从一个面板类绘制到另一个面板类

Question

我有两个类。第一类称为Fishy1，第二类称为Fishy2。这是我第一堂课的代码：

import java.awt.Graphics;
import javax.swing.JPanel;
public class Fishy1 extends JPanel {
Fishy1 fishy1 = new Fishy1();
/* Graphics goes here */
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.drawOval(50, 50, 50, 50);
}
}

如您所见，代码基本上在 fishy1 中绘制一个椭圆形。这是我第二节课的代码：

import java.awt.Graphics;
import javax.swing.JPanel;
public class Fishy2 extends JPanel {
Fishy2 fishy2 = new Fishy2();
}

如您所见，在第二类中，没有 paintComponet 方法来绘制到 fishy2。所以，我的问题是，有没有办法在第一堂课中使用paintComponent方法绘制到第二类？如果没有办法，请告诉我。谢谢。

Answer 1

同时实现 2 个摆动类之间的图形复制

public class Fishs extends JPanel {
    //Static list, all fishes panel will display the same objects at same positions
    private static List<OvalObj> lstOvalObjects;
    public Fishs() {
        //if the list is null just initialize it.
       lstOvalObjects = lstOvalObjects == null? new ArrayList():lstOvalObjects;
    }
    /* Graphics goes here */
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        lstOvalObjects.forEach(ovalObject ->  g.drawOval(ovalObject.getX(), ovalObject.getY(), ovalObject.getWidth(), ovalObject.getHeight()));
    }
    public static List<OvalObj> getLstOvalObjects() {
        return lstOvalObjects;
    }
    public static void setLstOvalObjects(List<OvalObj> lstOvalObjects) {
        Fishs.lstOvalObjects = lstOvalObjects;
    }
}

椭圆形对象：

public class OvalObj{
        private int x,y,width,height;
        public OvalObj(int x, int y, int width, int height) {
            this.x = x;
            this.y = y;
            this.width = width;
            this.height = height;
        }
        public int getX() {
            return x;
        }
        public void setX(int x) {
            this.x = x;
        }
        public int getY() {
            return y;
        }
        public void setY(int y) {
            this.y = y;
        }
        public int getWidth() {
            return width;
        }
        public void setWidth(int width) {
            this.width = width;
        }
        public int getHeight() {
            return height;
        }
        public void setHeight(int height) {
            this.height = height;
        }
    }

实现：

        //First Frame
        JFrame frame1 = new JFrame();
        frame1.setLayout(new BorderLayout());
        //First Fish Panel that will go to frame1
        Fishs fish1 = new Fishs();
        fish1.setVisible(true);
        frame1.add(fish1, BorderLayout.CENTER);
        frame1.pack();
        frame1.setVisible(true);

        //Second Frame
        JFrame frame2 = new JFrame();
        //Second Fish Panel that will go to frame2
        Fishs fish2 = new Fishs();
        fish2.setVisible(true);
        frame2.setLayout(new BorderLayout());
        frame2.add(fish2, BorderLayout.CENTER);
        frame2.pack();
        frame2.setVisible(true);
        /// you can add many objects to draw as you like in a static way anywhere in your code, they will render in every fish panel at same time
        Fishs.getLstOvalObjects().add(new OvalObj(0, 0, 50, 50));
        Fishs.getLstOvalObjects().add(new OvalObj(20, 20, 50, 50));