If a cell value is same, changing a cell background in JTable

Question

I have a question for JTable.

When I select a cell and then there are same value cell in JTable which I chose, that cells highlight background red color.

I don't know what to do....

P.S: I am sorry, I do not know how to enter the code in here...;;

Answer 1

You can implement ListSelectionListener to track selection changes in a table. Then implement TableCellRenderer that would change background of a cell with the same value of a selected object. Check out How to Use Tables for more details on JTable, renderers and selection.

Here is a very simple example that demonstrates this idea:

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;

import java.awt.Color;
import java.awt.Component;

public class TableDemo {
    private static void createAndShowGUI() {
        JFrame frame = new JFrame("TableDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel contentPanel = new JPanel();
        String[] columnNames = { "Column1", "Column2" };
        Object[][] data = { { "1", "3" }, { "2", "5" }, { "7", "1" },
                { "5", "3" } };

        JTable table = new JTable();
        MyModel model = new MyModel(Color.RED, table.getBackground());
        model.setDataVector(data, columnNames);

        table.setModel(model);
        table.setColumnSelectionAllowed(true);
        table.setDefaultRenderer(Object.class, new TestCellRenderer());

        SelectionListener listener = new SelectionListener(table);
        table.getSelectionModel().addListSelectionListener(listener);
        table.getColumnModel().getSelectionModel()
                .addListSelectionListener(listener);

        JScrollPane scrollPane = new JScrollPane(table);
        contentPanel.add(scrollPane);

        contentPanel.setOpaque(true);
        frame.add(contentPanel);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    static class TestCellRenderer extends DefaultTableCellRenderer {
        public Component getTableCellRendererComponent(JTable table,
                Object value, boolean isSelected, boolean hasFocus, int row,
                int column) {
            Component c = super.getTableCellRendererComponent(table, value,
                    isSelected, hasFocus, row, column);
            MyModel model = (MyModel) table.getModel();
            c.setBackground(model.getCellColor(row, column));
            return c;
        }
    }

    static class MyModel extends DefaultTableModel {
        private Object selectedObject;
        private Color selectedColor;
        private Color normalColor;

        public MyModel(Color selectedColor, Color normalColor) {
            this.selectedColor = selectedColor;
            this.normalColor = normalColor;
        }

        public Color getCellColor(int row, int column) {
            if (getValueAt(row, column).equals(selectedObject))
                return selectedColor;
            return normalColor;
        }

        public void setSelectedObject(Object selectedObject) {
            this.selectedObject = selectedObject;
            fireTableRowsUpdated(0, getRowCount());
        }
    }

    static class SelectionListener implements ListSelectionListener {
        private JTable table;

        SelectionListener(JTable table) {
            this.table = table;
        }

        public void valueChanged(ListSelectionEvent e) {
            int rowIndex = table.getSelectedRow();
            int colIndex = table.getSelectedColumn();
            if (!e.getValueIsAdjusting() && colIndex != -1 && rowIndex != -1) {
                ((MyModel) table.getModel()).setSelectedObject(table
                        .getValueAt(rowIndex, colIndex));
            }
        }
    }

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

Here is a result:

EDIT: solution using renderer only, without table model

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;

import java.awt.Color;
import java.awt.Component;

public class TableDemo {
    private static void createAndShowGUI() {
        JFrame frame = new JFrame("TableDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel contentPanel = new JPanel();
        String[] columnNames = { "Column1", "Column2" };
        Object[][] data = { { "1", "3" }, { "2", "5" }, { "7", "1" },
                { "5", "3" } };

        JTable table = new JTable(new DefaultTableModel(data, columnNames));
        table.setColumnSelectionAllowed(true);
        TestCellRenderer renderer = new TestCellRenderer();
        table.setDefaultRenderer(Object.class, renderer);

        SelectionListener listener = new SelectionListener(table);
        table.getSelectionModel().addListSelectionListener(listener);
        table.getColumnModel().getSelectionModel()
                .addListSelectionListener(listener);

        JScrollPane scrollPane = new JScrollPane(table);
        contentPanel.add(scrollPane);

        contentPanel.setOpaque(true);
        frame.add(contentPanel);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    static class TestCellRenderer extends DefaultTableCellRenderer {

        public Component getTableCellRendererComponent(JTable table, 
                Object value, boolean isSelected, boolean hasFocus, 
                int row, int column) {

            Component c = super.getTableCellRendererComponent(table, value,
                    isSelected, hasFocus, row, column);

            int columnIndex = table.getSelectedColumn();
            int rowIndex = table.getSelectedRow();

            if (columnIndex != -1 && rowIndex != -1){
                Object selectedValue = table.getValueAt(rowIndex, columnIndex);

                if (value.equals(selectedValue)) {
                    c.setBackground(Color.RED);
                } else {
                    c.setBackground(table.getBackground());
                }
            } 
            return c;
        }
    }

    static class SelectionListener implements ListSelectionListener {
        private JTable table;

        SelectionListener(JTable table) {
            this.table = table;
        }

        public void valueChanged(ListSelectionEvent e) {
            int rowIndex = table.getSelectedRow();
            int colIndex = table.getSelectedColumn();

            if (!e.getValueIsAdjusting() && colIndex != -1 && rowIndex != -1){
                table.repaint();
            }
        }
    }

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