在 kivy 中通过回调传递对象——链接对象的好主意？
passing objects through callbacks in kivy- a good idea for linking objects?
对于 voteapp 假设在它的 kv 文件中我定义了一个切换按钮：
....
...
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility(self) #<-----------
注意上面标记的行，将小部件作为参数传递给回调函数而不是注册 ObjectProperty() 并链接到它的 ID 有什么问题吗？当我稍后执行时，我收到一个 NoneType 对象返回的事件错误，例如出于某种原因按下按钮，所以我选择了前者。
编辑：我已经将导致 Nonetype 对象返回消息的错误代码放在末尾的回溯中。
执行以下代码时出现错误：
在 main.py 文件中：
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty
class Apibar(BoxLayout):
api_input_bar = ObjectProperty()
toggle_visibility_button = ObjectProperty()
#some code here not shown to keep minimal; only regular methods
def toggle_visibility(self):
#wanting to change the text inside the text input key
self.api_input_bar.text="your api key"
.kv 文件中的代码是：
<Apibar>:
BoxLayout:
orientation:"vertical"
padding: "5dp"
api_input_bar: api_input
toggle_visibility_button : toggle_visibility
BoxLayout:
orientation: "horizontal"
size_hint_y: 0.5
#some more rules for other widgets
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility()
#some more rules for other widgets
终端的回溯是：
File "main.py", line 43, in <module>
pictureapp().run()
File "/usr/lib/python3/dist-packages/kivy/app.py", line 828, in run
runTouchApp()
File "/usr/lib/python3/dist-packages/kivy/base.py", line 504, in runTouchApp
EventLoop.window.mainloop()
File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 663, in mainloop
self._mainloop()
File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 405, in _mainloop
EventLoop.idle()
File "/usr/lib/python3/dist-packages/kivy/base.py", line 342, in idle
self.dispatch_input()
File "/usr/lib/python3/dist-packages/kivy/base.py", line 327, in dispatch_input
post_dispatch_input(*pop(0))
File "/usr/lib/python3/dist-packages/kivy/base.py", line 233, in post_dispatch_input
listener.dispatch('on_motion', etype, me)
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/core/window/__init__.py", line 1188, in on_motion
self.dispatch('on_touch_down', me)
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/core/window/__init__.py", line 1204, in on_touch_down
if w.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 457, in on_touch_down
if child.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 457, in on_touch_down
if child.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 457, in on_touch_down
if child.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/behaviors/button.py", line 151, in on_touch_down
self.dispatch('on_press')
File "kivy/_event.pyx", line 714, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7681)
File "kivy/_event.pyx", line 1225, in kivy._event.EventObservers.dispatch (kivy/_event.c:13524)
File "kivy/_event.pyx", line 1109, in kivy._event.EventObservers._dispatch (kivy/_event.c:12356)
File "/usr/lib/python3/dist-packages/kivy/lang/builder.py", line 64, in custom_callback
exec(__kvlang__.co_value, idmap)
File "/home/xyzuser/project_folder/pythonprjs/pictureabarapp/picture.kv", line 37, in <module>
on_press: root.toggle_visibility()
File "main.py", line 35, in toggle_visibility
self.api_input_bar.text="your api key"
AttributeError: 'NoneType' object has no attribute 'text'
我完全按照提到的那样做了，但代码似乎不起作用。
问题是因为你在不合适的地方做赋值，api_input_bar属于Apibar，所以如果你想建立连接正确的地方在Apibar下面，因为它是它的范围：
<Apibar>:
# Apibar Scope
api_input_bar: api_input
toggle_visibility_button : toggle_visibility
BoxLayout:
# BoxLayout scope
orientation:"vertical"
padding: "5dp"
BoxLayout:
orientation: "horizontal"
size_hint_y: 0.5
#some more rules for other widgets
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility()
#some more rules for other widgets
在别处建立连接时，正在为 BoxLayout 创建一个新的 ObjectProperty。这可以使用以下示例进行检查：
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty
from kivy.lang.builder import Builder
class Apibar(BoxLayout):
api_input_bar = ObjectProperty()
toggle_visibility_button = ObjectProperty()
def toggle_visibility(self):
# self.ids.box.api_input_bar is different of self.api_input_bar
self.ids.box.api_input_bar.text="your api key"
Builder.load_string('''
<Apibar>:
BoxLayout:
id: box
orientation:"vertical"
padding: "5dp"
api_input_bar: api_input
toggle_visibility_button : toggle_visibility
BoxLayout:
orientation: "horizontal"
size_hint_y: 0.5
#some more rules for other widgets
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility()
#some more rules for other widgets
TextInput:
id: api_input
''')
class MyApp(App):
def build(self):
return Apibar()
if __name__ == '__main__':
MyApp().run()
对于 voteapp 假设在它的 kv 文件中我定义了一个切换按钮：
....
...
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility(self) #<-----------
注意上面标记的行，将小部件作为参数传递给回调函数而不是注册 ObjectProperty() 并链接到它的 ID 有什么问题吗？当我稍后执行时，我收到一个 NoneType 对象返回的事件错误，例如出于某种原因按下按钮，所以我选择了前者。
编辑：我已经将导致 Nonetype 对象返回消息的错误代码放在末尾的回溯中。
执行以下代码时出现错误：
在 main.py 文件中：
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty
class Apibar(BoxLayout):
api_input_bar = ObjectProperty()
toggle_visibility_button = ObjectProperty()
#some code here not shown to keep minimal; only regular methods
def toggle_visibility(self):
#wanting to change the text inside the text input key
self.api_input_bar.text="your api key"
.kv 文件中的代码是：
<Apibar>:
BoxLayout:
orientation:"vertical"
padding: "5dp"
api_input_bar: api_input
toggle_visibility_button : toggle_visibility
BoxLayout:
orientation: "horizontal"
size_hint_y: 0.5
#some more rules for other widgets
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility()
#some more rules for other widgets
终端的回溯是：
File "main.py", line 43, in <module>
pictureapp().run()
File "/usr/lib/python3/dist-packages/kivy/app.py", line 828, in run
runTouchApp()
File "/usr/lib/python3/dist-packages/kivy/base.py", line 504, in runTouchApp
EventLoop.window.mainloop()
File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 663, in mainloop
self._mainloop()
File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 405, in _mainloop
EventLoop.idle()
File "/usr/lib/python3/dist-packages/kivy/base.py", line 342, in idle
self.dispatch_input()
File "/usr/lib/python3/dist-packages/kivy/base.py", line 327, in dispatch_input
post_dispatch_input(*pop(0))
File "/usr/lib/python3/dist-packages/kivy/base.py", line 233, in post_dispatch_input
listener.dispatch('on_motion', etype, me)
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/core/window/__init__.py", line 1188, in on_motion
self.dispatch('on_touch_down', me)
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/core/window/__init__.py", line 1204, in on_touch_down
if w.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 457, in on_touch_down
if child.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 457, in on_touch_down
if child.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/widget.py", line 457, in on_touch_down
if child.dispatch('on_touch_down', touch):
File "kivy/_event.pyx", line 718, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7726)
File "/usr/lib/python3/dist-packages/kivy/uix/behaviors/button.py", line 151, in on_touch_down
self.dispatch('on_press')
File "kivy/_event.pyx", line 714, in kivy._event.EventDispatcher.dispatch (kivy/_event.c:7681)
File "kivy/_event.pyx", line 1225, in kivy._event.EventObservers.dispatch (kivy/_event.c:13524)
File "kivy/_event.pyx", line 1109, in kivy._event.EventObservers._dispatch (kivy/_event.c:12356)
File "/usr/lib/python3/dist-packages/kivy/lang/builder.py", line 64, in custom_callback
exec(__kvlang__.co_value, idmap)
File "/home/xyzuser/project_folder/pythonprjs/pictureabarapp/picture.kv", line 37, in <module>
on_press: root.toggle_visibility()
File "main.py", line 35, in toggle_visibility
self.api_input_bar.text="your api key"
AttributeError: 'NoneType' object has no attribute 'text'
我完全按照提到的那样做了，但代码似乎不起作用。
问题是因为你在不合适的地方做赋值，api_input_bar属于Apibar，所以如果你想建立连接正确的地方在Apibar下面，因为它是它的范围：
<Apibar>:
# Apibar Scope
api_input_bar: api_input
toggle_visibility_button : toggle_visibility
BoxLayout:
# BoxLayout scope
orientation:"vertical"
padding: "5dp"
BoxLayout:
orientation: "horizontal"
size_hint_y: 0.5
#some more rules for other widgets
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility()
#some more rules for other widgets
在别处建立连接时，正在为 BoxLayout 创建一个新的 ObjectProperty。这可以使用以下示例进行检查：
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.properties import ObjectProperty
from kivy.lang.builder import Builder
class Apibar(BoxLayout):
api_input_bar = ObjectProperty()
toggle_visibility_button = ObjectProperty()
def toggle_visibility(self):
# self.ids.box.api_input_bar is different of self.api_input_bar
self.ids.box.api_input_bar.text="your api key"
Builder.load_string('''
<Apibar>:
BoxLayout:
id: box
orientation:"vertical"
padding: "5dp"
api_input_bar: api_input
toggle_visibility_button : toggle_visibility
BoxLayout:
orientation: "horizontal"
size_hint_y: 0.5
#some more rules for other widgets
ToggleButton:
id: toggle_visibility
size_hint_x: 0.27
text: "Hide"
on_press: root.toggle_visibility()
#some more rules for other widgets
TextInput:
id: api_input
''')
class MyApp(App):
def build(self):
return Apibar()
if __name__ == '__main__':
MyApp().run()