#include <QApplication>
#include <QMainWindow>
#include <QVBoxLayout>
#include <QPushButton>
#include <QDialog>
#include <QDragEnterEvent>
#include <QDropEvent>
#include <QDebug>

class MainWindow:public QMainWindow
{
public:
    MainWindow():QMainWindow()
    {
        QWidget * centralWidget = new QWidget( this );
        QVBoxLayout * layout = new QVBoxLayout(centralWidget);

        QPushButton * mybutton = new QPushButton( centralWidget );
        layout->addWidget( mybutton );
        connect( mybutton, &QPushButton::clicked, this, &MainWindow::OpenDialog );
        centralWidget->setLayout( layout );
        setAcceptDrops(true);
        setCentralWidget( centralWidget );
    }

    void dragEnterEvent(QDragEnterEvent * inEvent ) override
    {
        inEvent->accept();
   }

    void dropEvent( QDropEvent * inEvent ) override
    {
        qDebug()<<"Item Dropped";
    }
public slots:
    void OpenDialog( bool )
    {
        QDialog * mdialog = new QDialog( this );
        mdialog->exec();
    }
};

int main(int argc, char *argv[])
{
    QApplication a( argc, argv );
    MainWindow main;

    main.show();
    return a.exec();
}