java - How do I color individual cells of a JTable based on the value in the cell?

Question

I am attempting to make a Tetris clone. The game uses a JTable as a representation of the board. The board is a 2D integer array.

I am trying to make it so, when a certain cell has a certain value, the cell will change to a certain color. I thought I had it working correctly, but it isn't working. I'd really appreciate some help.

Thank you.

Here is my code:

Board:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;

import javax.swing.Timer;
import javax.swing.table.*;
/**
 * @author _______________
 *
 * Board.java
 * 
 * The Board class gives information to the InitializeJTable class regarding 
 * the data-type of the JTable elements, how many rows/columns are in the JTable, etc;
 * 
 * I extended Board with AbstractTableModel, a class that allows me to display any data-type 
 * inside the elements of the JTable.
 * 
 * This class also has method declarations that are required by AbstractTableModel, these methods are:
 *      - getRowCount()
 *      - getColumnCount()
 *      - getValueAt(int, int)
 * 
 */

@SuppressWarnings("serial")
public class Board extends AbstractTableModel {

TableColorSetter TCS;
boolean lost = false;
InitializeGUI iGUI;
InitializeJTable iJT;
public int SPEED = 1000;
L l = new L();
public Block currentBlock = l;
public int[][] boxes;//A 2D Array of booleans that defines the status of the Tetris board. Used by InitializeJTable and InitializePreviewJTable



/*
 * boardType is an integer that works with the constructor. 
 * 
 * If boardType is equal to 0, the constructor generates a 22x10 array (This is used with the main board)
 * However, if boardType is equal to 1, the constructor generates a 4x4 array (This is used with the preview/hold board, a smaller board on the side)
 */

public Board(int boardType) {

    if(boardType == 0) {
        boxes = new int[22][10];
        loop();
    } else if(boardType == 1) boxes = new int[4][4];
}

/*
 * getRowCount()
 * 
 * getRowCount is a required declaration by the AbstractTableModel class. 
 * @return          the amount of rows in the boxes boolean
 */
@Override
public int getRowCount() {
    return boxes.length;
}

public int getTetrisType(Block block) {
    return block.getTetrisType();
}

public void letPieceDown(int origA, int origB, int tetrisType) {
    boxes[origA][origB] = 0;
    boxes[origA + 1][origB] = tetrisType;
}

/*
 * getColumnCount()
 * 
 * getColumnCount() is a required declaration by the AbstractTableModel class. 
 * @return          the amount of columns in the boxes boolean
 */
@Override
public int getColumnCount() {
    return boxes[0].length;
}

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

/*
 * getValueAt()
 * 
 * getValueAt() is a required declaration by the AbstractTableModel class. 
 * returns the amount of columns in the boxes boolean
 * 
 * @param   int rowIndex    The row index of the boolean that you want to return.
 *          int columnIndex The column index of the boolean that you want to return.
 * 
 * @return      the value of the boolean at the specified location in the boolean array.
 */
@Override
public Object getValueAt(int rowIndex, int columnIndex) {
    return boxes[rowIndex][columnIndex];
}

public int getVal(int row, int col) {
    return boxes[row][col];
}

/**
 * 
 * loop();
 * 
 * The loop() method is a very rough draft in regards to placing Tetris objects on the board and having them move, and stack.
 * 
 * TODO: 
 */

public void loop() {

    Timer timer = new

            Timer(SPEED, new ActionListener() {
        int x = 0;
        int y = 0;
          @Override
          public void actionPerformed(ActionEvent e) {
            while(lost = false) {
                for(int a = 0; a < getColumnCount(); a++) {
                    for(int b = 0; b < getRowCount(); b++) {
                        TCS.getTableCellRendererComponent(iJT.getTable(), "", false, false, b, a);
                    }
                }

            }
            if(x == getRowCount() - 1) { 
                x = 0;
            } else if(boxes[x + 1][y] != 0 && x == 0) {
                boxes[x][y] = getTetrisType(currentBlock);
                fireTableDataChanged();
                //System.out.println("GAME OVER!");
                //y++; //Just for testing.
                PlaySound sound = new PlaySound();
                sound.setSoundType(1);
                sound.start();
                ((Timer)e.getSource()).stop();
            } else if(boxes[x + 1][y] != 0) {
                x = 0;
            } else {
            //System.out.println("Pos: " + x + ", 0. Row count: " + getRowCount() + " -- " + x);
              letPieceDown(x, y, getTetrisType(currentBlock));
              fireTableDataChanged();
              x++;
            }
          }
      });
      timer.start();            
  }


}

InitializeJTable:

import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumnModel;

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

import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTable;

/**
 * @author _________________
 *
 * InitializeJTable.java
 * 
 * The InitializeJTable class sets up the JTable to look like a Tetris board.
 *
 * @TODO: Add more commenting
 */

@SuppressWarnings("serial")
public class InitializeJTable extends JPanel {

private int COLS = 10;
private int HEIGHT = 30;
Color white = Color.WHITE;
Color black = Color.BLACK;
Board tetrisBoard;
JTable table;

public Board returnBoard() {
    return tetrisBoard;
}

public JTable getTable() {
    return table;
}

public InitializeJTable() { //The InitializeJTable constructor
    tetrisBoard = new Board(0); //Create a new board of 22x10 booleans, with a boardType of 0.
    table = new JTable(tetrisBoard); //Apply the information from the Board constructor to the JTable. (Information like, how many rows/cols in the JTable, what data-type the JTable elements are, etc)
    //setLayout(new GridBagLayout()); //Sets the Layout of the JTable to a GridBagLayout. This means, it makes the JTable look like a grid.
    table.setCellSelectionEnabled(false); //Disables dragging/selection of columns on the JTable with the mouse. We won't be needing that.
    TableColumnModel columns = table.getColumnModel(); //Gets information about the columns of the JTable. I need this to set the length of the columns (to make them square) 
    table.setRowHeight(HEIGHT); //Sets the height of the JTable rows to HEIGHT int, currently set to 30. Can be easily changed.
    //table.setForeground(white); //Use this to make all blocks white. Still need to make it work correctly.
    /*
     * Sadly, there isn't a -- table.setColumnHeight(int) -- method in the JTable API. (to set the length of the columns to the specified integer)
     * 
     * So I have to manually set the width of each column. This is why I declared the TableColumnModel above
     */
    for(int a = 0; a < COLS; a++) {
        columns.getColumn(a).setPreferredWidth(HEIGHT); //Sets the height of the JTable columns to HEIGHT int, currently set to 30. Can be changed easily.
    }


    add(table);//The table's all set up correctly, add it.

    }
}

Answer 1

There is a relationship between the data/model and the view/table. The model maintains the "what", the view controls the "how".

JTable provides a means by which you can the behaviour of the "how" (stuff gets rendered) through the use of TableCellRenderers, these are responsible for determining how a cell should be "painted" based on the value from the "what" from the model.

Start by having a look at How to Use Tables and Using Custom Renderers

Now, this example uses a double value to determine the distance from 1 the cell value is, which represents the color (black = 0; white = 1) that the cell should be painted. To accomplish this, it uses a custom TableCellRenderer which converts the value in the model (the "what") into a color (or the "how")

public class PaintTableCellRenderer extends DefaultTableCellRenderer {

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
        super.getTableCellRendererComponent(table, "", isSelected, hasFocus, row, column);
        if (value instanceof Double) {
            double distance = (double) value;
            int part = (int) (255 * distance);
            Color color = new Color(part, part, part);
            setBackground(color);
        } else {
            setBackground(Color.WHITE);
        }
        return this;
    }

}

It also demonstrates a couple of other things you might need to know about the JTable as well.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.util.Enumeration;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableColumn;

public class Smile {

    public static void main(String[] args) {
        new Smile();
    }

    public Smile() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private double[][] smily = {
            {1, 1, 1, 1, 1, 0.996, 1, 0.843, 0.784, 0.788, 0.773, 0.769, 0.765, 0.765, 0.788, 0.784, 0.847, 1, 0.996, 1, 1, 1, 1, 0.996},
            {1, 1, 1, 1, 1, 0.871, 0.733, 0.761, 0.847, 0.941, 0.941, 0.941, 0.941, 0.941, 0.933, 0.843, 0.761, 0.733, 0.871, 1, 1, 1, 1, 1},
            {1, 1, 1, 1, 0.784, 0.733, 0.902, 0.941, 0.941, 0.941, 0.945, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.898, 0.733, 0.784, 1, 1, 1, 1},
            {1, 1, 1, 0.765, 0.773, 0.945, 0.945, 0.941, 0.929, 0.937, 0.941, 0.941, 0.945, 0.941, 0.957, 0.91, 0.941, 0.941, 0.941, 0.78, 0.761, 1, 1, 1},
            {1, 1, 0.808, 0.773, 0.941, 0.941, 0.941, 0.941, 0.294, 0.447, 0.941, 0.941, 0.941, 0.941, 0.702, 0.239, 0.886, 0.941, 0.945, 0.941, 0.78, 0.8, 1, 1},
            {1, 0.89, 0.725, 0.945, 0.941, 0.941, 0.945, 0.843, 0, 0, 0.922, 0.945, 0.941, 0.941, 0.408, 0, 0.663, 0.941, 0.941, 0.945, 0.941, 0.725, 0.89, 1},
            {0.992, 0.753, 0.902, 0.941, 0.945, 0.945, 0.941, 0.725, 0.051, 0, 0.808, 0.941, 0.941, 0.945, 0.294, 0.051, 0.553, 0.941, 0.941, 0.941, 0.941, 0.91, 0.741, 0.984},
            {0.871, 0.78, 0.941, 0.941, 0.945, 0.945, 0.941, 0.694, 0.051, 0, 0.784, 0.945, 0.941, 0.941, 0.278, 0, 0.518, 0.941, 0.941, 0.945, 0.941, 0.941, 0.78, 0.878},
            {0.816, 0.855, 0.941, 0.945, 0.945, 0.945, 0.941, 0.737, 0, 0.051, 0.82, 0.941, 0.941, 0.941, 0.302, 0.051, 0.565, 0.941, 0.949, 0.945, 0.941, 0.941, 0.863, 0.804},
            {0.8, 0.945, 0.941, 0.945, 0.945, 0.941, 0.941, 0.875, 0, 0, 0.937, 0.941, 0.941, 0.941, 0.443, 0, 0.694, 0.945, 0.945, 0.945, 0.945, 0.949, 0.941, 0.765},
            {0.769, 0.941, 0.945, 0.957, 0.961, 0.941, 0.945, 0.941, 0.443, 0.565, 0.945, 0.941, 0.941, 0.941, 0.769, 0.388, 0.918, 0.941, 0.941, 0.941, 0.945, 0.941, 0.941, 0.78},
            {0.753, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.953, 0.941, 0.941, 0.941, 0.941, 0.945, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.788},
            {0.741, 0.945, 0.839, 0.427, 0.624, 0.941, 0.941, 0.945, 0.941, 0.941, 0.941, 0.949, 0.945, 0.945, 0.941, 0.941, 0.941, 0.941, 0.941, 0.6, 0.376, 0.941, 0.945, 0.784},
            {0.749, 0.941, 0.914, 0.345, 0.647, 0.941, 0.945, 0.949, 0.945, 0.945, 0.941, 0.941, 0.945, 0.941, 0.945, 0.945, 0.945, 0.945, 0.941, 0.702, 0.384, 0.941, 0.941, 0.78},
            {0.796, 0.945, 0.941, 0.627, 0.592, 0.941, 0.941, 0.941, 0.945, 0.945, 0.945, 0.941, 0.949, 0.945, 0.941, 0.945, 0.945, 0.937, 0.945, 0.58, 0.631, 0.941, 0.937, 0.776},
            {0.812, 0.859, 0.941, 0.855, 0.384, 0.957, 0.941, 0.945, 0.945, 0.945, 0.941, 0.953, 0.941, 0.945, 0.945, 0.945, 0.941, 0.941, 0.941, 0.384, 0.941, 0.941, 0.867, 0.812},
            {0.871, 0.788, 0.941, 0.941, 0.533, 0.51, 0.941, 0.941, 0.941, 0.945, 0.949, 0.945, 0.945, 0.945, 0.941, 0.937, 0.941, 0.945, 0.522, 0.522, 0.941, 0.941, 0.792, 0.886},
            {0.992, 0.761, 0.914, 0.941, 0.941, 0.325, 0.612, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.624, 0.318, 0.941, 0.945, 0.91, 0.765, 0.988},
            {1, 0.882, 0.741, 0.941, 0.941, 0.922, 0.337, 0.475, 0.894, 0.941, 0.941, 0.941, 0.941, 0.941, 0.945, 0.894, 0.49, 0.325, 0.925, 0.941, 0.941, 0.753, 0.894, 1},
            {1, 1, 0.796, 0.78, 0.941, 0.941, 0.941, 0.592, 0.447, 0.565, 0.667, 0.737, 0.737, 0.667, 0.565, 0.451, 0.588, 0.941, 0.941, 0.941, 0.796, 0.808, 1, 1},
            {1, 1, 0.996, 0.753, 0.788, 0.941, 0.941, 0.941, 0.941, 0.702, 0.584, 0.557, 0.553, 0.592, 0.698, 0.906, 0.941, 0.945, 0.941, 0.796, 0.769, 0.996, 1, 1},
            {1, 1, 1, 1, 0.769, 0.745, 0.922, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.941, 0.918, 0.741, 0.776, 1, 1, 0.996, 1},
            {1, 0.996, 1, 1, 1, 0.851, 0.733, 0.773, 0.867, 0.945, 0.941, 0.941, 0.941, 0.941, 0.945, 0.867, 0.769, 0.725, 0.851, 1, 1, 1, 1, 1},
            {1, 1, 1, 1, 1, 1, 0.984, 0.843, 0.78, 0.761, 0.78, 0.796, 0.796, 0.784, 0.765, 0.78, 0.835, 0.984, 1, 1, 1, 1, 1, 1}
        };

        public TestPane() {
            AsciiTableModel model = new AsciiTableModel();
            model.setData(smily);

            JTable table = new JTable(model);
            table.setRowHeight(24);
            Enumeration<TableColumn> columns = table.getColumnModel().getColumns();
            while (columns.hasMoreElements()) {
                TableColumn col = columns.nextElement();
                col.setWidth(24);
                col.setPreferredWidth(24);
                col.setMinWidth(24);
                col.setMaxWidth(24);
            }
            table.setRowHeight(24);
            table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
            table.setDefaultRenderer(Object.class, new PaintTableCellRenderer());

            setLayout(new BorderLayout());
            add(new JScrollPane(table));
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

    public class PaintTableCellRenderer extends DefaultTableCellRenderer {

        @Override
        public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
            super.getTableCellRendererComponent(table, "", isSelected, hasFocus, row, column);
            if (value instanceof Double) {
                double distance = (double) value;
                int part = (int) (255 * distance);
                Color color = new Color(part, part, part);
                setBackground(color);
            } else {
                setBackground(Color.WHITE);
            }
            return this;
        }

    }

    public class AsciiTableModel extends AbstractTableModel {

        private double[][] data;

        public AsciiTableModel() {
            data = new double[24][24];
        }

        public void setData(double[][] value) {
            data = value;
            fireTableDataChanged();
        }

        @Override
        public int getRowCount() {
            return 24;
        }

        @Override
        public int getColumnCount() {
            return 24;
        }

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

    }

}

I had intended to provide a "sad" face which you could switch between, but my daughter wanted me to go paint with her, sorry ;)