simple question:the slot and signal of QTreeWidget

[weixj2003ld]

I create a class as follows:

class CTreeClass:public QTreeWidget
{
public:
      CTreeClass(QWidget *parent);
public slots:
     void showMessage(QTreeWidgetItem *item, int index);
};

class CTreeClass:public QTreeWidget
{
public:
      CTreeClass(QWidget *parent);
public slots:
     void showMessage(QTreeWidgetItem *item, int index);
};

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and in the function CTreeClass,the part of code as follows:

CTreeClass::CTreeClass(QWidget *parent)
:QTreeWidget(parent)
{
...
QObject::connect(this,SIGNAL(itemClicked(QTreeWidgetItem *, int)),this,SLOT(showMessage(QTreeWidgetItem *, int)));
....
}

CTreeClass::CTreeClass(QWidget *parent)
:QTreeWidget(parent)
{
...
QObject::connect(this,SIGNAL(itemClicked(QTreeWidgetItem *, int)),this,SLOT(showMessage(QTreeWidgetItem *, int)));
....
}

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The function showMessage is only show a message(as a test),but when I click the item of the tree,nothing does,Why?