Using ActionListener to Read a File Into a JTextArea

Question

I want to create a JTextArea in a Java Swing frame that reads the contents of a file when I click on a button. I created a JButton, the text area and added an ActionListener for the button, but I don't know how to make the actionPerformed method to read the file after clicking the button.

Here's my code:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.Scanner;

public class JavaGui extends JFrame implements ActionListener {
    JButton btn;
    JTextArea jtxt = new JTextArea(50, 50);

    public JavaGui() {
        super("This is the Title");
        setLayout(new FlowLayout());
        btn = new JButton("Click Here");
        btn.addActionListener(this);
        add(btn);
        add(jtxt);
    }

    public static void main(String[] args) throws IOException {
        //Open file for reading content
        FileInputStream file = new FileInputStream("abc.txt");
        Scanner scnr = new Scanner(file);
        System.out.println(file.nextLine());

        //Create the JFrame window
        JavaGui obj = new JavaGui();
        obj.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        obj.setSize(500, 500);
        obj.setVisible(true);
    }

    public void actionPerformed(ActionEvent e){
        // how to do this? 
    }
}

Answer 1

Something like this will do

@Override
public void actionPerformed( ActionEvent e )
{
    if( e.getSource() == btn ) // your button 
    {
        doAction();
    }
}

doAction() contains the logic you need to run when you click on the button reference btn

void doAction()
{
    StringBuilder sb = new StringBuilder();
    try( BufferedReader br = Files.newBufferedReader( Paths.get( "filename.txt" ) ) )
    {
        String line;
        while( ( line = br.readLine() ) != null )
        {
            sb.append( line ).append( "\n" );
        }
    }
    catch( IOException e )
    {
        System.err.format( "IOException: %s%n", e );
    }
    jtxt.setText( sb.toString() );
}