【Flutter】非同期処理と並列処理でUI描画に与える影響を比較してみた

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

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

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: FibonacciWidget(),
    );
  }
}

class FibonacciWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
        future: 関数A, //今回はここを変えます
        builder: (_, snapshot) {
          if (!snapshot.hasData) {
            return Scaffold(
              appBar: AppBar(
                title: const Text("fibonacci"),
              ),
              body: const Center(
                child: CircularProgressIndicator(),
              ),
            );
          } else {
            return Scaffold(
              appBar: AppBar(
                title: const Text("fibonacci"),
              ),
              body: Center(
                child: Text("${snapshot.data}"),
              ),
            );
          }
        });
  }
}

// 非同期でn秒待つだけの関数
Future<String> delayTime(int n) async {
  await Future.delayed(Duration(seconds: num));
  return "${n}秒経過しました";
}

// 非同期でn番目のフィボナッチ数列を求める関数
Future<int> asyncFibonacci(int n) async {
  return n < 2 ? n : (await asyncFibonacci(n - 1) + await asyncFibonacci(n - 2));
}

// 並列処理でn番目のフィボナッチ数列を求める関数
int paraFibonacci(int n) {
  return n < 2 ? n : (paraFibonacci(n - 1) + paraFibonacci(n - 2));
}