Help! GUI using two buttons

Question

Hello all:
I have created a class for reading and writing to a text file on my hard drive. Also, I have created another class for a GUI to use for opening the text file with a button labeled Display. As you will see in the code below, I have created another button labeled Update. I seek to be able to edit and save the text directly in the text area with the Update button after opening the file with the Display button. Any help would be greatly appreciated. Thanks!
/** Class TextFile */
import java.io.*;
public class TextFile
    public String read(String fileIn) throws IOException
        FileReader fr = new FileReader(fileIn);
        BufferedReader br = new BufferedReader(fr);
        String line;
        StringBuffer text = new StringBuffer();
        while((line = br.readLine()) != null)
          text.append(line+'\n');
        return text.toString();
    } //end read()
    public void write(String fileOut, String text, boolean append)
        throws IOException
        File file = new File(fileOut);
        FileWriter fw = new FileWriter(file, append);
        PrintWriter pw = new PrintWriter(fw);
        pw.println(text);
        fw.close();
    } // end write()
} // end class TextFile
/** Class TextFileGUI */
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class TextFileGUI implements ActionListener
    TextFile tf = new TextFile();
    JTextField filenameField = new JTextField (30);
    JTextArea fileTextArea = new JTextArea (10, 30);
    JButton displayButton = new JButton ("Display");
    JButton updateButton = new JButton ("Update");
    JPanel panel = new JPanel();
    JFrame frame = new JFrame("Text File GUI");
    public TextFileGUI()
        panel.add(new JLabel("Filename"));
        panel.add(filenameField);
        panel.add(fileTextArea);
        fileTextArea.setLineWrap(true);
        panel.add(displayButton);
        displayButton.addActionListener(this);
        panel.add(updateButton);
        updateButton.addActionListener(this);
        frame.setContentPane(panel);
        frame.setSize(400,400);
        frame.setVisible(true);
    } //end TextFileGUI()
    public void actionPerformed(ActionEvent e)
        String t;
        try
            t = tf.read(filenameField.getText());
            fileTextArea.setText(t);
        catch(Exception ex)
            fileTextArea.setText("Exception: "+ex);
        } //end try-catch
    } //end actionPerformed()
} //end TextFileGUI

Answer 1

Swing related questions should be posted in the Swing forum.
You are using the same ActionListener for both buttons, so you need to be able to tell which button was pressed. There are a couple of ways to do this:
a) use the getSource() method of the ActionEvent and compare the source against your two buttons to see which one was pressed and then invoke the appropriate code.
Object source = e.getSource();
if (source == displayButton)
    //  do display processing
else if (source == updateButton)
    //  do update processingb) Check the action command to determine which button was clicked. This approach is demonstrated in the Swing tutorial on [url http://java.sun.com/docs/books/tutorial/uiswing/components/button.html]How to Use Buttons
Another option is to create separate ActionListeners for each button so there is no confusion
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
class TextAreaLoad
     public static void main(String a[])
          final JTextArea edit = new JTextArea(5, 40);
          JButton read = new JButton("Read some.txt");
          read.addActionListener( new ActionListener()
               public void actionPerformed(ActionEvent e)
                    try
                         FileReader reader = new FileReader( "some.txt" );
                         BufferedReader br = new BufferedReader(reader);
                         edit.read( br, null );
                         edit.requestFocus();
                    catch(Exception e2) { System.out.println(e2); }
          JButton write = new JButton("Write some.txt");
          write.addActionListener( new ActionListener()
               public void actionPerformed(ActionEvent e)
                    try
                         FileWriter writer = new FileWriter( "some.txt" );
                         BufferedWriter bw = new BufferedWriter( writer );
                         edit.write( bw );
                         edit.setText("");
                         edit.requestFocus();
                    catch(Exception e2) {}
          JFrame frame = new JFrame("TextArea Load");
          frame.getContentPane().add( new JScrollPane(edit), BorderLayout.NORTH );
          frame.getContentPane().add(read, BorderLayout.WEST);
          frame.getContentPane().add(write, BorderLayout.EAST);
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.pack();
          frame.setLocationRelativeTo( null );
          frame.setVisible(true);
}