PlaceholderRenderer.java

package org.obo.app.swing;

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

import javax.swing.JTable;
import javax.swing.UIManager;
import javax.swing.table.DefaultTableCellRenderer;

/**
 * A table cell renderer which displays greyed-out placeholder text when the cell value is 
 * empty.
 * @author Jim Balhoff
 */
public class PlaceholderRenderer extends DefaultTableCellRenderer {

    private final String placeholder;

    /**
     * Create a new PlaceholderRenderer which displays the given text as a placeholder value. 
     * @param placeholder The placeholder text to display.
     */
    public PlaceholderRenderer(String placeholder) {
        super();
        this.placeholder = placeholder;
    }

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
        if ((value == null) || (value.equals(""))) {
            final Component component = super.getTableCellRendererComponent(table, this.placeholder, isSelected, hasFocus, row, column);
            component.setForeground(Color.GRAY);
            return component;
        } else {
            final Component component = super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
            if (isSelected) {
                component.setForeground(UIManager.getColor("Table.selectionForeground"));
            } else {
                component.setForeground(UIManager.getColor("Table.foreground"));
            }
            return component;
        }
    }

}