kivy前三节代码-添加控件按钮屏幕（app）

库安装
pip install docutils pygments pypiwin32 kivy.deps.sdl2 kivy.deps.glew
pip install kivy.deps.gstreamer
pip install kivy

import kivy
from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput
from kivy.uix.button import Button
from kivy.uix.screenmanager import ScreenManager, Screen
import os

kivy.require("1.10.1")

class ConnectPage(GridLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.cols = 2

        if os.path.isfile("prev_details.txt"):
            with open("prev_details.txt", "r") as f:
                d = f.read().split(",")

                prev_ip = d[0]
                prev_port = d[1]
                prev_username = d[2]
        else:
            prev_ip = ""
            prev_port = ""
            prev_username = ""


        self.add_widget(Label(text="IP:"))

        self.ip = TextInput(text=prev_ip,multiline=False)
        self.add_widget(self.ip)

        self.add_widget(Label(text="Port:"))

        self.port = TextInput(text=prev_port,multiline=False)
        self.add_widget(self.port)

        self.add_widget(Label(text="Username:"))

        self.username = TextInput(text=prev_username,multiline=False)
        self.add_widget(self.username)

        self.join = Button(text="join")
        self.join.bind(on_press=self.join_button)
        self.add_widget(Label())
        self.add_widget(self.join)

    def join_button(self, instance):
        port = self.port.text
        ip = self.ip.text
        username = self.username.text
        #print(f"Attempting to join {ip}:{port} as {username}")
        with open("prev_details.txt", "w") as f:
            f.write(f"{ip},{port},{username}")

        info = f"Attempting to join {ip}:{port} as {username}"
        chat_app.info_page.update_info(info)
        chat_app.screen_manager.current = "Info"


class InfoPage(GridLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.cols = 1
        self.message = Label(halign="center",valign="middle",font_size=30)
        self.message.bind(width=self.update_text_width)
        self.add_widget(self.message)

    def update_info(self, message):
        self.message.text = message

    def update_text_width(self, *_):
        self.message.text_size = (self.message.width*0.9, None)

class Epicapp(App):
    def build(self):
        #return ConnectPage()
        self.screen_manager = ScreenManager()
        self.connect_page = ConnectPage()
        screen = Screen(name="Connect")
        screen.add_widget(self.connect_page)
        self.screen_manager.add_widget(screen)
        self.info_page = InfoPage()
        screen = Screen(name="Info")
        screen.add_widget(self.info_page)
        self.screen_manager.add_widget(screen)

        return self.screen_manager


if __name__ == "__main__":
    chat_app = Epicapp()
    chat_app.run()