自定义 MaterialColor

import 'package:flutter/material.dart';
import 'login.dart';
import 'dart:ui';

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: createMaterialColor(Color(0xFF273470)),

      ),
      home:Scaffold(
        appBar: AppBar(
          title: const Text("Log In",style: TextStyle(fontSize: 20.0,color: Colors.white),),
        ),
        body: const Login(),
      ),
    );
  }
}


//调用的时候需要把hex改一下，比如#223344 needs change to 0xFF223344
//即把#换成0xFF即可

MaterialColor createMaterialColor(Color color) {
  List strengths = <double>[.05];
  Map<int, Color> swatch = {};
  final int r = color.red, g = color.green, b = color.blue;

  for (int i = 1; i < 10; i++) {
    strengths.add(0.1 * i);
  }
  strengths.forEach((strength) {
    final double ds = 0.5 - strength;
    swatch[(strength * 1000).round()] = Color.fromRGBO(
      r + ((ds < 0 ? r : (255 - r)) * ds).round(),
      g + ((ds < 0 ? g : (255 - g)) * ds).round(),
      b + ((ds < 0 ? b : (255 - b)) * ds).round(),
      1,
    );
  });
  return MaterialColor(color.value, swatch);
}