PyQt中如何使用QPainter在UI窗口中绘制图形？

import sys
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtGui import QPainter, QPen


class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(400, 300)

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

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))

    def paintEvent(self, event):  # 注意这里修改了事件参数名称
        qp = QPainter()
        qp.begin(self)
        self.drawLines(qp)
        qp.end()

    def drawLines(self, qp):
        pen = QPen(QtCore.Qt.black, 2, QtCore.Qt.SolidLine)
        qp.setPen(pen)
        qp.drawLine(120, 120, 120, 210)
        qp.drawLine(135, 94, 120, 120)
        qp.drawLine(135, 94, 150, 120)
        qp.drawLine(150, 120, 150, 210)
        qp.drawLine(120, 210, 150, 210)


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    Form = QtWidgets.QWidget()
    ui = Ui_Form()
    ui.setupUi(Form)
    Form.show()
    sys.exit(app.exec_())