Kivy应用加载时元素大小未更新

Question

我有一个叫 on_size() 的事件，当我调整窗口大小时，它能正常工作，但在应用程序加载时却不能像预期那样正常工作（虽然它能工作，但效果不太对）：

from random import random, randint

import kivy

kivy.require('1.8.0')

from kivy.config import Config

Config.set('graphics', 'fullscreen', '0')
Config.set('graphics', 'width', 640)
Config.set('graphics', 'height', 480)
Config.set('graphics', 'position', 'custom')
Config.set('graphics', 'top', 40)
Config.set('graphics', 'left', 40)

from kivy.app import App
from kivy.uix.layout import Layout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.graphics import Color, Line, Rectangle


class Main(BoxLayout):
    side_padding = 20

    def __init__(self, **kwargs):
        super(Main, self).__init__(**kwargs)
        self.size = (0, 0)  # Doesn't help.
        self.on_size()  # Doesn't help.

    def on_size(self, *args):
        left, middle, right = self.ids.left, self.ids.middle, self.ids.right
        left.width = max([x.texture_size[0] for x in left.children]) + self.side_padding
        right.width = max([x.texture_size[0] for x in right.children]) + self.side_padding
        available_space = self.width - left.width - right.width
        if available_space > self.height:
            middle.size = (self.height, self.height)
            extra = (self.width - self.height - left.width - right.width) // 2
            left.width += extra
            right.width += extra
        else:
            middle.size = (available_space, available_space)


class SidePanel(BoxLayout):
    def __init__(self, **kwargs):
        super(SidePanel, self).__init__(**kwargs)


class GameField(Layout):
    def __init__(self, **kwargs):
        super(GameField, self).__init__(**kwargs)
        self.array_size = randint(4, 8)
        self.bind(pos=self.update, size=self.update)
        self.update()

    def update(self, *args):
        s_padding = 1 / 16
        s_sq_size = 1 - 2 * s_padding
        self.canvas.clear()
        with self.canvas:
            block_size = self.width / self.array_size
            sq_size = block_size * s_sq_size
            padding = block_size * s_padding
            Color(1, 1, 1)
            for j in range(self.array_size):
                for i in range(self.array_size):
                    Rectangle(pos=(self.x + padding + i * block_size, self.y + padding + j * block_size),
                              size=(sq_size, sq_size))
            for i in range(self.array_size + 1):
                shift = self.width * i / self.array_size
                Line(points=(self.x, self.y + shift, self.x + self.width, self.y + shift))
                Line(points=(self.x + shift, self.y, self.x + shift, self.y + self.height))


    def on_touch_up(self, touch):
        self.array_size = randint(4, 8)
        self.update()


class Application(App):
    def build(self):
        return Main()


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

*.kv 文件：

#:kivy 1.8.0

<Main>:
    orientation: 'horizontal'
    canvas:
        Color:
            rgb: 1, 1, .9
        Rectangle:
            pos: self.pos
            size: self.size
    SidePanel:
        id: left
        Label:
            size_hint_y: None
            color: 0, 0, 0, 1
            text: 'Score'
        Label:
            color: 0, 0, 0, 1
            text: 'Event log log log loooooooooog'
        Label:
            color: 0, 0, 0, 1
            text: 'Event log log log\n123'
        Label:
            color: 0, 0, 0, 1
            text: '35mdbj65 qewr'
        Label:
            color: 0, 0, 0, 1
            text: '3qht6ju7ustju'
    GameField:
        id: middle
    SidePanel:
        id: right
        Button:
            size_hint_y: None
            text: 'Menu'
        Label:
            color: 0, 0, 0, 1
            text: 'Bonuses bonuses'
<SidePanel>:
    orientation: 'vertical'
    size_hint_x: None
    size: self.size

<GameField>:
    pos_hint: {'center_y': .5}
    size_hint: None, None
    canvas.before:
        Color:
            rgb: .9, .9, .9
        Rectangle:
            pos: self.pos
            size: self.size

可能哪里出错了？

Answer 1

我在更新我班级里孩子们的大小时，依据里面的标签和按钮，我给它们添加了一个 on_size 事件：

def on_size(self, *args):
    self.parent.parent.on_size()


class SideLabel(Label):
    on_size = on_size


class SideButton(Button):
    on_size = on_size

而且我还在这些类的 kv 文件中替换了按钮和标签。现在看起来一切都正常了。