pyqt如何连接停止按钮

Question

我试图设计一个pyqt gui，当我按下start时它启动函数fun1并在funbrowser中启动selenium脚本。当我按下“停止”时，我的意图是，无论funbrowser中的控件在哪里，函数funbrowser都会停止运行。并且pyqt窗口应该关闭，程序必须停止。但它仍然打印“HI”我正在使用spyder windows 7 python 3.6 那么我应该连接到按钮停止，以便有趣的浏览器停止。

class Example(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def funbrowser(self,browser,details):
        browser.get("https://fileml.com/l/0w5O")
        time.sleep(1)
        browser.switch_to.frame("offer-iframe")
        elemlist=browser.find_elements_by_xpath("//ul/li/a")
        list_of_names=[] #All those present
        for i in range(len(elemlist)):
            list_of_names.append(str(elemlist[i].text))
        print("\n")
        print(list_of_names)
        lon=len(list_of_names)*[0]
        available=[] #All those linked
        for i in range(len(elemlist)):
            if "Register for Free" in elemlist[i].text:
                lon[i]="register"
                available.append("register")
            if "Health Samples" in elemlist[i].text:
                lon[i]="health"
                available.append("health")
        print("Available",available)
        print("lon",lon)
        selected=random.choice(available)
        print("selected is ",selected)

        clickon=lon.index(selected)
        print(clickon)
        elemlist[clickon].click()
        alert = browser.switch_to.alert
        alert.accept()    

    def fun1(self):
        browser=webdriver.Firefox()
        self.funbrowser(browser,details)

    def fun2(self):
        import sys
        self.hide()
        quit()
        print("..")

    def launch_thread(self):
        import threading
        x=threading.Thread(target=self.fun1)
        x.start()

    def initUI(self):

        self.setGeometry(300, 300, 300, 220)
        self.setWindowTitle('Icon')
        self.setWindowIcon(QIcon('web.png'))        
        self.layout=QtWidgets.QGridLayout()
        self.btn1=QtWidgets.QPushButton("start",self)
        self.btn1.clicked.connect(self.launch_thread)
        self.btn2=QtWidgets.QPushButton("stop",self)
        self.btn2.clicked.connect()
        self.btn3=QtWidgets.QPushButton("quit",self)
        self.btn3.clicked.connect(self.close)
        self.layout.addWidget(self.btn1,0,0)
        self.layout.addWidget(self.btn2,0,1)
        self.layout.addWidget(self.btn3,0,2)
        self.setLayout(self.layout)
        self.show()

我应该有什么功能连接到self.btn2（“停止”）