"""
Components/Hero
===============
.. versionadded:: 1.0.0
.. rubric:: Use the :class:`~MDHeroFrom` widget to animate a widget from one
screen to the next.
- The hero refers to the widget that flies between screens.
- Create a hero animation using KivyMD’s :class:`~MDHeroFrom` widget.
- Fly the hero from one screen to another.
- Animate the transformation of a hero’s shape from circular to rectangular while flying it from one screen to another.
- The :class:`~MDHeroFrom` widget in KivyMD implements a style of animation commonly known as shared element transitions or shared element animations.
.. raw:: html
The widget that will move from screen A to screen B will be a hero. To move
a widget from one screen to another using hero animation, you need to do the
following:
- On screen **A**, place the :class:`~MDHeroFrom` container.
- Sets a tag (string) for the :class:`~MDHeroFrom` container.
- Place a hero in the :class:`~MDHeroFrom` container.
- On screen **B**, place the :class:`~MDHeroTo` container - our hero from screen **A **will fly into this container.
.. image:: https://github.com/HeaTTheatR/KivyMD-data/raw/master/gallery/kivymddoc/hero-base.png
:align: center
.. warning::
:class:`~MDHeroFrom` container cannot have more than one child widget.
Base example
------------
.. code-block:: python
from kivy.lang import Builder
from kivymd.app import MDApp
KV = '''
MDScreenManager:
MDScreen:
name: "screen A"
md_bg_color: "lightblue"
MDHeroFrom:
id: hero_from
tag: "hero"
size_hint: None, None
size: "120dp", "120dp"
pos_hint: {"top": .98}
x: 24
FitImage:
source: "https://github.com/kivymd/internal/raw/main/logo/kivymd_logo_blue.png"
size_hint: None, None
size: hero_from.size
MDRaisedButton:
text: "Move Hero To Screen B"
pos_hint: {"center_x": .5}
y: "36dp"
on_release:
root.current_hero = "hero"
root.current = "screen B"
MDScreen:
name: "screen B"
hero_to: hero_to
md_bg_color: "cadetblue"
MDHeroTo:
id: hero_to
size_hint: None, None
size: "220dp", "220dp"
pos_hint: {"center_x": .5, "center_y": .5}
MDRaisedButton:
text: "Move Hero To Screen A"
pos_hint: {"center_x": .5}
y: "36dp"
on_release:
root.current_hero = "hero"
root.current = "screen A"
'''
class Test(MDApp):
def build(self):
return Builder.load_string(KV)
Test().run()
.. image:: https://github.com/HeaTTheatR/KivyMD-data/raw/master/gallery/kivymddoc/hero-usage.gif
:align: center
Note that the child of the :class:`~MDHeroFrom` widget must have the size of the parent:
.. code-block:: kv
MDHeroFrom:
id: hero_from
FitImage:
size_hint: None, None
size: hero_from.size
To enable hero animation before setting the name of the current screen for the
screen manager, you must specify the name of the tag of the :class:`~MDHeroFrom`
container in which the hero is located:
.. code-block:: kv
MDRaisedButton:
text: "Move Hero To Screen B"
on_release:
root.current_hero = "hero"
root.current = "screen 2"
If you need to switch to a screen that does not contain heroes, set the
`current_hero` attribute for the screen manager as "" (empty string):
.. code-block:: kv
MDRaisedButton:
text: "Go To Another Screen"
on_release:
root.current_hero = ""
root.current = "another screen"
Example
-------
.. code-block:: python
from kivy.lang import Builder
from kivymd.app import MDApp
KV = '''
MDScreenManager:
MDScreen:
name: "screen A"
md_bg_color: "lightblue"
MDHeroFrom:
id: hero_from
tag: "hero"
size_hint: None, None
size: "120dp", "120dp"
pos_hint: {"top": .98}
x: 24
FitImage:
source: "https://github.com/kivymd/internal/raw/main/logo/kivymd_logo_blue.png"
size_hint: None, None
size: hero_from.size
MDRaisedButton:
text: "Move Hero To Screen B"
pos_hint: {"center_x": .5}
y: "36dp"
on_release:
root.current_hero = "hero"
root.current = "screen B"
MDScreen:
name: "screen B"
hero_to: hero_to
md_bg_color: "cadetblue"
MDHeroTo:
id: hero_to
size_hint: None, None
size: "220dp", "220dp"
pos_hint: {"center_x": .5, "center_y": .5}
MDRaisedButton:
text: "Go To Screen C"
pos_hint: {"center_x": .5}
y: "52dp"
on_release:
root.current_hero = ""
root.current = "screen C"
MDRaisedButton:
text: "Move Hero To Screen A"
pos_hint: {"center_x": .5}
y: "8dp"
on_release:
root.current_hero = "hero"
root.current = "screen A"
MDScreen:
name: "screen C"
MDLabel:
text: "Screen C"
halign: "center"
MDRaisedButton:
text: "Back To Screen B"
pos_hint: {"center_x": .5}
y: "36dp"
on_release:
root.current = "screen B"
'''
class Test(MDApp):
def build(self):
return Builder.load_string(KV)
Test().run()
.. image:: https://github.com/HeaTTheatR/KivyMD-data/raw/master/gallery/kivymddoc/hero-switch-another-screen.gif
:align: center
Events
------
Two events are available for the hero:
- `on_transform_in` - when the hero flies from screen **A** to screen **B**.
- `on_transform_out` - when the hero back from screen **B** to screen **A**.
The `on_transform_in`, `on_transform_out` events relate to the
:class:`~MDHeroFrom` container. For example, let's change the radius and
background color of the hero during the flight between the screens:
.. code-block:: python
from kivy import utils
from kivy.animation import Animation
from kivy.lang import Builder
from kivy.utils import get_color_from_hex
from kivymd.app import MDApp
from kivymd.uix.hero import MDHeroFrom
from kivymd.uix.relativelayout import MDRelativeLayout
KV = '''
MDScreenManager:
MDScreen:
name: "screen A"
md_bg_color: "lightblue"
MyHero:
id: hero_from
tag: "hero"
size_hint: None, None
size: "120dp", "120dp"
pos_hint: {"top": .98}
x: 24
MDRelativeLayout:
size_hint: None, None
size: hero_from.size
md_bg_color: "blue"
radius: [24, 12, 24, 12]
FitImage:
source: "https://github.com/kivymd/internal/raw/main/logo/kivymd_logo_blue.png"
MDRaisedButton:
text: "Move Hero To Screen B"
pos_hint: {"center_x": .5}
y: "36dp"
on_release:
root.current_hero = "hero"
root.current = "screen B"
MDScreen:
name: "screen B"
hero_to: hero_to
md_bg_color: "cadetblue"
MDHeroTo:
id: hero_to
size_hint: None, None
size: "220dp", "220dp"
pos_hint: {"center_x": .5, "center_y": .5}
MDRaisedButton:
text: "Move Hero To Screen A"
pos_hint: {"center_x": .5}
y: "36dp"
on_release:
root.current_hero = "hero"
root.current = "screen A"
'''
class Test(MDApp):
def build(self):
return Builder.load_string(KV)
class MyHero(MDHeroFrom):
def on_transform_in(
self, instance_hero_widget: MDRelativeLayout, duration: float
):
'''
Called when the hero flies from screen **A** to screen **B**.
:param instance_hero_widget: dhild widget of the `MDHeroFrom` class.
:param duration of the transition animation between screens.
'''
Animation(
radius=[12, 24, 12, 24],
duration=duration,
md_bg_color=(0, 1, 1, 1),
).start(instance_hero_widget)
def on_transform_out(
self, instance_hero_widget: MDRelativeLayout, duration: float
):
'''Called when the hero back from screen **B** to screen **A**.'''
Animation(
radius=[24, 12, 24, 12],
duration=duration,
md_bg_color=get_color_from_hex(utils.hex_colormap["blue"]),
).start(instance_hero_widget)
Test().run()
.. image:: https://github.com/HeaTTheatR/KivyMD-data/raw/master/gallery/kivymddoc/hero-events.gif
:align: center
Usage with ScrollView
---------------------
.. code-block:: python
from kivy.animation import Animation
from kivy.clock import Clock
from kivy.lang import Builder
from kivy.properties import StringProperty, ObjectProperty
from kivymd.app import MDApp
from kivymd.uix.hero import MDHeroFrom
KV = '''
size_hint_y: None
height: "200dp"
radius: 24
MDSmartTile:
id: tile
radius: 24
box_radius: 0, 0, 24, 24
box_color: 0, 0, 0, .5
source: "image.jpg"
size_hint: None, None
size: root.size
mipmap: True
on_release: root.on_release()
MDLabel:
text: root.tag
bold: True
font_style: "H6"
opposite_colors: True
MDScreenManager:
MDScreen:
name: "screen A"
ScrollView:
MDGridLayout:
id: box
cols: 2
spacing: "12dp"
padding: "12dp"
adaptive_height: True
MDScreen:
name: "screen B"
hero_to: hero_to
MDHeroTo:
id: hero_to
size_hint: 1, None
height: "220dp"
pos_hint: {"top": 1}
MDRaisedButton:
text: "Move Hero To Screen A"
pos_hint: {"center_x": .5}
y: "36dp"
on_release:
root.current_hero = "hero"
root.current = "screen A"
'''
class HeroItem(MDHeroFrom):
text = StringProperty()
manager = ObjectProperty()
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.ids.tile.ids.image.ripple_duration_in_fast = 0.05
def on_transform_in(self, instance_hero_widget, duration):
Animation(
radius=[0, 0, 0, 0],
box_radius=[0, 0, 0, 0],
duration=duration,
).start(instance_hero_widget)
def on_transform_out(self, instance_hero_widget, duration):
Animation(
radius=[24, 24, 24, 24],
box_radius=[0, 0, 24, 24],
duration=duration,
).start(instance_hero_widget)
def on_release(self):
def switch_screen(*args):
self.manager.current_hero = self.tag
self.manager.current = "screen B"
Clock.schedule_once(switch_screen, 0.2)
class Test(MDApp):
def build(self):
return Builder.load_string(KV)
def on_start(self):
for i in range(12):
hero_item = HeroItem(
text=f"Item {i + 1}", tag=f"Tag {i}", manager=self.root
)
if not i % 2:
hero_item.md_bg_color = "lightgrey"
self.root.ids.box.add_widget(hero_item)
Test().run()
.. image:: https://github.com/HeaTTheatR/KivyMD-data/raw/master/gallery/kivymddoc/hero-usage-with-scrollview.gif
:align: center
"""
from kivy.properties import StringProperty
from kivymd.uix.boxlayout import MDBoxLayout
class MDHeroFrom(MDBoxLayout):
"""
The container from which the hero begins his flight.
:Events:
`on_transform_in`
when the hero flies from screen **A** to screen **B**.
`on_transform_out`
Called when the hero back from screen **B** to screen **A**.
"""
tag = StringProperty(allownone=True)
"""
Tag ID for heroes.
:attr:`shift_right` is an :class:`~kivy.properties.StringProperty`
and defaults to `''`.
"""
def __init__(self, **kwargs):
super().__init__(**kwargs)
self.register_event_type("on_transform_in")
self.register_event_type("on_transform_out")
def on_transform_in(self, *args):
"""Called when the hero flies from screen **A** to screen **B**."""
def on_transform_out(self, *args):
"""Called when the hero back from screen **B** to screen **A**."""
class MDHeroTo(MDBoxLayout):
"""The container in which the hero comes."""