GUI shows elements only after dragging window

Question

        frame_ref = new Frame("Login");
        mainPanel_ref = new Panel();
        buttonPanel_ref = new Panel();
        grid_ref = new GridLayout(4,2);
        frame_ref.setSize(300,120);
        frame_ref.setVisible(true);

        email_ref = new TextField();
        password_ref = new JPasswordField();

        mainPanel_ref.setLayout(grid_ref);
        mainPanel_ref.add(new Label("E-Mail"));
        mainPanel_ref.add(email_ref);
        mainPanel_ref.add(new Label("Passwort"));
        mainPanel_ref.add(password_ref);

        mainPanel_ref.add(submitLogin_ref);
        mainPanel_ref.add(fehlerMeldung_ref);

        frame_ref.add(mainPanel_ref);

I set up a view in Java like above. The window is complete empty, but after I drag and drop its size, all the elements appear. Does somebody know how to fix this?

Answer 1

Call frame_ref.setVisible(true); after frame_ref.add(mainPanel_ref);.

What happens here is: You show frame by calling frame_ref.setVisible(true); and then add elements in it. So you get an empty frame. Afterwards when you drag or resize it gets repainted and you can see elements.

Answer 2

Call pack() on the JFrame after the components have been added. Doing so will cause the frame to assume the smallest size it needs to display the components. Finally call (setLocation()(4) &) setVisible(true).

import java.awt.GridLayout;
import javax.swing.*;
import javax.swing.border.EmptyBorder;

class FrameTest {

    public void init() {
        frame_ref = new JFrame("Login");
        frame_ref.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainPanel_ref = new JPanel(new GridLayout(4,2,6,3));
        mainPanel_ref.setBorder(new EmptyBorder(5,5,5,5));

        email_ref = new JTextField();
        password_ref = new JPasswordField();
        mainPanel_ref.add(new JLabel("E-Mail"));
        mainPanel_ref.add(email_ref);
        mainPanel_ref.add(new JLabel("Passwort"));
        mainPanel_ref.add(password_ref);

        mainPanel_ref.add(new JLabel(""));
        mainPanel_ref.add(new JLabel(""));
        mainPanel_ref.add(submitLogin_ref);
        mainPanel_ref.add(fehlerMeldung_ref);

        frame_ref.add(mainPanel_ref);

        //frame_ref.setSize(300,120);
        frame_ref.pack();
        frame_ref.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new FrameTest().init();
            }
        });
    }

    private JFrame frame_ref;
    private JPanel mainPanel_ref;
    private JTextField email_ref;
    private JPasswordField password_ref;
    private JButton submitLogin_ref = new JButton("Submit Login");
    private JButton fehlerMeldung_ref = new JButton("Fehler Meldung");
}

Other tips:

1. Don't mix Swing with AWT. At least, not the components, or not before targeting Java 7+.
2. A log-in component is often better suited to putting in a JDialog or JOptionPane rather than a JFrame.
3. This might be better suited to a nested layout, or some other layout than GridLayout
4. setLocation() might be swapped out for:
   • If the log-in has a 'parent' component, setLocationRelativeTo(Component).
   • If the log-in is the first screen visible, setLocationByPlatform(true) (1.6+).
5. Check the source closely for other tips.
6. For better help sooner, post an SSCCE.