Dynamic layout management

if(nullptr == _hLayout)
{
_hLayout=new QHBoxLayout(this);
}
// If the original layout exists , Delete layout
// if(this->layout()!=nullptr)
{
// First, empty the original layout control
while(_hLayout->count()!=0)
{
auto item=_hLayout->itemAt(0);

        // If it is a child control , Delete ;
        if(QWidget* widget=item->widget())
        {
            qDebug()<<" Deleted a child control ";
            delete widget;
            widget=nullptr;
        }
        // If it's a bullet spring , Delete :
        if(QSpacerItem* spaceItem=item->spacerItem())
        {
            qDebug()<<" Deleted a spring ";
            delete spaceItem;
            spaceItem=nullptr;
        }
        // Remove the sub object itself 
        _hLayout->removeItem(item);
        // Delete the object itself 
        delete item;
        item=nullptr;
    }
    // Finally delete layout 
    //        delete this->layout();
}
// New layout 
//    _hLayout=new QHBoxLayout();
_hLayout->setMargin(0);
_hLayout->setSpacing(0);

These codes cannot be put into paintevent Inside