是否要在同一类中创建JFrame和JPanel并拥有自己的paintComponent？

Question

I am trying to create a simple JFrame and JPanel in the same class but I do not want to extends either of the JFrame or JPanel Java classes. I want to be able to also include my own paintComponent() which will override the Panel paint component so that I can paint my own paint component. I would like to just create my

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

in one class. At somepoint I will use this to try and find a way to subtract and add bufferedimages but that is for a different question.

Class:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;


public class SubtractBufferedImage {
    private static final long serialVersionUID = 1L;

    Dimension dimension = new Dimension(755,450);

    public SubtractBufferedImage() {

        JFrame f = new JFrame();
        JPanel d = new JPanel();/*User defined class that is above*/
        d.setBackground(Color.BLACK);

        f.add(new myPanel());
        f.setSize(745,440); 
        f.setSize(dimension);
        f.setResizable(false);
        f.setLocationRelativeTo(null);
        f.setTitle("Subtract Buffered Images");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        SubtractBufferedImage t = new SubtractBufferedImage();

    }
}

class myPanel extends JPanel {
    private BufferedImage bTest1 = null;
    private BufferedImage bTest2 = null;

    Dimension dimension = new Dimension(755,450);

    private String iOne = "src/com/ddh/graphicsBook/CardImage/hold.jpg";
    private String iTwo = "src/com/ddh/graphicsBook/CardImage/draw.jpg";

    myPanel() {
        bTest1 = loadAnyImage(iOne);
        bTest2 = loadAnyImage(iTwo);
    }

    private BufferedImage loadAnyImage(String value){
        BufferedImage newImage = null;

        try {
            newImage = ImageIO.read(new File(value));
        } catch (IOException e) {
            e.printStackTrace();
        }
        return newImage;
    }

    private void drawImageToScreen(Graphics g,BufferedImage i,int x,int y){
        Graphics2D g2d = (Graphics2D) g;
        g2d.drawImage(i,x,y,null); 
    }

    public void paintComponent(Graphics g){
        super.paintComponent(g);  
            drawImageToScreen(g,bTest1,10,10);
            drawImageToScreen(g,bTest2,150,10);
    }
}

Answer 1

JPanel and JFrame are both Java classes and not interfaces, so you basically can't implement your own methods inside them (according to the SOLID rules, Open/Closed principle, they are open for extension but closed for modification). To implement your own paintComponent you must extend your JPanel and this is how it is usually done. I am not sure why you are reluctant to extend those classes, but if you do it you get all of the rest of your specification possible to fulfil:

• you can implement your own paintComponent method in the extending classes,
• you can have both extension of JPanel and extension of JFrame in one class.