为什么根小部件的窗口大小不同？

Question

我正在尝试使用带有a的自定义小部件GridLayout,但结果始终是角落中的一个非常小的网格,而不是整个窗口中的网格扩展.

示例代码:

import kivy
kivy.require('1.5.1')

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.widget import Widget
from kivy.uix.gridlayout import GridLayout



class MyWidget(Widget):
    def __init__(self):
        super(MyWidget, self).__init__()

        grid_layout = GridLayout(cols=3)
        grid_layout.add_widget(Button(text='A'))
        grid_layout.add_widget(Button(text='B'))
        grid_layout.add_widget(Label(text='text'))
        grid_layout.add_widget(Label(text='other'))
        grid_layout.add_widget(Button(text='text'))
        self.add_widget(grid_layout)


class MyApp(App):
    def build(self):
        float = 
        return MyWidget()


MyApp().run()

因为它Widget的默认值size_hint是(1,1)它应该在整个窗口中展开,而且GridLayout也是.为什么这不会发生？我怎样才能获得我想要的结果？

Answer 1

`class MyWidget(Widget):`

你的根小部件是MyWidget从一个继承Widget,而不是从布局之一,因此不控制它的孩子的尺寸如前所述这里,"该size_hint是使用值的元组的布局来管理他们的孩子的大小".

您的根小部件确实占用了窗口的整个空间.您可以通过向画布中添加一个Rectangle来测试这个,MyWidget例如::

with self.canvas.before:
    Color(1,0,0,1)
    Rectangle(pos=self.pos, size=self.size)

你应该熟悉canvas,canvas.before和canvas.after.它们基本上是指令组,前面的组是在窗口小部件的画布指令之前和之后的组之后绘制的.

Kivy的一个关键不同之处在于小部件的大小调整/布局会延迟到下一帧,所以如果你只是将上面的代码片段添加到你的代码中,那么::

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.widget import Widget
from kivy.uix.gridlayout import GridLayout
from kivy.graphics import *


class MyWidget(Widget):

    def __init__(self, **kwargs):
        # I'd make sure to pass of kwargs through to the super
        # as there are widgets's that process their initial
        # arguments through.
        super(MyWidget, self).__init__(**kwargs)

        grid_layout = GridLayout(cols=3)
        grid_layout.add_widget(Button(text='A'))
        grid_layout.add_widget(Button(text='B'))
        grid_layout.add_widget(Label(text='text'))
        grid_layout.add_widget(Label(text='other'))
        grid_layout.add_widget(Button(text='text'))
        self.add_widget(grid_layout)
        with self.canvas.before:
            Color(1,0,0,1)
            Rectangle(pos=self.pos, size=self.size)


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

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

这只会在窗口小部件的初始位置和大小处显示一个红色矩形,此时它的默认位置和大小分别为(0,0)和(100,100).

为了使红色rect符合小部件的大小,我们应该将它的大小绑定到小部件的大小,就像这样::

...
        grid_layout.add_widget(Button(text='text'))
        self.add_widget(grid_layout)
        with self.canvas.before:
            Color(1,0,0,1)
            self.rect = Rectangle(pos=self.pos, size=self.size)
        self.bind(size=self.update_rect)

    def update_rect(self, instance, value):
        self.rect.pos = self.pos
        self.rect.size = self.size

class MyApp(App):
    def build(self):
...

由于上面代码的输出将显示,您的小部件占用了整个窗口的大小.但是,这并不能解决您的问题,并且子布局仍然保留在原始位置和原始大小.这是因为如上所述,小部件不能控制其子节点的大小.

这里有两个选择,要么更新窗口小部件子项的大小和位置,就像更新rect一样(很快会让多个孩子感到复杂),或者使用其中一个布局作为根窗口小部件.

这也可以用kv这样完成::

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.lang import Builder

Builder.load_string('''
# this is the rule for MyWidget that defines
# what MyWidget looks like i.e.drawing
# instructions and widgets etc 
<MyWidget>:
    canvas.before:
        Color:
            rgba: 1, 0, 0, 1
        Rectangle:
            # this implicitly binds the size of the
            # rect to the size of the widget
            size: self.size
            # self here still refers to the widget as Rectangle is only a
            # graphics instruction and not a widget
            pos: self.pos
    GridLayout:
        cols: 3
        # root here refers to the `MyWidget`, bind the size of the
        # GridLayout to the size of your root widget
        size: root.size
        Button:
            text: 'A'
        Button:
            text: 'B'
        Label:
            text: 'text'
        Label:
            text: 'other'
        Button:
            text: 'text'        
''')


class MyWidget(Widget):
    pass


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

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

上面的示例将子项的大小绑定到它的父窗口小部件的大小.我仍然建议使用布局作为根窗口小部件,并且不要犹豫是否嵌套布局.