pyside2 app with QGraphicsWidget is closing immediately

Question

in my project ( a mastermind game), I have the special need to use the Graphics View Framework because I want to manage a graphic game with pawns which are moved by drag'n drop.

I manage displaying the window but there is nothing in the GraphicsWidget:

outrun.py

#!/usr/bin/python

from PySide2 import QtGui, QtWidgets as wids
import sys
import out
import PySide2

class ImageViewer(wids.QMainWindow, out.Ui_MainWindow):
    def __init__(self, parent=None):
        super(ImageViewer, self).__init__(parent)
        self.setupUi(self)

    def main(self):
        self.changeGraphicsView()
        self.show()

    def changeGraphicsView(self):
        scene=wids.QGraphicsScene() 
        self.graphicsView.setScene(scene)

        windowLayout=wids.QGraphicsGridLayout()

        title0=wids.QGraphicsSimpleTextItem()
        title0.setText("JEU DE MASTERMIND")
        title=wids.QGraphicsWidget(title0)
        windowLayout.addItem(title,0,0)

        title1=wids.QGraphicsSimpleTextItem()
        title1.setText("super!")
        title2=wids.QGraphicsWidget(title1)
        windowLayout.addItem(title2,0,1)

        form=wids.QGraphicsWidget()
        form.setLayout(windowLayout)
        scene.addItem(form)

        self.graphicsView.show()


if __name__=='__main__':
    app = wids.QApplication(sys.argv)
    imageViewer = ImageViewer()
    imageViewer.main()
    app.exec_()

and out.py (from the .ui file): The only interesting thing is the field 'self.graphicsView', which is used in the above code.

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 600)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.graphicsView = QtWidgets.QGraphicsView(self.centralwidget)
        self.graphicsView.setGeometry(QtCore.QRect(10, 100, 761, 441))
        brush = QtGui.QBrush(QtGui.QColor(107, 197, 190))
        brush.setStyle(QtCore.Qt.NoBrush)
        self.graphicsView.setBackgroundBrush(brush)
        self.graphicsView.setObjectName("graphicsView")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(10, 20, 781, 51))
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Maximum, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label.sizePolicy().hasHeightForWidth())
        self.label.setSizePolicy(sizePolicy)
        font = QtGui.QFont()
        font.setFamily("Mongolian Baiti")
        font.setPointSize(28)
        self.label.setFont(font)
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.label.setObjectName("label")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QtWidgets.QApplication.translate("MainWindow", "MainWindow", None, -1))
        self.label.setText(QtWidgets.QApplication.translate("MainWindow", "HELLO QT !", None, -1))

thank you.

Answer 1

It' not how QGraphicsWidget works: this class is used to embed widgets in a QGraphicsScene.

You should reconsider the way you want to build your UI (you don't have to embed everything in the scene).

This is how you should use it:

class Display(QGraphicsWidget):
    def __init__(self):
        QGraphicsWidget.__init__(self)
        #création du layout
        self.layout= QGraphicsGridLayout()
        self.setLayout(self.layout)
        self.layout.setRowMinimumHeight(1,400)
        self.layout.setColumnMinimumWidth(0,250)

        #ajout des composants
        title0= QGraphicsSimpleTextItem(self)
        title0.setText("JEU DE MASTERMIND")
        title0.setFont(QFont("Times",20,QFont.ExtraExpanded|QFont.ExtraBold))
        title= QGraphicsWidget(title0)
        self.layout.addItem(title,0,0,1,2)

        title02= QGraphicsSimpleTextItem(self)
        title02.setText("haha")
        title2= QGraphicsWidget(title02)
        self.layout.addItem(title2,1,0,1,1)

import sys

if __name__ == '__main__':
    app =  QApplication(sys.argv)
    window=Display()

    # Create a view and its scene
    scene= QGraphicsScene()
    view= QGraphicsView(scene)

    # Insert your Display item in the view
    scene.addItem(window)
    view.show()
    sys.exit(app.exec_())

Btw, your window is closed immediatly because there is no widget to display (the view was destroyed at the end of your constructor).