overflow-errors.dart

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

/// Click the content to expand / constact the card.
/// These overflow warnings are not helpful, and impact developer efficiency and joy. 
// It would be nice to turn them off for this specific widget.

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

class MyApp extends StatefulWidget {
  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool _isOpen = false;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: GestureDetector(
          onTap: () => setState(() => _isOpen = !_isOpen),
          child: Center(
            child: OpeningCard(
              isOpen: _isOpen,
              background: Container(color: Colors.grey),
              openBuilder: (_) => FlutterLogo(size: 300),
              closedBuilder: (_) => Text('I am small!'),
            ),
          ),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text(
      'Hello, World!',
      style: Theme.of(context).textTheme.headline4,
    );
  }
}

class MeasurableWidget extends SingleChildRenderObjectWidget {
  const MeasurableWidget(
      {Key? key, required this.onChange, required Widget child})
      : super(key: key, child: child);
  final void Function(Size size) onChange;
  @override
  RenderObject createRenderObject(BuildContext context) =>
      MeasureSizeRenderObject(onChange);
}

class MeasureSizeRenderObject extends RenderProxyBox {
  MeasureSizeRenderObject(this.onChange);
  void Function(Size size) onChange;

  Size _prevSize = Size.zero;
  @override
  void performLayout() {
    super.performLayout();
    Size newSize = child?.size ?? Size.zero;
    if (_prevSize == newSize) return;
    _prevSize = newSize;
    WidgetsBinding.instance?.addPostFrameCallback((_) => onChange(newSize));
  }
}

class OpeningCard extends StatefulWidget {
  const OpeningCard(
      {Key? key,
      required this.closedBuilder,
      required this.openBuilder,
      required this.isOpen,
      this.background,
      this.padding})
      : super(key: key);

  final Widget Function(BuildContext) closedBuilder;
  final Widget Function(BuildContext) openBuilder;
  final Widget? background;
  final bool isOpen;
  final EdgeInsets? padding;

  @override
  State<OpeningCard> createState() => _OpeningCardState();
}

class _OpeningCardState extends State<OpeningCard> {
  Size _size = Size.zero;
  @override
  Widget build(BuildContext context) {
    return TweenAnimationBuilder<Size>(
      duration: Duration(seconds: 1),
      curve: Curves.easeOut,
      builder: (_, value, child) => Stack(
        children: [
          if (widget.background != null) ...[
            Positioned.fill(child: widget.background!),
          ],
          Padding(
            padding: widget.padding ?? EdgeInsets.zero,
            child: SizedBox(
              width: value.width,
              height: value.height,
              child: child,
            ),
          ),
        ],
      ),
      tween: Tween(begin: _size, end: _size),
      child: AnimatedSwitcher(
        duration: Duration(seconds: 1),
        child: ClipRect(
          key: ValueKey(widget.isOpen),
          child: UnconstrainedBox(
            child: MeasurableWidget(
              onChange: (size) {
                setState(() => _size = size);
              },
              child: widget.isOpen
                  ? widget.openBuilder(context)
                  : widget.closedBuilder(context),
            ),
          ),
        ),
      ),
    );
  }
}