Need some help pls! whenever I click on the modify button it removes everything fine however gives me a null pointer exception on the indicated line. Please can someone explain how to fix it.
import greenfoot.*; // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
/**
* Write a description of class modifybutton here.
*
* @author (your name)
* @version (a version number or a date)
*/
public class modifybutton extends buttons
{
public int traction=0;
public int baysize=0;
/**
* Act - do whatever the modifybutton wants to do. This method is called whenever
* the 'Act' or 'Run' button gets pressed in the environment.
*/
public void act()
{
if (Greenfoot.mouseClicked(this))
{
getWorld().removeObjects(getWorld().getObjects(playbutton.class));
getWorld().removeObjects(getWorld().getObjects(exitbutton.class));
getWorld().removeObjects(getWorld().getObjects(modifybutton.class));
getWorld().setBackground(new GreenfootImage("modification background.fw.png")); //this line then comes up with a nullpointerexception
getWorld().addObject(new skisbutton(), 3 , 2);
getWorld().addObject(new tracksbutton(), 5 , 2);
getWorld().addObject(new wheelsbutton(), 7 , 2);
getWorld().addObject(new largebaybutton(), 7 , 3);
getWorld().addObject(new mediumbaybutton(), 5 , 3);
getWorld().addObject(new smallbaybutton(), 3 , 3);
getWorld().addObject(new backbutton(), 8 , 7);
}
}
}