Main.java Source code

Introduction

Here is the source code for Main.java

Source

import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JViewport;

public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.getContentPane().add(new MyPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}

class MyPanel extends JPanel {
    Rectangle RECT = new Rectangle(450, 400, 100, 100);
    Dimension INNER_PANEL_SIZE = new Dimension(600, 800);
    Dimension SCROLLPANE_SIZE = new Dimension(250, 300);
    String NOT_VISIBLE = "Not Visible";
    String VISIBLE = "Visible";
    InnerPanel innerPanel = new InnerPanel();
    JViewport viewport = new JViewport();
    JLabel statusLabel = new JLabel(NOT_VISIBLE);

    MyPanel() {
        JScrollPane scrollpane = new JScrollPane();
        scrollpane.setViewport(viewport);
        viewport.add(innerPanel);
        scrollpane.setPreferredSize(SCROLLPANE_SIZE);
        viewport.addChangeListener(e -> {
            Rectangle viewRect = viewport.getViewRect();
            if (viewRect.intersects(RECT)) {
                statusLabel.setText(VISIBLE);
            } else {
                statusLabel.setText(NOT_VISIBLE);
            }
        });

        setLayout(new BorderLayout());
        add(scrollpane, BorderLayout.CENTER);
        add(statusLabel, BorderLayout.SOUTH);
    }

    class InnerPanel extends JPanel {
        InnerPanel() {
            setPreferredSize(INNER_PANEL_SIZE);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.setColor(Color.red);
            g2.setStroke(new BasicStroke(4));
            g2.draw(RECT);
        }
    }
}