how would be implements autosugesion in JTextArea swing

Question

let me if have you anyone answer, this ans. basically required like as google search engine , when we press any key then it would be display suggestion related pressed key.<

Answer 1

I can propose my own implementation. It is based on JList shown in JWindow. As I wanted to use this code for a combo box, I've disabled UP and DOWN keys with keyEvent.consume() call.

import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.JTextComponent;
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class GAutoCompletionDecorator {

    private final JTextComponent textComponent;
    private final JWindow suggestionsPopup;
    private final JList completionList;
    private final DefaultListModel completionListModel;

    public static void decorate(JComboBox comboBox, JFrame parent) {
        comboBox.setEditable(true);
        final JTextComponent textComponent = (JTextComponent) comboBox.getEditor().getEditorComponent();
        decorate(textComponent, parent);
    }

    private static void decorate(JTextComponent textComponent, JFrame parent) {
        final GAutoCompletionDecorator autoCompletionDecorator = new GAutoCompletionDecorator(textComponent, parent);
        autoCompletionDecorator.decorate();
    }

    private GAutoCompletionDecorator(final JTextComponent textComponent, JFrame parent) {
        this.textComponent = textComponent;
        this.suggestionsPopup = new JWindow(parent);
        this.completionListModel = new DefaultListModel();
        this.completionList = new JList();
        this.completionList.setModel(completionListModel);

        this.suggestionsPopup.getContentPane().add(this.completionList);
    }

    private void decorate() {
        textComponent.getDocument().addDocumentListener(new DocumentListener() {
            public void insertUpdate(DocumentEvent documentEvent) {
                updateSuggestions();
            }

            public void removeUpdate(DocumentEvent documentEvent) {
                updateSuggestions();
            }

            public void changedUpdate(DocumentEvent documentEvent) {
                updateSuggestions();
            }
        });


        this.textComponent.addKeyListener(new KeyAdapter() {
            public void keyPressed(KeyEvent keyEvent) {
                if (keyEvent.getKeyCode() == KeyEvent.VK_DOWN || keyEvent.getKeyCode() == KeyEvent.VK_UP) {
                    updateSuggestions();
                    completionList.requestFocus();
                    completionList.dispatchEvent(keyEvent);
                    keyEvent.consume();
                }
            }

            public void keyReleased(KeyEvent keyEvent) {
                if (keyEvent.getKeyCode() == KeyEvent.VK_DOWN || keyEvent.getKeyCode() == KeyEvent.VK_UP) {
                    keyEvent.consume();
                }
            }
        });

        this.completionList.addKeyListener(new KeyAdapter() {
            public void keyPressed(KeyEvent keyEvent) {
                if (keyEvent.getKeyCode() == KeyEvent.VK_ESCAPE) {
                    textComponent.requestFocus();
                    hideSuggestionsPopup();
                } else if (keyEvent.getKeyCode() == KeyEvent.VK_UP) {
                    if (completionList.getSelectedIndex() == 0) {
                        completionList.setSelectedIndex(completionListModel.size() - 1);
                        keyEvent.consume();
                    }
                } else if (keyEvent.getKeyCode() == KeyEvent.VK_DOWN) {
                    if (completionList.getSelectedIndex() == completionListModel.size() - 1) {
                        completionList.setSelectedIndex(0);
                        keyEvent.consume();
                    }
                } else if (keyEvent.getKeyCode() == KeyEvent.VK_BACK_SPACE) {
                    textComponent.requestFocus();
                    hideSuggestionsPopup();
                    textComponent.dispatchEvent(keyEvent);
                } else if (keyEvent.getKeyCode() == KeyEvent.VK_ENTER) {
                    textComponent.requestFocus();
                    hideSuggestionsPopup();
                    final String selectedSuggestion = (String) completionList.getSelectedValue();
                    if (selectedSuggestion != null) {
                        try {
                            final int caretPosition = textComponent.getCaretPosition();
                            textComponent.getDocument().insertString(caretPosition, getCompletionString(selectedSuggestion, textComponent.getText(), caretPosition), null);
                        } catch (BadLocationException e) {
                            //ignore
                        }
                    }
                }
            }
        });
    }

    private String getCompletionString(String selectedSuggestion, String text, int caretPosition) {
        //we may insert selectedSuggestion fully of some part of it
        return selectedSuggestion;
    }

    private void updateSuggestions() {
        final String text = textComponent.getText();
        final int caretPosition = textComponent.getCaretPosition();
        final List suggestions = getSuggestions(text, caretPosition);
        if (suggestions == null || suggestions.size() == 0) {
            //hide suggestions window
            hideSuggestionsPopup();
        } else {
            //show suggestions window
            showSuggestionsPopup(suggestions);
        }
    }

    private void hideSuggestionsPopup() {
        suggestionsPopup.setVisible(false);
    }

    private void showSuggestionsPopup(List suggestions) {
        completionListModel.clear();
        for (String suggestion : suggestions) {
            completionListModel.addElement(suggestion);
        }

        final Point textComponentLocation = new Point(textComponent.getLocation());
        SwingUtilities.convertPointToScreen(textComponentLocation, textComponent);

        Point caretLocation = textComponent.getCaret().getMagicCaretPosition();
        if (caretLocation != null) {
            caretLocation = new Point(caretLocation);
            SwingUtilities.convertPointToScreen(caretLocation, textComponent);
        }
        suggestionsPopup.pack();
        suggestionsPopup.setLocation(caretLocation == null ? textComponentLocation.x : caretLocation.x,
                textComponentLocation.y + textComponent.getHeight());
        suggestionsPopup.setVisible(true);
    }

    private List getSuggestions(String text, int caretPosition) {
        final List words = new ArrayList();
        words.add("suggestion 1");
        words.add("suggestion 2");
        words.add("suggestion 3");
        words.add("suggestion 4");
        words.add("suggestion 5");
        //make suggestions funny
        return text.length() < words.size() ? words.subList(0, words.size() - text.length()) : Collections.emptyList();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                final JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                final JComboBox comboBox = new JComboBox(new String[] {"Choice1", "Choice2"});
                comboBox.setEditable(true);
                GAutoCompletionDecorator.decorate(comboBox, frame);

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

    }
}