How to Customize JComboBox in Java

In this tutorial, we are going to see how to create a JComboBox component in Java Swing with a custom look, rather than its default appearance.
 

How to Customize JComboBox in Java

Usually, it is possible to provide a custom GUI implementation for Swing-based components by providing the rendering and editor. For example:

//Create the comboBox
JComboBox comboBox = new JComboBox(items);
//Define the render
comboBox.setRenderer(new MyComboBoxRenderer());
//Define the editor
comboBox.setEditor(new MyComboBoxEditor());

 

 

Complete Example:

import javax.swing.*;
import java.awt.*;

public class MyComboBox extends JFrame 
{     
    public MyComboBox() 
    {
        //Call the constructor of the parent class JFrame
        super("Customize JComboBox");
        setLayout(new FlowLayout());
        //The elements of the comboBoxe
        String[] items = {"Java", "PHP", "Python", "C++"};
        //Create the comboBox
        JComboBox comboBox = new JComboBox(items);
        //Define the render
        comboBox.setRenderer(new MyComboBoxRenderer());
        //Define the editor
        comboBox.setEditor(new MyComboBoxEditor());
        //Change the size of the comboBox
        comboBox.setPreferredSize(new Dimension(130, 25));
        //Make the comboBox editable
        comboBox.setEditable(true);
        //Add the comboBox to the frame
        add(comboBox); 
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 100);
        //Center the comboBox on the screen
        setLocationRelativeTo(null);    
    }
     
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new MyComboBox().setVisible(true);
            }
        });
    }
}

 
The renderer class(MyComboBoxRenderer()) must implement the javax.swing.ListCellRenderer interface. It is used to render the component GUI in its normal state. For example, the following class, MyComboBoxRenderer, implements a simple renderer that is a JLabel:

import javax.swing.*;
import java.awt.*;

public class MyComboBoxRenderer extends JLabel implements ListCellRenderer {
 
  public MyComboBoxRenderer() {
      setOpaque(true);
      setFont(new Font("Times New Roman", Font.BOLD | Font.ITALIC, 15));
      setBackground(Color.BLACK);
      setForeground(Color.WHITE);
  }

  @Override
  public Component getListCellRendererComponent(JList l, Object val, 
  int i, boolean isSelected, boolean cellHasFocus) {
      setText(val.toString());
      return this;
   }
}

As we can see, the renderer class must override the getListCellRendererComponent() method that is defined by the ListCellRenderer interface. The method must return a subclass of the Component class that is rendered as a list item in the ComboBox. In the example above, it returns an instance of JLabel class, and the results in a drop-down list box look like this:

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