JAVA Swing: Can't add text area to a Border Layout

Question

MainFrame.java

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;

public class MainFrame extends JFrame{

    private JTextArea textArea;
    private JButton btn;
    private TextPanel textPanel;

    public MainFrame() {

        super("My First JAVA Swing Window");
        setLayout(new BorderLayout());

        textArea = new JTextArea();
        btn = new JButton("Click Me");
        textPanel = new TextPanel();


        btn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                textArea.append("Button has been clicked!\n");
                //textPanel.appendText("Button has been clicked!\n");
            }
        });

        add(textArea, BorderLayout.CENTER);
        add(btn, BorderLayout.SOUTH);

        setSize(600,500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
    }

}

My goal is to add a text (Button has been clicked.) to the text area if I click the button, I managed to do it but I tried to seperate the text area in a different class, and if I seperate it. it doesnt work anymore.. What I see is it dont even add the text area to the border layout..: This is how I try to seperate and thats the part thats not working. MainFrame.java

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;

public class MainFrame extends JFrame{

    //private JTextArea textArea;
    private JButton btn;
    private TextPanel textPanel;

    public MainFrame() {

        super("My First JAVA Swing Window");
        setLayout(new BorderLayout());

        //textArea = new JTextArea();
        btn = new JButton("Click Me");
        textPanel = new TextPanel();


        btn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                //textArea.append("Button has been clicked!\n");
                textPanel.appendText("Button has been clicked!\n");
            }
        });

        //add(textArea, BorderLayout.CENTER);
        add(btn, BorderLayout.SOUTH);

        setSize(600,500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
    }

}

TextPanel.java

import java.awt.BorderLayout;

import javax.swing.JPanel;
import javax.swing.JTextArea;

public class TextPanel extends JPanel{

    private JTextArea textArea;

    public TextPanel() {

        textArea = new JTextArea();
        setLayout(new BorderLayout());
        add(textArea, BorderLayout.CENTER);
    }

    public void appendText(String text) {
        textArea.append(text);
    }
}

And of course there is a Main class which runs the MainFrame...

Answer 1

The problem is that you called add(textArea, BorderLayout.CENTER); in your MainFrame.java before the refactoring. The add method there adds the textArea to the layout of the JFrame .

But afterwards you don't add the TextPanel to the JFrame , but only to a local BorderLayout of the JPanel your extending of. That BorderLayout isn't added anywhere.

It should work, if you still call add(textPanel, BorderLayout.CENTER) ;