Problem emiting signal in QTreeWidgetItem's subclass

[Shawn]

Since this is totally new question which has nothing to do with the title of my provious post, I post it here.

I have subclassed QTreeWidgetItem to MyTreeWidgetItem, which contains an Element* .
Then how can I know which item in QTreeWidget has been clicked?
Can I emit a signal like itemSelected(Element*) ?

I used to subclass the QGraphicsrectItem and emit a signal contains this Element* like this,

class MyRectItem : public QObject, public QGraphicsRectItem
{
	Q_OBJECT
public:
	...
		Element* pE;
signals:
	void itemisSelected(bool newState);
	void itemSelected(Element* pE);
protected:
	QVariant itemChange(GraphicsItemChange change, const QVariant &value)        
	{
		if (change == QGraphicsItem::ItemSelectedChange)
		{
			bool newState = value.toBool();
			if (newState == true) 
			{
				emit itemisSelected(newState);
			}
		} 
		return QGraphicsItem::itemChange(change, value);
	}
};

class MyRectItem : public QObject, public QGraphicsRectItem
{
	Q_OBJECT
public:
	...
		Element* pE;
signals:
	void itemisSelected(bool newState);
	void itemSelected(Element* pE);
protected:
	QVariant itemChange(GraphicsItemChange change, const QVariant &value)        
	{
		if (change == QGraphicsItem::ItemSelectedChange)
		{
			bool newState = value.toBool();
			if (newState == true) 
			{
				emit itemisSelected(newState);
			}
		} 
		return QGraphicsItem::itemChange(change, value);
	}
};

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I connected the signal itemisSelected(bool) with signal itemSelected(Element*) right after I new a MyRectItem. And it works well.

Is there any similar way to emit a signal(Element*) or signal(MyTreeWidgetItem*) in MyTreeWidgetItem?