How do animations work in Flutter?

Question

Accepted Answer

Flutter has powerful, flexible **animation** support — from simple implicit animations to fully-controlled explicit animations. Animations enhance UX with smooth transitions and motion, and Flutter's widget-based system makes them approachable. ## Implicit animations (the easy way) ```dart // implicitly-animated widgets animate AUTOMATICALLY when their properties change AnimatedContainer( duration: Duration(milliseconds: 300), width: _expanded ? 200 : 100, // change width → it animates smoothly height: _expanded ? 200 : 100, color: _expanded ? Colors.blue : Colors.red, ) // just change the value (with setState) → Flutter animates the transition // others: AnimatedOpacity, AnimatedPadding, AnimatedPositioned, etc. ``` Implicit animations (`AnimatedContainer`, `AnimatedOpacity`, etc.) animate automatically when their properties change — the easiest way to add animation. ## Explicit animations (full control) ```dart // explicit animations use an AnimationController for full control class _MyState extends State with SingleTickerProviderStateMixin { late AnimationController _controller; late Animation _animation; @override void initState() { super.initState(); _controller = AnimationController(duration: Duration(seconds: 1), vsync: this); _animation = Tween(begin: 0, end: 1).animate(_controller); _controller.forward(); // start the animation } @override void dispose() { _controller.dispose(); super.dispose(); } // CLEAN UP the controller! } ``` Explicit animations use an **AnimationController** (controlling playback) and **Tween** (defining the value range) for precise control — needed for custom, complex, or coordinated animations. ## Other animation tools ```text ✓ Hero animations → shared-element transitions between screens (an image flies/grows) ✓ AnimatedBuilder / AnimatedWidget → build UI from an animation efficiently ✓ Page route transitions; staggered animations; physics-based animations ✓ Packages (Rive, Lottie) for complex/designer animations ``` ## Why it matters Understanding animations in Flutter is valuable because **animations enhance user experience** with smooth transitions and motion that make apps feel polished and responsive, so it's useful practical knowledge. Flutter's animation system is powerful and flexible, and understanding the two main approaches is the key. **Implicit animations** (implicitly-animated widgets like `AnimatedContainer` and `AnimatedOpacity` that automatically animate when their properties change) are the **easy, approachable way** to add animation — just change a value and Flutter animates the transition smoothly, requiring minimal code, suitable for most common animation needs. **Explicit animations** (using an **AnimationController** for playback control and **Tween** for value ranges) provide **full control** for custom, complex, or coordinated animations — necessary when implicit animations aren't enough. Understanding both — and when to use each (implicit for simple property animations, explicit for precise control) — covers the spectrum of animation needs. Knowing **other tools** (Hero animations for shared-element screen transitions, AnimatedBuilder for efficient animation-driven UI, and packages like Rive/Lottie for complex designer animations) extends the toolkit. A practical note worth remembering is **disposing AnimationControllers** (to prevent leaks, connecting to the lifecycle knowledge). Since polished animations meaningfully improve user experience (smooth transitions, motion, feedback) and Flutter provides strong animation support, and since understanding the implicit and explicit approaches enables adding appropriate animations, understanding animations in Flutter is valuable, practically-relevant knowledge for building polished apps — useful for enhancing UX with motion, from simple implicit animations (the common case) to full-control explicit animations, a valuable skill for creating engaging, professional-feeling Flutter applications.