JFrame jf =new JFrame();
JPanel jp1,jp2;//略过jp1 jp2的初始化以及添加各种组件
Cardlayout c=new CardLayout();
jf.setLayout(c);
jf.add(jp1,"1");
jf.add(jp2,"2");
c.show(jf.getContentPane,"1");
c.next(jf.getContentPane());
最后两行代码对于JFrame对象都要调用getContentPane()方法,不调用而直接用JFrame对象的话会报错