flutter 普通路由跳转 劫持系统自带返回按钮

场景:用户在首页点击按钮跳转到详情页，然后点击详情页 左上角的按钮返回时候 对其进行拦截.

首页.jpg
详情页.jpg
方法一:在Scaffold下面用leading 属性覆盖;
方法二:在Scaffold外层用WillPopScope进行包裹;
main.dart

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
          primarySwatch: Colors.blue, splashColor: Colors.transparent),
      home: HomePage(),
    );
  }
}
class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
   String _message="首页默认显示";
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("首页"),
        ),
        body: Center(
          child: Column(
            children: [
              ElevatedButton (
                onPressed:()=>_jumpToDetail(context),
                child: Text("跳转到详情"),
                ),
                Text(_message)
            ],
          ),
        )
        );
  }
  _jumpToDetail(BuildContext context){
    final res= Navigator.of(context).push(MaterialPageRoute(builder:(ctx){
          return DetailPage("home 页面的值");
      }));
    res.then((value) => {
        setState(() {
            _message=value??"";
       })
    });
  }
}

a.dart

import 'package:flutter/material.dart';

class DetailPage extends StatelessWidget {
  final String _message;
  DetailPage(this._message);
  @override
  Widget build(BuildContext context) {
    return WillPopScope(
       //方法二 在Scaffold外层包裹一层WillPopScope
      // 当返回为true时,可以自动返回(flutter帮助我们执行返回操作)
      // 当返回为false时, 自行写返回代码
      onWillPop: () {
        _backToHome(context);
        return Future.value(false);
      },
      child: Scaffold(
        appBar: AppBar(
          title: Text("详情页"),
          // 方法一:
      //  leading: IconButton(
      //    icon: Icon(Icons.backpack),
      //    onPressed: () => _backToHome(context),
      //  ),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(_message, style: TextStyle(fontSize: 20),),
              ElevatedButton (
                child: Text("回到首页"),
                onPressed: () => _backToHome(context),
              )
            ],
          ),
        ),
      ),
    );
  }
  void _backToHome(BuildContext context) {
    Navigator.of(context).pop("a detail message");
  }
}