1 import java.awt.BorderLayout;

 2 import java.awt.Font;

 3 import java.awt.event.ActionEvent;

 4 import java.awt.event.ActionListener;

 5 import javax.swing.JButton;

 6 import javax.swing.JFrame;

 7 import javax.swing.JLabel;

 8 import javax.swing.JPanel;

 9

10 /**

11  * 主要是怎样刷新显示

12  * @author Administrator

13  *

14  */

15 public class TestPanel extends JFrame{

16     private ShowPanel panel;

17     public TestPanel() {

18         panel = new ShowPanel();

19         add(panel);

20         panel.ShowOne();

21     }

22     public static void main(String[] args) {

23         TestPanel testPanel = new TestPanel();

24         testPanel.setSize(500, 300);

25         testPanel.setLocationRelativeTo(null);

26         testPanel.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

27         testPanel.setVisible(true);

28     }

29     class ShowPanel extends JPanel{

30         JLabel jlb;

31         JLabel jlb2;

32         JButton jbt;

33         public ShowPanel(){

34             setLayout(new BorderLayout());

35             jbt = new JButton("PRESS");

36             jbt.addActionListener(new ActionListener() {

37                 @Override

38                 public void actionPerformed(ActionEvent e) {

39                     ShowTwo();                            //通过按钮增加一个label

40                 }

41             });

42             add(jbt, BorderLayout.NORTH);

43         }

44         public void ShowOne(){                            //显示一个label

45             jlb = new JLabel("LABEL1");

46             jlb.setFont(new Font("SansSerif", Font.BOLD, 80));

47             add(jlb, BorderLayout.CENTER);

48         }

49         public void ShowTwo(){                            //增加一个label

50             jlb2 = new JLabel("LABEL2");

51             jlb2.setFont(new Font("SansSerif", Font.BOLD, 80));

52             add(jlb2, BorderLayout.SOUTH);

53             validate();            //Validates this container and all of its subcomponents.

54             //如果此处没有validate()点击PRESS,不会主动显示LABEL2

55         }

56

57     }

58 }