SCROLLING BACKGROUND

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class MyWorld here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class MyWorld extends World
{

    /**
     * Constructor for objects of class MyWorld.
     * 
     */
    
    private Background img0, img1;
    
    public MyWorld()
    {    
        // Create a new world with 600x400 cells with a cell size of 1x1 pixels.
        super(900, 600, 1, false);
        
        img0 = new Background();
        addObject(img0, getWidth()/2, getHeight()/2);
        img1 = new Background();
        addObject(img1, getWidth() + getWidth()/2, getHeight()/2);
        
    }
    
    public void act()
    {
        //if(Greenfoot.isKeyDown("right"))     
        //{
        //    img0.scroll();
        //    img1.scroll();
        //}
        
        //if(Greenfoot.isKeyDown("left"));
        //{
            img0.scroll();
            img1.scroll();
        //}
    }
}

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class Background here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Background extends Actor
{
    /**
     * Act - do whatever the Background wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
        // Add your action code here.
    }
    
    public void scroll()
    {
        if(getX() < -getImage().getWidth()/2)
        {
            setLocation (getX() + getWorld().getWidth()*2, getY());
        }
        setLocation (getX()-5, getY());        
    }
}