jscrollpane has trailing image

I have a JPanel inside the JScrollPane and it does that whenever I try to scroll. Please help! 开发者_如何学PythonHow do I fix this?

EDIT

JScrollPane pane;
....
pane = new JScrollPane(GC.createGraph());
pane.setPreferredSize(new Dimension(480,480*2/3));

Placing as an answer for others to see. If you don't call the super.paintComponent, you'll get those artifacts. e.g.,

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;

import javax.swing.*;

public class ScrollPaneArtifacts extends JPanel {
   private static final int SPA_WIDTH = 600;
   private static final int SPA_HEIGHT = SPA_WIDTH;

   @Override
   protected void paintComponent(Graphics g) {
      //super.paintComponent(g);
      g.setColor(Color.red);
      g.drawLine(0, 0, getWidth(), getHeight());
      g.drawLine(getWidth(), 0, 0, getHeight());
   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(SPA_WIDTH, SPA_HEIGHT);
   }

   private static void createAndShowUI() {
      JScrollPane scrollpane = new JScrollPane(new ScrollPaneArtifacts());
      scrollpane.getViewport().setPreferredSize(new Dimension(400, 400));
      JFrame frame = new JFrame("ScrollPaneArtifacts");
      frame.getContentPane().add(scrollpane);
      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();
         }
      });
   }
}

You do not need to call super.paintComponent you can simply clear the area to ensure no artifacts are left on the panel from the previous render (which calling super.paintComponent will do).

@Override
protected void paintComponent(Graphics g) {
  g.clearRect(0,0,getWidth(),getHeight());
  g.setColor(Color.red);
  g.drawLine(0, 0, getWidth(), getHeight());
  g.drawLine(getWidth(), 0, 0, getHeight());
}

Try this in Hovercrafts code if you like.