Question

当我尝试导航到下一个屏幕时，抛出该错误。我之前已经面对过，在树中添加新的上下文通常是可行的。这次不是。我该怎么办？

Error:
E/flutter (22865): [ERROR:flutter/lib/ui/ui_dart_state.cc(166)] 
Unhandled Exception: NoSuchMethodError: The method 'findAncestorStateOfType' was called on null. 
E/flutter (22865): Receiver: null 
E/flutter (22865): Tried calling: findAncestorStateOfType()

class _LoginMainState extends State<LoginMain> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: SafeArea(
        child: Scaffold(
          appBar: AppBar(
            title: Text('Sorted.'),
            backgroundColor: Color(0xff0A3D62),
            flexibleSpace: Container(
              decoration: BoxDecoration(
                  gradient: LinearGradient(
                      begin: Alignment.topLeft,
                      end: Alignment.bottomRight,
                      colors: <Color>[
                    const Color(0xFF5761B2),
                    const Color(0xFF1FC588),
                  ])),
            ),
          ),
          drawer: null,
          body: Container(
              padding: EdgeInsets.only(top: 30),
              width: 360,
              height: 600,
              color: const Color(0xFF273748),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  SizedBox(
                    width: 300,
                    height: 400,
                    child: Container(
                      padding: EdgeInsets.all(15),
                      decoration: BoxDecoration(
                        shape: BoxShape.rectangle,
                        borderRadius: BorderRadius.circular(20.0),
                        gradient: LinearGradient(
                            begin: Alignment.topLeft,
                            end: Alignment.bottomRight,
                            colors: [Colors.white, Colors.grey[400]]),
                      ),
                      child: SizedBox(
                        width: 50,
                        height: 50,
                        child: Container(
                          child: MaterialButton(
                            color: Colors.green,
                            splashColor: Colors.teal,
                            textColor: Colors.white,
                            child: new Icon(Icons.arrow_forward),
                            onPressed: () async {
                              bool res = await AuthProvider().loginWithGoogle();
                              if (res) {
                                Navigator.push(
                                    context,
                                    MaterialPageRoute(
                                        builder: (context) => SortedMain()));
                              } else
                                print("Login failed");

谢谢！

Answer 1

问题是因为MaterialApp上方没有上下文。 Navigator取决于MaterialApp的上下文，并且由于唯一可用的上下文位于应用程序上方，因此会引发错误。

您提到您以前曾遇到过此问题，并通过添加其他上下文对其进行了修复。但是您没有指定添加的位置。

要解决此问题，只需使用Builder将内容包装在MaterialApp下，或将其移动到单独的无状态或有状态小部件。


class _LoginMainState extends State<LoginMain> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Added this
      home: Builder(
      builder: (context) => SafeArea(
        child: Scaffold(
          appBar: AppBar(
            title: Text('Sorted.'),
            backgroundColor: Color(0xff0A3D62),
            flexibleSpace: Container(
              decoration: BoxDecoration(
                  gradient: LinearGradient(
                      begin: Alignment.topLeft,
                      end: Alignment.bottomRight,
                      colors: <Color>[
                    const Color(0xFF5761B2),
                    const Color(0xFF1FC588),
                  ])),
            ),
          ),
          drawer: null,
          body: Container(
              padding: EdgeInsets.only(top: 30),
              width: 360,
              height: 600,
              color: const Color(0xFF273748),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  SizedBox(
                    width: 300,
                    height: 400,
                    child: Container(
                      padding: EdgeInsets.all(15),
                      decoration: BoxDecoration(
                        shape: BoxShape.rectangle,
                        borderRadius: BorderRadius.circular(20.0),
                        gradient: LinearGradient(
                            begin: Alignment.topLeft,
                            end: Alignment.bottomRight,
                            colors: [Colors.white, Colors.grey[400]]),
                      ),
                      child: SizedBox(
                        width: 50,
                        height: 50,
                        child: Container(
                          child: MaterialButton(
                            color: Colors.green,
                            splashColor: Colors.teal,
                            textColor: Colors.white,
                            child: new Icon(Icons.arrow_forward),
                            onPressed: () async {
                              bool res = await AuthProvider().loginWithGoogle();
                              if (res) {
                                Navigator.push(
                                    context,
                                    MaterialPageRoute(
                                        builder: (context) => SortedMain()));
                              } else
                                print("Login failed");

如果这行不通，只需将页面移至其他小部件（无状态或有状态）。

在null上调用了方法'findAncestorStateOfType'

1 个答案: