Python-Kivy：使用 Python 方法更改屏幕（在 Kivy 代码中创建的嵌套屏幕管理器）

Question

我是 Kivy 的新手，但使用 Tkinter 创建了一个库存程序。

我正在使用 Kivy 制作一个库存程序，并计划首先使用用户名的 TextInput 框（仅）创建一个登录屏幕，然后使用 on_text_verify 我希望它最终运行一个方法来检查用户名与数据库，但现在我只是想让它运行一种方法（在 Python 代码中），将屏幕更改为包含嵌套 ScreenManager 的方法。

我知道如何使用 KV 代码来更改屏幕，但是由于我需要根据数据库检查用户名，我需要它来运行一个 Python 方法来执行此操作，然后，如果用户名被接受，然后换屏幕。这是我目前所拥有的：

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.screenmanager import Screen, ScreenManager
from kivy.properties import ObjectProperty
from kivy.uix.popup import Popup
## I have imported all of these as I have been trying out different things ##

class LoginScreen(Screen):
    pass
class MainScreen(Screen):
    pass
class ScanScreen(Screen):
    pass
class InventoryScreen(Screen):
    pass
class ItemsScreen(Screen):
    pass
class LogsScreen(Screen):
    pass
class AlertsScreen(Screen):
    pass
class HelpScreen(Screen):
    pass


class MainWindow(FloatLayout):


    def __init__(self, **kwargs):
        super(MainWindow, self).__init__(**kwargs)

    def goto_Mainscr(self):
        self.current="Mainscr"


class Invtest3App(App):
    def build(self):
        return MainWindow()


if __name__ == '__main__':
    Invtest3App().run()

这是KV代码：

<MainWindow>:
    orientation: 'vertical'
    name: "mainw"
    id: mw
    ScreenManager:
        id: loginsm
        LoginScreen:
        MainScreen:

<ScanScreen>:
    name: "Scan"
    Button:
        text: "Scan In"
        pos_hint: {"x": 0, 'y': 0}
        size_hint: 1.0/5.0, 0.1
    Button:
        text: "Scan Out"
        pos_hint: {"x": 1.0/5.0, 'y': 0}
        size_hint: 1.0/5.0, 0.1
    Button:
        text: "Event"
        pos_hint: {"x": 2.0/5.0, 'y': 0}
        size_hint: 1.0/5.0, 0.1
    Button:
        text: "Recount"
        pos_hint: {"x": 3.0/5.0, 'y': 0}
        size_hint: 1.0/5.0, 0.1
    Button:
        text: "Logout"
        pos_hint: {"x": 4.0/5.0, 'y': 0}
        size_hint: 1.0/5.0, 0.1
        on_press: app.root.ids.loginsm.current = 'Loginscr'

<InventoryScreen>:
    name: "Inventory"
    Label:
        text: "Inventory Screen"

<ItemsScreen>:
    name: "Items"
    Label:
        text: "Items Screen"

<LogsScreen>:
    name: "Logs"
    Label:
        text: "Logs Screen"

<AlertsScreen>:
    name: "Alerts"
    Label:
        text: "Alerts Screen"

<HelpScreen>:
    name: "Help"
    Label:
        text: "Help Screen"

<LoginScreen>:
    name: "Loginscr"
    id: loginscr
    Label:
        name: "loginlabel"
        text: "Scan ID Barcode or Enter V# and Press Enter"
        pos_hint: {"center_x": .5, "center_y": .5}
    TextInput:
        hint_text: "Scan ID Barcode or Enter V# and Press Enter"
        id: login_input
        size_hint: 0.2, 0.1
        pos_hint: {"center_x": .5, "center_y": 0.2}
        multiline: False
        focus: True
        on_text_validate: app.root.goto_Mainscr; self.text=""
        #app.root.goto_Mainscr
        #app.root.ids.loginsm.current = "Mainscr"

<MainScreen>:
    name: "Mainscr"
    FloatLayout:
        pos_hint: {'top': 1}
        size_hint: 1, 0.1
        Button:
            name: "scanButton"
            text: "Scan"
            pos_hint: {'x': 0, 'y': 0}
            size_hint: 1.0/6.0, 1
            on_press: root.ids.sm.current = "Scan"
        Button:
            name: "inventoryButton"
            text: "Inventory"
            pos_hint: {'x': 1.0/6.0, 'y': 0}
            size_hint: 1.0/6.0, 1
            on_press: root.ids.sm.current = "Inventory"
        Button:
            name: "itemsButton"
            text: "Items"
            pos_hint: {'x': 2.0/6.0, 'y': 0}
            size_hint: 1.0/6.0, 1
            on_press: root.ids.sm.current = "Items"
        Button:
            name: "logsButton"
            text: "Logs"
            pos_hint: {'x': 3.0/6.0, 'y': 0}
            size_hint: 1.0/6.0, 1
            on_press: root.ids.sm.current = "Logs"
        Button:
            name: "alertsButton"
            text: "Alerts"
            pos_hint: {'x': 4.0/6.0, 'y': 0}
            size_hint: 1.0/6.0, 1
            on_press: root.ids.sm.current = "Alerts"
        Button:
            name: "helpButton"
            text: "Help"
            pos_hint: {'x': 5.0/6.0, 'y': 0}
            size_hint: 1.0/6.0, 1
            on_press: root.ids.sm.current = "Help"
    FloatLayout:
        ScreenManager:
            id: sm
            pos_hint: {'top': 0.9}
            size_hint: 1, 0.9
            ScanScreen:
            InventoryScreen:
            ItemsScreen:
            LogsScreen:
            AlertsScreen:
            HelpScreen:

Answer 1

如果你想在不使用 kv 的情况下管理屏幕，那么它看起来像这样：

1. 导入需要的类：

   from kivy.uix.screenmanager import ScreenManager, Screen
   

2. 创建一个屏幕管理器变量：

   scene=ScreenManager()
   

3. 创建一个屏幕：

   screen=Screen(name="login_screen")
   

4. 创建第二个屏幕：

   second_screen=Screen(name="main_screen")
   

现在您可以像这样更改屏幕：

scene.current="login_screen"
scene.current="main_screen"

您可以将小部件添加到这些屏幕。