drawEllipse在图形用户界面上没有显示任何内容

Question

我使用设计器创建了一个非常简单的GUI。我现在正试图在两个按钮之间画一个圆圈，但由于某种原因，我做不到。我尝试了几种我在网上搜索的方法，但没有一种对我有帮助。

这是我的密码：

from PyQt5 import QtCore, QtGui, QtWidgets

class ApplicationWindow(QtWidgets.QMainWindow):
   def __init__(self):
      super(ApplicationWindow, self).__init__()
      self.ui = Ui_MainWindow()
      self.ui.setupUi(self)

class Ui_MainWindow(object):
   def setupUi(self, MainWindow):
       MainWindow.setObjectName("Dialog")
       MainWindow.resize(298, 207)
       self.centralwidget = QtWidgets.QWidget(MainWindow)
       self.centralwidget.setObjectName("centralwidget")

       self.turnRed = QtWidgets.QPushButton(MainWindow)
       self.turnRed.setGeometry(QtCore.QRect(70, 90, 75, 23))
       self.turnRed.setObjectName("turnRed")

       self.turnBlue = QtWidgets.QPushButton(MainWindow)
       self.turnBlue.setGeometry(QtCore.QRect(190, 90, 75, 23))
       self.turnBlue.setObjectName("turnBlue")
       self.retranslateUi(MainWindow)
       QtCore.QMetaObject.connectSlotsByName(MainWindow)

   def paintEvent(self, e):
       painter = QtGui.QPainter(self)
       painter.setPen(QtGui.QPen(QtCore.Qt.blue, 8, QtCore.Qt.SolidLine))
       painter.drawEllipse(120,60,50,50)



   def retranslateUi(self, MainWindow):
       _translate = QtCore.QCoreApplication.translate
       MainWindow.setWindowTitle(_translate("Dialog", "Dialog"))
       self.turnRed.setText(_translate("Dialog", "RED"))
       self.turnBlue.setText(_translate("Dialog", "GREEN"))



if __name__ == "__main__":
   import sys
   app = QtWidgets.QApplication(sys.argv)
   application = ApplicationWindow()
   application.show()
   sys.exit(app.exec_())

这是GUI：

​

​

当我运行这个，我看到两个按钮，但我看不到椭圆/圆？我错过了什么？？

备注

我知道更改从设计器生成的代码是不好的，但是我只想看到椭圆，这样我就可以在我的项目上实现相同的东西。

Answer 1

如果您知道更改从构造函数生成的代码是不好的，那么为什么要弹出它呢？

从object继承的类没有paintEvent方法。

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
   def setupUi(self, MainWindow):
       MainWindow.setObjectName("Dialog")
       MainWindow.resize(298, 207)
       self.centralwidget = QtWidgets.QWidget(MainWindow)
       self.centralwidget.setObjectName("centralwidget")

       self.turnRed = QtWidgets.QPushButton(MainWindow)
       self.turnRed.setGeometry(QtCore.QRect(70, 90, 75, 23))
       self.turnRed.setObjectName("turnRed")

       self.turnBlue = QtWidgets.QPushButton(MainWindow)
       self.turnBlue.setGeometry(QtCore.QRect(190, 90, 75, 23))
       self.turnBlue.setObjectName("turnBlue")
       self.retranslateUi(MainWindow)
       QtCore.QMetaObject.connectSlotsByName(MainWindow)

   def retranslateUi(self, MainWindow):
       _translate = QtCore.QCoreApplication.translate
       MainWindow.setWindowTitle(_translate("Dialog", "Dialog"))
       self.turnRed.setText(_translate("Dialog", "RED"))
       self.turnBlue.setText(_translate("Dialog", "GREEN"))

class ApplicationWindow(QtWidgets.QMainWindow):
   def __init__(self):
      super(ApplicationWindow, self).__init__()
      self.ui = Ui_MainWindow()
      self.ui.setupUi(self)

   def paintEvent(self, e):
       painter = QtGui.QPainter(self)
       painter.setPen(QtGui.QPen(QtCore.Qt.blue, 8, QtCore.Qt.SolidLine))
       painter.drawEllipse(120, 60, 50, 50)


if __name__ == "__main__":
   import sys
   app = QtWidgets.QApplication(sys.argv)
   application = ApplicationWindow()
   application.show()
   sys.exit(app.exec_())

​

​

更新

但是现在我正试图改变画家的颜色，它不让我..。基本上，当我运行这个程序时，我得到了蓝色的圆圈，但是当我试图改变它时(通过点击红色按钮并通过函数连接它)，什么都不会发生。请帮我一把好吗？

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("Dialog")
        MainWindow.resize(298, 207)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")

        self.turnRed = QtWidgets.QPushButton(MainWindow)
        self.turnRed.setGeometry(QtCore.QRect(70, 90, 75, 23))
        self.turnRed.setObjectName("turnRed")

        self.turnBlue = QtWidgets.QPushButton(MainWindow)
        self.turnBlue.setGeometry(QtCore.QRect(190, 90, 75, 23))
        self.turnBlue.setObjectName("turnBlue")
        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("Dialog", "Dialog"))
        self.turnRed.setText(_translate("Dialog", "RED"))
        self.turnBlue.setText(_translate("Dialog", "GREEN"))

class ApplicationWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super(ApplicationWindow, self).__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        self.pen = QtGui.QPen(QtCore.Qt.blue, 8, QtCore.Qt.SolidLine)
        self.ui.turnRed.clicked.connect(self.onRed)
        self.ui.turnBlue.clicked.connect(self.onGreen)

    def paintEvent(self, e):
        painter = QtGui.QPainter(self)
        painter.setPen(self.pen)
        painter.drawEllipse(120, 60, 50, 50)

    def onRed(self):
        self.pen = QtGui.QPen(QtCore.Qt.red, 8, QtCore.Qt.SolidLine)
        self.update()

    def onGreen(self):
        self.pen = QtGui.QPen(QtCore.Qt.green, 8, QtCore.Qt.SolidLine)
        self.update()


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    application = ApplicationWindow()
    application.show()
    sys.exit(app.exec_())

​

​