Repaint（）不能清除框架

您是否尝试过在paintComponent方法中调用super.paintComponent（g）？这将清除您的JPanel中绘制的先前图像：

public void paintComponent(Graphics g){  super.paintComponent(g);  Graphics2D gui = (Graphics2D) g;  Rectangle2D rectangle = new Rectangle2D.Double(x,y,100,150);  gui.setPaint(Color.GREEN);  gui.fill(rectangle);  //time.start();}

另外，不要启动计时器或在paintComponent方法内执行任何程序逻辑。首先，您不能完全控制何时或是否将调用该方法，其次，此方法必须仅与绘画有关，而与其他无关，并且需要尽可能快。

例如：

import java.awt.*;import java.awt.event.*;import java.awt.geom.*;import javax.swing.*;public class Graphics2DTest extends JPanel implements ActionListener {    private Timer time = new Timer(5, (ActionListener) this);    int x = 0, y = 0;    public void paintComponent(Graphics g) {        super.paintComponent(g);        Graphics2D gui = (Graphics2D) g;        Rectangle2D rectangle = new Rectangle2D.Double(x, y, 100, 150);        gui.setPaint(Color.GREEN);        gui.fill(rectangle);        //time.start();    }    public void actionPerformed(ActionEvent arg0) {        x++;        y++;        repaint();    }    public Graphics2DTest() {        setPreferredSize(new Dimension(700, 500));        time.start();    }    private static void createAndShowUI() {        Jframe frame = new Jframe("Graphics2DTest");        frame.getContentPane().add(new Graphics2DTest());        frame.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE);        frame.pack();        frame.setLocationRelativeTo(null);        frame.setVisible(true);    }    public static void main(String[] args) {        java.awt.EventQueue.invokeLater(new Runnable() { public void run() {     createAndShowUI(); }        });    }}