java中解决组件重叠的问题（例如鼠标移动组件时）

import java.awt.Button;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JLayeredPane;

//实现鼠标移动组件的小程序
public class ParentAndChild {

	static Point oldPt;
	static JLayeredPane pane = new JLayeredPane();
	static Button btn = new Button(), btn1 = new Button("嘻嘻嘻");
	public static void main(String[] args) {
		Frame fm = new Frame("哈哈哈");
		fm.setVisible(true);
		pane.setLayout(new FlowLayout());
		fm.add(pane, "Center");
		btn.setLabel("啦啦啦");
		btn.addMouseListener(new MouseAdapter() {
				public void mousePressed(MouseEvent e) {
					oldPt=e.getLocationOnScreen();
				}
				public void mouseReleased(MouseEvent e) {
					 pane.setPosition(btn, -1);
				} 
		});
		
		btn.addMouseMotionListener(new MouseMotionAdapter() {
				public void mouseDragged(MouseEvent e) {
					 Point pt = e.getLocationOnScreen();
					 btn.setLocation(new Point(btn.getX() + pt.x-oldPt.x,
							         btn.getY() + pt.y-oldPt.y));
					 oldPt=pt;
				}
				
		});
			
		
		btn.setPreferredSize(new Dimension(200, 100));
		pane.add(btn);
		pane.add(btn1);
		fm.setSize(new Dimension(600, 800));
		
		
		fm.addWindowListener(new WindowAdapter() {
				public void windowClosing(WindowEvent e) {
					System.exit(0);
				}
		});
	}

}