jTable Cell background color

Question

I am trying to color a cell of a jTable using the renderers, but they are not working well, as they lag the table and make it impossible to see. here's my code:

            TableCellRenderer Tcr = jTable1.getCellRenderer(x, y);
            Component c = Tcr.getTableCellRendererComponent(jTable1, jTable1.getValueAt(x, y), false, false, x, y);


            if(x > 0 && x < (jTable1.getRowCount()-1) && y > 1 && y < (jTable1.getColumnCount()-1)){
                if(!jTable1.getValueAt(x, y).equals(null) && !jTable1.getValueAt(x, y).equals("F") && !jTable1.getValueAt(x, y).equals(" ")){
                    if(!jTable1.getValueAt(x, y).toString().contains("/P") && !jTable1.getValueAt(x, y).toString().equals("P")){                            
                        if(Double.parseDouble(jTable1.getValueAt(x, y).toString()) > 24){
                            setBackground(java.awt.Color.red);

                        }
                    }
                }    
            }

I haven't put it into a rendererclass because it lags, I've put it in a double for cicle, specifically, into the second cicle. I want it to color the cell that goes over 24, as it is now, it doesn't work, if I write

c.setBackground(Color.red);

it colors the table completely

EDIT

As asked, I created a small example that describes my problem, I don't know if there's a specific way to post a runnable example, but the following code( in netbeans) represents the complete program:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package fatturazione;

import ObjectModel.Timesheet;
import java.awt.Component;
import javax.swing.JLabel;
import javax.swing.table.TableCellRenderer;


/**
 *
 * @author xtphere
 */
public class Example extends javax.swing.JFrame {

    /**
     * Creates new form Main
     */
    public Example() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();
        CheckButton = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3", "Title 4"
            }
        ));
        jScrollPane1.setViewportView(jTable1);

        CheckButton.setText("Check the table");
        CheckButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                CheckButtonActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 375, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(CheckButton))
                .addContainerGap(15, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 275, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(CheckButton)
                .addGap(0, 35, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>                        

    private void CheckButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
        // TODO add your handling code here:
        int x, y, i = 1;


        for(x = 0; x < jTable1.getRowCount(); x++){

            for(y = 0;  y < jTable1.getColumnCount(); y++){

                TableCellRenderer Tcr = jTable1.getCellRenderer(x, y);
                Component c = Tcr.getTableCellRendererComponent(jTable1, jTable1.getValueAt(x, y), false, false, x, y);

                if(jTable1.getValueAt(x, y) == null)
                {
                    jTable1.setValueAt("P", x, y);
                }

                if(jTable1.getValueAt(x, y) != null && !jTable1.getValueAt(x, y).equals("F") && !jTable1.getValueAt(x, y).equals(" ")){
                        System.out.print(jTable1.getValueAt(x, y)+"\n");                          
                        if(!jTable1.getValueAt(x, y).toString().contains("/P") && !jTable1.getValueAt(x, y).toString().equals("P")){                            
                            System.out.print("prima del maggiore di 24");
                            if(Double.parseDouble(jTable1.getValueAt(x, y).toString()) > 24){
                                System.out.print("leggi il 25, almeno?");
                                c.setBackground(java.awt.Color.red);                                
                            }
                        }
                    }    


            }          
        } 


    }                                           

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Example().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton CheckButton;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    // End of variables declaration                   
}

Answer 1

First of all variable names should NOT start with an upper case character. Some of your variables are correct, others are not. Be consistent!!!

I've tried to color a cell of a jTable using the renderers, but they are useless they lag the table and make it impossible to see.

Just because you don't understand the concept does not make it useless. The problem is with your code, not the concept of renderers.

Your posted code makes no sense. You can't set the color of an individual cell. The color is determined when the cell is renderer, which is why you need to use a renderer.

it colors the table completely

Yes, once you set the background of the renderer all cells in the future will use that color. You need to reset the color to its default before rendering each cell

the background must be red just in case it's a number AND it's higher than 24,

Then do a positive check and forget about all those negative checks.

Using all the above suggestions you might have a renderer something like:

class ColorRenderer extends DefaultTableCellRenderer
{
    @Override
    public Component getTableCellRendererComponent(
        JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column)
    {
        super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);

        if (isSelected)
            setBackground( table.getSelectionBackground() );
        else
        {
            setBackground( table.getBackground() );

            try
            {
                int number = Integer.parseInt( value.toString() );

                if (number > 24)
                    setBackground( Color.RED );
            }
            catch(Exception e) {}
        }

        return this;
    }
}

Answer 2

After looking in the discussion thread, I come to this solution...

... don't try to get the rendered Component itself - tell the renderer to draw your desired component in ways you want it to...

CellRenderer renderer = new DefaultCellRenderer(){

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

        Component c = super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, col);
        JLabel label = (JLabel)c;

        if (yourAlgorithmToDetectTheProperCell){ //i can't insert your condition from above, it's overkill ^^
            label.setBackGround(Color.RED);
        }
  
        return label;
    }
};

table.setCellRenderer(renderer);

SDF

Answer 3

In your first code sample, you have a whole series of checks to end with setting the background color red. In all other cases you should set the background to the default background color. You can look up this background color by table.getBackground(); .