Java Tile Scrolling Issues

Question

I\'m fairly new to programming with graphics and I\'m attempting to code a side scrolling 2D game. At the moment, I\'m trying to figure out how to approach redrawing a scrol

Answer 1

This is a proof of concept only! I randomly generate the tiles that get painted, I hope you have some kind of virtual map setup so you know which tiles to paint at any given virtual point!

Basically, what this does, is when the screen is moved left or right, it shifts the "master" image left or right and stitches new tiles onto new edge

My test was using a style sheet of 31x31 cells (don't ask, I just grab it off the net)

This is VERY scaled down example of the output, it was running at 1100x700+

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Scroll {

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

    public Scroll() {
        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 TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage screen;
        private BufferedImage styleSheet;

        public TestPane() {
            try {
                styleSheet = ImageIO.read(getClass().getResource("/StyleSheet.png"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "left");
            im.put(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), "right");

            ActionMap am = getActionMap();
            am.put("left", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    stitch(-31);
                }
            });
            am.put("right", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    stitch(31);
                }
            });
        }

        @Override
        public void invalidate() {
            screen = null;
            super.invalidate();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void stitch(int direction) {
            if (screen == null) {
                prepareScreen();
            }

            Random r = new Random();
            BufferedImage update = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2d = update.createGraphics();
            g2d.drawImage(screen, direction, 0, this);
            int gap = direction < 0 ? (direction * -1) : direction;

            int xOffset = 0;
            if (direction < 0) {
                xOffset = getWidth() - gap;
            }

            for (int x = 0; x < gap; x += 31) {
                for (int y = 0; y < getHeight(); y += 31) {
                    xOffset += x;
                    int cellx = 2;
                    int celly = 2;
                    if (r.nextBoolean()) {
                        cellx = 7;
                        celly = 5;
                    }

                    BufferedImage tile = styleSheet.getSubimage((cellx * 33) + 1, (celly * 33) + 1, 31, 31);
                    g2d.drawImage(tile, xOffset, y, this);
                }
            }
            g2d.dispose();

            screen = update;

            repaint();

        }

        protected void prepareScreen() {

            if (screen == null) {
                screen = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
            }

            Random r = new Random();
            Graphics2D g2d = screen.createGraphics();
            for (int x = 0; x < getWidth(); x += 31) {
                for (int y = 0; y < getHeight(); y += 31) {

                    int cellx = 2;
                    int celly = 2;
                    if (r.nextBoolean()) {
                        cellx = 7;
                        celly = 5;
                    }

                    BufferedImage tile = styleSheet.getSubimage((cellx * 33) + 1, (celly * 33) + 1, 31, 31);
                    g2d.drawImage(tile, x, y, this);

                }
            }
            g2d.dispose();

        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            if (screen == null) {
                prepareScreen();
            }
            g2d.drawImage(screen, 0, 0, this);
            g2d.dispose();
        }
    }

}