从一页过渡到另一页 - Flutter

问题描述

所以，我有一个简单的单页应用程序。我在该页面上创建了一个复选框，以便在单击该复选框时转换到另一个页面。但是，复选框的 onChanged 参数出现错误。如下：

CheckBox(
value: false,onChanged: (bool newValue) {
Navigator.push(
context,new MaterialPageRoute(builder: (ctxt) => new SecondScreen()),);
})

但是最后一行代码给了我以下错误，我不知道如何解决：

*

返回类型“SecondScreen”不是 闭包的上下文。

因此，SecondScreen 不是无状态小部件。但是如何修改 MaterialPageRouter 以成功过渡到这个新页面。

我的第二屏如下：

   class SensorPage extends StatefulWidget {
   const SensorPage({Key key,this.device}) : super(key: key);
   final BluetoothDevice device;

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

   class SecondScreen extends State<SensorPage> {
   final String SERVICE_UUID = "0000ffe0-0000-1000-8000-00805f9b34fb";
   final String CHaraCTERISTIC_UUID = "0000ffe1-0000-1000-8000-00805f9b34fb";
  bool isReady;
  Stream<List<int>> stream;
  List<double> traceDust;

  String _dataParser2(List<int> dataFromDevice) {
    return utf8.decode(dataFromDevice);
  }

  @override
  void initState() {
    super.initState();
    isReady = false;
  }

  @override
  Widget build (BuildContext ctxt) {
    Oscilloscope oscilloscope = Oscilloscope(
      showYAxis: true,padding: 0.0,backgroundColor: Colors.black,traceColor: Colors.white,yAxisMax: 500.0,yAxisMin: 0.0,dataSet: traceDust,);

    return new Scaffold(
      appBar: new AppBar(
        title: new Text("Home"),),body: Container(
          child: !isReady
              ? Center(
            child: Text(
              "Waiting...",style: TextStyle(fontSize: 24,color: Colors.red),)
              : Container(
            child: StreamBuilder<List<int>>(
              stream: stream,builder: (BuildContext context,AsyncSnapshot<List<int>> snapshot) {
                if (snapshot.hasError)
                  return Text('Error: ${snapshot.error}');

                if (snapshot.connectionState ==
                    ConnectionState.active){
                  var currentValue2 = _dataParser2(snapshot.data);
                  traceDust.add(double.tryParse(currentValue2) ?? 0);
                  return Center(
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
                          Expanded(flex: 1,child:Column(
                              mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
                                Text('Home',style: TextStyle(fontSize: 14)),Text('${currentValue2} IamHome',style: TextStyle(
                                        fontWeight: FontWeight.bold,fontSize: 24))
                              ]),Expanded(
                            flex: 1,child: oscilloscope,)
                        ],));
                } else {
                  return Text('Check the stream');
                }
              },))
    );
  }
}

解决方法

您在应该使用 Navigator 的地方使用小部件 Navigator.of(context)。

您的代码应如下所示：

Checkbox(
    value: false,onChanged: (bool newValue) {
    Navigator.of(context).push(MaterialPageRoute(
                          builder: (BuildContext context) =>
                              SecondScreen()));
})

,

定义 SensorPage 状态的类名的方式有误。对于您的情况，它应该是 _SensorPageState

请查看以下代码：

import 'package:flutter/material.dart';
// add the rest of packages

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

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

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        body: Container(
          child: Checkbox(
            value: false,onChanged: (bool newValue) {
              Navigator.push(
                context,new MaterialPageRoute(builder: (context) => new SensorPage()),);
            }
          ),),);
  }
}

class SensorPage extends StatefulWidget {
  const SensorPage({Key key,this.device}) : super(key: key);
  final BluetoothDevice device;

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

class _SensorPageState extends State<SensorPage> {
  final String SERVICE_UUID = "0000ffe0-0000-1000-8000-00805f9b34fb";
  final String CHARACTERISTIC_UUID = "0000ffe1-0000-1000-8000-00805f9b34fb";
  bool isReady;
  Stream<List<int>> stream;
  List<double> traceDust;

  String _dataParser2(List<int> dataFromDevice) {
    return utf8.decode(dataFromDevice);
  }

  @override
  void initState() {
    super.initState();
    isReady = false;
  }

  @override
  Widget build (BuildContext ctxt) {
    Oscilloscope oscilloscope = Oscilloscope(
      showYAxis: true,padding: 0.0,backgroundColor: Colors.black,traceColor: Colors.white,yAxisMax: 500.0,yAxisMin: 0.0,dataSet: traceDust,);

    return new Scaffold(
        appBar: new AppBar(
          title: new Text("Home"),body: Container(
            child: !isReady
                ? Center(
              child: Text(
                "Waiting...",style: TextStyle(fontSize: 24,color: Colors.red),)
                : Container(
              child: StreamBuilder<List<int>>(
                stream: stream,builder: (BuildContext context,AsyncSnapshot<List<int>> snapshot) {
                  if (snapshot.hasError)
                    return Text('Error: ${snapshot.error}');

                  if (snapshot.connectionState ==
                      ConnectionState.active){
                    var currentValue2 = _dataParser2(snapshot.data);
                    traceDust.add(double.tryParse(currentValue2) ?? 0);
                    return Center(
                        child: Column(
                          mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
                            Expanded(flex: 1,child:Column(
                                mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
                                  Text('Home',style: TextStyle(fontSize: 14)),Text('${currentValue2} IamHome',style: TextStyle(
                                          fontWeight: FontWeight.bold,fontSize: 24))
                                ]),Expanded(
                              flex: 1,child: oscilloscope,)
                          ],));
                  } else {
                    return Text('Check the stream');
                  }
                },))
    );
  }
}