Kivy屏幕未加载

Question

我正在尝试用Kivy创建一个简单的屏幕。

下面是我的代码:

class invoice_screen(Screen):
def __init__(self, **kwargs):
super(invoice_screen, self).__init__(**kwargs)
self._window = BoxLayout(orientation='vertical')
self._window.add_widget(Label(text="something or another"))
scroll = ScrollView()
box = BoxLayout(orientation='vertical')
top_row = BoxLayout(orientation='horizontal')
top_row.add_widget(
Label(
text="item",
size_hint=(.8, 1)    
)
)
top_row.add_widget(
Label(
text="quantity",
size_hint=(.2, 1)    
)
)
box.add_widget(bot_row)
scroll.add_widget(box)
self._window.add_widget(scroll)
buttons = BoxLayout(orientation='horizontal')
button1 = Button(text="Complete!")
button1.bind(on_release=self.forward)
button2 = Button(text="Go Back")
button2.bind(on_release=self.back)
buttons.add_widget(button1, button2)
self._window.add_widget(buttons)

def back(self):
pass
def forward(self):
Popup(
title="Completed",
content=Label(text="You can close this NOW!"),
size=(400,400)
) 
class app(App):
def build(self):
mane_chan = ScreenManager()
mane_chan.add_widget(invoice_screen(name="invoice"))
mane_chan.current = "invoice"
return mane_chan
if __name__ == "__main__":
app().run()

但是当我运行它时，只有Kivy窗口显示出来。这里没有我在Screen中包含的任何元素。甚至没有错误。

我不知道我哪里做错了。

Answer 1

您将所有部件添加到self._window(BoxLayout)，但您忘记将此self._window添加到screen(self)

self.add_widget(self._window)

。

---

完整的工作代码和其他小的修复-参见代码

中的注释

# https://kivy.org/doc/stable/guide/basic.html
#import kivy
from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.uix.screenmanager import ScreenManager, Screen

from kivy.uix.boxlayout import BoxLayout
from kivy.uix.scrollview import ScrollView
from kivy.uix.popup import Popup
class InvoiceScreen(Screen):

def __init__(self, **kwargs):
super().__init__(**kwargs)
self._window = BoxLayout(orientation='vertical')
self.add_widget(self._window)  # <--- need to add `boxlayout` to `screen`
self._window.add_widget(Label(text="something or another"))
scroll = ScrollView()

box = BoxLayout(orientation='vertical')

top_row = BoxLayout(orientation='horizontal')
top_row.add_widget(
Label(
text="item",
size_hint=(.8, 1)    
)
)
top_row.add_widget(
Label(
text="quantity",
size_hint=(.2, 1)    
)
)
box.add_widget(top_row)   # <-- it has to be `top_row` instead of `bot_row`

scroll.add_widget(box)
self._window.add_widget(scroll)
buttons = BoxLayout(orientation='horizontal')

button1 = Button(text="Complete!")
button1.bind(on_release=self.forward)

button2 = Button(text="Go Back")
button2.bind(on_release=self.back)

#buttons.add_widget(button1, button2)  # <-- wrong
buttons.add_widget(button1)  # <-- it has to add only one widget
buttons.add_widget(button2)  # <-- it has to add only one widget

self._window.add_widget(buttons)

def back(self, event):
pass
def forward(self, event):
Popup(
title="Completed",
content=Label(text="You can close this NOW!"),
size=(400,400)
).open()   # <-- forgot `.open()`
class app(App):
def build(self):
mane_chan = ScreenManager()
mane_chan.add_widget(InvoiceScreen(name="invoice"))
mane_chan.current = "invoice"
return mane_chan
if __name__ == "__main__":
app().run()