Kivy AttributeError：“NoneType”对象没有属性“get_screen”

Question

我正在尝试使用 Buttons 的数量初始化 Screen，具体取决于对我的数据库的查询结果，但我得到的是 AttributeError。我认为这是因为当我初始化我的应用程序时没有 Information Screen 并阅读此答案：AttributeError: 'NoneType' object has no attribute 'current' 我需要使用Clock 来延迟我的Finder 类的初始化，以便我的Information 类有时间创建，但我不太确定如何在__init__ 方法中执行此操作，或者如果这甚至是正确的方法？

class Finder(Screen):
    layout_profiles = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(Finder, self).__init__(**kwargs)
        self.mydb = mysql.connector.connect(host="localhost", user="root", passwd="", database="")
        self.cur = self.mydb.cursor(buffered=True)
        self.cur.execute("SELECT gender, age, name FROM users WHERE location = %s AND date_of_visit = %s",
                         (self.manager.get_screen('information').location.text,
                          self.manager.get_screen('information').date))
        self.mydb.commit()
        self.results = cur.fetchall()
        self.cur.close()
        self.mydb.close()
        if self.results:
            for result in self.results:
                if result[0] == "male":
                    male_btn = MaleButton(text="{}, {}".format(result[1], result[2]))
                    self.layout_profiles.add_widget(male_btn)
                elif result[0] == "female":
                    female_btn = FemaleButton(text="{}, {}".format(result[1], result[2]))
                    self.layout_profiles.add_widget(female_btn)
                else:
                    unknown_btn = NoGenderButton(text="{}, {}".format(result[1], result[2]))
                    self.layout_profiles.add_widget(unknown_btn)

错误

line 249, in __init__
     (self.manager.get_screen('information').location.text,
 AttributeError: 'NoneType' object has no attribute 'get_screen'

Answer 1

, dt这是一种在屏幕初始化之后执行所有东西的方法

class Finder(Screen):
    layout_profiles = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(Finder, self).__init__(**kwargs)
        self.mydb = mysql.connector.connect(host="localhost", user="root", passwd="", database="")
        self.cur = self.mydb.cursor(buffered=True)
        Clock.schedule_once(self.do_stuff)

    def do_stuff(self, dt):
        self.cur.execute("SELECT gender, age, name FROM users WHERE location = %s AND date_of_visit = %s",
                         (self.manager.get_screen('information').location.text,
                          self.manager.get_screen('information').date))
        self.mydb.commit()
        self.results = self.cur.fetchall()
        self.cur.close()
        self.mydb.close()
        if self.results:
            for result in self.results:
                if result[0] == "male":
                    male_btn = MaleButton(text="{}, {}".format(result[1], result[2]))
                    self.layout_profiles.add_widget(male_btn)
                elif result[0] == "female":
                    female_btn = FemaleButton(text="{}, {}".format(result[1], result[2]))
                    self.layout_profiles.add_widget(female_btn)
                else:
                    unknown_btn = NoGenderButton(
                        text="{}, {}".format(result[1], result[2]))
                    self.layout_profiles.add_widget(unknown_btn)