"""
Components/Transition
=====================
.. rubric::
A set of classes for implementing transitions between application screens.
.. versionadded:: 1.0.0
Changing transitions
--------------------
You have multiple transitions available by default, such as:
- :class:`MDFadeSlideTransition`
state one: the new screen closes the previous screen by lifting from the
bottom of the screen and changing from transparent to non-transparent;
state two: the current screen goes down to the bottom of the screen,
passing from a non-transparent state to a transparent one, thus opening the
previous screen;
.. note::
You cannot control the direction of a slide using the direction attribute.
.. image:: https://github.com/HeaTTheatR/KivyMD-data/raw/master/gallery/kivymddoc/transition-md-fade-slide-transition.gif
:align: center
"""
__all__ = (
"MDFadeSlideTransition",
"MDSlideTransition",
"MDSwapTransition",
"MDTransitionBase",
)
from kivy import Logger
from kivy.animation import Animation, AnimationTransition
from kivy.properties import DictProperty
from kivy.uix.screenmanager import (
ScreenManagerException,
SlideTransition,
SwapTransition,
TransitionBase,
)
from kivymd.uix.hero import MDHeroFrom, MDHeroTo
from kivymd.uix.screenmanager import MDScreenManager
class MDTransitionBase(TransitionBase):
"""
TransitionBase is used to animate 2 screens within the
:class:`~kivymd.uix.screenmanager.MDScreenManager`.
For more
information, see in the :class:`~kivy.uix.screenmanager.TransitionBase`
class documentation.
"""
_direction = "in"
# Collection of child widgets of all 'MDHeroFrom' widgets that are
# on the screen, for example:
#
# MDScreen:
#
# MDHeroFrom:
# tag: "kivymd"
#
# FitImage:
#
# MDHeroFrom:
# tag: "kivy"
#
# FitImage:
#
# {
# 'kivy': <kivymd.uix.fitimage.fitimage.FitImage object>,
# 'kivymd': <kivymd.uix.fitimage.fitimage.FitImage object>,
# }
_hero_from_widget_children = DictProperty()
def start(self, instance_screen_manager: MDScreenManager) -> None:
super().start(instance_screen_manager)
{"in": self.animated_hero_in, "out": self.animated_hero_out}[
self._direction
]()
def animated_hero_in(self) -> None:
"""Animates the flight of heroes from screen **A** to screen **B**."""
if self.manager._heroes_data and self.manager.current_heroes:
for hero_from_widget in self.manager.get_hero_from_widget():
for heroes_tag in self.manager.current_heroes:
if heroes_tag == hero_from_widget.tag:
self._check_widget_properties(hero_from_widget)
# Get child widget of the 'MDHeroFrom' container.
hero_widget = hero_from_widget.children[0]
self._hero_from_widget_children[
hero_from_widget.tag
] = hero_widget
# Removing the child widget from the 'MDHeroFrom'
# container.
hero_from_widget.remove_widget(hero_widget)
# We set the size, position of the child widget of the
# 'MDHeroFrom' container and add this widget to the
# root window.
hero_widget.pos = self.screen_out.to_widget(
*hero_from_widget.to_window(*hero_from_widget.pos)
)
hero_widget.size = hero_from_widget.size
self.manager.get_root_window().add_widget(hero_widget)
# Animating widgets added to the root window.
if self.screen_in.heroes_to:
for hero_to_widget in self.screen_in.heroes_to:
self._check_hero_to_widget_tag(
hero_to_widget, hero_from_widget
)
if hero_to_widget.tag == heroes_tag:
Animation(
size=hero_to_widget.size,
d=self.duration,
pos=hero_to_widget.pos,
).start(hero_widget)
hero_from_widget.dispatch(
"on_transform_in",
hero_widget,
self.duration,
)
def animated_hero_out(self) -> None:
"""Animates the flight of heroes from screen **B** to screen **A**."""
if (
self.manager._heroes_data
and self.manager.current_heroes
and self.screen_out.heroes_to
):
for heroes_tag in self.manager.current_heroes:
for hero_to_widget in self.screen_out.heroes_to:
if hero_to_widget.tag == heroes_tag:
hero_from_children = self._hero_from_widget_children[
heroes_tag
]
hero_to_widget.remove_widget(hero_from_children)
self.manager.get_root_window().add_widget(
hero_from_children
)
for (
hero_from_widget
) in self.manager.get_hero_from_widget():
hero_from_widget.dispatch(
"on_transform_out",
self._hero_from_widget_children[
hero_from_widget.tag
],
self.duration,
)
Animation(
pos=self.screen_in.to_widget(
*hero_from_widget.to_window(
*hero_from_widget.pos
)
),
size=hero_from_widget.size,
d=self.duration,
).start(
self._hero_from_widget_children[
hero_from_widget.tag
]
)
def on_complete(self) -> None:
"""
Override method.
See :attr:`kivy.uix.screenmanager.TransitionBase.on_complete'.
"""
super().on_complete()
if self.manager._heroes_data and self.manager.current_heroes:
for hero_from_widget in self.manager.get_hero_from_widget():
for heroes_tag in self.manager.current_heroes:
if heroes_tag == hero_from_widget.tag:
hero_from_children = self._hero_from_widget_children[
heroes_tag
]
self.manager.get_root_window().remove_widget(
hero_from_children
)
# Adding a child widget from the 'MDHeraFrom' container
# to the 'MDHeroTo' container.
if self._direction == "in":
for hero_to_widget in self.screen_in.heroes_to:
if hero_to_widget.tag == heroes_tag:
hero_to_widget.add_widget(
hero_from_children
)
# Restores the child widget for the 'MDHeraFrom'
# container.
elif self._direction == "out":
hero_from_widget.add_widget(hero_from_children)
if self._direction == "out":
self._direction = "in"
else:
self._direction = "out"
# Checks the attributes for the 'self.screen_in' screen.
# Called from the animated_hero_in method.
def _check_widget_properties(self, hero_from_widget: MDHeroFrom):
if not self.screen_in.heroes_to:
raise Exception(
f"The `heroes_to` attribute is not specified for screen "
f"{self.screen_in}"
)
# The 'MDHeroFrom' widget allows you to place only one widget in
# itself.
if len(hero_from_widget.children) > 1:
raise Exception(
f"{hero_from_widget.__class__} accept only one widget"
)
# For new API support.
def _check_hero_to_widget_tag(
self, hero_to_widget: MDHeroTo, hero_from_widget: MDHeroFrom
) -> None:
if not hero_to_widget.tag:
Logger.warning(
"KivyMD: "
f"Set the tag '{hero_from_widget.tag}' "
f"for the {hero_to_widget} widget to the same "
f"as for the {hero_from_widget} widget"
)
hero_to_widget.tag = hero_from_widget.tag
class MDSwapTransition(SwapTransition, MDTransitionBase):
pass
class MDSlideTransition(SlideTransition, MDTransitionBase):
pass
class MDFadeSlideTransition(MDSlideTransition):
def start(self, instance_screen_manager: MDScreenManager) -> None:
if self.is_active:
raise ScreenManagerException("start() is called twice!")
self.manager = instance_screen_manager
self._anim = Animation(d=self.duration, s=0)
self._anim.bind(
on_progress=self._on_progress, on_complete=self._on_complete
)
if self._direction == "in":
self.add_screen(self.screen_in)
self.animated_hero_in()
else:
self.animated_hero_out()
self.add_screen(self.screen_in)
self.add_screen(self.screen_out)
self.screen_in.transition_progress = 0.0
self.screen_in.transition_state = "in"
self.screen_out.transition_progress = 0.0
self.screen_out.transition_state = "out"
self.screen_in.dispatch("on_pre_enter")
self.screen_out.dispatch("on_pre_leave")
self.is_active = True
self._anim.start(self)
self.dispatch("on_progress", 0)
if self._direction == "in":
self.screen_in.y = 0
self.screen_in.opacity = 0
def on_progress(self, progression: float) -> None:
progression = AnimationTransition.out_quad(progression)
if self._direction == "in":
self.screen_in.y = (
self.manager.y + self.manager.height * progression
) - self.screen_in.height
self.screen_in.opacity = progression
if self._direction == "out":
self.screen_out.y = (
self.manager.y - self.manager.height * progression
)
self.screen_out.opacity = 1 - progression