viewfile.java

来自「此源码为机械工业出版社出版的《Java语言程序设计》第三版所配套的书中所有源代码」· Java 代码 · 共 100 行

// ViewFile.java: Read a text file and store it in a text area
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;

public class ViewFile extends JFrame implements ActionListener
{
  // Button to view view
  private JButton jbtView = new JButton("View");

  // Text field to receive file name
  private JTextField jtfFilename = new JTextField(12);

  // Text area to display file
  private JTextArea jtaFile = new JTextArea();

  // Main method
  public static void main(String[] args)
  {
    ViewFile frame = new ViewFile();
    frame.setTitle("View File");
    frame.setDefaultCloseOperation(3);
    frame.setSize(400, 300);
    frame.setVisible(true);
  }

  // Constructor
  public ViewFile()
  {
    // Panel p to hold a label, a text field, and a button
    Panel p = new Panel();
    p.setLayout(new BorderLayout());
    p.add(new Label("Filename"), BorderLayout.WEST);
    p.add(jtfFilename, BorderLayout.CENTER);
    jtfFilename.setBackground(Color.yellow);
    jtfFilename.setForeground(Color.red);
    p.add(jbtView, BorderLayout.EAST);

    // Add jtaFile to a scroll pane
    JScrollPane jsp = new JScrollPane(jtaFile);

    // Add jsp and p to the frame
    getContentPane().add(jsp, BorderLayout.CENTER);
    getContentPane().add(p, BorderLayout.SOUTH);

    // Register listener
    jbtView.addActionListener(this);
  }

  // Handle the "View" button
  public void actionPerformed(ActionEvent e)
  {
    if (e.getSource() == jbtView)
      showFile();
  }

  // Display the file in the text area
  private void showFile()
  {
    // Use a BufferedReader to read text from the file
    BufferedReader infile = null;

    // Get file name from the text field
    String filename = jtfFilename.getText().trim();

    String inLine;

    try
    {
      // Create a buffered stream
      infile = new BufferedReader(new FileReader(filename));

      // Read a line and append the line to the text area
      while ((inLine = infile.readLine()) != null)
      {
        jtaFile.append(inLine + '\n');
      }
    }
    catch (FileNotFoundException ex)
    {
      System.out.println("File not found: " + filename);
    }
    catch (IOException ex)
    {
      System.out.println(ex.getMessage());
    }
    finally
    {
      try
      {
        if (infile != null) infile.close();
      }
      catch (IOException ex)
      {
        System.out.println(ex.getMessage());
      }
    }
  }
}