最近在学习flutter 哎，感觉到处都是坑，不说了，说多了都是泪，直接进入主题。

在使用跳转页面的时候报错

根据这个错误找了半天，感觉自己都快绝望了。突然想起前段时间获取屏幕宽高一样，需要在MaterialApp里面进行调用。无赖自己抱着侥幸的心里打算试一试。哪里知道一试就成功了，在这里自己标记一下。希望给后面的兄弟有一些帮助。代码如下

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_iot/util/SharePreferenceUtil.dart';
import 'dart:io';
import 'package:flutter_iot/net/ApiStores.dart';
import 'package:flutter_iot/net/RequestApi.dart';
import 'dart:convert';
import 'loging.dart';

void main() => runApp(new RunApp());

/**
 * 2019年4月11日15:03:12
 * 加载页面
 * ygang
 * **/
class RunApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return new LoadDart();
  }
}

var cont;

class LoadDart extends State<RunApp> {
  @override
  void initState() {
    super.initState();
    Timer timer = new Timer(new Duration(seconds: 1), () {
      Future<bool> b = getBool(IS_LOGIN);
      b.then((bool b) {
        if (b) {
          //已经登录
          print(">>>>>>true");
          getMyAccountMessage();
          getgetPermission();
        } else {
          //没有登录
          print(">>>>>>false");
          if (cont == null) {
            print(">>>>>>cont =false");
          }
          Navigator.of(cont).pushAndRemoveUntil(
              new MaterialPageRoute(builder: (BuildContext context) {
            return new Loging();
          }), (route) => route == null);
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new MaterialApp(
      title: "LoadActivity",
      home: new HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    cont = context;
    final size = MediaQuery.of(context).size;
    // TODO: implement build
    return new Stack(
      children: <Widget>[
        new Center(
          child: new Image.asset(
            "images/load_bg.png",
            fit: BoxFit.fill,
            height: size.height,
            width: size.width,
          ),
        ),
        new Positioned(
          left: 40,
          right: 40,
          top: size.height / 2 - 120,
          child: new Image.asset(
            "images/load_center.png",
          ),
        ),
        new Positioned(
          bottom: 20,
          left: 40,
          right: 40,
          child: new Image.asset(
            "images/load_botton.png",
          ),
        ),
        new Positioned(
          top: (size.height - 470) / 2,
          child: new Image.asset(
            "images/load_left.png",
            width: 198,
            height: 470,
          ),
        ),
        new Positioned(
          right: 0,
          child: new Image.asset(
            "images/load_right.png",
            width: 104,
            height: 554,
          ),
        )
      ],
    );
  }
}

/**
 * 获取个人账套的信息
 */
void getMyAccountMessage() async {
  var httpClient = new HttpClient();
  var uri = getUri() + getMyAccountMessagePath;
  String result;
  try {
    var request = await httpClient.getUrl(Uri.parse(uri));
    var response = await request.close();
    if (response.statusCode == HttpStatus.OK) {
      var json1 = await response.transform(utf8.decoder).join();
      var data = json.decode(json1);
      result = data['origin'];
    } else {
      result = 'Error getting IP address:\nHttp status ${response.statusCode}';
    }
  } catch (exception) {
    result = 'Failed getting IP address';
  }
}

/**
 * 获取权限标识
 */
void getgetPermission() async {}