Question

我有一个简单的例子，应该创建一组绿球，而只是创建一个。我想创建一个ArrayList来保存球，但有些事情是错误的。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

您需要在每个周期中创建新实例

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

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

    }

}

Answer 2

我想创建一个数组列表，其中包含绿球但问题我只得到一个绿球而不是（10）或更多

首先，这应该在循环中：

Bubbles blobsOb = new Bubbles(x, y , size , Color.GREEN);

然后你还需要在循环中插入下面的代码，以确保在每次迭代时都有一个新生成的随机值。

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

示例：

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

    for(int i = 0 ; i < 10; i++)
    {  
         int xr = rand.nextInt(400);
         int yr = rand.nextInt(400);
         int size = 10;
         Bubbles blobsOb = new Bubbles(xr, yr , size , Color.GREEN);
         balls.add(blobsOb);
         g.setColor(Color.green);
         g.fillOval(x, y, size, size);

    }

}

在将所有组件添加到.setVisible(true)后，您应始终致电frame。

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

最后但并非最不重要的是，您已将所有生成的Bubble对象添加到ArrayList ArrayList<Bubbles> balls = new ArrayList<Bubbles>()中，但是，您还没有使用balls ArrayList。

UI不是创建形状

2 个答案: