python - 为什么运行 py 和 kv 脚本时出现空白屏幕？

Question

当我启动该程序时，它给我一个空白的黑屏。我使用 python 文件来实现功能，使用 kv 文件来实现对象的属性。py文件:

import kivy
kivy.require('1.9.0')

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout


class FloatLayoutApp(App):   

    def build(self):
        return FloatLayout()

FlApp = FloatLayoutApp()
FlApp.run()

kv 文件:

<CustButton@Button>:
    font_size: 32
    color: 0, 0, 0, 1
    size: 150, 50
    background_normal: ""
    background_down: "bg-grey.jpg"
    background_color: .88, .88, .88, 1
    size_hint: .4, .3

<FloatLayout>:
    CustButton:
        text: "Top Left"
        pos_hint: {"x": 0, "top": 0}
    CustButton:
        text: "Bottom Left"
        pos_hint: {"right": 1, "y": 0}
    CustButton:
        text: "Top Right"
        pos_hint: {"right": 1, "top": 1}
    CustButton:
        text: "Bottom Left"
        pos_hint: {"left": 1, "bottom": 0}
    CustButton:
        text: "Center"
        pos_hint: {"center_x": 0, "center_y": 0}

Answer 1

您遇到黑屏/空白屏幕，因为在构建方法中它返回一个 FloatLayout 小部件作为根，并且没有任何小部件添加到根。

Kv language » How to load KV

There are two ways to load Kv code into your application:

By name convention:

Kivy looks for a Kv file with the same name as your App class in lowercase, minus “App” if it ends with ‘App’ e.g:

MyApp -> my.kv

If this file defines a Root Widget it will be attached to the App’s root attribute and used as the base of the application widget tree.

By Builder: You can tell Kivy to directly load a string or a file. If this string or file defines a root widget, it will be returned by the method:

Builder.load_file('path/to/file.kv')

or:

Builder.load_string(kv_string)

解决方案

这个问题有几种解决方案。

方法1

将您的 kv 文件重命名为 floatlayout.kv

方法2

kv 文件

替换类规则，<FloatLayout>:具有根规则，FloatLayout:

Python 脚本

1. 添加导入语句，from kivy.lang import Builder
2. 替换return FloatLayout()与 return Builder.load_file('kv-filename.kv')

输出