如何围绕程序中心旋转椭圆？

你不能在paint方法中做循环,因为它会立即竞争所有循环,导致没有aniation.在paint中或在事件线程中的任何地方进行一段时间(真实)循环将阻止您的程序进行绘制,这会使您的程序瘫痪到静止状态.代替:

使用Swing Timer来驱动动画.

在类中创建Ellipse实例,而不是在绘制方法中创建.

在Timer中增加您的旋转角度和调用repaint().

覆盖paintComponent不绘制

只做这种方法的绘画,没有逻辑.逻辑进入你的计时器.

在paintComponent方法中,使用Timer更改的角度进行仿射变换并绘制正确的椭圆.

在这个网站上搜索Java Swing动画的例子,因为这已被多次询问,导致许多示例程序(由我编写).

例如:

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class RotateEllipse extends JPanel {
   private static final double ELLIPSE_W = 80;
   private static final double ELLIPSE_H = 130;
   private static final int PREF_W = 400;
   private static final int PREF_H = 400;
   private static final Stroke STROKE = new BasicStroke(5f);
   private static final Color ELLIPSE_COLOR = Color.red;
   private static final Color BACKGROUND = Color.black;
   private static final double ELLIPSE_X = PREF_W / 2 - ELLIPSE_W / 2;
   private static final double ELLIPSE_Y = PREF_H / 2 - ELLIPSE_H / 2;
   private static final int TIMER_DELAY = 15;
   private static final double DELTA_THETA = Math.toRadians(2);

   private Ellipse2D ellipse2D;
   private AffineTransform transform = new AffineTransform();
   private double theta = 0;

   public RotateEllipse() {
      ellipse2D = new Ellipse2D.Double(ELLIPSE_X, ELLIPSE_Y, ELLIPSE_W,
            ELLIPSE_H);
      setBackground(BACKGROUND);
      new Timer(TIMER_DELAY, new TimerListener()).start();
   }

   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      Graphics2D g2 = (Graphics2D) g.create();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setStroke(STROKE);
      g2.setColor(ELLIPSE_COLOR);
      g2.setTransform(transform);
      g2.draw(ellipse2D);
      g2.dispose();
   }

   private class TimerListener implements ActionListener {
      @Override
      public void actionPerformed(ActionEvent e) {
         theta += DELTA_THETA;
         transform = AffineTransform.getRotateInstance(theta, 
               ELLIPSE_X + ELLIPSE_W / 2, ELLIPSE_Y + ELLIPSE_H / 2);
         repaint();
      }
   }

   private static void createAndShowGUI() {
      RotateEllipse paintEg = new RotateEllipse();

      JFrame frame = new JFrame("RotateEllipse");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(paintEg);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGUI();
         }
      });
   }
}