measured 0.0.2

displays the actual size every time the size of the child widget changes

example/lib/main.dart

import 'dart:math';
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
import 'package:align_positioned/align_positioned.dart';

import 'package:measured/measured.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: HomePage(),
    );
  }
}

class HomePage extends HookWidget {
  const HomePage({super.key});

  static String title = 'Home';

  @override
  Widget build(BuildContext context) {
    final length = useState('');
    final controller = useAnimationController();
    final align = useMemoized(() => controller.drive(AlignmentTween(
          begin: Alignment.topRight,
          end: Alignment.bottomLeft,
        )));
    useAnimation(align);

    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            AnimatedBuilder(
              animation: controller,
              builder: (context, child) {
                return Measured(
                  child: Container(
                    width: 300.0 + 80.0 * controller.value,
                    height: 400.0 + 150.0 * controller.value,
                    decoration: const BoxDecoration(
                      color: Colors.red,
                    ),
                    child: Stack(
                      fit: StackFit.expand,
                      children: [
                        AlignPositioned(
                          alignment: align.value,
                          child: Transform.rotate(
                            angle: controller.value * 2 * pi,
                            child: Measured(
                              backgroundColor: Colors.green.withAlpha(120),
                              lineColor: Colors.yellow,
                              lineWidth: 5.0,
                              style: const TextStyle(
                                  color: Colors.white,
                                  fontSize: 10.0,
                                  fontWeight: FontWeight.bold),
                              bOutlinedBorder: true,
                              onSizeChanged: (size) {
                                length.value = size.toString();
                              },
                              child: SizedBox(
                                width: 150.0 + 100 * controller.value,
                                height: 100.0 + 100 * (1 - controller.value),
                                child: const FlutterLogo(),
                              ),
                            ),
                          ),
                        ),
                        AlignPositioned(
                          alignment: Alignment.bottomRight,
                          child: Measured(
                            bOutlinedBorder: true,
                            child: SizedBox(
                              width: 150.0 + 60.0 * (1 - controller.value),
                              height: 80.0 + 30.0 * (1 - controller.value),
                              child: const FlutterLogo(),
                            ),
                          ),
                        ),
                        AlignPositioned(
                          alignment: Alignment.center,
                          child: Text(
                            length.value.toString(),
                            style: const TextStyle(
                              fontSize: 24.0,
                              color: Colors.black,
                              fontWeight: FontWeight.bold,
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                );
              },
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
          onPressed: () {
            if (controller.isAnimating) {
              controller.stop();
            } else {
              controller.repeat(
                reverse: true,
                period: const Duration(seconds: 1),
              );
            }
          },
          child: Icon(
            controller.isAnimating ? Icons.pause : Icons.play_arrow_rounded,
          )),
    );
  }
}