flutter_animate 2.0.1 flutter_animate: ^2.0.1 copied to clipboard
Add beautiful animated effects & builders in Flutter, via an easy, customizable, unified API.
Flutter Animate #
A performant library that makes it simple to add almost any kind of animated effect in Flutter.
- Pre-built effects, like fade, scale, slide, flip, blur, shake, shimmer, and color effects (saturation and tint)
- Easy custom effects and simplified animated builders
- Synchronize animations to scroll, notifiers, or anything
- Integrated events
All via a simple, unified API without fussing with AnimationController and StatefulWidget.
Above: The included example app.
Duration extensions #
Extension methods for
num, to make specifying durations easier. For example:
AnimatedController extensions #
loop extension method for
AnimatedController which is identical to
repeat, but adds a
count parameter to specifiy how many times to play.
To apply effects, wrap the target widget in
Animate, and specify a list of
Animate( effects: [FadeEffect(), ScaleEffect()], child: Text("Hello World!"), )
It also adds an
.animate() extension method to all widgets, which wraps the
Animate(). Each effect also adds a chainable extension method to
Animate to enable a shorthand syntax:
NOTE: The shortform style is used in this README, but all functionality is available in either format.
Delay, duration, curve #
Effects have optional
curve parameters. Effects run
in parallel, but you can use a
delay to run them sequentially:
Text("Hello").animate() .fade(duration: 500.ms) .scale(delay: 500.ms) // runs after fade.
Note that effects are "active" for the duration of the full animation, so for
example, two fade effects on the same target can have unexpected results
SwapEffect detailed below, can help address this).
If not specified (or null), these values are inherited from the previous effect,
Animate.defaultCurve if it is the first
Text("Hello World!").animate() .fadeIn() // uses `Animate.defaultDuration` .scale() // inherits duration from fadeIn .move(delay: 300.ms, duration: 600.ms) // runs after the above w/new duration .blurXY() // inherits the delay & duration from move
Animate has its own
delay parameter, which defines a delay before the
animation begins playing. Unlike the delay on an
Effect, it is only applied
once if the animation repeats.
Text("Hello").animate( delay: 1000.ms, // this delay only happens once at the very start onPlay: (controller) => controller.repeat(), // loop ).fadeIn(delay: 500.ms) // this delay happens at the start of each loop
Other Effect Parameters #
Most effects include
end parameters, which specify the start/end
values. These are usually "smart" in the sense that if only one is specified
then the other will default to a "neutral" value (ie. no visual effect). If
both are unspecified the effect should use visually pleasing defaults.
// an opacity of 1 is "neutral" Text("Hello").animate().fade() // begin=0, end=1 Text("Hello").animate().fade(begin: 0.5) // end=1 Text("Hello").animate().fade(end: 0.5) // begin=1
Many effects have additional parameters that influence their behavior. These should also use pleasant defaults if unspecified.
Sequencing with ThenEffect #
ThenEffect is a special "convenience" effect that simply sets its own
inheritable delay to the sum of the delay and duration of the previous effect,
and its own (optional) delay. This makes it easier to sequence effects.
In the following example, the slide would run immediately after the fade ended, then the blur would run 200ms after the slide ended.
Text("Hello").animate() .fadeIn(delay: 300.ms, duration: 500.ms) .then() // sets own delay to 800ms (300+500) .slide(duration: 400.ms) // inherits the 800ms delay .then(delay: 200.ms) // sets delay to 1400ms (800+400+200) .blur() // inherits the 1400ms delay // Explicitly setting delay overrides the inherited value. // This move effect will run BEFORE the initial fade: .move(delay: 0.ms)
Animating lists #
AnimateList class offers similar functionality for lists of widgets, with
the option to offset each child's animation by a specified
Column(children: AnimateList( interval: 400.ms, effects: [FadeEffect(duration: 300.ms)], children: [Text("Hello"), Text("World"), Text("Goodbye")], )) // or shorthand: Column( children: [Text("Hello"), Text("World"), Text("Goodbye")] .animate(interval: 400.ms).fade(duration: 300.ms), )
Shared effects #
Effect instances are immutable, they can be reused. This makes it easy
to create a global collection of effects that are used throughout your app and
updated in one place. This is also useful for design systems.
MyGlobalEffects.transitionIn = <Effect>[ FadeEffect(duration: 100.ms, curve: Curves.easeOut), ScaleEffect(begin: 0.8, curve: Curves.easeIn) ] // then: Text('Hello').animate(effects: MyGlobalEffects.transitionIn)
Custom effects & builders #
It is easy to write new resuable effects by extending
Effect, but you can also
easily create one-off custom effects by using
CustomEffect lets you build custom animated effects. Simply specify a
builder function that accepts a
child. The child is
the target of the animation (which may already have been wrapped in other
For example, this would add a background behind the text and fade it from red to blue:
Text("Hello World").animate().custom( duration: 300.ms, builder: (context, value, child) => Container( color: Color.lerp(Colors.red, Colors.blue, value), padding: EdgeInsets.all(8), child: child, // child is the Text widget being animated ) )
By default it provides a
0-1 (though some curves can generate
values outside this range), based on the current time, duration, and curve. You
can also specify
end values as demonstrated in the example below.
Animate can be created without a child, so you use
CustomEffect as a
simplified builder. For example, this would build text counting down from 10,
and fading out:
Animate().custom( duration: 10.seconds, begin: 10, end: 0, builder: (_, value, __) => Text(value.round()), ).fadeOut()
ToggleEffect also provides builder functionality, but instead of a
it provides a boolean value equal to
true before the end of the effect and
false after (ie. after its duration).
Animate().toggle( duration: 2.seconds, builder: (_, value, __) => Text(value ? "Before" : "After"), )
This can also be used to activate "Animated" widgets, like
by toggling their values with a minimal delay:
Animate().toggle( duration: 1.ms, builder: (_, value, __) => AnimatedContainer( duration: 1.seconds, color: value ? Colors.red : Colors.green, ), )
SwapEffect lets you swap out the whole target widget at a specified time:
Text("Before").animate() .swap(duration: 900.ms, builder: (_, __) => Text("After"))
This can also be useful for creating sequential effects, by swapping the target widget back in, effectively wiping all previous effects:
text.animate().fadeOut(300.ms) // fade out & then... // swap in original widget & fade back in via a new Animate: .swap(builder: (_, child) => child.animate().fadeIn())
Events & callbacks #
Animate includes the following callbacks:
onPlay: the animation has started playing after any
onComplete: the animation has finished
These callbacks return the
AnimationController, which can be used to
manipulate the animation (ex. repeat, reverse, etc).
Text("Horrible Pulsing Text") .animate(onPlay: (controller) => controller.repeat(reverse: true)) .fadeOut(curve: Curves.easeInOut)
For more nuanced callbacks, use
CallbackEffect lets you add a callback to an arbitrary postion in your
animations. For example, adding a callback halfway through a fade:
Text("Hello").animate().fadeIn(duration: 600.ms) .callback(duration: 300.ms, callback: (_) => print('halfway'))
As with other effects, it will inherit the delay and duration of prior effects:
Text("Hello").animate().scale(delay: 200.ms, duration: 400.ms) .callback(callback: (_) => print('scale is done'))
ListenEffect lets you register a callback to receive the animation value (as a
double) for a given delay, duration, curve, begin, and end.
Text("Hello").animate().fadeIn(curve: Curves.easeOutExpo) .listen(callback: (value) => print('current opacity: $value'))
The above example works, because the listen effect inherits duration and curve
from the fade, and both use
begin=0, end=1 by default.
Adapters and Controllers #
By default, all animations are driven by an internal
update based on elapsed time. For more control, you can specify your own
controller, or use an
Adapters synchronize the
AnimationController to an external source. For
ScrollAdapter updates an animation based on a
so you can run complex animations based on scroll interactions.
You still define animations using durations, but the external source must
Flutter Animate ships with a collection of useful adapters. Check them out for more information.
Grab it from pub.dev.