Greenfoot

bbwf

2013/1/17

#

Hey I was wondering what would the code be if when an actor hits the right or lefts edge of the world it will change the background?

Gevater_Tod4711

2013/1/17

#

First you need to know if the actor hits the edge of the world using a mehtod like this:

    public boolean atWorldEdge() {
        if(getX() < 20 || getX() > getWorld().getWidth() - 20) {
            return true;
        }
        if(getY() < 20 || getY() > getWorld().getHeight() - 20) {
            return true;
        }
        else {
            return false;
        }
    }

If this method return true you have to change the worldbackground like this:

((YourWorld) getWorld()).setBackground("filename.png"); //YourWorld has to be the classname of your world class.

Im not sure if the cast is necessary but it should work this way.

bbwf

2013/1/17

#

Where would I put the setbackground?

bbwf

2013/1/17

#

My world is named Background, I want to set the file to test.png I have replaced everything and tried it out and it won't compile. Says unreachable statement.

danpost

2013/1/17

#

'unreachable statement' error will only show when you place code somewhere where the logical execution of the method results in never being able to get to the statement indicated; possibly due to a 'return' statement before it. Check the logic of the method the error occurs in.

bbwf

2013/1/17

#

So than where do I put the setbackground?

vonmeth

2013/1/17

#

Where you check if the edge of the world has been hit ...

danpost

2013/1/17

#

Did you fix your 'unreachable statement' issue?

bbwf

2013/1/18

#

Sorry, I'm so confused.

bbwf

2013/1/18

#

And danpost I have not.

danpost

2013/1/18

#

Please show what code you have.

bbwf

2013/1/18

#

I do not have access to it right now, I can give it to you tomorrow when I get access.

danpost

2013/1/18

#

I'll be happy to help you out, if I can. Until then.

bbwf

2013/1/18

#

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

/**
 * Write a description of class bob here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class bob extends Actor
{
    /**
     * Act - do whatever the bob wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
       checkForArrowKeys(4);
       
       
    }
    public void checkForArrowKeys (int adjust)
    {
        if ( Greenfoot.isKeyDown("a") )

        {
            setLocation(getX() - adjust, getY());
        }
        if ( Greenfoot.isKeyDown("d") )
 

        {
            setLocation(getX() + adjust, getY() );
        }
        //if ( Greenfoot.isKeyDown("w") )

       // {
          //  s//etLocation(getX() , getY() - adjust );
       // }
        //if ( Greenfoot.isKeyDown("s") )

      //  {
            //setLocation(getX() , getY() + adjust );
        //}

    }
    public boolean atWorldEdge() {
        if(getX() < 20 || getX() > getWorld().getWidth() - 20) {
            return true;
        }
        if(getY() < 20 || getY() > getWorld().getHeight() - 20) {
            return true;
         ((Background) getWorld()).setBackground("lol.png"); //YourWorld has to be the classname of your world class.
        }
        else {
            return false;
        }
    }
    
}

danpost

2013/1/18

#

Line 52 is not reachable because you have a 'return' statement immediately before it.

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How to change the background if an actor hits the edge of the world?