如何删除仅通过鼠标单击创建的对象？ （创建另一个时）

Question

我一直在寻找答案和所有答案，但找不到解决我问题的方法。我希望我可以在创建新圆圈时删除上一个圆圈（通过鼠标单击创建）吗？

非常感谢您。 ：）

package javaapplication1;

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;

public class CercuriRandom extends Applet implements MouseListener{

    int x,y,z,r,v,a;
    Thread t;
    Color culoare;
    Random rand;

    @Override
    public void init(){
        t=new Thread();
        rand= new Random();
        culoare=new Color(r, v, a);
        addMouseListener(this);
    }

    @Override
    public void update(Graphics g){
        g.setColor(culoare);
        g.fillRoundRect(x, y, z, z, z, z);
        try {
            Thread.sleep(25);
        } catch (InterruptedException e) { }
        //repaint();
    }

    @Override
    public void mouseClicked(MouseEvent me) {
        if (me.getButton()==MouseEvent.BUTTON1) {
            r=rand.nextInt(256);
            v=rand.nextInt(256);
            a=rand.nextInt(256);
            culoare=new Color(r,v,a);
            x=rand.nextInt(getWidth());
            y=rand.nextInt(getWidth());
            z=rand.nextInt(100);
            repaint();
        }
    }

    @Override
    public void mousePressed(MouseEvent me) {

    }

    @Override
    public void mouseReleased(MouseEvent me) {

    }

    @Override
    public void mouseEntered(MouseEvent me) {

    }

    @Override
    public void mouseExited(MouseEvent me) {

    }

}

我将在此处保留创建圆所需的代码。 我一直在寻找答案和所有答案，但找不到解决我问题的方法。我希望我可以在创建新圆圈时删除上一个圆圈（通过鼠标单击创建）吗？

非常感谢您。 ：）

Answer 1

您可以通过将最后绘制的圆的值存储为类变量来引用圆：

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;

public class CercuriRandom extends Applet implements MouseListener {

    int x, y, z, r, v, a;
    // class attributes that store the last circle that was drawn
    int lastX, lastY, lastZ;
    Thread t;
    Color culoare;
    Random rand;

    @Override
    public void init() {
        t = new Thread();
        rand = new Random();
        culoare = new Color(r, v, a);
        addMouseListener(this);
    }

    @Override
    public void update(Graphics g){
        // clear the last drawn rectangle (before painting the new one)
        g.clearRect(lastX, lastY, lastZ, lastZ);

        g.setColor(culoare);
        g.fillRoundRect(x, y, z, z, z, z);

        // store the last values in order to delete them on next draw
        lastX = x;
        lastY = y;
        lastZ = z;
        try {
            Thread.sleep(25);
        } catch (InterruptedException e) { }
        //repaint();
    }

    @Override
    public void mouseClicked(MouseEvent me) {
        if (me.getButton() == MouseEvent.BUTTON1) {
            r = rand.nextInt(256);
            v = rand.nextInt(256);
            a = rand.nextInt(256);
            culoare = new Color(r, v, a);
            x = rand.nextInt(getWidth());
            y = rand.nextInt(getWidth());
            z = rand.nextInt(100);
            repaint();
        }
    }

    @Override
    public void mousePressed(MouseEvent me) {

    }

    @Override
    public void mouseReleased(MouseEvent me) {

    }

    @Override
    public void mouseEntered(MouseEvent me) {

    }

    @Override
    public void mouseExited(MouseEvent me) {

    }

}