手势捕获异常：处理手势时抛出以下 NoSuchMethodError：

问题描述

我是编程和 Flutter 的新手。

在我的应用程序中，我构建了一个带有 int 变量的页面导航器。更改整数值后，我希望应用程序将用户路由到特定的指定页面。但是，我在pressed 上收到了“匿名关闭”错误。

如果有人能解释为什么我会收到此错误并发布此代码的更正版本，我们将不胜感激？

以下是调试器中的完整错误片段。

Reloaded 1 of 529 libraries in 885ms.
Flutter: Page #1 Clicked

════════ Exception caught by gesture ═══════════════════════════════════════════
The following NoSuchMethodError was thrown while handling a gesture:
The method 'call' was called on null.
Receiver: null
Tried calling: call()

When the exception was thrown,this was the stack
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1      _MyHomePageState.build.<anonymous closure>
package:navigator_test/main.dart:45
#2      _InkResponseState._handleTap
package:Flutter/…/material/ink_well.dart:993
#3      _InkResponseState.build.<anonymous closure>
package:Flutter/…/material/ink_well.dart:1111
#4      GestureRecognizer.invokeCallback
package:Flutter/…/gestures/recognizer.dart:183
...
Handler: "onTap"
Recognizer: TapGestureRecognizer#5df0c
    debugOwner: GestureDetector
    state: possible
    won arena
    finalPosition: Offset(208.7,509.7)
    finalLocalPosition: Offset(76.7,19.7)
    button: 1
    sent tap down
════════════════════════════════════════════════════════════════════════════════

以下是导航器的描述

import 'package:Flutter/material.dart';
import 'package:navigator_test/main.dart';
import 'package:navigator_test/page1.dart';

class Navigator extends StatefulWidget {
  @override
  _NavigatorState createState() => _NavigatorState();
}

class _NavigatorState extends State<Navigator> {
  int nav = 0;

  void page1() {
    setState(() {
      nav = 1;
    });
  }

  @override
  Widget build(BuildContext context) {
    if (nav < 1) {
      return MyHomePage(page1: page1);
    } else if (nav < 2) {
      return Page1();
    } else {
      return null;
    }
  }
}

我正在主页面上导入函数。

import 'package:Flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primarySwatch: Colors.blue,visualDensity: VisualDensity.adaptivePlatformDensity,),home: MyHomePage(),);
  }
}

class MyHomePage extends StatefulWidget {
  final Function page1;
  MyHomePage({this.page1});

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Navigation Test'),body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
            SizedBox(height: 20),FlatButton.icon(
              onpressed: () {
                print('Page #1 Clicked');
                widget.page1();
              },icon: Icon(Icons.add_shopping_cart),label: Text('Goto Page #1'),)
          ],// This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

解决方法

您收到此错误是因为您直接在 MyApp 中调用 MyHomePage，而不传递参数 page1，因此当您按“转到页面 #1”时，将调用一个空函数。要解决该问题，您可以改为在 MyApp 中调用 Navigator：

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primarySwatch: Colors.blue,visualDensity: VisualDensity.adaptivePlatformDensity,),home: Navigator(),);
  }
}

但是无需调用 setState 导航到新页面的主要方法是使用 Flutter 的 Navigator 类，如下所示 （请记住先删除您的 Navigator 类，这样 IDE 将知道你正在调用 flutter 的 Navigator 类）：

onPressed: () {
  print('Page #1 Clicked');
  //push the new route,but allowing you to go back to the previous one
  Navigator.of(context).push(

    //Default page transition of android
    MaterialPageRoute(
      builder: (context) => Page1(),);
},

或者：

Navigator.of(context).push(
  //Default page transition of IOS
  CupertinoPageRoute(
    builder: (context) => Page1(),);

有关详细信息，请参阅 docs。