textviewer.java

Java程序设计技巧与开发实例附书源代码。

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();
  }
}