從一個面板類繪制到另一個面板類。

Question

我有兩節課。 第一類稱為Fishy1，第二類稱為Fishy2。 這是我第一堂課的代碼：

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);

}

}

如您所見，該代碼基本上在fishy1中繪制了一個橢圓形。 這是我第二節課的代碼：

import java.awt.Graphics;
import javax.swing.JPanel;

public class Fishy2 extends JPanel {

Fishy2 fishy2 = new Fishy2();

}

如您所見，在第二類中，沒有paintComponet方法可繪制到fishy2。 所以，我的問題是，有沒有辦法使用第一類中的paintComponent方法繪制第二類？ 如果沒有辦法，請告訴我。 謝謝。

Answer 1

同時實現兩個Swing類之間的圖形復制

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;
    }

}

橢圓形物體：

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;
        }

    }

實現方式：

        //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));