Question

我正在做一个简单的登录应用程序，我似乎得到了一个

if current_property[:3] == 'on_':
 TypeError: 'NoneType' object is not subscriptable

这是我的代码：

ScreenManager:
    Password:
    Second_Screen:     

<Password@Screen>
    id: 'main'
    MDCard:
        size_hint: None, None
        size: 600, 800
        pos_hint: {'center_x': .5, "center_y": .5}
        elevation: 10
        padding: 25
        spacing: 25
        orientation: 'vertical'

        FitImage:
            source: "pfa2.jpg"

        MDLabel:
            id: welcome_label
            text: "Velkommen til PFRemmøde"
            font_size: 40
            halign: 'center'
            size_hint_y: None
            height: self.texture_size[1]
            padding_y: 15

        MDTextFieldRound:
            id: user
            hint_text: "Brugernavn"
            icon_right: "account"
            size_hint_x: None
            width: 225
            font_size: 20
            pos_hint: {"center_x": 0.5}

        MDTextFieldRound:
            id: password
            hint_text: "Password"
            icon_right: "eye-off"
            size_hint_x: None
            width: 225
            font_size: 20
            pos_hint: {"center_x": 0.5}
            password: True

        MDRoundFlatButton:
            text: "Log ind"
            width: 200
            font_size: 12
            pos_hint: {"center_x": 0.5}
            on_release:
                app.root.current = "second" if password.text =="1234" else "main"
                root.manager.transition.direction = "right"

        MDRoundFlatButton:
            text: "Afslut"
            width: 200
            font_size: 12
            pos_hint: {"center_x": 0.5}
            on_press: app.clear()

<Second_Screen>:
    id: 'second' 

    MDRoundFlatButton:
            text: "Log ind"
            width: 200
            font_size: 12
            pos_hint: {"center_x": 0.5}
            on_release:
                app.root.current = "second" if passw.text == "pswd" else "main"
                root.manager.transition.direction = "left"

我运行的对象：


class MainApp(MDApp):    
    def build(self):
        self.theme_cls.theme_style = "Dark"
        self.theme_cls.primary_palette = "Red"
        return Builder.load_file('login.kv')


def logger(self):
    self.root.ids.welcome_label.text = f'Velkommen {self.root.ids.user.text}!'
  

def clear(self):
    self.root.ids.welcome_label.text = "WELCOME"        
    self.root.ids.user.text = ""        
    self.root.ids.password.text = ""        
    
MainApp().run()

我是否遗漏了一些明显的东西？我的理想结果是，如果输入“1234”作为密码，屏幕应该切换到应用程序的“登录”版本。这似乎不起作用，但是......我对 KivyMD 很陌生，所以请耐心等待 :-)

Answer 1

您的代码有问题：

您必须为您的 Screens 提供名称：

 ScreenManager:
     Password:
         name: 'passw'
     Second_Screen:
         name: 'second'

您的 SecondScreen 类应该扩展 Screen：
```
 <Second_Screen@Screen>:
```

您的 SecondScreen 规则缩进不正确，这导致了您看到的错误。这是更正的版本：

 <Second_Screen@Screen>:
     id: 'second' 

     MDRoundFlatButton:
         text: "Log ind"
         width: 200
         font_size: 12
         pos_hint: {"center_x": 0.5}
         on_release:
             app.root.current = "second" if passw.text == "pswd" else "main"
             root.manager.transition.direction = "left"

KivyMD 按下按钮时切换屏幕？

1 个答案: