dart – Flutter – 改变appbar的颜色不起作用

根据下图选择颜色0x673AB7时,AppBar变为灰色而不是紫色.

import "package:flutter/material.dart";

void main() {
  runApp(new ControlleApp());
}

class ControlleApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: "Controlle Financeiro",home: new HomePage(),);
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        backgroundColor: new Color(0x673AB7),),);
  }
}