Java Swing的高手看过来:::::的问题: 用CardLayout 布局,但是显示不出来容器其中的组件?

Question

CardLayout是覆盖式的，你只能看见最上面一个。

Answer 1

我一般都自己setBounds，布局有时候很难看～

Answer 2

关键是我连最上面的那个都看不到,下面是我的代码:
public class TestCardLayout extends JFrame{
private CardLayout layout_ = new CardLayout(); 
private JPanel panel_;
public TestCardLayout(){
this.setSize(400,400);
panel_ = (JPanel)this.getContentPane();
init();
this.setVisible(true);

}
private void init(){
panel_.setLayout(layout_);

layout_.addLayoutComponent("button1",new JButton("button1"));
layout_.addLayoutComponent("button2",new JButton("button2")); layout_.show(panel_,"button1");

}    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
             TestCardLayout frame = new TestCardLayout();
                //createAndShowGUI();
            }
        });
    }}