Simple Dropdown menu in Java

Question

I am working on a very simple GUI in Java.

In this GUI I want to display:

1. A label with some text on the top of the page
2. A JComboBox under the mentioned label
3. A JButton under the mentioned JComboBox

Here's my code:

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Prova {

public static void main(String[] args) {

    JFrame frame = new JFrame("A Simple GUI");
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(500, 500);
    frame.setLocation(430, 100);

    JPanel panel = new JPanel();

    frame.add(panel);

    JLabel lbl = new JLabel("Select one of the possible choices and click OK");
    lbl.setVisible(true);

    panel.add(lbl);

    String[] choices = { "CHOICE 1","CHOICE 2", "CHOICE 3","CHOICE 4","CHOICE 5","CHOICE 6"};

    final JComboBox<String> cb = new JComboBox<String>(choices);

    cb.setVisible(true);
    panel.add(cb);

    JButton btn = new JButton("OK");
    panel.add(btn);

    }
}

Unfortunately, the result I get is

As you can see in the image, the label, the JComboBox and the JButton are on the same line!

Instead, I want them "stacked" as described above:

JLabel

JComboBox

JButton

I tried using the setLocation(int x, int y) method, but they always show in the same position.

Many thanks!

Answer 1

If I've understood your question, the following code accomplishes what you are trying to do without being overly complicated:

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.BoxLayout; // added code
import java.awt.Component; // added code

public class Prova {

public static void main(String[] args) {

    JFrame frame = new JFrame("A Simple GUI");
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(500, 500);
    frame.setLocation(430, 100);

    JPanel panel = new JPanel();
    panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); // added code

    frame.add(panel);

    JLabel lbl = new JLabel("Select one of the possible choices and click OK");
    lbl.setAlignmentX(Component.CENTER_ALIGNMENT);
    //lbl.setVisible(true); // Not needed

    panel.add(lbl);

    String[] choices = { "CHOICE 1", "CHOICE 2", "CHOICE 3", "CHOICE 4",
                         "CHOICE 5", "CHOICE 6" };

    final JComboBox<String> cb = new JComboBox<String>(choices);

    cb.setMaximumSize(cb.getPreferredSize()); // added code
    cb.setAlignmentX(Component.CENTER_ALIGNMENT);// added code
    //cb.setVisible(true); // Not needed
    panel.add(cb);

    JButton btn = new JButton("OK");
    btn.setAlignmentX(Component.CENTER_ALIGNMENT); // added code
    panel.add(btn);

    frame.setVisible(true); // added code

    }
}

The setLocation method is often overly complicated unless you have very specific (artistic?) goals for the layout. For this problem, an easier solution is to use a BoxLayout and specify that you want things added in the y-direction (vertically downwards.) Note that you will have to specify the dimensions of the JComboBox (and some other GUI elements that you might want to add later) to avoid a giant drop-down menu. cf. another stackoverflow post, JComboBox width

Answer 2

use frame.setLayout(null); this will allow you to place the Label, Button etc. where you like