Finestra non viene visualizzata

[fermat]

ciao!

mi sono reso conto che a forza di creare gui con gli editor visuali, mi sono dimenticato parecchie cose.
così, dovendo riscrivere un programmino, ho pensato di creare la gui a mano.
solo che quando lancio il programma, la finestra praticamente non compare a video.
come se non venisse diesgnata:

public class MainWindow extends JFrame {

    private JFrame mainFrame;
    private JTextPane textPane;
    private JScrollPane scrollPane;
    private JMenuBar menuBar;
    private JMenu menuFile;
    private JMenuItem itemChoose;
    private JMenuItem itemSave;
    private JMenuItem itemExit;

    public MainWindow() {
        createGui();
    }

    private void createGui() {
        mainFrame = new JFrame("Lista directory");
        textPane = new JTextPane();
        scrollPane = new JScrollPane();
        menuBar = new JMenuBar();
        menuFile = new JMenu();
        itemChoose = new JMenuItem();
        itemSave = new JMenuItem();
        itemExit = new JMenuItem();
        mainFrame.setSize(new Dimension(700, 700));
        mainFrame.setLayout(new BorderLayout());
        mainFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        mainFrame.setResizable(false);
        mainFrame.setLocationRelativeTo(null);
        textPane.setEditable(false);
        scrollPane.setViewportView(textPane);
        menuFile.setText("File");
        menuFile.add(itemChoose);
        menuFile.add(itemSave);
        menuFile.add(itemExit);
        menuBar.add(menuFile);
        mainFrame.setJMenuBar(menuBar);
        mainFrame.getContentPane().add(scrollPane, BorderLayout.CENTER);
        mainFrame.pack();
    }

    public static void main(String args[]) {
        if (System.getProperty("os.name").toLowerCase().contains("mac")) {
            System.setProperty("apple.laf.useScreenMenuBar", "true");
        } else {
            try {
                for (UIManager.LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
                    if ("Nimbus".equals(info.getName())) {
                        UIManager.setLookAndFeel(info.getClassName());
                        break;
                    }
                }
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                JOptionPane.showMessageDialog(null, ex.getMessage());
            }
        }

        EventQueue.invokeLater(() -> {
            new MainWindow().setVisible(true);
        });
    }
}

dove sto sbagliando??

[schumy2000]

Perché nella classe estendi JFrame

public class MainWindow extends JFrame

e poi lo dichiari nuovamente nel metodo?

private void createGui() {
        mainFrame = new JFrame("Lista directory");

non devi dichiararla se la estendi nella classe.

Puoi fare semplicemente:

private void createGui() {
        super("Lista Directory");
        ....
        setSize(new Dimension(700, 700));
        setLayout(new BorderLayout());
        ....
        ....
}

Ciao.

[fermat]

ciao!

si mi ero risposto da solo nel frattempo.
scemenza mia:

import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.WindowConstants;

public class MainWindow extends JFrame {

    private JTextPane textPane;
    private JScrollPane scrollPane;
    private JMenuBar menuBar;
    private JMenu menuFile;
    private JMenuItem itemChoose;
    private JMenuItem itemSave;
    private JMenuItem itemExit;

    public MainWindow() {
        super("Lista directory");
        createGui();
    }

    private void createGui() {
        textPane = new JTextPane();
        scrollPane = new JScrollPane();
        menuBar = new JMenuBar();
        menuFile = new JMenu();
        itemChoose = new JMenuItem();
        itemSave = new JMenuItem();
        itemExit = new JMenuItem();
        setPreferredSize(new Dimension(700, 700));
        setLayout(new BorderLayout());
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setResizable(false);
        textPane.setEditable(false);
        scrollPane.setViewportView(textPane);
        getContentPane().add(scrollPane, BorderLayout.CENTER);
        menuFile.setText("File");
        menuFile.add(itemChoose);
        menuFile.add(itemSave);
        menuFile.add(itemExit);
        menuBar.add(menuFile);
        setJMenuBar(menuBar);
        pack();
        setLocationRelativeTo(null);
    }

    public static void main(String args[]) {
        if (System.getProperty("os.name").toLowerCase().contains("mac")) {
            System.setProperty("apple.laf.useScreenMenuBar", "true");
        } else {
            try {
                for (UIManager.LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
                    if ("Nimbus".equals(info.getName())) {
                        UIManager.setLookAndFeel(info.getClassName());
                        break;
                    }
                }
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                JOptionPane.showMessageDialog(null, ex.getMessage());
            }
        }

        SwingUtilities.invokeLater(() -> {
            new MainWindow().setVisible(true);
        });
    }
}

grazie!!