如何将 JPanel 添加到 JFrame 十次 [重复]

Question

我的目标是创建一个随机的汽车或卡车十次，它应该有一个随机的位置。当我尝试向我的 JFrame 添加大量 JPanel 时，似乎只出现了一个。如何调用 randomVehicle() 方法一次绘制不止一辆车辆，我尝试添加打印语句并检查我的逻辑，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);
    }

}

车辆类别

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;

}

汽车

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));
    }

}

卡车

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 for 循环.. 如下所示..

Vehicle frame1 = new Vehicle();

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

frame.setVisible(true);