滚动条,方块相互控制

import javax.swing.*;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.*;

public class MouseMoveDemo extends JPanel implements AdjustmentListener,
        MouseMotionListener {
    JScrollBar jsx, jsy;
    JTextField text;
    int x = 50;
    int y = 50;
    int fx, fy;
    MyPanel pane;

    MouseMoveDemo() {
        jsx = new JScrollBar(JScrollBar.HORIZONTAL, x, 1, 0, 101);
        jsy = new JScrollBar(JScrollBar.VERTICAL, y, 1, 0, 101);
        jsx.addAdjustmentListener(this);
        jsy.addAdjustmentListener(this);
        // text = new JTextField(5);
        // this.add(text);
        pane = new MyPanel();
        pane.addMouseMotionListener(this);

        this.setLayout(new BorderLayout());

        this.add(pane, BorderLayout.CENTER);
        this.add(jsx, BorderLayout.SOUTH);
        this.add(jsy, BorderLayout.EAST);

    }

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

    public static void createAndShowGUI() {
        JFrame frame = new JFrame("MouseMoveDemo");
        frame.setSize(500, 500);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.add(new MouseMoveDemo());
        frame.setVisible(true);
        frame.pack();
    }

    @Override
    public void adjustmentValueChanged(AdjustmentEvent e) {
        JScrollBar temp = (JScrollBar) e.getSource();
        if (temp == jsx)
            x = temp.getValue();
        else if (temp == jsy)
            y = temp.getValue();
        pane.repaint();

    }

    public void mouseDragged(MouseEvent e) {
        int x = e.getX();
        int y = e.getY();
        if (!((x <= fx + 20) && (x >= fx - 20) && (y <= fy + 20) && (y >= fy - 20)))
            return;
        this.x = (int) (x / 300.0 * 100);
        this.y = (int) (y / 300.0 * 100);
        updateScroll();
        pane.repaint();
    }

    public void mouseMoved(MouseEvent e) {

    }

    private void updateScroll() {
        jsx.setValue(x);
        jsy.setValue(y);
    }

    class MyPanel extends JPanel {

        MyPanel() {
            this.setPreferredSize(new Dimension(340, 340));
            // repaint();
        }

        public void paint(Graphics g) {
            fx = (int) (x / 100.0 * 300);
            fy = (int) (y / 100.0 * 300);
            if (fx >= 280)
                fx = 280;
            if (fy >= 280)
                fy = 280;
            if (fx <= 20)
                fx = 20;
            if (fy <= 20)
                fy = 20;
            g.setColor(Color.BLACK);
            g.fillRect(0, 0, 300, 300);
            g.setColor(Color.BLUE);
            g.fillRect(fx - 20, fy - 20, 40, 40);
        }
    }
}