问使用热重新加载时，简单的字符串标题不会更新。

EN

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    String text = "Hello world";
    return Center(
      child: new Text(text, textDirection: TextDirection.ltr),
    );
  }
}

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.

  @override
  Widget build(BuildContext context) {
  String  text="Hello World"
    return MaterialApp(
        home: Scaffold(
            body: Center(
      child: Text(text,textDirection: TextDirection.ltr),
    )));
  }
}