How to list suggestions to when typing inside the text field

Question

Hi in my Java swing application I need to show all possible existing entries with same initial characters while user typing in a text field. Lets say user type letter \'A\'

Answer 1

I had a similar problem:
I wanted a Textfield for free entering text, but with the possibility to suggest existing values.

I first found this post, but swingX hasn't allowed to enter text other than the suggested ones. Then I found an other post linking to this page: http://www.jroller.com/santhosh/date/20050620

Some modifications and I changed from directory selection to my own Strings. Might post this here for completion and the help for later searchers:

He made an abstract class AutoCompleter which handels the events:

// @author Santhosh Kumar T - santhosh@in.fiorano.com 
public abstract class AutoCompleter{ 
    JList list = new JList(); 
    JPopupMenu popup = new JPopupMenu(); 
    JTextComponent textComp; 
    private static final String AUTOCOMPLETER = "AUTOCOMPLETER"; //NOI18N 

    public AutoCompleter(JTextComponent comp){ 
        textComp = comp; 
        textComp.putClientProperty(AUTOCOMPLETER, this); 
        JScrollPane scroll = new JScrollPane(list); 
        scroll.setBorder(null); 

        list.setFocusable( false ); 
        scroll.getVerticalScrollBar().setFocusable( false ); 
        scroll.getHorizontalScrollBar().setFocusable( false ); 

        popup.setBorder(BorderFactory.createLineBorder(Color.black)); 
        popup.add(scroll); 

        if(textComp instanceof JTextField){ 
            textComp.registerKeyboardAction(showAction, KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), JComponent.WHEN_FOCUSED); 
            textComp.getDocument().addDocumentListener(documentListener); 
        }else 
            textComp.registerKeyboardAction(showAction, KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, KeyEvent.CTRL_MASK), JComponent.WHEN_FOCUSED); 

        textComp.registerKeyboardAction(upAction, KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), JComponent.WHEN_FOCUSED); 
        textComp.registerKeyboardAction(hidePopupAction, KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0), JComponent.WHEN_FOCUSED); 

        popup.addPopupMenuListener(new PopupMenuListener(){ 
            public void popupMenuWillBecomeVisible(PopupMenuEvent e){ 
            } 

            public void popupMenuWillBecomeInvisible(PopupMenuEvent e){ 
                textComp.unregisterKeyboardAction(KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0)); 
            } 

            public void popupMenuCanceled(PopupMenuEvent e){ 
            } 
        }); 
        list.setRequestFocusEnabled(false); 
    } 

    static Action acceptAction = new AbstractAction(){ 
        public void actionPerformed(ActionEvent e){ 
            JComponent tf = (JComponent)e.getSource(); 
            AutoCompleter completer = (AutoCompleter)tf.getClientProperty(AUTOCOMPLETER); 
            completer.popup.setVisible(false); 
            completer.acceptedListItem((String)completer.list.getSelectedValue()); 
        } 
    }; 

    DocumentListener documentListener = new DocumentListener(){ 
        public void insertUpdate(DocumentEvent e){ 
            showPopup(); 
        } 

        public void removeUpdate(DocumentEvent e){ 
            showPopup(); 
        } 

        public void changedUpdate(DocumentEvent e){} 
    }; 

    private void showPopup(){ 
        popup.setVisible(false); 
        if(textComp.isEnabled() && updateListData() && list.getModel().getSize()!=0){ 
            if(!(textComp instanceof JTextField)) 
                textComp.getDocument().addDocumentListener(documentListener); 
            textComp.registerKeyboardAction(acceptAction, KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0), JComponent.WHEN_FOCUSED); 
            int size = list.getModel().getSize(); 
            list.setVisibleRowCount(size<10 ? size : 10); 

            int x = 0; 
            try{ 
                int pos = Math.min(textComp.getCaret().getDot(), textComp.getCaret().getMark()); 
                x = textComp.getUI().modelToView(textComp, pos).x; 
            } catch(BadLocationException e){ 
                // this should never happen!!! 
                e.printStackTrace(); 
            } 
            popup.show(textComp, x, textComp.getHeight()); 
        }else 
            popup.setVisible(false); 
        textComp.requestFocus(); 
    } 

    static Action showAction = new AbstractAction(){ 
        public void actionPerformed(ActionEvent e){ 
            JComponent tf = (JComponent)e.getSource(); 
            AutoCompleter completer = (AutoCompleter)tf.getClientProperty(AUTOCOMPLETER); 
            if(tf.isEnabled()){ 
                if(completer.popup.isVisible()) 
                    completer.selectNextPossibleValue(); 
                else 
                    completer.showPopup(); 
            } 
        } 
    }; 

    static Action upAction = new AbstractAction(){ 
        public void actionPerformed(ActionEvent e){ 
            JComponent tf = (JComponent)e.getSource(); 
            AutoCompleter completer = (AutoCompleter)tf.getClientProperty(AUTOCOMPLETER); 
            if(tf.isEnabled()){ 
                if(completer.popup.isVisible()) 
                    completer.selectPreviousPossibleValue(); 
            } 
        } 
    }; 

    static Action hidePopupAction = new AbstractAction(){ 
        public void actionPerformed(ActionEvent e){ 
            JComponent tf = (JComponent)e.getSource(); 
            AutoCompleter completer = (AutoCompleter)tf.getClientProperty(AUTOCOMPLETER); 
            if(tf.isEnabled()) 
                completer.popup.setVisible(false); 
        } 
    }; 

    /** 
     * Selects the next item in the list.  It won't change the selection if the 
     * currently selected item is already the last item. 
     */ 
    protected void selectNextPossibleValue(){ 
        int si = list.getSelectedIndex(); 

        if(si < list.getModel().getSize() - 1){ 
            list.setSelectedIndex(si + 1); 
            list.ensureIndexIsVisible(si + 1); 
        } 
    } 

    /** 
     * Selects the previous item in the list.  It won't change the selection if the 
     * currently selected item is already the first item. 
     */ 
    protected void selectPreviousPossibleValue(){ 
        int si = list.getSelectedIndex(); 

        if(si > 0){ 
            list.setSelectedIndex(si - 1); 
            list.ensureIndexIsVisible(si - 1); 
        } 
    } 

    // update list model depending on the data in textfield 
    protected abstract boolean updateListData(); 

    // user has selected some item in the list. update textfield accordingly... 
    protected abstract void acceptedListItem(String selected); 
}

And an Instance to handle the Content of the PopUp:

// @author Santhosh Kumar T - santhosh@in.fiorano.com 
public class FileAutoCompleter extends AutoCompleter{ 
    public FileAutoCompleter(JTextComponent comp){ 
        super(comp); 
    } 

    protected boolean updateListData(){ 
        String value = textComp.getText(); 
        int index1 = value.lastIndexOf('\\'); 
        int index2 = value.lastIndexOf('/'); 
        int index = Math.max(index1, index2); 
        if(index==-1) 
            return false; 
        String dir = value.substring(0, index+1); 
        final String prefix = index==value.length()-1 ? null : value.substring(index + 1).toLowerCase(); 
        String[] files = new File(dir).list(new FilenameFilter(){ 
            public boolean accept(File dir, String name){ 
                return prefix!=null ? name.toLowerCase().startsWith(prefix) : true; 
            } 
        }); 
        if(files == null){ 
            list.setListData(new String[0]); 
            return true; 
        } else{ 
            if(files.length==1 && files[0].equalsIgnoreCase(prefix)) 
                list.setListData(new String[0]); 
            else 
                list.setListData(files); 
            return true; 
        } 
    } 

    protected void acceptedListItem(String selected){ 
        if(selected==null) 
            return; 

        String value = textComp.getText(); 
        int index1 = value.lastIndexOf('\\'); 
        int index2 = value.lastIndexOf('/'); 
        int index = Math.max(index1, index2); 
        if(index==-1) 
            return; 
        int prefixlen = textComp.getDocument().getLength()-index-1; 
        try{ 
            textComp.getDocument().insertString(textComp.getCaretPosition(), selected.substring(prefixlen), null); 
        } catch(BadLocationException e){ 
            e.printStackTrace(); 
        } 
    } 
}

All is called in the program with

new FileAutoCompleter(yourJTextField);