您忘记将参数BuildContext context添加到函数中
代码段

functionOne(BuildContext context) {
    Navigator.push(
        context,new MaterialPageRoute(builder: (context) => RamOne()));
  }

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:linear_gradient/linear_gradient.dart';
import 'package:gradient_text/gradient_text.dart';
//import 'package:apple_beauty/cdetails.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then,without quitting the app,try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",// or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,),home: MyHomePage(title: 'Flutter Demo Home Page'),);
  }
}

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

  // This widget is the home page of your application. It is stateful,meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State,which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(),then the build method would not be
      // called again,and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called,for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast,so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method,and use it to set our appbar title.
        title: Text(widget.title),body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default,it sizes itself to fit its
          // children horizontally,and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console,choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio,or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
            Expanded(flex:5,child: RamList()),Text(
              'You have pushed the button this many times:',Text(
              '$_counter',style: Theme.of(context).textTheme.display1,],floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,tooltip: 'Increment',child: Icon(Icons.add),// This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Gradient gradient =
    LinearGradient(colors: [Colors.teal,Colors.deepOrange,Colors.pink]);

class RamList extends StatefulWidget {
  @override
  _RamListState createState() => _RamListState();
}

class _RamListState extends State<RamList> {
  @override
  Widget build(BuildContext context) {
    return _myListView(context);
  }
}

Widget _myListView(BuildContext context) {
  final titles = [
    '1st','2nd','3rd','4th','5th',];

  final numbers = [
    '1 ','2 ','3 ','4 ','5 ',];

  functionOne(BuildContext context) {
    Navigator.push(
        context,new MaterialPageRoute(builder: (context) => RamOne()));
  }

  functionTwo(BuildContext context) {
    Navigator.push(context,MaterialPageRoute(builder: (context) => RamTwo()));
  }

  functionThree(BuildContext context) {
    Navigator.push(
        context,MaterialPageRoute(builder: (context) => RamThree()));
  }

  functionFour(BuildContext context) {
    Navigator.push(context,MaterialPageRoute(builder: (context) => RamFour()));
  }

  functionFive(BuildContext context) => _onAlertButtonPressed1(context);

  final List<Function> onTaps = [
    functionOne,functionTwo,functionThree,functionFour,functionFive,];

  return ListView.builder(
      itemCount: titles.length,itemBuilder: (context,index) {
        return Card(
            elevation: 50,child: InkWell(
              splashColor: Colors.green,highlightColor: Colors.red,child: Row(
                children: <Widget>[
                  Container(
                    height: 100.0,width: 50.0,decoration: BoxDecoration(
                        gradient: LinearGradientStyle.linearGradient(
                            orientation:
                                LinearGradientStyle.ORIENTATION_HORIZONTAL,gradientType:
                                LinearGradientStyle.GRADIENT_TYPE_AMIN)),Container(
                      margin: EdgeInsets.all(10),child: Text(
                        numbers[index],)),Flexible(
                      child: Container(
                    margin: EdgeInsets.all(10),child: GradientText(
                      (titles[index]),gradient: gradient,style: TextStyle(
                        fontSize: 20.0,fontWeight: FontWeight.bold,//Text(titles[index]),))
                ],onTap: () => onTaps[index](context),));
      });
}

_onAlertButtonPressed1(context) {
  AlertDialog alert = AlertDialog(
    title: Text('Coming soon'),content: Text("This link will be available in future updates"),actions: [],);

  showDialog(
    context: context,builder: (BuildContext context) {
      return alert;
    },);
}

class RamOne extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text("RamOne");
  }
}

class RamTwo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text("RamTwo");
  }
}

class RamThree extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text("RamThree");
  }
}

class RamFour extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text("RamFour");
  }
}