Question : In the following snippet, I wish to draw different shapes such as rectangles, circles, triangles etc. I will be creating different class files for each of such objects, as I did for Rectangle class here.

I've been trying to invoke the draw method of Rectangle object from Stage object, but I am unable to do so. If I make a plain call to the draw method of the Rectangle object, I can draw the object.

Can some one suggest me how is this possible ? Also, I had many other queries which I'd tried to put in comments. Please have a look at them and kindly help me in figuring out the concept beneath it.

Disclaimer : I am new to game programming, started with Libgdx.

Following is the Scan class :

package com.mygdx.scan.game;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
import com.badlogic.gdx.graphics.glutils.ShapeRenderer.ShapeType;
import com.badlogic.gdx.scenes.scene2d.Stage;

public class Scan extends ApplicationAdapter {
private Stage stage;
public static ShapeRenderer shapeRenderer;

@Override
public void create () {
    stage = new Stage();
    shapeRenderer = new ShapeRenderer();
    Rectangle rect1 = new Rectangle(50, 50, 100, 100);
    stage.addActor(rect1);

}

@Override
public void render () {
    Gdx.gl.glClearColor(1, 1, 1, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    shapeRenderer.setProjectionMatrix(stage.getCamera().combined);
    shapeRenderer.begin(ShapeType.Filled);
    shapeRenderer.setColor(Color.BLACK);
    //new Rectangle(50, 50, 100, 100).draw();
    shapeRenderer.end();
    // This should call Rectangles draw method. I want a Shapetype.Filled Rectangle. 
    // But I'm unable to invoke this method if I add the actor in stage object and invoke it's draw method. 
    stage.draw(); 
}

public void dispose() {
    stage.dispose();
}
}

Following is the Rectangle Actor class :

package com.mygdx.scan.game;

import com.badlogic.gdx.scenes.scene2d.Actor;

public class Rectangle extends Actor {

float xcord, ycord, width, height;
public Rectangle(float x , float y , float width, float height) {
    this.xcord = x;
    this.ycord = y;
    this.width = width;
    this.height = height;
}

// This needs to be called in the Scan class. I just want the draw       method to be invoked. 
// Also I wish to draw many such rectangles. What is the best practice to get hold of ShapeRenderer object from Scan class ?
// Should I use one instance of  ShapeRenderer object in Scan class or should I create ShapeRenderer object for each of the Rectangle object ??
// I also plan to repeat the activity for another object such as circles. So I would like to know the best practice here.
public void draw() {
    Scan.shapeRenderer.rect(this.xcord, this.ycord, this.width, this.height);
}

}