如何在JTables中对JComboBox的字符串排序？

Question

I have following problem:

I've inserted into the 5th column of my JTable for each row an JComboBox-Object. Everything is fine until I want to rowsort the column with setAutoCreateRowSorter(true) . In this case im getting following exception:

ClassCastException: java.lang.String cannot be cast to javax.swing.JComboBox

Here are my classes that im using for my JTable:

The TableModel:

private class MyTableModel implements TableModel {

        @Override
        public void addTableModelListener(TableModelListener l) {
        }

        @Override
        public Class<?> getColumnClass(int columnIndex) {

            switch (columnIndex) {
            case 0:
                return String.class;
            case 1:
                return String.class;
            case 2:
                return String.class;
            case 3:
                return Number.class;
            case 4:
                return Boolean.class;
            case 5:
                return JComboBox.class;  // modifyed!

            default:
                return null;
            }

        }

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

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

        @Override
        public int getRowCount() {
            return data[0].length - 1;
        }

        @Override
        public Object getValueAt(int rowIndex, int columnIndex) {
            return data[rowIndex][columnIndex];

        }

        @Override
        public boolean isCellEditable(int rowIndex, int columnIndex) {
            switch (columnIndex) {
            case 5:
                return true;
            default:
                return false;
            }

        }

        @Override
        public void removeTableModelListener(TableModelListener l) {
        }

        @Override
        public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
            data[rowIndex][columnIndex] = aValue;

        }

    }

The TableCellRenderer:

public class StringTableCellRenderer extends JLabel implements
        TableCellRenderer {

    private static final long serialVersionUID = 1L;

    public StringTableCellRenderer() {
        setOpaque(true);
        setLayout(new BorderLayout());
    }

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value,
            boolean isSelected, boolean hasFocus, int row, int column) {
        Font font = getFont().deriveFont(Font.BOLD, 15);

        if ((row % 2) == 0) {
            setBackground(new Color(240, 255, 255));
        } else {
            setBackground(new Color(191, 239, 255));
        }

        if (isSelected) {
            setBackground(new Color(0, 191, 255));
        }

        setHorizontalAlignment(JLabel.CENTER);
        setForeground(Color.BLACK);
        setFont(font);

        if (value instanceof JComboBox) {
            System.out.println("Renderer: "+column+" "+row+" "+((JComboBox<?>)value).getSelectedIndex());

            setText((String) ((JComboBox<?>) value).getSelectedItem());
        } else {
            setText(value.toString());
        }

        return this;
    }

}

The TableCellEditor:

  public class MyTableCellEditor extends AbstractCellEditor implements
        TableCellEditor, ActionListener {

    private static final long serialVersionUID = 1L;
    private JComboBox<?>[] comboList = new JComboBox<?>[5];
    private int column = 0;

    @SuppressWarnings("unchecked")
    public MyTableCellEditor() {

        for (int i = 0; i < comboList.length; i++) {
            comboList[i] = new JComboBox<String>();
            setComboBox((JComboBox<String>) comboList[i]);
            comboList[i].setName("ComboBox_" + i);
        }

    }

    public void setComboBox(JComboBox<String> comboBox) {
        comboBox.addItem("Me");
        comboBox.addItem("You");
        comboBox.addItem("They");
        comboBox.addItem("Us");
        comboBox.addItem("We");
    }

    @Override
    public void actionPerformed(ActionEvent event) {
    }

    @Override
    public Object getCellEditorValue() {
        System.out.println("Editor: getCellEditorValue() "+comboList[column].getSelectedIndex());
        if (comboList[column].getSelectedIndex()==-1) {
            return (String) comboList[column].getItemAt(0);
        } else {
            return (String) comboList[column].getSelectedItem(); // returns String not JCombobox!
        }
    }

    @Override
    public Component getTableCellEditorComponent(JTable table, Object value,
            boolean isSelected, int row, int column) {

        String fieldValue = null;
        System.out.println("Editor: getTableCellEditorComponent");
        if (value instanceof JComboBox<?>) {
            fieldValue = (String) ((JComboBox<?>) value).getSelectedItem();
        }
        this.column = column - 1;
        comboList[column - 1].setSelectedItem(fieldValue);

        return comboList[column - 1]; // for each row of column 5 an own JComboBox object

    }

}

I solved the problem by myself :

In the TableModel the getColumnClass() -method for column 5 returns JCombobox.class -object.

In the TableCellEditor there is for each row in the 5th column an own JComboBox -Object and the getCellEditorValue() -method returns the getSelectedItem() of the concerning JComboBox -Object.

So the Jtable has indeed an JComboBox -object ( getValueAt() -method for column 5 from TableModel and getTableCellEditorComponent() -method from TableCellEditor) but the return value is nevertheless a String (getCellEditorValue() from TableCellEditor and getTableCellRendererComponent() -method from TableCellRenderer).

Hopes this helps anyone with similar problems...

Answer 1

Why are you creating a custom Comparator? The data in the TableModel is String data, not a JCombobox. The RowSorter of the table already knows how to sort String data.

You should NEVER actually store a JComboBox in the TableModel. If you are in fact doing this then get rid of it.

Then get rid of your custom Comparator and it should work fine.

If you are trying to use different values for the combo box in different rows then you should try something like: how to add different cell editors for one column in JTable?