A library that makes it simple to add virtually any kind of animated effect in Flutter.
- Pre-built effects, like blur, fade, scale, and slide
- Easy custom effects
- Simplified animated builders
- Synchronized events
All via a simple, unified API without fussing with AnimationController and StatefulWidget.
NOTE: This library is currently in prerelease. Some aspects of the API will change as it is refined. Your feedback is welcome via Github issues.
This package includes extension methods for
num, to make specifying durations
easier. For example:
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 .blur(end: 8.0) // inherits the delay & duration from move
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), )
Custom effects & builders
It is easy to write new resuable effects by extending
Effect, but you can also
create one-off custom effects easily 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 ) )
value provides a value from
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 display 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 (ie.
after its duration) and
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.second, color: value ? Colors.red : Colors.green, ), )
SwapEffect lets you swap out the 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:
Widget text = Text("Hello World!"); // then: text.animate().fadeOut(300.ms) // fade out & then... .swap(builder: (_) => text.fadeIn()) // swap in original widget & fade back in
Events & callbacks
onComplete callbacks on
Animate that trigger when the
whole animation starts or ends. Use the provided the
manipulate the animation (ex. repeat, reverse, etc).
Text("Pulsing Text") .animate(onComplete: (controller) => controller.repeat(reverse: true)) .fadeOut(delay: 300.ms, duration: 300.ms, curve: Curves.easeIn)
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, and curve.
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.