Java swing drawing：动画对象时如何清除背景
我已经编写了一些java swing代码，它使用Timer和其他一些废话在JPanel中激活一些球，并且它不刷新背景，所以它有条纹效果（我不知道该怎么称呼它）。 我怎么能解决这个问题呢？ 另外，我该如何选择最佳答案？ 谢谢老兄。 这是相关的代码：
public void paintComponent(Graphics g){ super.paintComponents(g); for (Particle b: ballArr){ g.setColor(b.getColor()); g.fillOval(b.getXCoor(),b.getYCoor(), b.getTheSize(),b.getTheSize()); } } class TimerListener implements ActionListener { public void actionPerformed(ActionEvent e){ for (Particle b: ballArr) b.move(); setBackground(Color.WHITE); repaint(); } 和完整的代码：
import java.util.Random; import java.util.ArrayList; import java.awt.Color; import javax.swing.*; import java.awt.event.*; import java.awt.*; import javax.swing.*; ////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////// public class Ball extends JApplet{ public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { JFrame frame = new JFrame(); frame.setTitle("And so the ball rolls"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); initContainer(frame); frame.pack(); frame.setVisible(true); } }); } public static void initContainer(Container container){ GraphicsPanel graphicsPanel = new GraphicsPanel(); MainPanel mainPanel = new MainPanel(graphicsPanel); container.add(mainPanel); graphicsPanel.startTimer(); } // // @Override // public void init(){ // initContainer(this); // } } /////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////// class MainPanel extends JPanel { JLabel label = new JLabel("Particles"); GraphicsPanel gPanel; public MainPanel(GraphicsPanel gPanel){ this.gPanel = gPanel; add(gPanel); add(label); } } /////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////// class GraphicsPanel extends JPanel implements MouseListener { private ArrayList ballArr = new ArrayList(); private String state="p"; //"s"=spiral, "p"=particle private int speed=50; //~20 Hz private Timer timer; public GraphicsPanel(){ System.out.println("echo from gpanel"); setPreferredSize(new Dimension(600,500)); timer = new Timer(speed, new TimerListener()); addMouseListener(this); } public void startTimer(){ timer.start(); } @Override public void paintComponent(Graphics g){ super.paintComponents(g); for (Particle b: ballArr){ g.setColor(b.getColor()); g.fillOval(b.getXCoor(),b.getYCoor(), b.getTheSize(),b.getTheSize()); } } public void mousePressed(MouseEvent e) { System.out.println("becho"); ballArr.add(new Particle(e.getX(), e.getY(), "p")); } public void mouseReleased(MouseEvent e) {} public void mouseEntered(MouseEvent e){} public void mouseExited(MouseEvent e){} public void mouseClicked(MouseEvent e) {} class TimerListener implements ActionListener { public void actionPerformed(ActionEvent e){ for (Particle b: ballArr) b.move(); setBackground(Color.WHITE); repaint(); } } } ////////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////////// class Particle { private static int instanceCount; {{instanceCount++;}} private int z = 11, t=1, u=1; private int[] RGB = new int[3]; private int[] randomizeColor = new int[3]; private double radius, theta; private int x, y, centerX, centerY, size, spiralDirection=1, ballSizeLowerBound, ballSizeUpperBound, radiusLowerBound, radiusUpperBound, mouseInputX, mouseInputY, radiusXMultiplier, radiusYMultiplier; private Color color; private String state; private Random random = new Random(); /////////////////////////////////////////////////////////////////////////// public Particle(int x, int y, int centerX, int centerY, int radius, int theta, int size, Color color){ this.x=x;this.y=y;this.centerX=centerX;this.centerY=centerY; this.radius=radius;this.theta=theta;this.size=size;this.color=color; } public Particle(int mouseInputX, int mouseInputY, String state){ this.mouseInputX=mouseInputX; this.mouseInputY=mouseInputY; this.state=state; //randomize color RGB[0] = random.nextInt(255); RGB[1] = random.nextInt(255); RGB[2] = random.nextInt(255); randomizeColor[0] = 1+random.nextInt(3); randomizeColor[0] = 1+random.nextInt(3); randomizeColor[0] = 1+random.nextInt(3); centerX=mouseInputX; centerY=mouseInputY; if (state.equals("s")){ //setup spiral state ballSizeLowerBound=5; ballSizeUpperBound=18; radiusLowerBound=0; radiusUpperBound=50; radiusXMultiplier=1; radiusYMultiplier=1; } if (state.equals("p")){ //setup particle state ballSizeLowerBound = 15; ballSizeUpperBound =20 + random.nextInt(15); radiusLowerBound = 5; radiusUpperBound = 15+ random.nextInt(40); radiusXMultiplier=1 + random.nextInt(3); radiusYMultiplier=1 + random.nextInt(3); } size = ballSizeUpperBound-1; //ball size radius = radiusUpperBound-1; if (instanceCount %2 == 0) // alternate spiral direction spiralDirection=-spiralDirection; } /////////////////////////////////////////////////////////////////////////// public int getXCoor(){return centerX+x*spiralDirection;} public int getYCoor(){return centerY+y;} public int getTheSize(){return size;} public Color getColor(){return color;} ////////////////////////////////////////////////////////////////////////// void move(){ //spiral: dr/dt changes at bounds if (radius > radiusUpperBound || radius < radiusLowerBound) u = -u; //spiral shape formula: parametric equation for the //polar equation radius = theta x = (int) (radius * radiusXMultiplier * Math.cos(theta)); y = (int) (radius * radiusYMultiplier * Math.sin(theta)); radius += .3*u; theta += .3; //ball size formula if (size == ballSizeUpperBound || size == ballSizeLowerBound) t = -t; size += t; //ball colors change for (int i = 0; i = 250 || RGB[i] <= 3) randomizeColor[i] = -randomizeColor[i]; RGB[0]+= randomizeColor[0]; RGB[1]+= randomizeColor[1]; RGB[2]+= randomizeColor[2]; color = new Color(RGB[0],RGB[1],RGB[2]); } }
super.paintComponents(g); 应该是super.paintComponent(g);