How to set content at position 0 with field disabled?

Question

I need that when my component receives a text (it will receive through a query), the text is "set" at the beginning of the field, because in many cases, the text is extended and the beginning is omitted. The detail that is complicating the solution is that the component this disable.

I used as a basis this other issue: How to set cursor at the beginning of the field?

However, in the question above, he does this through the event of gaining focus, which will not be possible in my case.

Example:

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import javax.swing.JButton;

import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.text.JTextComponent;

public class Position extends JFrame {

    private final JTextField campo = new JTextField();
    private JButton botao = new JButton("Clique");

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            Position tela = new Position();
            tela.setVisible(true);
        });

    }

    public Position() {
        add(colocaCampo());
        setSize(500, 150);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    private JComponent colocaCampo() {

        JPanel painel = new JPanel();
        JLabel label = new JLabel("TextField");

        campo.setPreferredSize(new Dimension(120, 22));
        campo.addFocusListener(new CaretPosition());
        painel.add(label);
        painel.add(campo);
        campo.setEditable(false);

        painel.add(botao);
        botao.addActionListener((ActionEvent e) -> {
            campo.setText("Texto longo, realmente grande esse texto !");
        });
        botao.setPreferredSize(new Dimension(90, 22));
        return painel;
    }

    class CaretPosition extends FocusAdapter {

        @Override
        public void focusGained(FocusEvent e) {

            JTextComponent comp = (JTextComponent) e.getSource();
            comp.setCaretPosition(0);
        }
    }
}

Answer 1

In your own code is the solution, only put in the wrong place. To define the position of the Caret of a text component is through the method setCaretPosition, and if the text is going to be appended to the field via a button’s Listener, then this method should be called after inserting the text:

botao.addActionListener((ActionEvent e) -> {
    campo.setText("Texto longo, realmente grande esse texto !");
    campo.setCaretPosition(0);
});

Of course this is a simplistic solution, nothing prevents you from overwriting the method setText and force in it the starting position of the Caret, but I believe that this is an alternative that generates unnecessary complexity.