java - UI 不是创建形状

Question

我有一个简单的例子，它应该创建一组绿球，但实际上只创建了一个。我想创建一个 ArrayList 来存放球，但出了点问题。请帮忙。

import javax.swing.JPanel;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.ArrayList;
import java.util.Random;
import javax.security.auth.x500.X500Principal;
import javax.swing.*;

public class MyBall extends JPanel{

    Random rand = new Random();
    int xr = rand.nextInt(400);
    int yr = rand.nextInt(400);
    int size = 10 ;
    int x = xr ;
    int y = yr ;

    Ellipse2D.Double ball = new Ellipse2D.Double(0, 0, 30, 30);
    ArrayList<Bubbles> balls = new ArrayList<Bubbles>();
    Bubbles blobsOb = new Bubbles(x, y , size , Color.GREEN);


    public void paintComponent(Graphics g){
        super.paintComponent(g);
        Graphics2D g2 =(Graphics2D)g;


        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setColor(Color.BLUE);
        g2.fill(ball);
        g2.setColor(Color.green);

        for (int j = 0 ;  j < 10 ; j++)]{
          for(int i = 0 ; i < 10; i++){
              balls.add(blobsOb);
              g.setColor(Color.green);
              g.fillOval(x, y, size, size);

          }         
      }
  }

}

//SECOND CLASS 
import javax.swing.*;

public  class Main   {

    public static void main(String[] args) {

        MyBall p = new MyBall();
        JFrame f = new JFrame();

        f.add(p);
        f.setVisible(true);
        f.setLocation(200,200);
        f.setSize(400, 420);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }

}


//Third Class

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;

// this class is for the properties of green balls 
public class Bubbles extends Component {
    public int x;
    public int y;
    public int size;
    public Color color;
    public static Bubbles blob = new Bubbles(250,250,100,Color.BLUE);

    Bubbles(int x, int y, int size, Color c){
        this.x = x;
        this.y = y;
        this.size = size;
        this.color = c;
    }

    public void paint(Graphics g){
        g.setColor(color);
        g.fillOval(x, y, size, size);
    }

}

Answer 1

你需要在每个循环中创建新的实例

for(int j = 0; j < 10; j++){

    for(int i = 0 ; i < 10; i++)
    {  
         // ...
         balls.add(new Bubbles(xr, yr , size , Color.GREEN));

    }

}