textviewer.java

用JAVA 写的一个类记事本的程序

import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class TextViewer extends Frame implements ActionListener
{
	private Menu fileMenu=new Menu("File");
	private MenuItem fileOpen=new MenuItem("Open");
	private MenuItem fileExit=new MenuItem("Exit");
	private TextArea text=new TextArea();
	public TextViewer()
	{
		super("Text Viewer");
		fileMenu.add(fileOpen);fileOpen.addActionListener(this);
		fileMenu.addSeparator();
		fileMenu.add(fileExit);fileExit.addActionListener(this);
		MenuBar menu=new MenuBar();
		menu.add(fileMenu);
		setMenuBar(menu);
		setLayout(new BorderLayout());
		add("Center",text);
		text.setEditable(false);
		setSize(400,400);
		setVisible(true);
	}
	public void readFile(String file)
	{
		text.setText("");
		try
		{
			BufferedReader in=new BufferedReader(new FileReader(file));
			String line;
			while((line=in.readLine())!=null)
				text.append(line+"\n");
				in.close();
				text.setCaretPosition(0);
		}
		catch (IOException ioe)
		{
			System.err.println(ioe);
		}
	}
	public void actionPerformed(ActionEvent ae)
	{
		if(ae.getSource()==fileExit)
			System.exit(0);
		else if(ae.getSource()==fileOpen)
		{
			FileDialog fd=new FileDialog(this ,"Open File",FileDialog.LOAD);
			fd.setVisible(true);
			if(fd.getFile()!=null)
			{
				File file=new File(fd.getDirectory()+fd.getFile());
				if(file.exists())
					readFile(file.toString());
				else
					text.setText("File name:"+file+"invalid.");
			}
			fd.dispose();
		}
	}
	public static void main(String args[])
	{
		TextViewer editor=new TextViewer();
	}
}