Kivy使用ScreenManager跨屏幕传值出现AttributeError问题求助

• 1. 计算结果未保存为实例属性：counting方法返回的day_distance/daily_consumption/gasoline_left是局部变量，没有赋值给self对应的实例属性，导致set_values调用时找不到对应属性，直接触发AttributeError。
• 2. calculations方法缩进错误：counting的调用逻辑被写在except代码块内，只有输入转换报错时才会执行，正常合法输入场景下根本不会触发计算。
• 3. counting方法判断逻辑错误：判断条件写的是self.added_fuel == 0，但self.added_fuel是TextInput组件对象，不是输入的数值，应该用方法入参的added_fuel变量。
• 4. 冗余调用逻辑：KV文件中按钮同时绑定了两次on_press事件，且ResultScreen的on_enter又重复调用set_values，多次调用容易引发逻辑混乱。
• 5. 赋值逻辑不统一：set_values中对结果标签赋值时，混用了ids访问和直接属性访问，容易因为绑定问题报错。

1. 修改main.py代码 #

仅需要调整CalculateScreen类的逻辑即可，其余代码保留不变：

class CalculateScreen(Screen):
    start_distance = ObjectProperty()
    finish_distance = ObjectProperty()
    start_gasoline = ObjectProperty()
    added_fuel = ObjectProperty()
    normal_consumption = ObjectProperty()
    # 定义实例属性存储计算结果
    day_distance = StringProperty("0")
    daily_consumption = StringProperty("0")
    gasoline_left = StringProperty("0")
    
    def counting(self, start_distance, finish_distance, start_gasoline, added_fuel, normal_consumption):
        if added_fuel == 0:
            day_distance = str(finish_distance-start_distance)
            daily_consumption = str((int(day_distance)*normal_consumption)/100)
            gasoline_left = str(start_gasoline-float(daily_consumption))
        else:
            day_distance = str(finish_distance-start_distance) 
            daily_consumption = str((float(day_distance)*normal_consumption)/100)
            gasoline_left = str((start_gasoline+added_fuel)-float(daily_consumption))
        # 将计算结果赋值给实例属性
        self.day_distance = day_distance
        self.daily_consumption = daily_consumption
        self.gasoline_left = gasoline_left
        
    def calculations(self):
        try:
            start_distance = float(self.start_distance.text)
            finish_distance = float(self.finish_distance.text)
            start_gasoline = float(self.start_gasoline.text)
            added_fuel = float(self.added_fuel.text)
            normal_consumption = float(self.normal_consumption.text)
        except:
            start_distance = 0
            finish_distance = 0
            start_gasoline = 0
            added_fuel = 0
            normal_consumption = 0
        # 调整缩进，所有场景下都执行计算
        self.counting(start_distance, finish_distance, start_gasoline, added_fuel, normal_consumption)
    
    def set_values(self):
        # 先触发计算逻辑
        self.calculations()
        result_screen = self.manager.get_screen("result")
        # 统一用绑定好的ObjectProperty赋值
        result_screen.day_distance_result.text = self.day_distance
        result_screen.daily_consumption_result.text = self.daily_consumption
        result_screen.gasoline_after_result.text = self.gasoline_left

2. 修改my.kv代码 #

删除冗余调用逻辑，其余布局代码保留不变：

<CalculateScreen>
    # ... 其余布局代码完全保留
    Button:
        text:'Calculate'
        # 合并调用逻辑，删除重复的on_press绑定
        on_press: root.set_values()
        on_release: root.manager.current = "result"

<ResultScreen>
    name: "result"
    # 删除这行冗余的on_enter调用即可，其余代码保留
    # on_enter: root.manager.get_screen("calculator").set_values()
    # ... 其余布局代码完全保留

内容的提问来源于stack exchange，提问作者Анна Мешальникова