Kivy：无法从另一个类更新文本输入值

Question

我是kivy的新手。我正在尝试从另一个类更改文本输入值（TextInput框中显示的字符串值，但是什么也没通过。

我在class MyFirstScreen中有以下小部件：

• 一个RecycleView有多个项目（每个项目是一个dictionary）
• 两个TextInput s

我想做什么：选择RecycleView中的每个项目时，应更新TextInput并加载所选项目dictionary的相应值。

但是当我尝试从另一个类（TextInput）访问当前class SelectableLabel的值时：

class SelectableLabel(RecycleDataViewBehavior, Label):
    #...
    def update_text_inputs(self, *kwarg):
        my_text_input = MyFirstScreen().ids.system_name_text_input_id #<--i can access to widget
        print("my_print_val is:", my_text_input.text) #<--but widget's current text value is : ''
        my_text_input.text = "Updated Value"

我可以访问my_text_input小部件，但其文本（my_text_input.text）是一个空字符串（''）。此外，当我更改my_text_input.text的值时，TextInput的框中没有任何反应。] >

有人知道我在这里做错什么或如何使这项工作吗？预先谢谢你...

这是我的.py代码：

from kivy.app import App
from kivy.lang import Builder
from kivy.properties import ObjectProperty
from kivy.uix.label import Label
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.recycleview import RecycleView
from kivy.uix.recycleview.views import RecycleDataViewBehavior
from kivy.properties import BooleanProperty
from kivy.uix.recycleboxlayout import RecycleBoxLayout
from kivy.uix.behaviors import FocusBehavior
from kivy.uix.recycleview.layout import LayoutSelectionBehavior


class Manager(ScreenManager):

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


class MyFirstScreen(Screen):
    system_name_text_input_id = ObjectProperty(None)

    def __init__(self, **kwarg):
        super().__init__(**kwarg)
        print("__init__ of MyFirstScreen is Called")

    def get_text_inputs(self):
        ret_val = self.ids.system_name_text_input_id.text
        print("get_text_input is called, ret_val:", ret_val)
        return ret_val


class RecycleViewWidget(RecycleView):
    def __init__(self, **kwargs):
        super(RecycleViewWidget, self).__init__(**kwargs)
        self.items_of_rv = []
        for i in range(1, 21):
            self.items_of_rv.append(
                {"color": (0, 0, 0, 1), "font_size": "20", "text": f"User {i}",
                 "user_id": f"{100 * i}"})
        self.data = [item for item in self.items_of_rv]


class SelectableRecycleBoxLayout(FocusBehavior, LayoutSelectionBehavior, RecycleBoxLayout):
    """ Adds selection and focus behaviour to the view. """


class SelectableLabel(RecycleDataViewBehavior, Label):
    """ Add selection support to the Label """
    index = None
    selected = BooleanProperty(False)
    selectable = BooleanProperty(True)

    def refresh_view_attrs(self, rv, index, data):
        """ Catch and handle the view changes """
        self.index = index
        return super(SelectableLabel, self).refresh_view_attrs(rv, index, data)

    def on_touch_down(self, touch):
        """ Add selection on touch down """
        if super(SelectableLabel, self).on_touch_down(touch):
            return True
        if self.collide_point(*touch.pos) and self.selectable:
            return self.parent.select_with_touch(self.index, touch)

    def apply_selection(self, rv, index, is_selected):
        """ Respond to the selection of items in the view. """

        self.selected = not is_selected
        if is_selected:
            rv.data[index].update({'color': (1, 1, 1, 1)})
            self.refresh_view_attrs(RecycleViewWidget(), index, rv.data[index])
            print("selection changed to {0}".format(rv.data[index]))
            self.update_text_inputs()
        else:
            if rv.data[index].get("color") == (1, 1, 1, 1):
                rv.data[index].update({'color': (0, 0, 0, 1)})
                self.refresh_view_attrs(RecycleViewWidget(), index, rv.data[index])
        self.selected = not self.selected

    def update_text_inputs(self, *kwarg):
        my_text_input = MyFirstScreen().ids.system_name_text_input_id#<--i can access to widget
        print("my_print_val is:", my_text_input.text)#<--but widget's current text value is : ''
        # my_text_input.text = "Updated Value" 

main_style = Builder.load_file("test.kv")


class MyApp(App):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

    def build(self):
        return main_style


if __name__ == '__main__':
    MyApp().run()
还有我的.kv代码：

Manager:
    MyFirstScreen:

<SelectableLabel>:
    canvas.before:
        Color:
            rgba: (0, 0, 1, 1) if self.selected else (1, 1, 1, 1)
        Rectangle:
            pos: self.pos
            size: self.size
<RecycleViewWidget>:
    viewclass: 'SelectableLabel'
    SelectableRecycleBoxLayout:
        default_size: None, dp(56)
        default_size_hint: 1, None
        size_hint_y: None
        height: self.minimum_height
        orientation: 'vertical'

<MyFirstScreen>:
    name: 'system_setup_page'
    system_name_text_input_id:system_name_text_input_id
    GridLayout:
        cols: 2
        BoxLayout:
            cols: 1
            padding: 20
            RecycleViewWidget:
        FloatLayout:
            Label:
                size_hint: None, None
                text: "Name:"
                font_size: 22
                pos_hint: {'center': (20/100, 90/100)}
            TextInput:
                id: system_name_text_input_id
                size_hint: None, None
                hint_text: "Type Your Name..."
                size: 200, 30
                multiline: False
                pos_hint: {'center': (65/100, 90/100)}
                on_text: root.get_text_inputs()
            Label:
                size_hint: None, None
                text: "User ID:"
                font_size: 20
                pos_hint: {'center': (20/100, 70/100)}
            TextInput:
                size_hint: None, None
                size: 200, 30
                hint_text: "Type Your ID..."
                pos_hint: {'center': (65/100, 70/100)}

我是kivy的新手。我正在尝试从另一个类更改文本输入值（在TextInput框中显示的字符串值），但是什么也没通过。我在MyFirstScreen类中有以下小部件：一个...

Answer 1

问题是因为在MyFirstScreen()中使用update_text_inputs()创建了类MyFirstScreen的新实例，但必须使用现有实例。