Greenfoot

swapon

2012/11/16

#

Hello, first of all I'm sorry for my English, it's far from being perfect. So, we've started programming with Java & Greenfoot a few weeks ago and I never used Java before. Our task is do create some kind of RPG with different levels. I want my hero (Robot) to switch levels as soon as a door in World 1 is removed which happens when Robot has a key in his inventory. This function is placed into the Robot class. So I tried to implement a bool return statement as soon as this happens. Switching levels has to be controlled by a subclass of World, "Weltenverwalter" (World-Administration). But I always get an error message that there is no such variable. These parts of my sourcecode are here; From my robot class;

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/**
 * Checks if a door can be removed
 */
public boolean unlockDoor()
{
    Actor object = getOneIntersectingObject(Door.class);
    if (object != null && !inventory.isEmpty() 
            && inventory.get() instanceof Key) { // Bonusaufgabe
        inventory.clear();
        getWorld().removeObject(object);
        return true;
    } else {
        return false;
    }
}

and the part from my World-Administration;

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public void checkWorld()
    {
        if(Robot.unlockDoor);
        { 
            if(Greenfoot.getWorld == Background);
            {
                Greenfoot.setWorld(Welt2);
            }
         
            if(Greenfoot.getWorld == Welt2);
            {
                Greenfoot.setWorld(Background);
            }
        }
    }

groengeel

2012/11/16

#

Try adding "()" in your if statement in the checkWorld() method.

groengeel

2012/11/16

#

To be clear the line should look like this:

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public void checkWorld()  
    {  
        if(Robot.unlockDoor())
        {   
            // This doesn't work like this:    
            if(Greenfoot.getWorld() == Background)
            {  
                 // Same here (You are now calling the variable "Welt2")
                Greenfoot.setWorld(Welt2);  
            }  
 
            // This doesn't work like this:         
            if(Greenfoot.getWorld() == Welt2)
            {  
                 // Same here (You are now calling the variable "Background")
                Greenfoot.setWorld(Background);  
            }  
        }  
    }

Try this. I: - removed ";" at the end of your if statements. - added "()" where you meant to use methods. If you are calling a method make sure you use () at the end of the name. Otherwise Java thinks you're calling a variable.

swapon

2012/11/16

#

Thank you, but it still doesn't really work. In the same line;

1	`if(Robot.unlockDoor())`

I now get an error "non-static method unlockDoor() cannot be referenced from a static context" when compiling, although there is nothing static?

davmac

2012/11/16

#

"Robot" is a class, not an object; that's what's meant by "static context". You can only call static methods on classes. You need a reference to a particular robot. You have a similar problem with your setWorld(...) commands: Greenfoot.setWorld(Background); // set world to a class, doesn't make sense Should probably be: Greenfoot.setWorld(new Background()); // set world to a world object

groengeel

2012/11/16

#

And as I pointed out in the code, I don't think this would work: if (Greenfoot.getWorld() == Background) I'd use: if (Greenfoot.getWorld() instanceof Background)

danpost

2012/11/16

#

groengeel wrote...

I'd use: if (Greenfoot.getWorld() instanceof Background)

I do not this this would work either. If the method 'checkWorld' is in a sub-class of World, then you should use

1	`if` `(this` `instanceof` `Background)`

'getWorld()' is an Actor class method and can only be used on an actor object.

groengeel

2012/11/16

#

@danpost I stand corrected ;)

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