What libraries or approaches to creating animations have you used in Flutter?

In Flutter, built-in packages like animation and widgets such as AnimatedContainer, AnimatedOpacity, AnimatedBuilder are often used to create animations. For more complex animations, animation controllers (AnimationController) and curves (Curves) are employed.

Additionally, third-party libraries are popular, for example:

• flutter_animate — simplifies creating chains of animations.
• rive — for integrating interactive vector animations.
• flare_flutter — for animations created in Flare.

An example of a simple animation using AnimationController:

class MyAnimatedWidget extends StatefulWidget {
  @override
  _MyAnimatedWidgetState createState() => _MyAnimatedWidgetState();
}

class _MyAnimatedWidgetState extends State<MyAnimatedWidget> with SingleTickerProviderStateMixin {
  late AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 2),
      vsync: this,
    )..repeat(reverse: true);
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return FadeTransition(
      opacity: _controller,
      child: const FlutterLogo(size: 100),
    );
  }
}