python - 如何使用Python kivy在启动时确定Spinner值

Question

我正在使用 Python kivy 制作 GUI。 我想在启动时在 GUI 上显示一个随机值。

我认为应该在 __init__ 函数中完成，并尝试了以下代码。

测试.py

import random
from kivy.config import Config
from kivy.app import App
from kivy.uix.widget import Widget

Config.set('graphics', 'width', 300)
Config.set('graphics', 'height', 300)
Config.set('graphics', 'resizable', False)

class TestWidget(Widget):
    def __init__(self, **kwargs):
        super(TestWidget, self).__init__(**kwargs)
        first = random.random()
        second = random.random()
        third = random.random()
        self.ids.spinner_test.values = [str(first),str(second),str(third)]

class TestApp(App):
    def __init__(self, **kwargs):
        super(TestApp, self).__init__(**kwargs)
        self.title = 'random value'

    def build(self):
        return TestWidget()

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

测试.kv

TestWidget:

<TestWidget>:
    BoxLayout:
        size:root.size
        orientation: 'vertical'

        Spinner:
            id:spinner_test
            text: ""
            values: []

        Label:
            text: ""

        Label:
            text: ""

        Label:
            text: ""

但是，出现以下错误并且 GUI 未启动。 如何修复代码？

 Traceback (most recent call last):
   File "kivy\properties.pyx", line 860, in kivy.properties.ObservableDict.__getattr__
 KeyError: 'spinner_test'

 During handling of the above exception, another exception occurred:

AttributeError: 'super' object has no attribute '__getattr__'

Answer 1

问题是 TestWidget 构造函数在 .kv 之前使用，因此 id“spinner_test”当时不存在。

鉴于此，一个可能的解决方案是在显示 GUI 后立即进行更改:

# ...
<b>from kivy.clock import Clock</b>
# ...

class TestWidget(Widget):
    def __init__(self, **kwargs):
        super(TestWidget, self).__init__(**kwargs)
        <b>Clock.schedule_once(self.update)

    def update(self, *args):
        first = random.random()
        second = random.random()
        third = random.random()
        self.ids.spinner_test.values = [str(first), str(second), str(third)]

# ...</b>

另一个选项是创建一个 ListProperty，在其中设置值，然后与 Spinner 的“values”属性进行绑定(bind):

TestWidget:

<TestWidget>:
    BoxLayout:
        size:root.size
        orientation: 'vertical'

        Spinner:
            id:spinner_test
            text: ""
            values: root.values # <---

        Label:
            text: ""

        Label:
            text: ""

        Label:
            text: ""

# ...
<b>from kivy.properties import ListProperty</b>

# ...


class TestWidget(Widget):
    <b>values = ListProperty()</b>

    def __init__(self, **kwargs):
        super(TestWidget, self).__init__(**kwargs)
        first = random.random()
        second = random.random()
        third = random.random()
        <b>self.values = [str(first), str(second), str(third)]</b>

# ...