filelister.java

java应用举例2

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.text.DateFormat;
import java.util.Date;

public class FileLister extends Frame implements ActionListener, ItemListener {
    //创建程序所需的组件
    List list;                  
    TextField details;         
    Panel buttons;             
    Button up, close;           
    File currentDir;            
    FilenameFilter filter;      
    String[] files;
    //设定日期格式             
    DateFormat dateFormatter =  
         DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT);
    //构造方法
    public FileLister(String directory, FilenameFilter filter) { 
        super("文件信息获取");              
        this.filter = filter;              
        //使窗口上的关闭按钮生效    
	    addWindowListener(new WindowAdapter() {
		     public void windowClosing(WindowEvent e) { 
		       dispose(); 
		   }
	    });
        //创建列表并添加监视器
        list = new List(12, false);        
        list.addActionListener(this);
        list.addItemListener(this);
        //创建文本框并使其不能编辑，只用来显示信息
        details = new TextField();         
        details.setEditable(false);
        //创建按钮，并添加监视器
        buttons = new Panel();             
        buttons.setLayout(new FlowLayout(FlowLayout.RIGHT, 15, 5));
        up = new Button("上一级目录"); 
        close = new Button("关闭");
        up.addActionListener(this);
        close.addActionListener(this);
        buttons.add(up);                  
        buttons.add(close);
        //将组件加入应用程序
        this.add(list, "Center");          
        this.add(details, "North");
        this.add(buttons, "South");
        this.setSize(500, 350);        
        listDirectory(directory);         
    } 
    public void listDirectory(String directory) {
        File dir = new File(directory);
        if (!dir.isDirectory()) 
        //如果文件指定的路径不存在，则抛出异常
           throw new IllegalArgumentException("文件信息列表: 没有这个路径");
        //将路径下的文件名称保存起来，并对其排序
        files = dir.list(filter);        
	    java.util.Arrays.sort(files);
        list.removeAll();
        list.add("[上一级目录]");  
        for(int i = 0; i < files.length; i++) list.add(files[i]);
        this.setTitle(directory);
        details.setText(directory);
        currentDir = dir;
    }   
    public void itemStateChanged(ItemEvent e) {
        int i = list.getSelectedIndex() - 1;  
        if (i < 0) return;
        //取得文件名称
        String filename = files[i];               
        File f = new File(currentDir, filename);  
        if (!f.exists())                          
            throw new IllegalArgumentException("没有这个文件");
        //编辑文件信息，这是本程序的关键所在    
        String info = filename;
        if (f.isDirectory()) info += File.separator;
        info += " " + f.length() + " 字节 ";
        info += dateFormatter.format(new java.util.Date(f.lastModified()));
        if (f.canRead()) info += " 可读";
        if (f.canWrite()) info += " 可写";	
        details.setText(info);
    }  
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == close) this.dispose();
        else if (e.getSource() == up) { up(); }
        else if (e.getSource() == list) {  
            int i = list.getSelectedIndex(); 
            if (i == 0) up();                
            else {                           
                String name = files[i-1]; 
                File f = new File(currentDir, name);    
                String fullname = f.getAbsolutePath();
                if (f.isDirectory()) listDirectory(fullname); 
            }
        }
    }   
    protected void up() {
        //获得上一级目录名称，并转到上一级目录
        String parent = currentDir.getParent();
        if (parent == null) return;
        listDirectory(parent);
    }
    public static void main(String args[]) throws IOException {
        FileLister f;
        FilenameFilter filter = null;  
        String directory = null;               
        if (directory == null) directory = System.getProperty("user.dir");
        //创建文件信息列表对象，并显示它
        f = new FileLister(directory, filter);
        f.show();
    }
}