Dynamically adding components to JFrame

Question

I'm looking for a way to dynamically add a Component inside a JFrame after it has been set visible. Specifically, I'm making a request to a database and based on the length of the result, I want to show a JRadioButton on the screen. I'm using this code:

try {
        Class.forName(Mavenproject1.SQL_DRIVER);
        Connection c = (Connection) DriverManager.getConnection(Mavenproject1.DB, Mavenproject1.ROOT, Mavenproject1.PASSWORD);
        PreparedStatement ps = c.prepareStatement("Select * from calendriers where user = ?");
        ps.setString(1, Login.USER);
        ResultSet rs = ps.executeQuery();
        if (rs.next()) {
            int cal_id = rs.getInt(1);
            ps = c.prepareStatement("Select * from creneaux where calendrier = ?");
            ps.setInt(1, cal_id);
            rs = ps.executeQuery();
            while (rs.next()) {
                JRadioButton radio = new JRadioButton("Hello world");
                radio.setVisible(true);
                Date debut = Date.getDateFromString(rs.getString(2), true);
                Date fin = Date.getDateFromString(rs.getString(3), true);
                Creneau cr = new Creneau(debut, fin);
                creneaux.add(cr);
                System.out.println(cr.toString());
                getContentPane().add(radio);
                getContentPane().revalidate();
                getContentPane().repaint();
            }
            Component[] components = getContentPane().getComponents();
            for (Component component : components) {
                System.out.println(component.getClass().getName());
            }
        }
    } catch (Exception ex) {
        JOptionPane.showMessageDialog(null, "Error", "error", 1);
    }

As an output, I'm having the corresponding JRadioButtons are components of the content pane but I'm unable to see it on the screen ,I checked the location using getLocation() it said 0,0 , I changed it to 100,100 but still nothing..

Answer 1

You have to make the UI changes on the event dispatch thread. Assuming the database access is done on a dedicated thread, wrap the UI changes in SwingUtilities.invokeLater(), for example:

SwingUtilities.invokeLater(() -> {
    JRadioButton radio = new JRadioButton("Hello world");
    radio.setVisible(true);
    getContentPane().add(radio);
    getContentPane().revalidate();
    getContentPane().repaint();
});

Using a SwingWorker might be a good idea too.