Auto-suggestion ComboBox

I have a JComboBox and the JComboBox has so many items. I want to add “auto-suggestion” feature on the JComboBox.

Like this: I have 3 items, “Artpop”, “Born This Way”, and “Chromatica”. If I type “Way” then the autocomplete selects the “Born This Way" item. If I type "matica" then the autocomplete selects the "Chromatica" item.

I was looking for it on StackOverflow, but all the answers are outdated (I'm using Swing, while the answers are for AWT. When I do the answers, I've got several errors).

How to make auto-suggestion Swing JComboBox?

It takes a JTextField and a JComboBox to create an auto-suggestion combo box.

Here's an example I put together. Unfortunately, the GUI picture doesn't display the JComboBox correctly.

I created a simple GUI with a JTextField and a JComboBox.

When you type a character in the JTextField, the JComboBox options are reduced to the Strings that contain that character. The search is not case sensitive. If you type a w, it will return all Strings with a w or a W.

Here's the complete, runnable code I used.

import java.awt.BorderLayout;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class AutoSuggestionExample implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new AutoSuggestionExample());
}
private DefaultComboBoxModel<String> comboBoxModel;
private JTextField autoSuggestionField;
private List<String> masterList;
public AutoSuggestionExample() {
String[] masterList = { "Artpop", "Born This Way", "Chromatica" };
this.masterList = Arrays.asList(masterList);
this.comboBoxModel = new DefaultComboBoxModel<>(masterList);
}
@Override
public void run() {
JFrame frame = new JFrame("Auto Suggestion Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createMainPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createMainPanel() {
JPanel panel = new JPanel();
autoSuggestionField = new JTextField(20);
autoSuggestionField.addKeyListener(new AutoSuggestionListener());
panel.add(autoSuggestionField);
JComboBox<String> comboBox = new JComboBox<>(comboBoxModel);
comboBox.setSelectedIndex(0);
panel.add(comboBox);
return panel;
}
public List<String> createSelectedList(String search) {
if (search.isEmpty()) {
return masterList;
}
search = search.toLowerCase();
List<String> selectedList = new ArrayList<>();
for (String s : masterList) {
if (s.toLowerCase().contains(search)) {
selectedList.add(s);
}
}
return selectedList;
}
public void updateComboBox(List<String> selectedList) {
comboBoxModel.removeAllElements();
comboBoxModel.addAll(selectedList);
if (selectedList.size() > 0) {
comboBoxModel.setSelectedItem(selectedList.get(0));
}
}
public class AutoSuggestionListener extends KeyAdapter {
@Override
public void keyPressed(KeyEvent event) {
String text = autoSuggestionField.getText() + event.getKeyChar();
updateComboBox(createSelectedList(text));
}
}
}

As Andrew Thompson commented: "When a combo box is in focus and the user types the first letters of an item it contains, that item will become selected" <br/>
This behavior is defined in the public method JComboBox.selectWithKeyChar(char keyChar).
You can extend JComboBox to override selectWithKeyChar(char keyChar) to define a different behavior.