JButtons不断重绘

Question

我试图制作一个目标管理器程序，并希望能够使用矩形边框移动的按钮进行放大和缩小，但是当我按下放大或缩小按钮时，它会保留原始程序它在哪里并在它上面创造一个新的。此外，按钮显示在我编码的位置，但它们也显示在屏幕顶部。

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JPanel;
public class Screen extends JPanel implements Runnable{
/**
 * 
 */
private static final long serialVersionUID = 1L;
Frame frame;
Thread thread = new Thread(this);
public JButton one;
public JButton two;
public JButton zoomIn;
public JButton zoomOut;
public JButton next;
public JButton xv;
int buttonW = 100;
int buttonH = 50;
int zoomLevel = 5;
int fps;


public boolean running = true;
public Screen(Frame frame) {
    this.frame = frame;

    thread.start(); 
}



public void run() {
    long lastFrame = System.currentTimeMillis();
    int frames = 0;

    running = true;

    while(running){
        repaint();

        frames++;

        if(System.currentTimeMillis() - 1000 >= lastFrame){
            fps = frames;
            frames = 0;
            lastFrame = System.currentTimeMillis();
        }

        try {
            Thread.sleep(2);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
public void paintComponent(Graphics g){
    Color bgc = new Color (192,192,192);



    int screenW = this.getWidth();
    int screenH = this.getHeight();
    int centerH = screenH / 2;
    int centerW = screenW / 2;

    g.setColor(bgc);
    g.fillRect(0, 0, this.getWidth(), this.getHeight());

    /*---------------------------button-stuff------------------------------            **/


    Icon plus = new ImageIcon("res/buttons/plus.png");
    Icon minus = new ImageIcon("res/buttons/minus.png");

    /*---------------------------zoom buttons------------------------------**/

    zoomOut = new JButton("", minus);
    zoomOut.setBounds(screenW - 30, 32, 20, 20);
        zoomOut.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e) {
                buttonH = buttonH-10;
                buttonW = buttonW-20;
                zoomLevel = zoomLevel-1;
            }
        });

    zoomIn = new JButton("", plus);
    zoomIn.setBounds(screenW - 30, 10, 20, 20);
    zoomIn.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
            buttonH = buttonH+10;
            buttonW = buttonW+20;
            zoomLevel = zoomLevel+1;
        }
    });
    /*------------------------------------Next--------------------------------------------------------**/
    next = new JButton("");

    next.setBounds(centerW + ((buttonW / 2) - 5), centerH - 5, 10, 10);
    next.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent arg0) {
            JButton oo = new JButton("new");
            oo.setBounds(10,10,10,10);
            add(oo);
        }
    });

    xv = new JButton("");
    add(xv);
    xv.setBounds(centerW -10, centerH - ((buttonH / 2) + 10), 20, 20);

    /*------------------------------Add Buttons----------------------------------------------------------**/
    add(zoomOut);
    add(zoomIn);
    add(next);

    g.setColor(Color.GREEN);
    g.fillRect(centerW - (buttonW / 2), centerH - (buttonH / 2), buttonW,         buttonH);
   }
}