Setting a tooltip for a value from JComboBox's

Question

I would like to set a tooltip value for the values in a custom combo box. Basically, my combobox contains a list of initials of people - when they hover over i want it to display the fullname of the person. My combo box is basically a cell/column of a JTable that has its own TableCellRenderer and DefaultCellEditor. The list is a JList (inner class within the model) - iv tried setting the 'setToolTipText' method directly but that doesnt seem to work.

Here is the code:

*Code within the JTable: *

public void setupUserCombo(Container container){
      TableColumn col = getColumnModel().getColumn(3);
      Set<ComboUser> values = new LinkedHashSet<ComboUser>();

      ComboUser comboUser = new ComboUser(new User("Test User"));
      values.add(comboUser);

      col.setCellEditor(new MyComboBoxEditor((ComboUser[])values.toArray(new ComboUser[0])));
      col.setCellRenderer(new MyComboBoxRenderer((ComboUser[])values.toArray(new ComboUser[0])));
      repaint();
}

public class MyComboBoxRenderer extends JComboBox implements TableCellRenderer {
    private static final long serialVersionUID = 1L;

    public MyComboBoxRenderer(ComboUser[] items) {
        super(items);
        repaint();
    }

    public Component getTableCellRendererComponent(JTable table, Object value,
            boolean isSelected, boolean hasFocus, int row, int column) {
        if (value != null){
            System.out.println("Setting tooltip");
            ((ComboUser)value).setToolTipText("TESTING!!");
        }
        setSelectedItem(value);

        return this;
    }
}

public class MyComboBoxEditor extends DefaultCellEditor {
    private static final long serialVersionUID = 1L;

    public MyComboBoxEditor(ComboUser[] items) {
        super(new JComboBox(items));
    }
}

*Subclass within the model: *

public class ComboUser extends JLabel{

    private User user;

    public ComboUser(User user){
        if (user != null){
            this.user = user;
        } else {
            this.user = new User("");
        }
    }

    @Override
    public String toString() {
        return user.getInitials();
    }

Answer 1

If you want tooltips in the editing combobox, you'll have to so in a custom renderer of that combobox. Below is a short example:

// some data
User[] users = new User[] { 
        new User("Clara Zetkin", "CZ"),
        new User("Rosa Luxemburg", "RL"),
        new User("Susan Sontag", "SS"),
};
// the renderer for use in the editor
ListCellRenderer comboRenderer = new DefaultListCellRenderer() {

    @Override
    public Component getListCellRendererComponent(JList<?> list,
            Object value, int index, boolean isSelected,
            boolean cellHasFocus) {
        if (value instanceof User) {
            setToolTipText(((User) value).getName());
            value = ((User) value).getInitials();
        } else {
            setToolTipText(null);
        }
        return super.getListCellRendererComponent(list, value, index, isSelected,
                cellHasFocus);
    }

};
JComboBox editingCombo = new JComboBox(users);
editingCombo.setRenderer(comboRenderer);

JTable table = new JTable(3, 2);
// set up the editor for the first column
table.getColumnModel().getColumn(0).setCellEditor(new DefaultCellEditor(editingCombo));
// the renderer to use in the table
TableCellRenderer renderer = new DefaultTableCellRenderer() {

    @Override
    protected void setValue(Object value) {
        if (value instanceof User) {
            setToolTipText(((User) value).getInitials());
            value = ((User) value).getName();
        } else {
            setToolTipText(null);
        }
        super.setValue(value);
    }

};
table.getColumnModel().getColumn(0).setCellRenderer(renderer);

Answer 2

see JTable tutorial, test code examples, for example

import java.awt.BorderLayout;
import javax.swing.DefaultCellEditor;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumn;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JList;
import javax.swing.plaf.basic.BasicComboBoxRenderer;

public class TableRenderDemo extends JPanel {

    private static final long serialVersionUID = 1L;

    public TableRenderDemo() {
        super(new BorderLayout(5, 5));
        final JTable table = new JTable(new MyTableModel());
        table.setPreferredScrollableViewportSize(table.getPreferredSize());
        table.setFillsViewportHeight(true);
        table.setRowHeight(20);
        JScrollPane scrollPane = new JScrollPane(table);
        initColumnSizes(table);
        setUpSportColumn(table, table.getColumnModel().getColumn(2));
        add(scrollPane, BorderLayout.CENTER);
        JButton resetButton = new JButton("Reset to default");
        resetButton.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                for (int i = 0; i < table.getRowCount(); i++) {
                    table.getModel().setValueAt("None of the above", i, 2);
                }
            }
        });
        add(resetButton, BorderLayout.SOUTH);
    }

    private void initColumnSizes(JTable table) {
        MyTableModel model = (MyTableModel) table.getModel();
        TableColumn column = null;
        Component comp = null;
        int headerWidth = 0;
        int cellWidth = 0;
        Object[] longValues = model.longValues;
        TableCellRenderer headerRenderer = table.getTableHeader().getDefaultRenderer();
        for (int i = 0; i < 5; i++) {
            column = table.getColumnModel().getColumn(i);
            comp = headerRenderer.getTableCellRendererComponent(null, column.getHeaderValue(), false, false, 0, 0);
            headerWidth = comp.getPreferredSize().width;
            comp = table.getDefaultRenderer(model.getColumnClass(i)).getTableCellRendererComponent(table, longValues[i], false, false, 0, i);
            cellWidth = comp.getPreferredSize().width;
            column.setPreferredWidth(Math.max(headerWidth, cellWidth));
        }
    }

    private void setUpSportColumn(JTable table, TableColumn sportColumn) {
        ArrayList<String> listSomeString = new ArrayList<String>();
        listSomeString.add("Snowboarding");
        listSomeString.add("Rowing");
        listSomeString.add("Knitting");
        listSomeString.add("Speed reading");
        listSomeString.add("Pool");
        listSomeString.add("None of the above");
        JComboBox comboBox = new JComboBox();
        comboBox.addItem(new Item(1, "-"));
        comboBox.addItem(new Item(2, "Snowboarding"));
        comboBox.addItem(new Item(3, "Rowing"));
        comboBox.addItem(new Item(4, "Knitting"));
        comboBox.addItem(new Item(5, "Speed reading"));
        comboBox.addItem(new Item(6, "Pool"));
        comboBox.addItem(new Item(7, "None of the above"));
        comboBox.setMaximumRowCount(3);
        comboBox.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                JComboBox comboBox = (JComboBox) e.getSource();
                Item item = (Item) comboBox.getSelectedItem();
                System.out.println(item.getId() + " : " + item.getDescription());
            }
        });
        //comboBox.setRenderer(new ItemRenderer());
        sportColumn.setCellEditor(new DefaultCellEditor(comboBox));
        DefaultTableCellRenderer renderer = new DefaultTableCellRenderer();
        renderer.setToolTipText("Click for combo box");
        sportColumn.setCellRenderer(renderer);
    }

    class ItemRenderer extends BasicComboBoxRenderer {

        @Override
        public Component getListCellRendererComponent(JList list, Object value,
                int index, boolean isSelected, boolean cellHasFocus) {
            super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
            if (value != null) {
                Item item = (Item) value;
                setText(item.getDescription().toUpperCase());
            }
            if (index == -1) {
                Item item = (Item) value;
                setText("" + item.getId());
            }
            return this;
        }
    }

    class Item {

        private int id;
        private String description;

        public Item(int id, String description) {
            this.id = id;
            this.description = description;
        }

        public int getId() {
            return id;
        }

        public String getDescription() {
            return description;
        }

        @Override
        public String toString() {
            return description;
        }
    }

    class MyTableModel extends AbstractTableModel {

        private static final long serialVersionUID = 1L;
        private String[] columnNames = {"First Name", "Last Name", "Sport", "# of Years", "Vegetarian"};
        private Object[][] data = {{"Kathy", "Smith", "Snowboarding", new Integer(5), false},
            {"John", "Doe", "Rowing", new Integer(3), true}, {"Sue", "Black", "Knitting", new Integer(2), false},
            {"Jane", "White", "Speed reading", new Integer(20), true}, {"Joe", "Brown", "Pool", new Integer(10), false}};
        public final Object[] longValues = {"Jane", "Kathy", "None of the above", new Integer(20), Boolean.TRUE};

        @Override
        public int getColumnCount() {
            return columnNames.length;
        }

        @Override
        public int getRowCount() {
            return data.length;
        }

        @Override
        public String getColumnName(int col) {
            return columnNames[col];
        }

        @Override
        public Object getValueAt(int row, int col) {
            return data[row][col];
        }

        @Override
        public Class<?> getColumnClass(int c) {
            return getValueAt(0, c).getClass();
        }

        @Override
        public boolean isCellEditable(int row, int col) {
            if (col < 2) {
                return false;
            } else {
                return true;
            }
        }

        @Override
        public void setValueAt(Object value, int row, int col) {
            data[row][col] = value;
            fireTableCellUpdated(row, col);
            System.out.println("New value of data: " + getValueAt(row, col));
        }
    }

    private static void createAndShowGUI() {
        JFrame frame = new JFrame("TableRenderDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        TableRenderDemo newContentPane = new TableRenderDemo();
        frame.setContentPane(newContentPane);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                createAndShowGUI();
            }
        });
    }
}