Invalid conversion from 'QObject*' to 'QWidget*'

void FormsManager::openPrinterForm() {
    this->engine->load( QUrl( FORM_PRINTER ) );
 
    this->printerForm = new PrinterForm(engine->rootObjects()[0]);
    this->engine->rootContext()->setContextProperty("printerClass", printerForm);
}

#include "PrinterForm.h"
#include "FormsManager.h"
 
PrinterForm::PrinterForm(QWidget *pwgt/*=0*/) :QWidget(pwgt){
    m_pprinter = new QPrinter; //constructor
    //this->m_pprinter=pwgt;
}
 
/*virtual*/ PrinterForm::~PrinterForm()
{
    delete m_pprinter;
}
 
void PrinterForm::paintEvent(QPaintEvent* pe)
{
    draw(this);
}
 
void PrinterForm::slotPrint()
{
    QPrintDialog dlg(m_pprinter, this);
    dlg.setMinMax(1,10);
    if (dlg.exec()==QDialog::Accepted)
    {
        draw(m_pprinter);
    }
}
 
void PrinterForm::draw(QPaintDevice* ppd)
{
    QPainter painter(ppd);
    QImage image("D:/test.png");
    QRect r = painter.viewport();
    QSize size = image.size();
    size.scale(r.size(), QSize::ScaleMin);
    painter.setViewport(r.x(), r.y(), size.width(), size.height());
    painter.setWindow(image.r());
    painter.drawImage(0, 0, image);
 
}

#ifndef PRINTERFORM_H
#define PRINTERFORM_H
#pragma once
 
#include <QDebug>
#include <QImage>
#include <QPixmap>
#include <QPainter>
#include <QDir>
#include <QFile>
#include <QtCore>
#include <QWidget>
#include <QPaintDevice>
#include <QPrintDialog>
 
class QPrinter;
class QPaintDevice;
 
class PrinterForm : public QWidget
{
    Q_OBJECT
 
private:
    QPrinter* m_pprinter;
 
protected:
    virtual void paintEvent(QPaintEvent* pe);
    void draw(QPaintDevice* ppd);
 
public:
    PrinterForm(QWidget* pwgt=0);
    virtual ~PrinterForm();
 
signals:
 
public slots:
    void slotPrint();
 
protected:
};
 
#endif // PRINTERFORM_H

this->printerForm = new PrinterForm(qobject_cast<QWidget *>(engine->rootObjects()[0]));

m_pprinter = New QPrinter;

B* b1 = dynamic_cast<B*>(reinterpret_cast<A*>(c));