fileviewer.java

java应用举例2

import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class FileViewer extends Frame implements ActionListener {
    String directory;  
    TextArea textarea; 
    public FileViewer() { this(null, null); }
    public FileViewer(String filename) { this(null, filename); }
    public FileViewer(String directory, String filename) {
        super();  
	addWindowListener(new WindowAdapter() {
		public void windowClosing(WindowEvent e) { dispose(); }
	    });

        textarea = new TextArea("", 24, 80);
        textarea.setFont(new Font("MonoSpaced", Font.PLAIN, 12));
        textarea.setEditable(false);
        this.add("Center", textarea);
        Panel p = new Panel();
        p.setLayout(new FlowLayout(FlowLayout.RIGHT, 10, 5));
        this.add(p, "South");
	
        Font font = new Font("SansSerif", Font.BOLD, 14);
        Button openfile = new Button("Open File");
        Button close = new Button("Close");
        openfile.addActionListener(this);
        openfile.setActionCommand("open");
        openfile.setFont(font);
        close.addActionListener(this);
        close.setActionCommand("close");
        close.setFont(font);
        p.add(openfile);
        p.add(close);
	
        this.pack();
        if (directory == null) {
            File f;
            if ((filename != null)&& (f = new File(filename)).isAbsolute()) {
                directory = f.getParent();
                filename = f.getName();
            }
            else directory = System.getProperty("user.dir");
        }
	
        this.directory = directory;   
        setFile(directory, filename); 
    }
    
    public void setFile(String directory, String filename) {
        if ((filename == null) || (filename.length() == 0)) return;
        File f;
        FileReader in = null;
        try {
            f = new File(directory, filename); 
            in = new FileReader(f);            
            char[] buffer = new char[4096];    
            int len;                           
            textarea.setText("");              
            while((len = in.read(buffer)) != -1) {
                String s = new String(buffer, 0, len); 
                textarea.append(s);                    
            }
            this.setTitle("FileViewer: " + filename);  
            textarea.setCaretPosition(0);              
        }
        catch (IOException e) { 
            textarea.setText(e.getClass().getName() + ": " + e.getMessage());
            this.setTitle("FileViewer: " + filename + ": I/O Exception");
        }
        finally { try { if (in!=null) in.close(); } catch (IOException e) {} }
    }

    public void actionPerformed(ActionEvent e) {
        String cmd = e.getActionCommand();
        if (cmd.equals("open")) {          
            FileDialog f = new FileDialog(this, "Open File", FileDialog.LOAD);
            f.setDirectory(directory);       

            f.show();                        

            directory = f.getDirectory();   
            setFile(directory, f.getFile()); 
            f.dispose();                    
        }
        else if (cmd.equals("close"))      
            this.dispose();                  
    }
    
    static public void main(String[] args) throws IOException {
        Frame f = new FileViewer((args.length == 1)?args[0]:null);
        f.addWindowListener(new WindowAdapter() {
		public void windowClosed(WindowEvent e) { System.exit(0); }
	    });
        f.show();
    }
}