On Hover for Kivy ActionBar ActionButton

问题

According to This Github File, I was trying to create a hover for an action button in python 3.7.5 windows 10 platform. This is what i tried:

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.base import runTouchApp
from kivy.lang import Builder
from kivy.uix.label import Label
from kivy.core.window import Window
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.actionbar import *
from kivy.properties import ObjectProperty
from kivy.properties import BooleanProperty
class HoverBehavior(object):

    hovered = BooleanProperty(False)
    border_point= ObjectProperty(None)
    def __init__(self, **kwargs):
        self.register_event_type('on_enter')
        self.register_event_type('on_leave')
        Window.bind(mouse_pos=self.on_mouse_pos)
        super(HoverBehavior, self).__init__(**kwargs)

    def on_mouse_pos(self, *args):
        if not self.get_root_window():
            return # do proceed if I'm not displayed <=> If have no parent
        pos = args[1]
        #Next line to_widget allow to compensate for relative layout
        inside = self.collide_point(*self.to_widget(*pos))
        if self.hovered == inside:
            #We have already done what was needed
            return
        self.border_point = pos
        self.hovered = inside
        if inside:
            self.dispatch('on_enter')
        else:
            self.dispatch('on_leave')

    def on_enter(self):
        pass

    def on_leave(self):
        pass
from kivy.factory import Factory
Factory.register('HoverBehavior', HoverBehavior)
Builder.load_string("""
<TitleBar>:
    ActionBar:
        pos_hint: {'top':1}
        width: 50
        color: [ 1, 1, 1, 1]
        ActionView:
            use_separator: True
            ActionPrevious:
                title: 'Hello'
                with_previous: False
                color: [ 0, 0, 0, 1]
            ActionOverflow:
            ActionButton:
                icon: 'icons/app_close_init.png' if self.hovered else "icons/app_close_hover.png"
                on_press: app.closing()
            ActionButton:
                important: True
                text: 'Important'
                color: [ 0, 0, 0, 1]
            ActionButton:
                text: 'Btn2'
            ActionButton:
                text: 'Btn3'
            ActionButton:
                text: 'Btn4'
""")
class TitleBar(FloatLayout):
    pass

class TetraApp(App):

    def build(self):
        Window.size=(875,575)
        Window.clearcolor = (1, 1, 1, 1)
        Window.borderless=True
        return TitleBar()
    def on_press_button(self):
        return self.root.add_widget(Label(text='Hello'))
    def closing(self):
        app.stop()
if __name__=='__main__':
    app=TetraApp()
    app.run()

The Error says that Action Button has no attribute hovered but I have defined the HoverBehaviour class. What have I done Wrong? The action button is meant to change the icon image from one to another when the mouse hovers on it.
EDITED
Also tried:

class HoverBehavior(object):
    def __init__(self, **kwargs):
        self.hovered = BooleanProperty(False)
        self.border_point= ObjectProperty(None)
        self.register_event_type('on_enter')
        self.register_event_type('on_leave')
        Window.bind(mouse_pos=self.on_mouse_pos)
        super(HoverBehavior, self).__init__(**kwargs)

    def on_mouse_pos(self, *args):
        if not self.get_root_window():

But that too shows the Attribute Error.

回答1:

You have defined your HoverBehavior, but you haven't actually used it, so the ActionButton knows nothing about HoverBehavior. To use it, define your own custom ActionButton like:

class MyActionButton(HoverBehavior, ActionButton):
    pass

Then, in your kv file, replace ActionButton with MyActionButton:

        MyActionButton:
            icon: 'icons/app_close_init.png' if self.hovered else "icons/app_close_hover.png"
            on_press: app.closing()

来源：https://stackoverflow.com/questions/60985374/on-hover-for-kivy-actionbar-actionbutton