关于CardLayout通过鼠标单击的问题？

Question

public class CardApplet extends Applet{  CardLayout cardLayout; Panel panel1,panel2; Button button1,button2,button3,button4,button5,button6; public void init(){  panel1 = new Panel();  panel2 = new Panel();  add(panel1);  add(panel2);  cardLayout = new CardLayout(0,0);  panel1.setLayout(cardLayout);  button1 = new Button("button1");  button2 = new Button("button2");  button3 = new Button("button3");  button4 = new Button("button4");  button5 = new Button("button5");  button6 = new Button("button6");    panel1.add("button1", button1);  panel1.add("button2", button2);  panel1.add("button3", button3);    panel2.add("button4", button4);  panel2.add("button5", button5);  panel2.add("button6", button6); } public boolean action(Event evt,Object arg){  cardLayout.next (panel1);  return true;   } public static void main(String[] args) {  // TODO Auto-generated method stub }}期望的是第一个页面出现button1、2、3。单击任意一个按钮出现button4、5、6。可是和出现的是1、4、5、6。单击的时候1、2、3会依次切换，但是4、5、6一直都在。