如何正确设置能够运行模拟的画布

Question

I'm brand new to Java and have only recently learnt about object oriented programming. I'm trying to create a program which can run a simulation, the general idea is that I want a part of the screen dedicated to buttons/sliders and another part to be dedicated the the Canvas running the simulation. For now I'm not worried about the simulation itself, I'm just trying to get some graphics on the canvas (which is smaller than the JFrame).

Here is my code (I'll try to leave some explanation below it)

public class Launcher {

    public static void main(String[] args){

        Display display = new Display();

    }

}

.

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

public class Display {

    public final int width = 1280, height = 720;
    public final int cwidth = 894, cheight = 504;
    public final String title = "Mechancis Simulator";
    private JFrame frame;
    //private JPanel panel;
    private Canvas canvas;
    private Simulation simulation;

    public Display(){

        initDisplay();

        simulation = new Simulation();

    }

    private void initDisplay(){

        frame = new JFrame(title);
        frame.setSize(width, height);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        /*panel = new JPanel();
        panel.setSize(width, height);
        panel.setLocation(0,0); */

        canvas = new Canvas();
        canvas.setPreferredSize(new Dimension(cwidth, cheight));
        canvas.setMaximumSize(new Dimension(cwidth, cheight));
        canvas.setMinimumSize(new Dimension(cwidth, cheight));
        canvas.setLocation(width - (cwidth +15), 15);

        //panel.add(canvas);
        frame.add(canvas);

        /* Add code for buttons/sliders/boxes here */

        /* Add these to panel */

    }

    public JFrame getFrame(){
        return frame;
    }

    public Canvas getCanvas(){
        return canvas;
    }

}

.

import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.*;
import javax.swing.*;

public class Simulation extends Display implements Runnable {

    private boolean running = false;
    private Thread thread;

    private BufferStrategy bs;
    private Graphics g;

    public Simulation(){

    }

    private void init(){

    }

    private void tick(){

    }

    private void render(){
        bs = getCanvas().getBufferStrategy();
        if(bs == null){
            getCanvas().createBufferStrategy(3);
            return;
        }
        g = bs.getDrawGraphics();
        //Draw Here!


        //End Drawing!
        bs.show();
        g.dispose();
    }

    public void run(){

        init();

        while(running){
            tick();
            render();
        }

        stop();

    }

    public synchronized void start(){
        if(running)
            return;
        running = true;
        thread = new Thread(this);
        thread.start();
    }

    public synchronized void stop(){
        if(!running)
            return;
        running = false;
        try {
            thread.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

When I run the program the window starts going crazy. I'm quite new to classes and threading so maybe that is the problem. I just want to be able to run the simulation after setting up Frame and Canvas in the Display object.

Thanks.

Answer 1

What you're doing basically is this:

class Display {
    private final Simulation sim;
    public Display() { sim = new Simulation(); }
}

class Simulation extends Display {
    public Simulation() { }
}

when you create a new Display the constructor creates a new Simulation which is a Display which creates a new Simulation which is a Display which creates a new Simulation which is a Display which creates a new Simulation ...*

So don't. There's no reason for your Simulation to be a display and to own another Simulation . If you want all the control in Display define a constructor that takes as an argument the Simulation it's displaying and give it a simulation when you create it:

class Display {
    private final Simulation sim;
    public Display(Simulation sim) { this.sim = sim; }
}

class Simulation {
}

...

Display display = new Display(new Simulation());

*I suggest you google for a tutorial on inheritance, if you wish to know more. Here's the tutorial from oracle to get you started: "You can write a subclass constructor that invokes the constructor of the superclass, either implicitly or by using the keyword super." In your code example the constructor super() is invoked implicitly.