Create a autocompleting textbox in Java with a dropdown list

I want to create a auto-suggest text box which would query the database at each key release event. That part is easy, but I want to give nice visual to it. Something similar to the auto-suggest text box we see in websites like searching in Facebook.

How to make such an interface ?

A naive idea would be to have a JList placed just below the text box and set it visible with the results in it on finding one.

Any better idea or a standard way of doing it?

@syb0rg's answer is easier, as it uses an 3rd party library.

However I used an alternate approach:

It uses a custom class called AutoSuggestor which accepts a JTextField, its Window an ArrayList<String> of words to check typed words against, a background color and text color, and suggestion focus colour as well as an opacity value. By passing JTextField reference a DocumentListener is added which will do the work of checking what word is typed and whether to display suggestions or not and if so what suggestions to display. When a word is typed the DocumentListener will firewordTyped(String wordTyped) method with the current word being typed or (at least how much ever of the word has been typed), in wordTyped(..) the word will be checked against those in the AutoSuggestors classes dictionary which is a basic ArrayList of String this can be set on the fly as seen in the below example:

(For now you will have to use mouse and click the word you want to be auto completed, or use DOWN to transverse suggestions and the textfield and ENTER to select suggestion when traversing using down key. I have not yet implemented UP yet):

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.AbstractAction;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.JWindow;
import javax.swing.KeyStroke;
import javax.swing.SwingUtilities;
import javax.swing.border.LineBorder;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

/**
 * @author David
 */
public class Test {

    public Test() {

        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


        JTextField f = new JTextField(10);

        AutoSuggestor autoSuggestor = new AutoSuggestor(f, frame, null, Color.WHITE.brighter(), Color.BLUE, Color.RED, 0.75f) {
            @Override
            boolean wordTyped(String typedWord) {

                //create list for dictionary this in your case might be done via calling a method which queries db and returns results as arraylist
                ArrayList<String> words = new ArrayList<>();
                words.add("hello");
                words.add("heritage");
                words.add("happiness");
                words.add("goodbye");
                words.add("cruel");
                words.add("car");
                words.add("war");
                words.add("will");
                words.add("world");
                words.add("wall");


                setDictionary(words);
                //addToDictionary("bye");//adds a single word

                return super.wordTyped(typedWord);//now call super to check for any matches against newest dictionary
            }
        };

        JPanel p = new JPanel();

        p.add(f);

        frame.add(p);

        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Test();
            }
        });
    }
}

class AutoSuggestor {

    private final JTextField textField;
    private final Window container;
    private JPanel suggestionsPanel;
    private JWindow autoSuggestionPopUpWindow;
    private String typedWord;
    private final ArrayList<String> dictionary = new ArrayList<>();
    private int currentIndexOfSpace, tW, tH;
    private DocumentListener documentListener = new DocumentListener() {
        @Override
        public void insertUpdate(DocumentEvent de) {
            checkForAndShowSuggestions();
        }

        @Override
        public void removeUpdate(DocumentEvent de) {
            checkForAndShowSuggestions();
        }

        @Override
        public void changedUpdate(DocumentEvent de) {
            checkForAndShowSuggestions();
        }
    };
    private final Color suggestionsTextColor;
    private final Color suggestionFocusedColor;

    public AutoSuggestor(JTextField textField, Window mainWindow, ArrayList<String> words, Color popUpBackground, Color textColor, Color suggestionFocusedColor, float opacity) {
        this.textField = textField;
        this.suggestionsTextColor = textColor;
        this.container = mainWindow;
        this.suggestionFocusedColor = suggestionFocusedColor;
        this.textField.getDocument().addDocumentListener(documentListener);

        setDictionary(words);

        typedWord = "";
        currentIndexOfSpace = 0;
        tW = 0;
        tH = 0;

        autoSuggestionPopUpWindow = new JWindow(mainWindow);
        autoSuggestionPopUpWindow.setOpacity(opacity);

        suggestionsPanel = new JPanel();
        suggestionsPanel.setLayout(new GridLayout(0, 1));
        suggestionsPanel.setBackground(popUpBackground);

        addKeyBindingToRequestFocusInPopUpWindow();
    }

    private void addKeyBindingToRequestFocusInPopUpWindow() {
        textField.getInputMap(JComponent.WHEN_FOCUSED).put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true), "Down released");
        textField.getActionMap().put("Down released", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent ae) {//focuses the first label on popwindow
                for (int i = 0; i < suggestionsPanel.getComponentCount(); i++) {
                    if (suggestionsPanel.getComponent(i) instanceof SuggestionLabel) {
                        ((SuggestionLabel) suggestionsPanel.getComponent(i)).setFocused(true);
                        autoSuggestionPopUpWindow.toFront();
                        autoSuggestionPopUpWindow.requestFocusInWindow();
                        suggestionsPanel.requestFocusInWindow();
                        suggestionsPanel.getComponent(i).requestFocusInWindow();
                        break;
                    }
                }
            }
        });
        suggestionsPanel.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT).put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true), "Down released");
        suggestionsPanel.getActionMap().put("Down released", new AbstractAction() {
            int lastFocusableIndex = 0;

            @Override
            public void actionPerformed(ActionEvent ae) {//allows scrolling of labels in pop window (I know very hacky for now :))

                ArrayList<SuggestionLabel> sls = getAddedSuggestionLabels();
                int max = sls.size();

                if (max > 1) {//more than 1 suggestion
                    for (int i = 0; i < max; i++) {
                        SuggestionLabel sl = sls.get(i);
                        if (sl.isFocused()) {
                            if (lastFocusableIndex == max - 1) {
                                lastFocusableIndex = 0;
                                sl.setFocused(false);
                                autoSuggestionPopUpWindow.setVisible(false);
                                setFocusToTextField();
                                checkForAndShowSuggestions();//fire method as if document listener change occured and fired it

                            } else {
                                sl.setFocused(false);
                                lastFocusableIndex = i;
                            }
                        } else if (lastFocusableIndex <= i) {
                            if (i < max) {
                                sl.setFocused(true);
                                autoSuggestionPopUpWindow.toFront();
                                autoSuggestionPopUpWindow.requestFocusInWindow();
                                suggestionsPanel.requestFocusInWindow();
                                suggestionsPanel.getComponent(i).requestFocusInWindow();
                                lastFocusableIndex = i;
                                break;
                            }
                        }
                    }
                } else {//only a single suggestion was given
                    autoSuggestionPopUpWindow.setVisible(false);
                    setFocusToTextField();
                    checkForAndShowSuggestions();//fire method as if document listener change occured and fired it
                }
            }
        });
    }

    private void setFocusToTextField() {
        container.toFront();
        container.requestFocusInWindow();
        textField.requestFocusInWindow();
    }

    public ArrayList<SuggestionLabel> getAddedSuggestionLabels() {
        ArrayList<SuggestionLabel> sls = new ArrayList<>();
        for (int i = 0; i < suggestionsPanel.getComponentCount(); i++) {
            if (suggestionsPanel.getComponent(i) instanceof SuggestionLabel) {
                SuggestionLabel sl = (SuggestionLabel) suggestionsPanel.getComponent(i);
                sls.add(sl);
            }
        }
        return sls;
    }

    private void checkForAndShowSuggestions() {
        typedWord = getCurrentlyTypedWord();

        suggestionsPanel.removeAll();//remove previos words/jlabels that were added

        //used to calcualte size of JWindow as new Jlabels are added
        tW = 0;
        tH = 0;

        boolean added = wordTyped(typedWord);

        if (!added) {
            if (autoSuggestionPopUpWindow.isVisible()) {
                autoSuggestionPopUpWindow.setVisible(false);
            }
        } else {
            showPopUpWindow();
            setFocusToTextField();
        }
    }

    protected void addWordToSuggestions(String word) {
        SuggestionLabel suggestionLabel = new SuggestionLabel(word, suggestionFocusedColor, suggestionsTextColor, this);

        calculatePopUpWindowSize(suggestionLabel);

        suggestionsPanel.add(suggestionLabel);
    }

    public String getCurrentlyTypedWord() {//get newest word after last white spaceif any or the first word if no white spaces
        String text = textField.getText();
        String wordBeingTyped = "";
        if (text.contains(" ")) {
            int tmp = text.lastIndexOf(" ");
            if (tmp >= currentIndexOfSpace) {
                currentIndexOfSpace = tmp;
                wordBeingTyped = text.substring(text.lastIndexOf(" "));
            }
        } else {
            wordBeingTyped = text;
        }
        return wordBeingTyped.trim();
    }

    private void calculatePopUpWindowSize(JLabel label) {
        //so we can size the JWindow correctly
        if (tW < label.getPreferredSize().width) {
            tW = label.getPreferredSize().width;
        }
        tH += label.getPreferredSize().height;
    }

    private void showPopUpWindow() {
        autoSuggestionPopUpWindow.getContentPane().add(suggestionsPanel);
        autoSuggestionPopUpWindow.setMinimumSize(new Dimension(textField.getWidth(), 30));
        autoSuggestionPopUpWindow.setSize(tW, tH);
        autoSuggestionPopUpWindow.setVisible(true);

        int windowX = 0;
        int windowY = 0;

        windowX = container.getX() + textField.getX() + 5;
        if (suggestionsPanel.getHeight() > autoSuggestionPopUpWindow.getMinimumSize().height) {
            windowY = container.getY() + textField.getY() + textField.getHeight() + autoSuggestionPopUpWindow.getMinimumSize().height;
        } else {
            windowY = container.getY() + textField.getY() + textField.getHeight() + autoSuggestionPopUpWindow.getHeight();
        }

        autoSuggestionPopUpWindow.setLocation(windowX, windowY);
        autoSuggestionPopUpWindow.setMinimumSize(new Dimension(textField.getWidth(), 30));
        autoSuggestionPopUpWindow.revalidate();
        autoSuggestionPopUpWindow.repaint();

    }

    public void setDictionary(ArrayList<String> words) {
        dictionary.clear();
        if (words == null) {
            return;//so we can call constructor with null value for dictionary without exception thrown
        }
        for (String word : words) {
            dictionary.add(word);
        }
    }

    public JWindow getAutoSuggestionPopUpWindow() {
        return autoSuggestionPopUpWindow;
    }

    public Window getContainer() {
        return container;
    }

    public JTextField getTextField() {
        return textField;
    }

    public void addToDictionary(String word) {
        dictionary.add(word);
    }

    boolean wordTyped(String typedWord) {

        if (typedWord.isEmpty()) {
            return false;
        }
        //System.out.println("Typed word: " + typedWord);

        boolean suggestionAdded = false;

        for (String word : dictionary) {//get words in the dictionary which we added
            boolean fullymatches = true;
            for (int i = 0; i < typedWord.length(); i++) {//each string in the word
                if (!typedWord.toLowerCase().startsWith(String.valueOf(word.toLowerCase().charAt(i)), i)) {//check for match
                    fullymatches = false;
                    break;
                }
            }
            if (fullymatches) {
                addWordToSuggestions(word);
                suggestionAdded = true;
            }
        }
        return suggestionAdded;
    }
}

class SuggestionLabel extends JLabel {

    private boolean focused = false;
    private final JWindow autoSuggestionsPopUpWindow;
    private final JTextField textField;
    private final AutoSuggestor autoSuggestor;
    private Color suggestionsTextColor, suggestionBorderColor;

    public SuggestionLabel(String string, final Color borderColor, Color suggestionsTextColor, AutoSuggestor autoSuggestor) {
        super(string);

        this.suggestionsTextColor = suggestionsTextColor;
        this.autoSuggestor = autoSuggestor;
        this.textField = autoSuggestor.getTextField();
        this.suggestionBorderColor = borderColor;
        this.autoSuggestionsPopUpWindow = autoSuggestor.getAutoSuggestionPopUpWindow();

        initComponent();
    }

    private void initComponent() {
        setFocusable(true);
        setForeground(suggestionsTextColor);

        addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent me) {
                super.mouseClicked(me);

                replaceWithSuggestedText();

                autoSuggestionsPopUpWindow.setVisible(false);
            }
        });

        getInputMap(JComponent.WHEN_FOCUSED).put(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0, true), "Enter released");
        getActionMap().put("Enter released", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                replaceWithSuggestedText();
                autoSuggestionsPopUpWindow.setVisible(false);
            }
        });
    }

    public void setFocused(boolean focused) {
        if (focused) {
            setBorder(new LineBorder(suggestionBorderColor));
        } else {
            setBorder(null);
        }
        repaint();
        this.focused = focused;
    }

    public boolean isFocused() {
        return focused;
    }

    private void replaceWithSuggestedText() {
        String suggestedWord = getText();
        String text = textField.getText();
        String typedWord = autoSuggestor.getCurrentlyTypedWord();
        String t = text.substring(0, text.lastIndexOf(typedWord));
        String tmp = t + text.substring(text.lastIndexOf(typedWord)).replace(typedWord, suggestedWord);
        textField.setText(tmp + " ");
    }
}

As it stands the only possible needed additions IMO is:

• UP key Focus traversablity for items within the popup autosuggestions box so we can go in a upward direction.

If there are any kinks lemme know I'll see what I can do. But Seems to be running fine (touch wood).