Main.java Source code

Introduction

Here is the source code for Main.java

Source

import java.awt.KeyboardFocusManager;
import java.awt.Rectangle;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import javax.swing.BoxLayout;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JViewport;

public class Main {
    public static void main(String[] args) {
        int ROWS = 100;
        JPanel content = new JPanel();
        content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
        content.add(new JLabel("Thanks for helping out. Use tab to move around."));
        for (int i = 0; i < ROWS; i++) {
            JTextField field = new JTextField("" + i);
            field.setName("field#" + i);
            content.add(field);
        }
        KeyboardFocusManager.getCurrentKeyboardFocusManager().addPropertyChangeListener("focusOwner",
                new PropertyChangeListener() {
                    @Override
                    public void propertyChange(PropertyChangeEvent evt) {
                        if (!(evt.getNewValue() instanceof JComponent)) {
                            return;
                        }
                        JViewport viewport = (JViewport) content.getParent();
                        JComponent focused = (JComponent) evt.getNewValue();
                        if (content.isAncestorOf(focused)) {
                            Rectangle rect = focused.getBounds();
                            Rectangle r2 = viewport.getVisibleRect();
                            content.scrollRectToVisible(
                                    new Rectangle(rect.x, rect.y, (int) r2.getWidth(), (int) r2.getHeight()));
                        }
                    }
                });
        JFrame window = new JFrame();
        window.setContentPane(new JScrollPane(content));
        window.setSize(200, 200);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setVisible(true);
    }
}