Using JComboBox with custom renderer as JTable cell renderer/editor (architecture)

Question

I'm new to GUI design and I'm trying to plan this out before I go too far the wrong way, any help would be nice. I'm trying to display a JTable with rows of Employee, which itself has datatypes of String and ArrayList<Cert>. Cert contains a String.

I'd like to have the table present the data for editing, but for a few of the columns I'd like to implement a JComboBox for selection of a String from a set of valid strings, as well as color each option differently (different background colors in the JComboBox).

Also, the ArrayList<Cert> currently displays in a cell as [xxx, xxx, ...] where XXX is the return from the toString() function for each item in the ArrayList. I think I'd like to display that ArrayList<Cert> as a read-only JComboBox, but I'm not as concerned with this item.

I'm questioning how many classes I need to create to make this happen. I already have a custom model for the JTable extending AbstractTableModel. Do I need to write an extension of JComboBox or do I just need to extend the appropriate renderer for a JComboBox as a cell and do the magic there, then assign that custom renderer to the cell renderer for the String cell?

Here's what I have so far, lightly abridged:

public class EmployeeTableModel extends AbstractTableModel {
  ...
  private ArrayList<Employee> myDataObjects = new ArrayList<Employee>();
  ...
  @Override
  public Object getValueAt(int row, int column) {
      Employee emp = myDataObjects.get(row);

      switch (column) {
          case 0:
              return emp.getName();
          case 1:
              return emp.getShift();
          case 2:
              return emp.getCertifications();
          default:
              return "";
      }
   }
}

Employees:

public class Employee {
  private String name;
  private String shift;
  private ArrayList<Cert> certs;
  ...
  public String getName() {
    return name;
  }

  public String getShift() {
    return shift;
  }

  public ArrayList<Cert> getCerts() {
    return certs;
  }
  ...
}

And the initializations:

EmployeeTableModel etm = new EmployeeTableModel();
JTable employeeTable = new JTable();
employeeTable.setModel( etm );

[this is](http://stackoverflow.com/questions/12107545/12108024#12108024) — Roman C, Nov 05 '12 at 20:55
See this [example](http://stackoverflow.com/a/7356518/230513) using `DefaultCellEditor`. — trashgod, Nov 05 '12 at 21:06

score 6 · Accepted Answer · edited May 23 '17 at 11:58

you can to start with, simplest code as is possible, maybe depends if you want to see JComboBox as Renderer too by @aterai

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();
            }
        });
    }
}

That cleared up a lot of my confusion. I think I'll just extend `JComboBox` and have an inner `Renderer` with a `HashMap` of the style for each type of `String` used. — Sam, Nov 05 '12 at 23:31

Using JComboBox with custom renderer as JTable cell renderer/editor (architecture)

1 Answers1