如何从不同的布局管理屏幕

Question

我正在尝试使用一组按钮来控制显示哪个屏幕，同时仍然显示这些按钮。

bobo.py

import kivy
kivy.require("1.9.0")

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.boxlayout import BoxLayout

class ButtSection(BoxLayout):
    pass

class Welcome(Screen):
    pass

class AccountOne(Screen):
    pass

class AccountTwo(Screen):
    pass

class ScreenManagement(ScreenManager):
    pass

presentation = Builder.load_file("Bobo.kv")

class BoboApp(App):
    def build(self):
        return presentation

main = BoboApp()
main.run()

Bobo.kv

BoxLayout:
    orientation: "horizontal"
    BoxLayout:
        ButtSection:
            orientation: "vertical"
            Button:
                text: "Account One"
                on_press: app.root.current = "a1"
            Button:
                text: "Account Two"
                on_press: app.root.current = "a2"
            Button:
                text: "Account Three"
                on_press: app.root.current = "a3"

    ScreenManagement:
        Welcome:
            name: "wel"
            Label:
                text: "Welcome To Bobot"
        AccountOne:
            name: "a1"
            Label:
                text: "Page: Account One"
        AccountTwo:
            name: "a2"
            Label:
                text: "Page: Account One"

当我运行脚本时，欢迎屏幕是当前屏幕。当我点击一个按钮时，它什么也不做，即使我输入了'on_press: app.root.current =‘。

Answer 1

您必须分析app.root的含义，看看它是否是ScreenManager。

主是指作为BoboApp实例的应用程序，即app。root是指返回应用程序的build方法的对象，即presentation。presentation是.kv的根对象，也就是BoxLayout。根据我们得出的结论，app.root不是错误有效的ScreenManager。

不使用根作为访问ScreenManager的方法，可以通过id访问它，因为id在整个树中都是可访问的。

另一方面，我已经更改了屏幕的名称，以匹配您想要设置的名称。

BoxLayout:
    orientation: "horizontal"
    BoxLayout:
        ButtSection:
            orientation: "vertical"
            Button:
                text: "Account One"
                on_press: manager.current = "a1" # <---
            Button:
                text: "Account Two"
                on_press: manager.current = "a2" # <---
            Button:
                text: "Account Three"
                on_press: manager.current = "a3" # <---

    ScreenManagement:
        id: manager # <---
        Welcome:
            name: "a1" # <---
            Label:
                text: "Welcome To Bobot"
        AccountOne:
            name: "a2" # <---
            Label:
                text: "Page: Account One"
        AccountTwo:
            name: "a3" # <---
            Label:
                text: "Page: Account One"