python - 如何在kivy中动态创建屏幕内的布局？

Question

我编写了这段 python 代码来在屏幕内动态创建 BoxLayout。

from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button

class ListScreen(Screen):
    def __init__(self,**kwargs):
        super(ListScreen, self).__init__(**kwargs)          
        layout = BoxLayout(orientation ='vertical')
        top_buttons=BoxLayout()
        layout.add_widget(top_buttons) 
        top_buttons.add_widget(Button(text='Save'))

class ExampleApp(App):
    def build(self):    
        root=ScreenManager()
        root.add_widget(ListScreen(name='list'))
        return root


ExampleApp().run()

它运行时没有任何编译错误，但输出只是一个空白屏幕。

Answer 1

问题是您尚未将 layout 添加到 ListScreen 实例中:

from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button

class ListScreen(Screen):
    def __init__(self,**kwargs):
        super(ListScreen, self).__init__(**kwargs)          
        layout = BoxLayout(orientation ='vertical')
        self.add_widget(layout)                         #<<<<<<<<<<<<<<<<<
        top_buttons=BoxLayout()
        layout.add_widget(top_buttons) 
        layout.add_widget(Button(text='Save'))

class ExampleApp(App):
    def build(self):    
        root=ListScreen()
        root.add_widget(ListScreen(name='list'))
        return root


ExampleApp().run()