'Must qualify the allocation with an enclosing instance of type Types'

Question

Firstly, I know this question has already been answered, however, I've looked through all the answers I could find and none of them helped.

I'm making a game in LibGDX, to simulate physics with large pixels. To create the different kinds of pixels, I've decided to make classes inside my Types class, empty space will also be a kind of pixel which I'll render as black, so I have a class within Types called None, which will be used for emptiness.

In my Main class, I create an ArrayList which contains ArrayLists which contains instances of Types:

public ArrayList<ArrayList<Types>> grid;

...

for (int y = 0; y < 151; y++) {
    ArrayList<Types> row = new ArrayList<Types>();
    for (int x = 0; x < 105; x++) {
        row.add(Types.None);
    }
    grid.add(row);
}

And, my Types class looks like this:

package io.j4cobgarby.github;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input.Keys;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.math.Vector2;

public class Types {

    public static Types None = new None();

    public float mass;
    public Color colour;
    public boolean dynamic;
    public boolean conducts_electrons;
    public float conducts_heat;


    public Types(float mass, Color colour, boolean dynamic, boolean conducts_electrons, float conducts_heat) {
        this.mass = mass;
        this.colour = colour;
        this.dynamic = dynamic;
        this.conducts_electrons = conducts_electrons;
        this.conducts_heat = conducts_heat;
    }

    public void getInput() {

    }

    public void dynamUpdate() {

    }

    public void staticUpdate() {

    }

    public void delete() {

    }

    public class None extends Types {

        public None() {
            super(0.0f, Color.BLACK, false, false, 0.0f);
        }

        @Override
        public void getInput () {
            if (Gdx.input.isKeyJustPressed(Keys.T)) {
                System.out.println("T pressed");
            }
        }

    }

}

So what I hopes was that I would now have an ArrayList containing 151 other ArrayLists, each containing 105 instances of Types.None But, this doesn't work.

On line 10 of Types - public static Types None = new None(); - I get this error:

No enclosing instance of type Types is accessible. Must qualify the allocation with an enclosing instance of type Types (e.g. x.new A() where x is an instance of Types).

Why is this? I've tried many things, but I can't seem to get it working.

Thanks.

Answer 1

Since you are assigning an instance of the None class to a static field, the None class must also be decleared static. Non-static inner classes can only exist within an instance of their outer class.

public static class None extends Types {
    ...
}