JAVA:事件监听器之练习

练习1：

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

练习2： 

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

练习3：获取文件目录

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class MyWindowEvent3
{
   private Frame f;
   private Button bt;
   private TextField tf;
   private TextArea ta;
   public MyWindowEvent3()
   {
       init();
    }
    private void init()
    {
        f = new Frame("My window");
        bt = new Button("转到");
        tf = new TextField(40);
        ta = new TextArea(10,50);
        
        f.setLayout(new FlowLayout(FlowLayout.LEFT));
        f.setBounds(300,200,400,300);
        
        f.add(tf);
        f.add(bt);
        f.add(ta);
        
        myEvent();
        
        f.setVisible(true);
    }
    public void myEvent()
    {
        f.addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });
        bt.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent a)
            {
                String dirPath = tf.getText();
                File dir = new File(dirPath);
                if(dir.exists() && dir.isDirectory() )//判断dir是否存在并且是个目录
                {
                    ta.setText("");
                    String[] names = dir.list();
                    for(String name : names)//foreach循环
                    {
                        ta.append(name+"\n");
                    }
                }
                else
                {
                    ta.setText("");
                    ta.setText("不存在！");
                }
            }
        });
    }
    
    public static void main(String[] agrs)
    {
        new MyWindowEvent3();
    }
}