JAVA:事件监听器之练习

练习1：

View Code

 1  1 import javax.swing.*;
 2  2 import java.awt.*;
 3  3 import java.awt.event.*;
 4  4 public class MyWindowEvent
 5  5 {
 6  6    private Frame f;
 7  7    private Button bt;
 8  8    private TextField tf;
 9  9    private TextArea ta;
10 10    public MyWindowEvent()
11 11    {
12 12        init();
13 13     }
14 14     private void init()
15 15     {
16 16         f = new Frame("My window");
17 17         bt = new Button("转到");
18 18         tf = new TextField(40);
19 19         ta = new TextArea(10,50);
20 20         
21 21         f.setLayout(new FlowLayout(FlowLayout.LEFT));
22 22         f.setBounds(300,200,400,300);
23 23         
24 24         f.add(tf);
25 25         f.add(bt);
26 26         f.add(ta);
27 27         
28 28         myEvent();
29 29         
30 30         f.setVisible(true);
31 31     }
32 32     public void myEvent()
33 33     {
34 34         f.addWindowListener(new WindowAdapter()
35 35         {
36 36             public void windowClosing(WindowEvent e)
37 37             {
38 38                 System.exit(0);
39 39             }
40 40         });
41 41     }
42 42     
43 43     public static void main(String[] agrs)
44 44     {
45 45         new MyWindowEvent();
46 46     }
47 47 }

练习2：

View Code

 1 1 import javax.swing.*;
 2  2 import java.awt.*;
 3  3 import java.awt.event.*;
 4  4 public class MyWindowEvent2
 5  5 {
 6  6    private Frame f;
 7  7    private Button bt;
 8  8    private TextField tf;
 9  9    private TextArea ta;
10 10    public MyWindowEvent2()
11 11    {
12 12        init();
13 13     }
14 14     private void init()
15 15     {
16 16         f = new Frame("My window");
17 17         bt = new Button("转到");
18 18         tf = new TextField(40);
19 19         ta = new TextArea(10,50);
20 20         
21 21         f.setLayout(new FlowLayout(FlowLayout.LEFT));
22 22         f.setBounds(300,200,400,300);
23 23         
24 24         f.add(tf);
25 25         f.add(bt);
26 26         f.add(ta);
27 27         
28 28         myEvent();
29 29         
30 30         f.setVisible(true);
31 31     }
32 32     public void myEvent()
33 33     {
34 34         f.addWindowListener(new WindowAdapter()
35 35         {
36 36             public void windowClosing(WindowEvent e)
37 37             {
38 38                 System.exit(0);
39 39             }
40 40         });
41 41         bt.addActionListener(new ActionListener()
42 42         {
43 43             public void actionPerformed(ActionEvent a)
44 44             {
45 45                 String text = tf.getText();//返回此文本组件表示的文本。
46 46                 ta.setText(text);//  将此文本组件显示的文本设置为指定文本。
47 47                 
48 48                 tf.setText("");//清空输入中的内容
49 49             }
50 50         });
51 51     }
52 52     
53 53     public static void main(String[] agrs)
54 54     {
55 55         new MyWindowEvent2();
56 56     }
57 57 }

练习3：获取文件目录

View Code

 1 import javax.swing.*;
 2 import java.awt.*;
 3 import java.awt.event.*;
 4 import java.io.*;
 5 public class MyWindowEvent3
 6 {
 7    private Frame f;
 8    private Button bt;
 9    private TextField tf;
10    private TextArea ta;
11    public MyWindowEvent3()
12    {
13        init();
14     }
15     private void init()
16     {
17         f = new Frame("My window");
18         bt = new Button("转到");
19         tf = new TextField(40);
20         ta = new TextArea(10,50);
21         
22         f.setLayout(new FlowLayout(FlowLayout.LEFT));
23         f.setBounds(300,200,400,300);
24         
25         f.add(tf);
26         f.add(bt);
27         f.add(ta);
28         
29         myEvent();
30         
31         f.setVisible(true);
32     }
33     public void myEvent()
34     {
35         f.addWindowListener(new WindowAdapter()
36         {
37             public void windowClosing(WindowEvent e)
38             {
39                 System.exit(0);
40             }
41         });
42         bt.addActionListener(new ActionListener()
43         {
44             public void actionPerformed(ActionEvent a)
45             {
46                 String dirPath = tf.getText();
47                 File dir = new File(dirPath);
48                 if(dir.exists() && dir.isDirectory() )//判断dir是否存在并且是个目录
49                 {
50                     ta.setText("");
51                     String[] names = dir.list();
52                     for(String name : names)//foreach循环
53                     {
54                         ta.append(name+"\n");
55                     }
56                 }
57                 else
58                 {
59                     ta.setText("");
60                     ta.setText("不存在！");
61                 }
62             }
63         });
64     }
65     
66     public static void main(String[] agrs)
67     {
68         new MyWindowEvent3();
69     }
70 }