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AnimatedSwitcher

Examples#

Live example

Animated switching between two containers with scale effect#

import flet as ft


def main(page: ft.Page):
    c1 = ft.Container(
        content=ft.Text("Hello!", theme_style=ft.TextThemeStyle.HEADLINE_MEDIUM),
        alignment=ft.Alignment.CENTER,
        width=200,
        height=200,
        bgcolor=ft.Colors.GREEN,
    )
    c2 = ft.Container(
        content=ft.Text("Bye!", size=50),
        alignment=ft.Alignment.CENTER,
        width=200,
        height=200,
        bgcolor=ft.Colors.YELLOW,
    )
    switcher = ft.AnimatedSwitcher(
        content=c1,
        transition=ft.AnimatedSwitcherTransition.SCALE,
        duration=500,
        reverse_duration=100,
        switch_in_curve=ft.AnimationCurve.BOUNCE_OUT,
        switch_out_curve=ft.AnimationCurve.BOUNCE_IN,
    )

    def scale(e):
        switcher.content = c2 if switcher.content == c1 else c1
        switcher.transition = ft.AnimatedSwitcherTransition.SCALE
        switcher.update()

    def fade(e):
        switcher.content = c2 if switcher.content == c1 else c1
        switcher.transition = ft.AnimatedSwitcherTransition.FADE
        switcher.update()

    def rotate(e):
        switcher.content = c2 if switcher.content == c1 else c1
        switcher.transition = ft.AnimatedSwitcherTransition.ROTATION
        switcher.update()

    page.add(
        switcher,
        ft.Button("Scale", on_click=scale),
        ft.Button("Fade", on_click=fade),
        ft.Button("Rotate", on_click=rotate),
    )


ft.run(main)

scale-effect

Animate Image switch#

import time

import flet as ft


def main(page: ft.Page):
    def animate(e: ft.Event[ft.Button]):
        switcher.content = ft.Image(
            src=f"https://picsum.photos/200/300?{time.time()}",
            width=200,
            height=300,
        )
        page.update()

    page.add(
        switcher := ft.AnimatedSwitcher(
            content=ft.Image(
                src="https://picsum.photos/200/300",
                width=200,
                height=300,
            ),
            transition=ft.AnimatedSwitcherTransition.SCALE,
            duration=500,
            reverse_duration=100,
            switch_in_curve=ft.AnimationCurve.BOUNCE_OUT,
            switch_out_curve=ft.AnimationCurve.BOUNCE_IN,
        ),
        ft.Button("Animate!", on_click=animate),
    )


ft.run(main)

Animate Image switch buffered#

import base64
import time

import httpx

import flet as ft


class BufferingSwitcher(ft.AnimatedSwitcher):
    image_queue = []

    def __init__(self, image: ft.Image, page: ft.Page):
        super().__init__(image)
        self.transition = ft.AnimatedSwitcherTransition.SCALE
        self.duration = 500
        self.reverse_duration = 100
        self.switch_in_curve = ft.AnimationCurve.EASE_IN
        self.switch_out_curve = ft.AnimationCurve.EASE_OUT
        self.image_queue.append(image)
        self.page = page

    def animate(self, e):
        self.content = ft.Image(
            src_base64=self.image_queue.pop(),
            width=200,
            height=300,
            gapless_playback=True,
        )
        self.update()

    async def fill_queue(self):
        while len(self.image_queue) < 10:
            self.image_queue.append(
                await self.image_to_base64(
                    f"https://picsum.photos/200/300?{time.time()}"
                )
            )

    async def image_to_base64(self, url):
        print("image_to_base64 called")
        response = await httpx.AsyncClient(follow_redirects=True).get(url)
        if response.status_code == 200:
            base64_str = (
                base64.standard_b64encode(response.content).decode("utf-8").strip()
            )
            return base64_str
        else:
            print(f"Image request failed with {response.status_code}")
            return None

    def before_update(self):
        self.page.run_task(self.fill_queue)
        print(len(self.image_queue))


def main(page: ft.Page):
    switcher = BufferingSwitcher(
        ft.Image(
            src=f"https://picsum.photos/200/300?{time.time()}", width=200, height=300
        ),
        page,
    )

    page.add(
        switcher,
        ft.Button("Animate!", on_click=switcher.animate),
    )


ft.run(main)

AnimatedSwitcher #

Bases: LayoutControl

Used to switch between controls with an animation.

RAISES DESCRIPTION
AssertionError

The content must be provided and visible.

align #

align: Alignment | None = None

Alignment of the control within its parent.

animate_align #

animate_align: AnimationValue | None = None

Enables implicit animation of the [align][flet.LayoutControl.] property.

More information here.

animate_margin #

animate_margin: AnimationValue | None = None

Enables implicit animation of the [margin][flet.LayoutControl.] property.

More information here.

animate_offset #

animate_offset: AnimationValue | None = None

Enables implicit animation of the [offset][flet.LayoutControl.] property.

More information here.

animate_opacity #

animate_opacity: AnimationValue | None = None

Enables implicit animation of the [opacity][flet.LayoutControl.] property.

More information here.

animate_position #

animate_position: AnimationValue | None = None

Enables implicit animation of the positioning properties ([left][flet.LayoutControl.], [right][flet.LayoutControl.], [top][flet.LayoutControl.] and [bottom][flet.LayoutControl.]).

More information here.

animate_rotation #

animate_rotation: AnimationValue | None = None

Enables implicit animation of the [rotate][flet.LayoutControl.] property.

More information here.

animate_scale #

animate_scale: AnimationValue | None = None

Enables implicit animation of the [scale][flet.LayoutControl.] property.

More information here.

animate_size #

animate_size: AnimationValue | None = None

TBD

aspect_ratio #

aspect_ratio: Number | None = None

The aspect ratio of the control. It is defined as the ratio of the width to the height.

badge #

badge: BadgeValue | None = None

A badge to show on top of this control.

bottom #

bottom: Number | None = None

The distance that the child's bottom edge is inset from the bottom of the stack.

Note

Effective only if this control is a descendant of one of the following: [Stack][flet.] control, [Page.overlay][flet.] list.

col #

col: ResponsiveNumber = 12

If a parent of this control is a [ResponsiveRow][flet.], this property is used to determine how many virtual columns of a screen this control will span.

Can be a number or a dictionary configured to have a different value for specific breakpoints, for example col={"sm": 6}.

This control spans the 12 virtual columns by default.

Dimensions
Breakpoint Dimension
xs <576px
sm ≥576px
md ≥768px
lg ≥992px
xl ≥1200px
xxl ≥1400px

content #

content: Control

The content to display.

When it changes, this switcher will animate the transition from the old/previous content to the new one.

data #

data: Any = skip_field()

Arbitrary data of any type.

disabled #

disabled: bool = False

Every control has disabled property which is False by default - control and all its children are enabled.

Note

The value of this property will be propagated down to all children controls recursively.

Example

For example, if you have a form with multiple entry controls you can disable them all together by disabling container:

ft.Column(
    disabled = True,
    controls=[
        ft.TextField(),
        ft.TextField()
    ]
)

duration #

duration: DurationValue = field(
    default_factory=lambda: Duration(seconds=1)
)

The duration of the transition from the old content to the new one.

expand #

expand: bool | int | None = None

Specifies whether/how this control should expand to fill available space in its parent layout.

More information here.

Note

Has effect only if the direct parent of this control is one of the following controls, or their subclasses: [Column][flet.], [Row][flet.], [View][flet.], [Page][flet.].

expand_loose #

expand_loose: bool = False

Allows the control to expand along the main axis if space is available, but does not require it to fill all available space.

More information here.

Note

If expand_loose is True, it will have effect only if:

  • expand is not None and
  • the direct parent of this control is one of the following controls, or their subclasses: [Column][flet.], [Row][flet.], [View][flet.], [Page][flet.].

height #

height: Number | None = None

Imposed Control height in virtual pixels.

key #

key: KeyValue | None = None

left #

left: Number | None = None

The distance that the child's left edge is inset from the left of the stack.

Note

Effective only if this control is a descendant of one of the following: [Stack][flet.] control, [Page.overlay][flet.] list.

margin #

margin: MarginValue | None = None

Sets the margin of the control.

offset #

offset: OffsetValue | None = None

Applies a translation transformation before painting the control.

The translation is expressed as an Offset scaled to the control's size. So, Offset(x=0.25, y=0), for example, will result in a horizontal translation of one quarter the width of this control.

Example

The following example displays container at 0, 0 top left corner of a stack as transform applies -1 * 100, -1 * 100 (offset * control's size) horizontal and vertical translations to the control:

import flet as ft

def main(page: ft.Page):
    page.add(
        ft.Stack(
            width=1000,
            height=1000,
            controls=[
                ft.Container(
                    bgcolor="red",
                    width=100,
                    height=100,
                    left=100,
                    top=100,
                    offset=ft.Offset(-1, -1),
                )
            ],
        )
    )

ft.run(main)

on_animation_end #

on_animation_end: (
    ControlEventHandler[LayoutControl] | None
) = None

Called when animation completes.

Can be used to chain multiple animations.

The data property of the event handler argument contains the name of the animation.

More information here.

opacity #

opacity: Number = 1.0

Defines the transparency of the control.

Value ranges from 0.0 (completely transparent) to 1.0 (completely opaque without any transparency).

page #

page: Page | BasePage | None

The page to which this control belongs to.

parent #

parent: BaseControl | None

The direct ancestor(parent) of this control.

It defaults to None and will only have a value when this control is mounted (added to the page tree).

The Page control (which is the root of the tree) is an exception - it always has parent=None.

reverse_duration #

reverse_duration: DurationValue = field(
    default_factory=lambda: Duration(seconds=1)
)

The duration of the transition from the new content to the old one.

right #

right: Number | None = None

The distance that the child's right edge is inset from the right of the stack.

Note

Effective only if this control is a descendant of one of the following: [Stack][flet.] control, [Page.overlay][flet.] list.

rotate #

rotate: RotateValue | None = None

Transforms this control using a rotation around its center.

The value of rotate property could be one of the following types:

  • number - a rotation in clockwise radians. Full circle 360° is math.pi * 2 radians, 90° is pi / 2, 45° is pi / 4, etc.
  • Rotate - allows to specify rotation angle as well as alignment - the location of rotation center.
Example

For example: 

ft.Image(
    src="https://picsum.photos/100/100",
    width=100,
    height=100,
    border_radius=5,
    rotate=Rotate(angle=0.25 * pi, alignment=ft.Alignment.CENTER_LEFT)
)

rtl #

rtl: bool = False

Whether the text direction of the control should be right-to-left (RTL).

scale #

scale: ScaleValue | None = None

Scales this control along the 2D plane. Default scale factor is 1.0, meaning no-scale.

Setting this property to 0.5, for example, makes this control twice smaller, while 2.0 makes it twice larger.

Different scale multipliers can be specified for x and y axis, by setting Control.scale property to an instance of Scale class. Either scale or scale_x and scale_y could be specified, but not all of them.

Example 
ft.Image(
    src="https://picsum.photos/100/100",
    width=100,
    height=100,
    border_radius=5,
    scale=ft.Scale(scale_x=2, scale_y=0.5)
)

switch_in_curve #

switch_in_curve: AnimationCurve = LINEAR

The animation curve to use when transitioning in a new content.

switch_out_curve #

switch_out_curve: AnimationCurve = LINEAR

The animation curve to use when transitioning an old content out.

tooltip #

tooltip: TooltipValue | None = None

The tooltip ot show when this control is hovered over.

top #

top: Number | None = None

The distance that the child's top edge is inset from the top of the stack.

Note

Effective only if this control is a descendant of one of the following: [Stack][flet.] control, [Page.overlay][flet.] list.

transition #

transition: AnimatedSwitcherTransition = FADE

An animation type to transition between new and old content.

visible #

visible: bool = True

Every control has visible property which is True by default - control is rendered on the page. Setting visible to False completely prevents control (and all its children if any) from rendering on a page canvas. Hidden controls cannot be focused or selected with a keyboard or mouse and they do not emit any events.

width #

width: Number | None = None

Imposed Control width in virtual pixels.

before_event #

before_event(e: ControlEvent)

before_update #

before_update()

build #

build()

Called once during control initialization to define its child controls. self.page is available in this method.

clean #

clean() -> None

did_mount #

did_mount()

init #

init()

is_isolated #

is_isolated()

update #

update() -> None

will_unmount #

will_unmount()