Qt treewidget setheaderitem为什么只显示文字

我的代码：

group0 = new QTreeWidgetItem();

group0->setText(0, codec1->toUnicode("全部"));
group0->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
group0->setCheckState(0, Qt::Unchecked);

treeWidget->setHeaderItem(group0);

结果：

继承QHeaderView，自己实现。
#ifndef CHECKBOXHEADERVIEW_H
#define CHECKBOXHEADERVIEW_H
#include 

class CCheckBoxHeaderView : public QHeaderView
{
    Q_OBJECT
public:
    CCheckBoxHeaderView( int checkColumnIndex,
             Qt::Orientation orientation,
             QWidget * parent = 0) :
    QHeaderView(orientation, parent)
    {
        m_checkColIdx = checkColumnIndex;
    }
protected:
    void paintSection(QPainter *painter, const QRect &rect, int logicalIndex) const
    {
        painter->save();
        QHeaderView::paintSection(painter, rect, logicalIndex); 
        painter->restore();
        if (logicalIndex == m_checkColIdx)
        {
            QStyleOptionButton option;
            int width = 10;
            for (int i=0; i                 width += sectionSize( i );
            option.rect = QRect(width, 5, 15, 15);
            if (isOn)
                option.state = QStyle::State_On;
            else
                option.state = QStyle::State_Off;
//        this->style()->drawPrimitive(QStyle::PE_IndicatorCheckBox, &option, painter);
            this->style()->drawControl(QStyle::CE_CheckBox, &option, painter);
        }
    }

    void mousePressEvent(QMouseEvent *event)
    {
        if (visualIndexAt(event->pos().x()) == m_checkColIdx) 
        {
    //        setSortIndicatorShown( false );
            isOn = !isOn;
            this->updateSection(m_checkColIdx);
        }
    //    else
    //        setSortIndicatorShown( true );
        QHeaderView::mousePressEvent(event);
    }
private:
    bool isOn;
    int m_checkColIdx;
};

#if 0
int main(int argc, char **argv)
{
  QApplication app(argc, argv);
  QTableWidget table;
  table.setRowCount(4);
  table.setColumnCount(3);
  CCheckBoxHeaderView *myHeader = new CCheckBoxHeaderView(0, Qt::Horizontal, &table);
  table.setHorizontalHeader(myHeader); 
  table.show();
  return app.exec();
}
#endif
#endif

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