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 }
