小部件测试失败，未找到任何 MediaQuery 小部件答案

【问题标题】：Widget test fails with No MediaQuery widget found小部件测试失败，未找到任何 MediaQuery 小部件
【发布时间】：2018-07-07 23:57:04
【问题描述】：

我的问题是关于颤振小部件测试，测试现有小部件包装新 Scaffold(...) 的正确方法是什么？我找到了MediaQuery.of，但它接受BuildContext 而不是Widget。

详细信息：我编写了简单的登录表单小部件并尝试为其实现小部件测试。执行测试后出现异常：

Expected: 'Sorry, only customer can login from mobile device. [Mock]'
  Actual: FlutterError:<No MediaQuery widget found.
          Scaffold widgets require a MediaQuery widget ancestor.
          The specific widget that could not find a MediaQuery ancestor was:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee]
          The ownership chain for the affected widget is:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee] ← LoginForm ← [root]
          Typically, the MediaQuery widget is introduced by the MaterialApp or WidgetsApp widget at
          the top of your application widget tree.>
   Which: FlutterError:<No MediaQuery widget found.
          Scaffold widgets require a MediaQuery widget ancestor.
          The specific widget that could not find a MediaQuery ancestor was:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee]
          The ownership chain for the affected widget is:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee] ← LoginForm ← [root]
          Typically, the MediaQuery widget is introduced by the MaterialApp or WidgetsApp widget at
          the top of your application widget tree.>is not a string

When the exception was thrown, this was the stack:
#4      main.<anonymous closure> (C:\Work\app_mobile\test\login_widget_test.dart:21:5)
<asynchronous suspension>
#5      testWidgets.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:flutter_test\src\widget_tester.dart:61:25)
#6      TestWidgetsFlutterBinding._runTestBody (package:flutter_test\src\binding.dart:471:19)
<asynchronous suspension>
#9      TestWidgetsFlutterBinding._runTest (package:flutter_test\src\binding.dart:458:14)
#10     AutomatedTestWidgetsFlutterBinding.runTest.<anonymous closure> (package:flutter_test\src\binding.dart:640:24)
#11     _FakeAsync.run.<anonymous closure> (package:quiver\testing\src\async\fake_async.dart:186:24)
#15     _FakeAsync.run (package:quiver\testing\src\async\fake_async.dart:185:11)
#16     AutomatedTestWidgetsFlutterBinding.runTest (package:flutter_test\src\binding.dart:638:16)
#17     testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test\src\widget_tester.dart:60:24)
#18     Declarer.test.<anonymous closure>.<anonymous closure> (package:test\src\backend\declarer.dart:160:19)
<asynchronous suspension>
#19     Invoker.waitForOutstandingCallbacks.<anonymous closure> (package:test\src\backend\invoker.dart:206:15)
<asynchronous suspension>
#23     Invoker.waitForOutstandingCallbacks (package:test\src\backend\invoker.dart:203:5)
#24     Declarer.test.<anonymous closure> (package:test\src\backend\declarer.dart:158:29)
<asynchronous suspension>
#25     Invoker._onRun.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test\src\backend\invoker.dart:351:23)
<asynchronous suspension>
#27     StackZoneSpecification._run (package:stack_trace\src\stack_zone_specification.dart:209:15)
#28     StackZoneSpecification._registerCallback.<anonymous closure> (package:stack_trace\src\stack_zone_specification.dart:119:48)
#33     StackZoneSpecification._run (package:stack_trace\src\stack_zone_specification.dart:209:15)
#34     StackZoneSpecification._registerCallback.<anonymous closure> (package:stack_trace\src\stack_zone_specification.dart:119:48)
#39     _Timer._runTimers (dart:isolate-patch/dart:isolate/timer_impl.dart:367)
#40     _Timer._handleMessage (dart:isolate-patch/dart:isolate/timer_impl.dart:401)
#41     _RawReceivePortImpl._handleMessage (dart:isolate-patch/dart:isolate/isolate_patch.dart:163)
(elided 17 frames from package dart:async and package dart:async-patch)

这里是登录表单小部件：

import 'dart:async';
import 'dart:convert';

import 'package:app_facade/app_facade.dart';
import 'package:app_mobile/utils/dependency_injection.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:flutter/services.dart';

class LoginForm extends StatefulWidget {
  const LoginForm({ Key key }) : super(key: key);

  static GlobalKey<FormFieldState<String>> emailFieldKey = new GlobalKey<FormFieldState<String>>();
  static GlobalKey<FormFieldState<String>> passwordFieldKey = new GlobalKey<FormFieldState<String>>();
  static const String routeName = '/';

  @override
  LoginFormState createState() => new LoginFormState();
}

class LoginData {
  String email = '';
  String password = '';
}

class LoginFormState extends State<LoginForm> {
  final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();

  LoginData loginData = new LoginData();

  UserApi _userApi;

  void showInSnackBar(String value) {
    _scaffoldKey.currentState.showSnackBar(new SnackBar(
        content: new Text(value)
    ));
  }

  bool _autovalidate = false;
  bool _formWasEdited = false;
  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();


  @override
  void initState() {
    super.initState();
    _userApi = new Injector().userApi;
  }

  Future<Null> _handleSubmitted() async {
    final FormState form = _formKey.currentState;
    if (!form.validate()) {
      _autovalidate = true;  // Start validating on every change.
      showInSnackBar('Please fix the errors in red before submitting.');
    } else {
      form.save();
      login();
    }
  }

  Future<Null> login() async {
    try {
      await _userApi.login(loginData.email, loginData.password);
      Navigator.popAndPushNamed(context, '/user');
    } catch (e) {
      showInSnackBar(e.toString());
    }
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      key: _scaffoldKey,
      appBar: new AppBar(
        title: const Text('Some'),
      ),
      body: new Form(
          key: _formKey,
          autovalidate: _autovalidate,
          child: new ListView(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            children: <Widget>[
              new TextFormField(
                key: new Key('email'),
                decoration: const InputDecoration(
                  icon: const Icon(Icons.person),
                  hintText: 'Your email',
                  labelText: 'Email *',
                ),
                onSaved: (String value) { loginData.email = value; },
              ),
              new TextFormField(
                key: LoginForm.passwordFieldKey,
                decoration: const InputDecoration(
                  icon: const Icon(Icons.security),
                  hintText: 'Your password',
                  labelText: 'Password *',
                  ),
                obscureText: true,
                onSaved: (String value) { loginData.password = value; },
              ),
              new Container(
                padding: const EdgeInsets.all(20.0),
                alignment: const FractionalOffset(0.5, 0.5),
                child: new RaisedButton(
                  child: const Text('SUBMIT'),
                  onPressed: _handleSubmitted,
                ),
              ),
              new Container(
                padding: const EdgeInsets.only(top: 20.0),
                child: new Text('* indicates required field', style: Theme.of(context).textTheme.caption),
              ),
            ],
          )
      ),
    );
  }
}

这是小部件测试：

import 'package:app_facade/app_facade.dart';
import 'package:app_mobile/login_form.dart';
import 'package:app_mobile/utils/dependency_injection.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('login widget test', (WidgetTester tester) async {
    Injector.configure(BackendType.MOCK);
    // Tells the tester to build a UI based on the widget tree passed to it
    var loginForm = new LoginForm();
    await tester.pumpWidget(
      loginForm
    );

    tester.enterText(find.byKey(LoginForm.emailFieldKey), "login");
    tester.enterText(find.byKey(LoginForm.passwordFieldKey), "password");

    var exception = tester.takeException();
    print(exception);
    expect(exception, equals('Sorry, only customer can login from mobile device. [Mock]'));
  });
}

我找到了MediaQuery.of，但不明白它如何与现有的小部件一起使用？它接受BuildContext 作为参数。

【问题讨论】：

标签： flutter dart flutter-test

【解决方案1】：

包装你的主要方法 从此

 void main() {
  runApp( YourScreen(),
     );
}

到

    void main() {
  runApp(
    MaterialApp(
      home: LoginScreen(),
    ),
  );
}

我的完整代码

    void main() {
  runApp(
    MaterialApp(
      home: LoginScreen(),
    ),
  );
}

class LoginScreen extends StatefulWidget {
  @override
  _LoginScreen createState() => _LoginScreen();
}

class _LoginScreen extends State<LoginScreen> {

  @override
  void initState() {
    super.initState();
  }


  @override
  Widget build(BuildContext context) {
      return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text(
            "Salezrobot",
            style: TextStyle(
              fontSize: 24,
              color: Colors.white,
              fontWeight: FontWeight.bold,
              fontFamily: 'HelveticaNeue',
            ),
          ),
        ),
        body: Text(""),
      ),
    );
  }
}

【讨论】：

【解决方案2】：

用MaterialApp() 包装您的小部件，并将新类传递给MaterialApp() 小部件的home 属性。

void main(){
  runApp(MyApp());
}
    
class MyApp extends StatelessWidget{
  @override
  Widget build(BuildContext context) {
    return MaterialApp( //use MaterialApp() widget like this
      home: Home() //create new widget class for this 'home' to 
                   // escape 'No MediaQuery widget found' error
    );
  }
}

参考来自：How to Solve ’No MediaQuery widget found’ Error in Flutter

【讨论】：

【解决方案3】：

替换这个

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

有了这个

void main() {
  runApp(
    const MaterialApp(
      home: MyApp(),
    ),
  );
}

【讨论】：

【解决方案4】：

scaffold() 小部件应如何成为MaterialApp() 的子级的完美示例

import 'package:flutter/material.dart';

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'title'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key Key, this.title}) : super(key: Key);

  @override
  _MyHomePageState createState() => _MyHomePageState();

}

class _MyHomePageState extends State<MyHomePage> {
  Widget build(BuildContext context) {
    return new Scaffold
    (
        appBar: AppBar(
    backgroundColor: Colors.transparent,
    title: widget.title
    )
  }

【讨论】：

【解决方案5】：

在测试环境中使用MaterialApp 包装您的小部件。

替换这个：

await tester.pumpWidget(HomeScreen());

与：

await tester.pumpWidget(MaterialApp(home:HomeScreen()));

【讨论】：

【解决方案6】：

我也遇到了同样的问题，用下面的方法解决了。

注意：我使用的是 bloc。

void main() {
 testWidgets('Find an app bar with name of weather search',
  (WidgetTester tester) async {
 await tester.pumpWidget(BlocProvider(
  create: (context) => WeatherBloc(WeatherRepo()),
  child: const MaterialApp(
  home: CounterHomePage(),
  ),
 ));

 expect(find.text('Weather Search'), findsOneWidget);
 });
}

【讨论】：

【解决方案7】：

我遇到了同样的问题，我还必须将它包装在 MaterialApp 中，但我以其他方式做到了这一点，没有使用 MediaQuery。就我而言，它有效

void main() {

Widget createWidgetForTesting({Widget child}){
return MaterialApp(
  home: child,
);
}

testWidgets('Login Page smoke test', (WidgetTester tester) async {

await tester.pumpWidget(createWidgetForTesting(child: new LoginPage()));

await tester.pumpAndSettle();

});
}

【讨论】：

【解决方案8】：

您需要用MediaQuery(...) 实例包装您的小部件，并且因为您使用的是Scaffold(..)，所以您必须将它包装在MaterialApp(..) 中