CODEWITHSUNDEEP
pythonpyqtpyqt5qgraphicsviewqmainwindow
Aquarius_Girl
Aquarius_Girl

Reputation: 22936

PyQt: Scrollbars are not shown with QGraphicsView class being nested under QMainWindow

I am supposed to add scrollbars to the screen. The class design shown below is the part of a software that I am supposed to modify and add scrollbars to. The scroll bar code in Window class has been added by me.

It doesn't get shown when I run the program. What am I supposed to correct?

import sys

from PyQt4 import QtGui
from PyQt4 import QtCore

class Window(QtGui.QGraphicsView):

  def __init__(self, parent=None):

        QtGui.QGraphicsView.__init__(self, parent)
        self.scene = QtGui.QGraphicsScene(self)
        self.scene.setBackgroundBrush(QtGui.QBrush(QtCore.Qt.darkGray, QtCore.Qt.SolidPattern))
        self.setScene(self.scene)

        self.setDragMode(QtGui.QGraphicsView.ScrollHandDrag)
        self.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
        self.viewport().setCursor(QtCore.Qt.CrossCursor)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)


class CityscapesLabelTool(QtGui.QMainWindow):
    def __init__(self, parent=None):

        QtGui.QMainWindow.__init__(self, parent)

        Window()

app = QtGui.QApplication(sys.argv)
GUI = CityscapesLabelTool()
GUI.show()
sys.exit(app.exec_())

Upvotes: 0

Views: 558

Answers (1)

eyllanesc
eyllanesc

Reputation: 244162

A local variable is deleted when the program leaves its scope, and in your case Window() is a local variable that when it finishes executing the constructor is eliminated. For that variable not to be destroyed, it must be related to another variable that has a larger scope. In this case it is appropriate to set the Window() with the centralWidget of QMainWindow.

import sys

from PyQt4 import QtGui
from PyQt4 import QtCore

class Window(QtGui.QGraphicsView):
  def __init__(self, parent=None):
        QtGui.QGraphicsView.__init__(self, parent)
        self.scene = QtGui.QGraphicsScene(self)
        self.scene.setBackgroundBrush(QtGui.QBrush(QtCore.Qt.darkGray, QtCore.Qt.SolidPattern))
        self.setScene(self.scene)

        self.setDragMode(QtGui.QGraphicsView.ScrollHandDrag)
        self.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
        self.viewport().setCursor(QtCore.Qt.CrossCursor)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn)


class CityscapesLabelTool(QtGui.QMainWindow):
    def __init__(self, parent=None):
        QtGui.QMainWindow.__init__(self, parent)
        centralwidget = Window()
        self.setCentralWidget(centralwidget)

app = QtGui.QApplication(sys.argv)
GUI = CityscapesLabelTool()
GUI.show()
sys.exit(app.exec_())

Upvotes: 1

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