把canvas 改成 Jpanel, 就不会主动刷新了，为什么
Java codeimport javax.swing.JFrame;import javax.swing.JPanel;import java.awt.Graphics;import java.awt.Dimension;import java.awt.Color;import java.awt.Font;import java.awt.event.KeyAdapter;import java.awt.event.KeyEvent;import java.awt.event.ActionListener;import java.awt.event.ActionEvent;import javax.swing.Timer;import java.util.Random;public class SwingPinball { // panel private static final int TABLE_WIDTH = 480; private static final int TABLE_HEIGHT = 640; // plank private static final int PLANK_WIDTH = 60; private static final int PLANK_HEIGHT = 15; private static final int PLANK_Y = 600; // ball private static final int BALL_2R = 15; // Random plank & ball x,y private Random rand = new Random(); private int nPlank_X = rand.nextInt(TABLE_WIDTH - PLANK_WIDTH); private int nBall_X = rand.nextInt(TABLE_WIDTH - BALL_2R); private int nBall_Y = BALL_2R; // ball speed; private int nBallSpeed_Y = 10; private int nBallSpeed_X = (rand.nextInt() - 1) * nBallSpeed_Y; private JFrame jfrmMain = new JFrame("Pinball"); private JMainPanel jPinball = new JMainPanel(); private Timer tmrTask = null; private boolean isLose = false; public void init() { jPinball.setPreferredSize(new Dimension(TABLE_WIDTH, TABLE_HEIGHT)); jPinball.setBackground(Color.WHITE); jfrmMain.add(jPinball); KeyAdapter LeftRightListener = new KeyAdapter() { public void keyPressed(KeyEvent ke) { if (ke.getKeyCode() == KeyEvent.VK_LEFT) { if (nPlank_X - 10 > 0) { nPlank_X -= 10; } else { nPlank_X = 0; } } if (ke.getKeyCode() == KeyEvent.VK_RIGHT) { if (nPlank_X + PLANK_WIDTH + 10 < TABLE_WIDTH) { nPlank_X += 10; } else { nPlank_X = TABLE_WIDTH - PLANK_WIDTH; } } } }; jPinball.addKeyListener(LeftRightListener); jfrmMain.addKeyListener(LeftRightListener); tmrTask = new Timer(100, new ActionListener() { public void actionPerformed(ActionEvent ae) { if (nBall_X == 0 || nBall_X == TABLE_WIDTH - BALL_2R) { nBallSpeed_X = -nBallSpeed_X; } if (nBall_Y <= 0 || (nBall_Y + BALL_2R >= PLANK_Y && nBall_X >= nPlank_X && nPlank_X + PLANK_WIDTH >= nBall_X)) { nBallSpeed_Y = -nBallSpeed_Y; } if (nBall_Y + BALL_2R >= PLANK_Y && (nBall_X < nPlank_X || nPlank_X + PLANK_WIDTH < nBall_X)) { tmrTask.stop(); isLose = true; jPinball.repaint(); } nBall_X += nBallSpeed_X; nBall_Y += nBallSpeed_Y; jPinball.repaint(); } }); tmrTask.start(); jfrmMain.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); jfrmMain.pack(); jfrmMain.setVisible(true); } class JMainPanel extends JPanel { public void paint(Graphics g) { if (isLose) { g.setColor(Color.RED); g.setFont(new Font("Times", Font.BOLD, 32)); g.drawString("Game over", 50, 200); } else { g.setColor(Color.YELLOW); g.fillOval(nBall_X, nBall_Y, BALL_2R, BALL_2R); g.setColor(Color.GREEN); g.fillRect(nPlank_X, PLANK_Y, PLANK_WIDTH, PLANK_HEIGHT); } } } public static void main(String[] args) { new SwingPinball().init(); }}