颤动：navigator.pop() 在我的代码中无法正常工作

Question

我有下面的代码在颤动，当我按下后退箭头按钮时，它使应用程序崩溃并出现白屏，但是默认情况下出现在其他页面中，我在其他页面中手动实现了它...有人可以告诉我吗我这里有什么问题因为我想不通？

提前致谢

// ignore_for_file: avoid_function_literals_in_foreach_calls, prefer_const_constructors, prefer_const_literals_to_create_immutables, use_key_in_widget_constructors, avoid_unnecessary_containers, curly_braces_in_flow_control_structures, sized_box_for_whitespace, deprecated_member_use, file_names

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:material_design_icons_flutter/material_design_icons_flutter.dart';
// ignore: unused_import
import 'package:google_fonts/google_fonts.dart';
import 'package:hexcolor/hexcolor.dart';
// ignore: unused_import
import 'package:localize_and_translate/localize_and_translate.dart';
import 'package:menu_app/About.dart';

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

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



class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var screenHeight = MediaQuery.of(context).size.height;
    var screenWidth = MediaQuery.of(context).size.width;

    Future<List<Widget>> createList() async {
      List<Widget> items = <Widget>[];
      String dataString = await rootBundle
          .loadString(translator.translate("assets/hotDrinks.json"));
      List<dynamic> dataJSON = jsonDecode(dataString);

      dataJSON.forEach((object) {
        String finalString = "";
        List<dynamic> dataList = object["placeItems"];
        dataList.forEach((item) {
          finalString = finalString + item + " | ";
        });

        items.add(Padding(
          padding: EdgeInsets.all(2.0),
          child: Container(
            decoration: BoxDecoration(
                color: Color.fromRGBO(255, 255, 255, 0.7),
                borderRadius: BorderRadius.all(Radius.circular(10.0)),
                boxShadow: [
                  BoxShadow(
                      color: Colors.black12,
                      spreadRadius: 2.0,
                      blurRadius: 5.0),
                ]),
            margin: EdgeInsets.all(5.0),
            child: Column(
              mainAxisSize: MainAxisSize.max,
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                ClipRRect(
        
                  child: Image.asset(
                    object["placeImage"],
                    fit: BoxFit.cover,
                    width: 280,
                    height: 180,
                  ),
                ),
                SizedBox(
                  width: 250,
                  child: Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: <Widget>[
                        Text(
                          translator.translate(object["placeName"]),
                          style: GoogleFonts.elMessiri(
                              textStyle: TextStyle(
                                  fontSize: 15.0, color: Colors.black54)),
                        ),
           
                        Text(
                          translator.translate(" ${object["minOrder"]} IQD"),
                          style:
                              TextStyle(fontSize: 12.0, color: Colors.black54),
                        )
                      ],
                    ),
                  ),
                )
              ],
            ),
          ),
        ));
      });

      return items;
    }

    return Scaffold(
      appBar: AppBar(
        backgroundColor: HexColor("#242424"),
        leading: IconButton(
          icon: Icon(Icons.arrow_back_ios),
          iconSize: 20.0,
          onPressed: () {
            Navigator.pop(context); //not working
          },
        ),
        title: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Image.asset(
              "assets/images/logo.png",
              fit: BoxFit.contain,
              height: 40,
            ),
          ],
        ),
      ),
      body: SafeArea(
          child: SingleChildScrollView(
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.center,
          mainAxisSize: MainAxisSize.min, // set min
          children: <Widget>[
            Container(
              decoration: BoxDecoration(
                image: DecorationImage(
                  image: AssetImage("assets/images/backg.png"),
                  fit: BoxFit.cover,
                ),
              ),
              height: 3000,
              width: screenWidth,
              child: FutureBuilder<List<Widget>>(
                  initialData: [Text("")],
                  future: createList(),
                  builder: (context, snapshot) {
                    if (snapshot.connectionState == ConnectionState.waiting)
                      return Text("Loading");

                    if (snapshot.hasError) {
                      return Text("Error ${snapshot.error}");
                    }
                    if (snapshot.hasData) {
                      return Padding(
                          padding: EdgeInsets.all(8.0),
                          child: GridView.count(
                            childAspectRatio: 1, // items' width/height
                            crossAxisCount: 2,
                            shrinkWrap: true,
                            physics: NeverScrollableScrollPhysics(),
                            children: [
                              // ignore: sdk_version_ui_as_code
                              ...?snapshot.data,
                            ],
                          ));
                    } else {
                      return CircularProgressIndicator();
                    }
                  }),
            )
          ],
        ),
      )),
      floatingActionButton: FloatingActionButton(
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => About()),
            );
          },
          backgroundColor: Colors.black,
          child: Icon(
            MdiIcons.information,
            color: Colors.white,
          )),
    );
  }
}

Answer 1

因为MyHomePage.

“下面”什么也没有

以下是路由在 Flutter 中的工作方式 - 将其视为一堆屏幕。初始路线（堆栈底部）是您打开应用程序时看到的第一个屏幕，在您的例子中是 MyHomePage。如果您在此屏幕顶部推送一条路线，旧屏幕 (MyHomePage) 仍然存在，但隐藏在您刚刚推送的新屏幕下方。因此，如果您在这个新屏幕中使用 pop()，它将终止它并带您回到下面的路线 - MyHomePage.

在你的例子中，当你打开应用程序时，主屏幕是MyHomePage并且下面没有任何东西，因此没有任何东西可以显示。

为了形象化这一点，请查看 this video 处的 11:00 标记。

颤动：navigator.pop() 在我的代码中无法正常工作

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