Java problem

[english tyrant]

I have 3 classes, lets just call them Class1 Class2 and Class3.
Class1 contains my Public Static Main etc method, in which it declares an instance of Class2.
Class2 InstanceClass2 = new Class2();
Class1 also calls the Repaint method of InstanceClass2

Class2 extends JFrame.
Class2 declares an instance of Class3.
Class3 InstanceClass3 = new Class3();
Class2 then inside it's repaint method calls some methods from Class3.

Class3 in one of it's methods called by InstanceClass2 tries to access the getHeight() method from InstanceClass2.
InstanceClass2.getHeight();
The Error I recieve is that the symbol "InstanceClass2" is not valid. Or something along those lines.

All Methods and classes are public.
I have tried saving the getHeight method to a public variable within Class2, but Class3 still couldn't access it.


Help!



Visual aid =




I hope you could understand that. I thought it would be easier to use generic names rather than the actual names I have used, but in retrospect, I've made it look more complicated than it actually is.

[Juvenal]

I think we need to see your actual code... it isn't clear where the Class3 method is getting its reference to instanceClass2, or exactly how it is trying to use it.

[Dewy]

The problem is the way you're referencing the instance of class 2 in class 3. Class 3 doesn't know what the instance is. That's what I gathered from what you said but I can't be sure as I haven't seen the code.

[english tyrant]

The problem is the way you're referencing the instance of class 2 in class 3. Class 3 doesn't know what the instance is. That's what I gathered from what you said but I can't be sure as I haven't seen the code.

Sounds about right.

Class 1

Spoiler Alert, click show to read: 

public class Launcher {
    
    public static void main( String args[]) {
        simplegraphics SG = new simplegraphics();
        
        while(true) {
            SG.repaint();
        }
        
    }
}

Class 2

Spoiler Alert, click show to read: 

import java.awt.*;
import javax.swing.*;

public class simplegraphics extends JFrame {

    Square MySquare = new Square();
    public int Height = getHeight(); //just testing if I could access it after it has been stored as a public variable, apparently not.
    public int Width = getWidth();
    
    public simplegraphics(){
        setVisible(true);
        setSize(1200,1000);
    }

     public void clear(Graphics Window) {
        Window.setColor(Color.white);                   // set to white
        Window.fillRect(0, 0, getWidth(), getHeight()); // clear background
    }   
     
     
     
    public void paint(Graphics Window){
        Window.translate(0, 25);         //Accounts for titlebar

        clear(Window);
        MySquare.move();
        MySquare.draw(Window);       
    }    
}

Class 3

Spoiler Alert, click show to read: 

import java.awt.*;
import javax.swing.*;

public class Square extends JFrame{
    
    int x = 50, y = 50, xsize = 100, ysize = 100, xvel = 1, yvel = 1, speed = 1;
    
    
    void move() {
        if(x > SG.getWidth()) // this
            xvel = -xvel;
        if(x < 0)
            xvel = -xvel;
        if(y > SG.getHeight()) // and this. Are my problems.
            yvel = -yvel;
        if(y < 0)
            yvel = -yvel;
        
        x = x + xvel;
        y = y + yvel;    
        
        
    }
    
    
    void draw(Graphics Window) {
        Window.setColor(Color.black);                   // set to black
        Window.fillRect(x, y, xsize, ysize);            // draw square
    }
}

[Juvenal]

When you create an instance of Square, you need to pass a reference to the instance of simplegraphics which created it. The easiest way to do this is in the constructor:

public class Square extends JFrame{ 

    int x = 50, y = 50, xsize = 100, ysize = 100, xvel = 1, yvel = 1, speed = 1; 
    simplegraphics myParent;

    Square (simplegraphics daddy) {
        myParent = daddy;
    }

    void move() {
        if(x > myParent.getWidth()) // this
            xvel = -xvel;
        if(x < 0)
            xvel = -xvel;
        if(y > myParent.getHeight()) // and this. Are my problems.
            yvel = -yvel;
        if(y < 0)
            yvel = -yvel;
        
        x = x + xvel;
        y = y + yvel;    
    }
}

Don't forget in simplegraphics to pass the instance when creating Square:

Square MySquare = new Square(this);

I ran this in NetBeans and got a nice bouncing box.

[english tyrant]

Ahh, of course, that makes sense now.
Thankyou very much. This had been irritating me for a while.