PyQt：QGraphicsView class 嵌套在 QMainWindow 下时不显示滚动条

Question

我应该在屏幕上添加滚动条。下面显示的 class 设计是我应该修改并添加滚动条的软件的一部分。 Windowclass中的滚动条代码是我加的

当我运行程序时没有显示。我应该纠正什么？

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_())

Answer 1

当程序离开其范围时，局部变量将被删除，在您的情况下，Window() 是一个局部变量，当它完成执行构造函数时，该变量将被删除。为了使该变量不被销毁，它必须与另一个具有更大范围的变量相关。在这种情况下，将 Window() 设置为 QMainWindow.

的 centralWidget 是合适的

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_())

PyQt：QGraphicsView class 嵌套在 QMainWindow 下时不显示滚动条

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

python

pyqt

qgraphicsview

qmainwindow

pyqt5