Flutter: ウィジェットをキャッシュするユーティリティウィジェット

class CacheWidget extends StatefulWidget {
  const CacheWidget({
    super.key,
    required Widget child,
    required bool shouldRebuild,
  })  : _child = child,
        _shouldRebuild = shouldRebuild;

  final Widget _child;
  final bool _shouldRebuild;

  @override
  State<CacheWidget> createState() => _CacheWidgetState();
}

class _CacheWidgetState extends State<CacheWidget> {
  Widget? _cache;

  @override
  Widget build(BuildContext context) {
    return _cache =
        _cache == null || widget._shouldRebuild ? widget._child : _cache!;
  }
}

import 'dart:math';

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({
    super.key,
  });

  @override
  Widget build(BuildContext context) {
    final isDataUpdated = Random().nextBool();

    return MaterialApp(
      home: CacheWidget(
        shouldRebuild: isDataUpdated,
        child: Scaffold(
          appBar: AppBar(
            title: const Text('My title'),
          ),
          body: const Center(
            child: Text('Hello, World!'),
          ),
        ),
      ),
    );
  }
}