在Kivy中如何通过函数实现向新Screen的过渡？

Question

我想在点击按钮后实现到新屏幕的转换，我想通过函数来实现。我有这个kv代码

<ScreenFrame@BoxLayout>:
    orientation: 'vertical'
    cols: 3

    ActionBar:
        ActionView:
            pos_hint: {'top':1}
            use_separator: True
            ActionPrevious:
                title: "Title"
                with_previous: False
            ActionButton:
                text: "+"


    Label:
        text: "Content"


    BoxLayout:
        orientation: 'horizontal'
        cols: 4
        size_hint: 1, 0.15

        Button:
            text: "Notes"
            #don't work
            on_press: root.manager.current = 'nts'
        Button:
            text: "Docs"
            #don't work
            on_release: root.go_to_dcs()

        Button:
            text: "Videos"
            #don't work
            on_release: root.manager.current = "vds"
        Button:
            text: "Pictures"
            # don't work
            on_release: root.manager.current = 'pctrs'

<NtsScreen>:
    BoxLayout:
        orientation: "vertical"
        cols: 2

        ScreenFrame:
        Button:
            text: "f"
            #work, but me need implementaion through function
            on_press: root.manager.current = "vds"

<DocsScreen>:
    ScreenFrame:

<VdsScreen>:
    ScreenFrame:

<PctrsScreen>:
    ScreenFrame:

和这个文件

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.widget import Widget
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder
from kivy.uix.button import Button
from kivy.properties import StringProperty
from kivy.uix.widget import Widget


Builder.load_file("main.kv")

class ScreenFrame():
    def go_to_dcs(self):
        sm.current = "dcs"

class NtsScreen(Screen):
    pass

class DcsScreen(Screen):
    def go_to_dcs(self):
        sm.current = 'dcs'

class VdsScreen(Screen):
    pass

class PctrsScreen(Screen):
    pass


# Create the screen manager
sm = ScreenManager()
sm.add_widget(NtsScreen(name='nts'))
sm.add_widget(DcsScreen(name='dcs'))
sm.add_widget(VdsScreen(name='vds'))
sm.add_widget(PctrsScreen(name='pctrs'))


class MainApp(App):
    def build(self):
        return sm

if __name__ == "__main__":
    MainApp().run()

，但是当我运行并按下 Docs 按钮时，出现此错误

 Traceback (most recent call last):
   File "main.py", line 45, in <module>
     MainApp().run()
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/app.py", line 826, in run
     runTouchApp()
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/base.py", line 502, in runTouchApp
     EventLoop.window.mainloop()
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/core/window/window_pygame.py", line 403, in mainloop
     self._mainloop()
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/core/window/window_pygame.py", line 289, in _mainloop
     EventLoop.idle()
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/base.py", line 340, in idle
     self.dispatch_input()
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/base.py", line 325, in dispatch_input
     post_dispatch_input(*pop(0))
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/base.py", line 291, in post_dispatch_input
     wid.dispatch('on_touch_up', me)
   File "kivy/_event.pyx", line 707, in kivy._event.EventDispatcher.dispatch
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/uix/behaviors/button.py", line 179, in on_touch_up
     self.dispatch('on_release')
   File "kivy/_event.pyx", line 703, in kivy._event.EventDispatcher.dispatch
   File "kivy/_event.pyx", line 1214, in kivy._event.EventObservers.dispatch
   File "kivy/_event.pyx", line 1098, in kivy._event.EventObservers._dispatch
   File "/home/parvektor228/TAOKF/lib/python3.6/site-packages/kivy/lang/builder.py", line 64, in custom_callback
     exec(__kvlang__.co_value, idmap)
   File "/home/parvektor228/TAOKF/KivyApp/memfier/main.kv", line 32, in <module>
     on_release: root.go_to_dcs()
   File "kivy/weakproxy.pyx", line 30, in kivy.weakproxy.WeakProxy.__getattr__
 AttributeError: 'ScreenFrame' object has no attribute 'go_to_dcs'

哪里出错了或者我有什么不懂的地方？

更多细节，以便错误通知消失。更多细节，以便错误通知消失。更多详细信息，以便错误通知消失。

Answer 1

出现您的问题是因为 ScreenFrame 是 BoxLayout（根据您的 kv 文件），而不是 Screen。因此，您调用的 root（在本例中为 ScreenFrame）没有关联的 manager。 manager 与 Screen 本身相关联。

您必须引用 ScreenFrame 小部件的父级小部件才能引用当前 Screen，并且它是关联的 manager。为清楚起见，我建议按如下方式重组您的 Python 代码和 kv 文件：

Python代码：

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder
from kivy.uix.button import Button
from kivy.uix.widget import Widget

Builder.load_file("testthis.kv")

class ScreenFrame(BoxLayout):

    def go_to_screen(self, val):
        self.parent.manager.current = val

class NtsScreen(Screen):
    pass

class DcsScreen(Screen):
    pass

class VdsScreen(Screen):
    pass

class PctrsScreen(Screen):
    pass

class MyScreenManager(ScreenManager):
    pass

class MainApp(App):

    def build(self):
        self.sm = MyScreenManager()
        return self.sm

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

kv 文件：

<MyScreenManager>:
    NtsScreen:
        name: 'nts'
    DcsScreen:
        name: 'dcs'
    VdsScreen:
        name: 'vds'
    PctrsScreen:
        name: 'pctrs'

<NtsScreen>:
    ScreenFrame:

<DocsScreen>:
    ScreenFrame:

<VdsScreen>:
    ScreenFrame:

<PctrsScreen>:
    ScreenFrame:

<ScreenFrame>:

    orientation: 'vertical'
    rows: 3

    ActionBar:
        ActionView:
            pos_hint: {'top':1}
            use_separator: True
            ActionPrevious:
                title: "Title"
                with_previous: False
            ActionButton:
                text: "+"

    Label:
        text: "Content"

    BoxLayout:
        orientation: 'horizontal'
        cols: 4
        size_hint: 1, 0.15

        Button:
            text: "Notes"
            on_press: root.go_to_screen('nts')
        Button:
            text: "Docs"
            on_release: root.go_to_screen('dcs')
        Button:
            text: "Videos"
            on_release: root.go_to_screen('vds')
        Button:
            text: "Pictures"
            on_release: root.go_to_screen('pctrs')

Answer 2

问题 - 属性错误

有两个AttributeErrors，它们如下：

AttributeError: go_to_dcs() 方法

     on_release: root.go_to_dcs()
   File "kivy/weakproxy.pyx", line 30, in kivy.weakproxy.WeakProxy.__getattr__
 AttributeError: 'ScreenFrame' object has no attribute 'go_to_dcs'

在 kv 文件中，定义了 dynamic class、<ScreenFrame@BoxLayout>:，但没有实现 go_to_dcs() 方法。

属性错误：经理

     on_press: root.manager.current = 'nts'
   File "kivy/weakproxy.pyx", line 30, in kivy.weakproxy.WeakProxy.__getattr__
 AttributeError: 'ScreenFrame' object has no attribute 'manager'

动态 class、<ScreenFrame@BoxLayout>: 具有 BoxLayout 继承，但没有 Screen 继承。因此，它没有属性调用，manager.

解决方案

kv 文件

将动态 class、<ScreenFrame@BoxLayout>: 替换为 class 规则、<ScreenFrame>:
在 class 规则中，<ScreenFrame>: - 将 root.manager.current 替换为 app.root.current

片段

<ScreenFrame>:

        Button:
            text: "Notes"
            on_press: app.root.current = 'nts'
        Button:
            text: "Docs"
            on_release: root.go_to_dcs()    
        Button:
            text: "Videos"
            on_press: app.root.current = 'vds'
        Button:
            text: "Pictures"
            on_press: app.root.current = 'pctrs'

Kv language » Three Keywords

There are three keywords specific to Kv language:

app: always refers to the instance of your application.

root: refers to the base widget/template in the current rule

self: always refer to the current widget

Python代码

添加导入语句，from kivy.uix.boxlayout import BoxLayout
将class ScreenFrame():替换为class ScreenFrame(BoxLayout):

示例

main.py

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder


Builder.load_file("main.kv")


class ScreenFrame(BoxLayout):
    def go_to_dcs(self):
        print("\nScreenFrame.go_to_dcs")
        sm.current = "dcs"


class NtsScreen(Screen):
    pass


class DcsScreen(Screen):
    def go_to_dcs(self):
        sm.current = 'dcs'


class VdsScreen(Screen):
    pass


class PctrsScreen(Screen):
    pass


# Create the screen manager
sm = ScreenManager()
sm.add_widget(NtsScreen(name='nts'))
sm.add_widget(DcsScreen(name='dcs'))
sm.add_widget(VdsScreen(name='vds'))
sm.add_widget(PctrsScreen(name='pctrs'))


class MainApp(App):
    def build(self):
        return sm


if __name__ == "__main__":
    MainApp().run()

main.kv

#:kivy 1.11.0

<ScreenFrame>:
    orientation: 'vertical'
    cols: 3

    ActionBar:
        ActionView:
            pos_hint: {'top':1}
            use_separator: True
            ActionPrevious:
                title: "Title"
                with_previous: False
            ActionButton:
                text: "+"


    Label:
        text: "Content"


    BoxLayout:
        orientation: 'horizontal'
        cols: 4
        size_hint: 1, 0.15

        Button:
            text: "Notes"
            on_press: app.root.current = 'nts'

        Button:
            text: "Docs"
            on_release: root.go_to_dcs()

        Button:
            text: "Videos"
            on_press: app.root.current = 'vds'

        Button:
            text: "Pictures"
            on_press: app.root.current = 'pctrs'

<NtsScreen>:
    BoxLayout:
        orientation: "vertical"
        cols: 2

        ScreenFrame:
        Button:
            text: "f"
            #work, but me need implementaion through function
            on_press: root.manager.current = "vds"

<DcsScreen>:
    ScreenFrame:

<VdsScreen>:
    ScreenFrame:

<PctrsScreen>:
    ScreenFrame:

在Kivy中如何通过函数实现向新Screen的过渡？

How in Kivy to implement the transition to a new Screen through the function?

python

python-3.x

kivy

kivy-language