如何为 MDLabel 中的文本使用变量？

Posted 2023-04-14

【中文标题】如何为 MDLabel 中的文本使用变量？

【英文标题】：How do I use a variable for the text in an MDLabel?

【发布时间】：2021-04-22 11:57:42

【问题描述】：

我正在尝试将我从 MDTextField 输入的用户名放入 MDLabel 文本中。在我的例子中，MDLabel 位于用户按下提交按钮并进入下一个屏幕后出现的 MDNavigationDrawer 中。

目前我能想到的只是在提交屏幕中将 usn 声明为字符串属性：

class SubmitScreen(Screen):

    usn = StringProperty()

然后创建了一个方法来将 usn 设置为我的应用程序中 MDTextfield 的输入：

def getname(self):
        usn = (self.root.get_screen("menu").ids.userdata.text)

然后我将 MDLabel 中的文本设置为 root.usn

MDLabel:
    
                    text: root.usn                
                    font_style: 'Subtitle1'
                    size_hint_y:None
                    height: self.texture_size[1]      

当我进入下一个屏幕时，MDLabel 是空白的。它没有给我一个错误，但它没有显示我在 MDTextField 中输入的内容，它只是空白。

这是我的完整代码：

screen_helper = """
ScreenManager:
    MenuScreen:
    SubmitScreen:
<MenuScreen>:
    name: 'menu'

    MDTextField:
        id : userdata
        hint_text: "Enter Username"
        helper_text: "or click on forgot username"
        #helper_text_mode: "persistent"
        helper_text_mode: "on_focus"
        icon_right: "account"
        icon_right_color: app.theme_cls.primary_color
        pos_hint : 'center_x': 0.5, 'center_y': 0.4
        size_hint_x:None    
        width:250
        mode : "rectangle"    
    MDTextField:
        id: userpass
        hint_text: "Enter Password"
        helper_text: "or click on forgot Password"
        #helper_text_mode: "persistent"
        password : True
        
        helper_text_mode: "on_focus"
        icon_right: "eye-off"
        icon_right_color: app.theme_cls.primary_color
        pos_hint : 'center_x': 0.5, 'center_y': 0.3
        size_hint_x:None 
        width:250        
        mode : "rectangle"      
    MDLabel:
        text: "Company X"
        pos_hint: 'center_x':0.5, 'center_y':0.7
        font_style: 'H3'
        halign: 'center'

    MDRectangleFlatButton:
        text: 'Submit'
        pos_hint: 'center_x':0.5, 'center_y':0.2
        font_size : 20
        on_press:
            app.getname()
            app.root.current = 'submit'



<SubmitScreen>:
    name: 'submit'
    NavigationLayout:
        ScreenManager:
            Screen:
                BoxLayout:
                    orientation: 'vertical'
                 
                    MDToolbar:
                        title: "Company X"
                        left_action_items: [["menu", lambda x : nav_drawer.toggle_nav_drawer()]]
                        elevation: 11
                    Widget:
              
                    MDFillRoundFlatIconButton:
                        spacing: '8dp'
                        padding: '20dp'
                        text: 'Menu'
                        pos_hint: 'center_x':0.5, 'center_y':0.9
                        icon: 'account-child'
                        on_press: root.manager.current = 'menu'
    
              
                    MDFillRoundFlatIconButton:
                        text: 'View Account'
                        pos_hint: 'center_x':0.5, 'center_y':1
                        font_size : 20
                        icon: 'account-cash'
                        on_press:
                                 
                    
                    MDBottomAppBar:
                 
                        md_bg_color: 0, 1, 0, 1    
                        MDToolbar:
                            title: "by Tech Company"
                            left_action_items: [["coffee", lambda x : app.navigation_draw0()]]
                            right_action_items: [["clock", lambda x : app.navigation_draw1()]]
                            mode: 'free-end'
                            elevation: 13
                            
                            type: 'bottom'
                      
                            icon: 'account-check'
        MDNavigationDrawer:
    
            id: nav_drawer 
    
            BoxLayout:
                orientation: 'vertical'
                spacing: '8dp'
                padding: '12dp'
                Image:
                    source: 'img.jpg'
                MDLabel:
    
                    text: root.usn                
                    font_style: 'Subtitle1'
                    size_hint_y:None
                    height: self.texture_size[1]               
                MDLabel:
                    text: '[e-mail]'
                    font_style: 'Caption'
                    size_hint_y:None
                    height: self.texture_size[1]
                ScrollView:                
                    MDList:
                            #OneLineListItem:
                        OneLineIconListItem:
                            text: 'Profile'
                            IconLeftWidget:
                                icon: 'face-profile'
                        OneLineIconListItem:
                            text: 'Upload'
                            IconLeftWidget:
                                icon: 'upload'                             
                        OneLineIconListItem:
                            text: 'Logout'
                            conLeftWidget:
                            icon: 'logout'   
    
                MDRectangleFlatButton:
                    text: 'Menu'
                    pos_hint: 'center_x':0.5, 'center_y':0.4
                    on_press: root.manager.current = 'menu'
    
                MDRectangleFlatButton:
                    text: 'View Account'
                    pos_hint: 'center_x':0.5, 'center_y':0.3
                    on_press:
                        
                   
         


"""


class MenuScreen(Screen):
    pass


class SubmitScreen(Screen):

    usn = StringProperty()
    





sm = ScreenManager()
sm.add_widget(MenuScreen(name='menu'))
sm.add_widget(SubmitScreen(name='submit'))
sm.add_widget(UploadScreen(name='upload'))
sm.add_widget(AccountScreen(name='account'))


class DemoApp(MDApp):

    def build(self):

        screen = Builder.load_string(screen_helper)
        self.theme_cls.primary_palette = "Purple"
        self.theme_cls.accent_palette = 'Blue'
        self.theme_cls.primary_hue = "200"
        self.theme_cls.theme_style = "Dark"
        return screen
    
     def getname(self):
        usn = (self.root.get_screen("menu").ids.userdata.text)

    


DemoApp().run()

【参考方案1】：

为 MDLabel 设置一个 ID，然后在 getname 函数中将 MDLabel 文本更改为 MDTextField 的输入。

千伏：

MDLabel:
    text: "Text before"
    id: label

在python中：

def getname(self):
    usn = (self.root.get_screen("menu").ids.userdata.text)
    self.root.ids.label.text = usn