Flutter trick: using AnimatedBuilder for efficient animations.

When you want to add animations that don’t rebuild the entire widget tree, AnimatedBuilder is an efficient way to create smooth, high-performance animations.

Example: Rotating Icon Animation

This example shows how to use AnimatedBuilder to smoothly rotate an icon without rebuilding unnecessary parts of the widget tree:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text("Rotating Icon")),
        body: Center(child: RotatingIcon()),
      ),
    );
  }
}

class RotatingIcon extends StatefulWidget {
  @override
  _RotatingIconState createState() => _RotatingIconState();
}

class _RotatingIconState extends State<RotatingIcon>
    with SingleTickerProviderStateMixin {
  late AnimationController _controller;

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

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

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: _controller,
      builder: (context, child) {
        return Transform.rotate(
          angle: _controller.value * 2.0 * 3.1416, // Full circle
          child: child,
        );
      },
      child: Icon(
        Icons.sync,
        size: 100,
        color: Colors.blue,
      ),
    );
  }
}

Explanation

• AnimationController: Controls the animation’s duration and state (we set it to repeat indefinitely here).

• AnimatedBuilder: Efficiently rebuilds only the parts of the widget that need updating, keeping performance smooth.

• Transform.rotate: Rotates the icon based on the controller’s current animation value.

Using AnimatedBuilder like this is a highly efficient way to add animations to your Flutter app without rebuilding the widget tree, which keeps animations smooth and improves app performance.