Thread: Method sharing question.

Just a quick question. What is a way this could be coded?

Imagine this:

• I have a class called "Monster."
• Class "Werewolf" extends "Monster."
• "Werewolf" has a method called "update()" for updating everything that's in "Werewolf."
• "Werewolf" has a method called "anim()" for animating a walking pattern.
• "Werewolf" has many variables that are used in "anim()." Mainly "Speed."

What I'm trying to do:

• Make it so "anim()" can be moved to "Monster" and still work.
• Make it so "update()" in "Werewolf" contains "{anim();}" but in a way that "anim()" uses the variables in "Werewolf."

What I tried, but didn't work:

• As soon as I moved the method, I noticed I had to fix something with the variables. I can't just put the variables in "Monster" because, sure, werewolves are monsters, but I'm trying to make it so in every subclass of "Monster" I only need to make new variables and call the method "anim()" in some way.
• Someone told me to use "this.*methodNameHere*()" but it doesn't work.

I want to call a method from a superclass in every subclass. The method has a variable "Speed" that is a different value in every subclass. The variable is the same name in every subclass, like this:

Werewolf.Speed
Ghost.Speed
Clown.Speed

And in those subclasses, there's a method "update()." Like this:

Werewolf.update();
Ghost.update();
Clown.update();

I'm not sure how to describe it, but I want those updates to contain "anim()" in a way that this happens:

• Werewolf.update(); calls Monster.anim(); in a way that Werewolf.Speed is used.
• Ghost.update(); calls Monster.anim(); in a way that Ghost.Speed is used.
• Clown.update(); calls Monster.anim(); in a way that Clown.Speed is used.

All I'm trying to do is use a method as a simple framework for animating an animation, keeping the method in a superclass while letting all of its subclasses call the method, while using their own variables/variable values.

So, all I really need is a way to call methods but in some way that the values change. Like Monster.Speed is the basis and the subclass variables of the same name somehow extend that? I don't know.

This thing that I'm trying to do is extremely new to me and I don't know where to go.
Lol I've been stuck on this one problem for 2 weeks.

Why can't you pass the speed from each subclass to the parent method, something like:

In class Werewolf:
super.anim( speed ); // (the 'super' isn't required, but helps make it clear)

Where speed is Werewolf's speed.

I think that answers the rest of your question about update(), but I'm not sure.

That was exactly what I was looking for.
Making variables IN the method while make a constructor solved part of my problem, but now I have an issue with one certain variable.

Say I have 4 animated sprites in my "Werewolf" class:
AnimatedSprite up,
AnimatedSprite down,
AnimatedSprite left,
and AnimatedSprite right.


I have this in "Monster:"

public void moveAnim(AnimatedSprite up, AnimatedSprite down, AnimatedSprite left, AnimatedSprite right) {
		AnimatedSprite animSprite = down;
		if (walking) animSprite.update();
		else animSprite.setFrame(0);
		if (movingUp) {
			dir = Direction.UP;
			animSprite = up;
		} else if (movingDown) {
			dir = Direction.DOWN;
			animSprite = down;
		}
		if (movingLeft) { 
			dir = Direction.LEFT;
			animSprite = left;
		} else if (movingRight) { 
			dir = Direction.RIGHT;
			animSprite = right;
		}
	}

"animSprite" is a variable used to set the direction to either up, down, left, or right. Never equal to more than 1 of the variables.

The problem is animSprite. I can't find a way to use it since it's defined in a method and not in the class.
I'm trying to get that animSprite variable in the method to go here:

sprite = animSprite.getSprite();

There's a red line under "animSprite" that I can't get rid of.
Is there a way to use moveAnim's animSprite variable?

By convention in Java, class names are capitalized, variable and method names begin with lowercase letters, and all are camel-cased thereafter. Constants (or final variables) are typically all caps with names separated by underscores.

Your moveAnim() method seems way more complicated than it needs to be, and it's hurting my head, so I haven't tried to simplify it. See if you can do it.

As for your question about the variable animSprite, define it outside the method as an instance variable, and then give access to the variable by other classes using a 'getter' (or accessor) method:

public class Animal  // or whatever the right class is
{
    AnimatedSprite animSprite;
 
    //  etc . . . 
 
    public void moveAnim()
    {
        animSprite = down;  // however it's set
 
        // etc. . . .
 
    }
 
    // etc . . .
 
    // an accessor that allows outside access to the variable animSprite
    public AnimatedSprite getAnimSprite()
    {
        return animSprite;
    }
 
}

You should have a firm foundation that includes a complete understanding and familiarity with these OOP concepts and practices before starting a project of this magnitude. You'll ignore me and continue on. When you end up with a big pile of code that doesn't do what you want, you don't know how to fix it, and you give up frustrated, remember you were told. Slow down, take a few steps back, and learn the basics.

Oh, haha. Sorry if it hurt your head, I was showing that animSprite's value is supposed to change according to direction.
This is the whole method I should have shown before:

public void moveAnim(AnimatedSprite up, AnimatedSprite down, AnimatedSprite left, AnimatedSprite right, double xa, double ya) {
		animSprite = down;
		if (walking) animSprite.update();
		else animSprite.setFrame(0);
		if (ya < 0) {
			dir = Direction.UP;
			animSprite = up;
		} else if (ya > 0) {
			dir = Direction.DOWN;
			animSprite = down;
		}
		if (xa < 0) { 
			dir = Direction.LEFT;
			animSprite = left;
		} else if (xa > 0) { 
			dir = Direction.RIGHT;
			animSprite = right;
		}
		if (xa != 0 || ya != 0) { 
			move(xa, ya);
			walking = true;
		} else {
			walking = false;
		}
	}

Your solution works, but the way I have my AnimatedSprite class coded, animSprite has to be equal to a variable or else I get a
null pointer exception. I think.

It seems, even with "animSprite = down;" animSprite is still null, so, with all honesty, I have no clue what's going on.

Here's where the issue started off:
In the constructor, I made a spot for separate animSprite variables to go from each subclass, but, again, animSprite had to be initialized, so I set it to "down." That made the character's animation only show the downward animation. So it's like I either set it to down or else it's null.

It seems, even with "animSprite = down;" animSprite is still null

Impossible, unless: 1) down is null, or 2) you've created another animSprite variable that hasn't been properly initialized. If animSprite = down, then somewhere 'down' should have been initialized as in:

down = new AnimatedSprite();

Indeed, down is initialized by this line:

public AnimatedSprite down = new AnimatedSprite(SpriteSheet.dummy_down, 32, 32, 4);

Nothing in that line is null, so I'm guessing it all has to do with animSprite needing to be initialized outside of a method .

And the only animSprite variable I can see is the one I initialized in moveAnim().

EDIT: I got rid of the animSprite variable and used up, down, left, and right in its place,
while moving some other things around.

Everything seems to be working fine, I just need to reorder some code. Thanks again.