如何將JPanel添加到JFrame十次

Question

我的目標是創建一個應該有隨機位置的隨機車或卡車十次。當我嘗試向我的JFrame添加大量JPanel時，只有一個顯示出來。我怎樣才能調用randomVehicle（）方法一次繪製多個車輛，我嘗試添加打印語句並檢查邏輯，但我不知所措。

import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Rectangle; 
import java.awt.geom.Ellipse2D; 
import java.awt.geom.Line2D; 
import java.awt.geom.Point2D; 

import javax.swing.JComponent; 
import javax.swing.JFrame; 
public class GraphicsTester { 

    public static void main(String[] args) { 
     //1. Create the frame. 
     JFrame frame = new JFrame(); 
     //2. Optional: What happens when the frame closes? 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     //4. Size the frame. 
     frame.setSize(2000, 2000); 
     //5. Show it. 

     Vehicle frame1 = new Vehicle(); 
     frame.add(frame1.randomVehicle()); 
     frame.add(frame1.randomVehicle()); 
     frame.setVisible(true); 
    } 

} 

汽車類

import java.awt.Graphics2D; 
import java.awt.Rectangle; 
import java.awt.geom.Ellipse2D; 
import java.awt.geom.Line2D; 
import java.awt.geom.Point2D; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 

import java.awt.Graphics; 
public class Vehicle extends JPanel { 

    public Vehicle() { 
    xPos = (int) (Math.random() * 500) + 1; 
    yPos = (int) (Math.random() * 500) + 1; 
    } 

    public Vehicle randomVehicle() { 
     int vehicleRandom = (int) (Math.random() * 2) + 1; 
     System.out.println(vehicleRandom); 
     if (vehicleRandom==1) { 
      return new Car(); 
     } 
     if (vehicleRandom==2) { 
      return new Truck(); 
     } 
     return null; 
    } 


    protected int xPos; 
    protected int yPos; 

} 

汽車

import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Rectangle; 
import java.awt.geom.Ellipse2D; 
import java.awt.geom.Line2D; 
import java.awt.geom.Point2D; 
import javax.swing.JFrame; 

public class Car extends Vehicle { 

    public Car() { 
     super(); 
     System.out.println(xPos); 
     System.out.println(yPos); 
    } 

    public void paint(Graphics g) { 
     Graphics2D g2d = (Graphics2D) g; 
     g2d.draw(new Rectangle(xPos + 100, yPos + 100, 200, 50)); 
     g2d.draw(new Rectangle(xPos + 150, yPos + 85, 100, 15)); 
     g2d.draw(new Ellipse2D.Double(xPos + 120, yPos + 150, 50, 35)); 
     g2d.draw(new Ellipse2D.Double(xPos + 220, yPos + 150, 50, 35)); 
    } 

} 

卡車

import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Rectangle; 
import java.awt.geom.Ellipse2D; 

public class Truck extends Vehicle { 

    public Truck() { 
     super(); 
     System.out.println(xPos); 
     System.out.println(yPos); 
    } 

    public void paint(Graphics g) { 
     Graphics2D g2d = (Graphics2D) g; 
     g2d.draw(new Rectangle(xPos + 100, yPos + 100, 50, 75)); 
     g2d.draw(new Ellipse2D.Double(xPos + 110, yPos + 175, 35, 35)); 
     g2d.draw(new Rectangle(xPos + 180, yPos + 70, 350, 106)); 
     g2d.draw(new Ellipse2D.Double(xPos + 190, yPos + 175, 35, 35)); 
     g2d.draw(new Ellipse2D.Double(xPos + 225, yPos + 175, 35, 35)); 
     g2d.draw(new Ellipse2D.Double(xPos + 475, yPos + 175, 35, 35)); 
     g2d.draw(new Ellipse2D.Double(xPos + 440, yPos + 175, 35, 35)); 
    } 

} 

Answer 1

使用一個循環..像下面..

Vehicle frame1 = new Vehicle(); 

for(int i=0;i<10;i++) { 
frame.add(frame1.randomVehicle()); 
} 

frame.setVisible(true);