如何在委托类中添加样式表？

Question

在我的应用程序中，我有一个表格小部件。我创建了一个新类来实现表格单元格对齐的委托作为中心。委托工作正常，但样式表无法正常工作。下面是我实现委托类的方法：

//i create new class with "QStyledItemDelegate" as base class
 //QAlignmentDelegate.h
#ifndef QALIGNMENTDELEGATE_H
#define QALIGNMENTDELEGATE_H

#include <QStyledItemDelegate>

class QAlignmentDelegate : public QStyledItemDelegate
{
 public:
   QAlignmentDelegate(Qt::Alignment alignment);
   virtual void paint(QPainter* painter,
   const QStyleOptionViewItem& option,
   const QModelIndex& index) const;

 private:
   Qt::Alignment  m_alignment;

};

#endif // QALIGNMENTDELEGATE_H

//QAlignmentDelegate.cpp
#include "qalignmentdelegate.h"

 QAlignmentDelegate::QAlignmentDelegate(Qt::Alignment alignment)
 {
  m_alignment=alignment;
 }

  void QAlignmentDelegate::
  paint(QPainter *painter, const QStyleOptionViewItem &option,
  const QModelIndex &index) const
  {
     QStyleOptionViewItem alignedOption(option);
     alignedOption.displayAlignment = m_alignment;
     QStyledItemDelegate::paint(painter, alignedOption, index);
  }

  //main.cpp
  QTableWidgetItem * protoitem = new QTableWidgetItem();
  protoitem->setTextAlignment(Qt::AlignRight);
  QTableWidgetItem * newitem = protoitem->clone();
  tableWidget->setItemPrototype(newitem);

现在如何在这个委托类中实现样式表？