantage and to let these managers do the heavy lifting of calculating component sizes and placements for you. For example:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;

import javax.swing.*;

public class ScrollDemo2 extends JPanel {
   public static final Color[] COLORS = {Color.green, Color.red, Color.blue};
   private static final Dimension PANEL_SIZE = new Dimension(300, 300);
   public ScrollDemo2() {
      JPanel innerPanel = new JPanel(new GridLayout(0, 1));
      for (int i = 0; i < COLORS.length; i++) {
         JPanel colorPanel = new JPanel();
         colorPanel.setPreferredSize(PANEL_SIZE);
         colorPanel.setBackground(COLORS[i]);
         innerPanel.add(colorPanel);
      }
      JScrollPane scrollPane = new JScrollPane(innerPanel);
      scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
      scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
      scrollPane.getViewport().setPreferredSize(PANEL_SIZE);

      int eb = 10;
      setBorder(BorderFactory.createEmptyBorder(eb, eb, eb, eb));
      setLayout(new BorderLayout());
      add(scrollPane, BorderLayout.CENTER);
   }

   private static void createAndShowGui() {
      ScrollDemo2 mainPanel = new ScrollDemo2();

      JFrame frame = new JFrame("ScrollDemo2");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}