Kivy切换窗口时如何更新TextInput的text参数？

问题根源 #

你在MainWindow的on_press方法中调用ThirdWindow().write()时，新建了一个ThirdWindow实例，而不是操作ScreenManager中已经加载的那个ThirdWindow对象。这个新实例从未被添加到界面中，所以即使修改了它的TextInput内容，也不会在屏幕上显示。

修复方案 #

通过ScreenManager的get_screen()方法获取已经存在的ThirdWindow实例，再调用它的write()方法。

修改后的Python代码 #

from kivy.app import App
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.animation import Animation
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.clock import Clock
from functools import partial

Window.size = (500, 700)
Window.clearcolor = "#1b1a28"


class MainWindow(Screen):
    def go_window(self, window, widget, *args):
        self.manager.current = window
        animate = Animation(duration=0.4, background_color=(96/255, 85/255, 83/255, 1), color=(1,1,1,1))
        animate.start(widget)

    def animation(self, widget, *args):
        animate = Animation(duration=0.1)
        animate += Animation(size_hint=(1.2,1.2),duration=0.1,background_color=(0,0,0,-1))
        animate += Animation(size_hint=(1,1),duration=0.1,color=(0,0,1,0))
        animate.start(widget)

    def on_press(self, widget, *args):
        if widget.gid == "accounts":
            self.animation(widget)
            Clock.schedule_once(partial(self.go_window, "second", widget), 0.5)
        if widget.gid == "notes":
            self.animation(widget)
            Clock.schedule_once(partial(self.go_window, "third", widget), 0.5)
            # 关键修改：获取已存在的ThirdWindow实例
            self.manager.get_screen("third").write()

class SecondWindow(Screen):
    pass


class ThirdWindow(Screen):
    def __init__(self, **kwargs):
        super(ThirdWindow, self).__init__(**kwargs)
        Window.bind(on_request_close=self.exit_program)

    def go_back(self, widget, *args):
        if widget.gid == "notes":
            print(self.ids.notes2.text)
        self.manager.current = "main"

    def write(self):
        self.ids.notes2.text = "test"
        print(1)


    def exit_program(self, *args):
        print(self.ids.notes2.text)


class WindowManager(ScreenManager):
    pass


kv = Builder.load_file("widgets.kv")


class MyApp(App):
    def build(self):
        return kv

if __name__ == "__main__":
    MyApp().run()

说明 #

• self.manager.get_screen("third")会从ScreenManager中获取名为"third"的已加载屏幕实例，这个实例就是KV文件中定义的那个ThirdWindow。
• 调用这个实例的write()方法，修改的就是界面上实际显示的TextInput控件，所以内容会正常更新。

内容的提问来源于stack exchange，提问作者Александр Безпалый