Accompanies the article at http://thoughtsofthree.com/2011/02/creating-a-gwt-radiobuttoncell/

RadioButtonCell.java

package com.tot.samples.RadioButtonCellSample;

import com.google.gwt.cell.client.AbstractEditableCell;
import com.google.gwt.cell.client.Cell;
import com.google.gwt.cell.client.ValueUpdater;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.InputElement;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.event.dom.client.KeyCodes;
import com.google.gwt.safehtml.shared.SafeHtml;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.safehtml.shared.SafeHtmlUtils;

/**
 * A {@link Cell} used to render a radio button. The value of the radio button 
 * may be toggled using the ENTER key as well as via mouse click.
 */
public class RadioButtonCell extends AbstractEditableCell<Boolean, Boolean> {

	/**
	 * An html string representation of a checked radio button.
	 */
	private static final SafeHtml INPUT_CHECKED = SafeHtmlUtils.fromSafeConstant("<input type=\"radio\" tabindex=\"-1\" checked=\"checked\"/>");

	/**
	 * An html string representation of an unchecked radio button.
	 */
	private static final SafeHtml INPUT_UNCHECKED = SafeHtmlUtils.fromSafeConstant("<input type=\"radio\" tabindex=\"-1\"/>");

	private boolean dependsOnSelection, handlesSelection;

	/**
	 * Constructs a new {@link RadioButtonCell} that does not depend on
	 * selection and does not handle selection.
	 */
	public RadioButtonCell() {
		super("change", "keydown");
	}

	/**
	 * Constructs a new {@link RadioButtonCell} that can be configured to depend
	 * and/or handle selection
	 * 
	 * @param groupName
	 *            HTML name attribute of the radiobutton
	 * @param dependsOnSelection
	 *            true if the cell depends on the selection state
	 * @param handlesSelection
	 *            true if the cell modifies the selection state
	 */
	public RadioButtonCell(boolean dependsOnSelection, boolean handlesSelection) {
		this();
		this.dependsOnSelection = dependsOnSelection;
		this.handlesSelection = handlesSelection;
	}
	

	@Override
	public boolean dependsOnSelection() {
		return dependsOnSelection;
	}

	@Override
	public boolean handlesSelection() {
		return handlesSelection;
	}

	@Override
	public void onBrowserEvent(Element parent, Boolean value, Object key,
			NativeEvent event, ValueUpdater<Boolean> valueUpdater) {
		String type = event.getType();

		boolean enterPressed = "keydown".equals(type)
		        && event.getKeyCode() == KeyCodes.KEY_ENTER;
		if ("change".equals(type) || enterPressed) {
			InputElement input = parent.getFirstChild().cast();
			Boolean isChecked = input.isChecked();
			
			/**
			 * Check the radio button if the enter key was pressed and the cell handles
			 * selection or doesn't depend on selection. If the cell depends on
			 * selection but doesn't handle selection, then ignore the enter key and
			 * let the SelectionEventManager determine which keys will trigger a
			 * change.
			 */
			if (enterPressed && (handlesSelection() || !dependsOnSelection())) {
				isChecked = true;
				input.setChecked(isChecked);
			}

			/**
			 * Save the new value. However, if the cell depends on the selection, then
			 * do not save the value because we can get into an inconsistent state.
			 */
			if (value != isChecked && !dependsOnSelection()) {
				setViewData(key, isChecked);
			} else {
				clearViewData(key);
			}
			
			if (valueUpdater != null) {
				valueUpdater.update(isChecked);
			}
		}
	}
	
	@Override
	public boolean isEditing(Element parent, Boolean value, Object key) {
		// A radio button is never in "edit mode". There is no intermediate state
		// between checked and unchecked.
		return false;
	}

	@Override
	public void render(Boolean value, Object key, SafeHtmlBuilder sb) {
		Boolean viewData = getViewData(key);
		if (viewData != null && viewData.equals(value)) {
			clearViewData(key);
			viewData = null;
		}
		    
		if (value != null && ((viewData != null) ? viewData : value)) {
			sb.append(INPUT_CHECKED);
		} else {
			sb.append(INPUT_UNCHECKED);
		}
	}

}