Exploring Flutter’s Animation Library
Learn how Flutter’s animation library is built up and understand the fundamentals of it
Flutter offers a robust animation library that enhances the interactivity and visual appeal of apps. This article will take a look at the heart of the animations in Flutter, the animations library. We will take a look at the foundational concepts of the animation library as well as practical applications.
Basics of Flutter Animation
Flutter’s animation architecture is based on the animation.dart package, which is tightly integrated with core Dart libraries and specifically, the physics.dart library. At the heart of this architecture is the Animation class, a central element that represents a value changing over time. Whether it's fading a widget in and out or transitioning colors, Animation objects manage these changes by providing both the current value and the animation's status. This status could indicate whether the animation is moving forward, reversing, or has come to a halt.
Animation Control with AnimationController
Controlling an animation is where AnimationController comes into play. AnimationController is a special kind of Animation. It progresses its value in sync with the device’s frame rate—typically around 60 frames per second. The AnimationController not only controls the timing but also the type of animation, such as linear progress or more dynamic effects. The AnimationController also gives us, as the name suggests, control over the animations, such as starting, stopping, or reversing the animation at any point.
Enhancing Animations with Curves and Animatable
Till now, Animation and AnimationController only gave us linear animations. Flutter has a class named Curves that modifies the rate of change in animations. A CurvedAnimation can, for example, accelerate early and slow down towards the end, mimicking natural motion. Additionally, the Animatable<T> class allows us to define animations that transition between a range of values of any type, like animating a widget’s size or its color from one state to another.
Practical Implementation: Tweens and TweenSequences
Tweens are used to interpolate between specified start and end values so that we have a smooth transition. For example, a ColorTween can transition a widget's background color from blue to red. TweenSequences offer more fine-tuned control by allowing animations to execute in stages, which can be weighted differently for timing adjustments. This staged approach is important for more complex animations that require control over the sequence of transitions.
Advanced Widgets: ImplicitlyAnimatedWidget and AnimatedWidget
Flutter simplifies the implementation of animations with ImplicitlyAnimatedWidgets and AnimatedWidgets. ImplicitlyAnimatedWidgets automatically animate changes in widget properties, while AnimatedWidgets require explicit definitions of the animations. There is no right or wrong which one to use. It all depends on the use case and the desired level of control over the animation details.
Conclusion
Flutter’s animation library opens up a world of possibilities for us app developers. But to get the most out of it, we need to understand the basic building blocks provided by Flutter, so that we can implement a wider range of animation effects.
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