import org.eclipse.core.commands.operations.IOperationHistoryListener; //导入依赖的package包/类
@Override
protected final void after() {
    final IOperationHistory theOperationHistory = theWorkspaceCommandStack.getOperationHistory();
    final IUndoContext theDefaultUndoContext = theWorkspaceCommandStack.getDefaultUndoContext();
    final IUndoableOperation[] theUndoHistory = theOperationHistory.getUndoHistory(theDefaultUndoContext);
    final IUndoableOperation theEditLabelOperation = theUndoHistory[theUndoHistory.length - 1];
    final IUndoableOperation theCreateElementOperation = theUndoHistory[theUndoHistory.length - 2];
    final IOperationHistoryListener theOperationHistoryListener = new AtomicElementLabelingSupport(
            theWorkspaceCommandStack, theEditLabelOperation, theCreateElementOperation);
    theOperationHistory.addOperationHistoryListener(theOperationHistoryListener);
}
 

import org.eclipse.core.commands.operations.IOperationHistoryListener; //导入依赖的package包/类
@Override
public void removeOperationHistoryListener(
		IOperationHistoryListener listener) {
	listeners.remove(listener);
}
 

import org.eclipse.core.commands.operations.IOperationHistoryListener; //导入依赖的package包/类
/**
 * <p>
 * Add the specified listener to the list of operation history listeners
 * that are notified about changes in the history or operations that are
 * executed, undone, or redone. This method has no effect if the instance
 * being added is already in the list.
 * </p>
 * <p>
 * Operation history listeners must be prepared to receive notifications
 * from a background thread. Any UI access occurring inside the
 * implementation must be properly synchronized using the techniques
 * specified by the client's widget library.
 * </p>
 * 
 * @param listener
 *            the IOperationHistoryListener to be added as a listener.
 * 
 * @see org.eclipse.core.commands.operations.IOperationHistoryListener
 * @see org.eclipse.core.commands.operations.OperationHistoryEvent
 */
@Override
public void addOperationHistoryListener(IOperationHistoryListener listener) {
	listeners.add(listener);
}