Flutter - 使用 laravel 获取方法 api
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【中文标题】Flutter - 使用 laravel 获取方法 api【英文标题】：Flutter - Get method api with laravel 【发布时间】：2019-11-07 20:26:36 【问题描述】：我有颤振的应用程序，我正在尝试调用 api，并获取 json，但它不适用于我
它向我显示了这个错误 I/flutter (13300)：在 null 上调用了 getter 'length'。 I/颤振（13300）：接收器：空 I/flutter (13300)：尝试调用：长度
模型 Category_list.dart
class Category
List<Data> data;
String status;
Category(this.data, this.status);
factory Category.fromJson(Map<String, dynamic> json)
var list1=json['data'] as List;
List<Data> data= list1.map((i)=> Data.fromJson(i)).toList();
return Category(
data: data,
status: json['status']
);
class Data
int id;
String name;
String image;
String items;
Data(this.id, this.name, this.image, this.items);
factory Data.fromJson(Map<String, dynamic> json)
return Data(
id: json['id'],
name: json['name'],
image: json['image'],
items: json['items'],
);
服务 Category_list_services.dart
import 'dart:convert';
import 'package:scoped_model/scoped_model.dart';
import 'dart:async' as future;
import 'package:dio/dio.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../Models/Category_list.dart';
class CategoryListModel extends Model
bool _CategoryLoading = false;
Category _category;
bool get CategoryLoading => _CategoryLoading;
Dio dio = Dio();
Future<Response<dynamic>> getCategory() async
_CategoryLoading = true;
notifyListeners();
final SharedPreferences prefs = await SharedPreferences.getInstance();
dio.options.headers = 'lang': 'en', 'Authorization': prefs.get('token');
dio.options.baseUrl = "I put here my api url";
return await dio.get('/category/list');
Future<Category> loadCategoryResponse() async
var jsonString, jsonResponse;
try
jsonString = await getCategory();
jsonResponse = json.decode(jsonString.toString());
print(jsonResponse);
_category = Category.fromJson(jsonResponse);
if (jsonString.statusCode >= 200 && jsonString.statusCode < 300)
_CategoryLoading = true;
notifyListeners();
return _category;
else
throw Exception("atefffffffffffffffff");
// _CategoryLoading = false;
// notifyListeners();
//
// return _category;
on DioError catch (e)
if (e.response != null)
_CategoryLoading = false;
notifyListeners();
return _category;
屏幕分类页面.dart
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import '../Models/Category_list.dart';
import '../Scoped_model/main_model.dart';
class CategoriesPage extends StatefulWidget
@override
_CategoriesPageState createState() => _CategoriesPageState();
class _CategoriesPageState extends State<CategoriesPage>
MainModel model = MainModel();
Category category = Category();
var dataa;
@override
void initState()
model.loadCategoryResponse().then((data)
setState(()
this.dataa= data;
);
);
super.initState();
@override
Widget build(BuildContext context)
// TODO: implement build
return Scaffold(
backgroundColor: Theme.of(context).primaryColor,
appBar: AppBar(
backgroundColor: Theme.of(context).accentColor,
elevation: 0.0,
title: Text(
" الاقسام",
style: TextStyle(
color: Colors.white,
),
),
centerTitle: true,
leading: Icon(
Icons.search,
color: Colors.white,
),
),
endDrawer: Drawer(
child: Container(
color: Theme.of(context).accentColor,
child: Directionality(
textDirection: TextDirection.rtl,
child: Center(
child: ListView(
children: <Widget>[
SizedBox(
height: 100,
),
//------------------home----------
ListTile(
onTap: ()
Navigator.of(context).pushNamed("/homepage");
,
title: Text(
"الصفحة الرئيسية",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.home,
color: Colors.white,
),
),
//------------------latest--------------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.of(context).pushNamed("/latest");
,
title: Text(
"الاخيرة",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.view_list,
color: Colors.white,
),
),
//--------------------Popular---------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.of(context).pushNamed("/popular");
,
title: Text(
"شائع",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.local_florist,
color: Colors.white,
),
),
//--------------rated------------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.of(context).pushNamed("/rated");
,
title: Text(
"تقيم",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.group,
color: Colors.white,
),
),
//-----------------categories--------------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.pop(context);
,
title: Text(
"الاقسام",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.folder_open,
color: Colors.white,
),
),
//---------------------Gifs-------------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.of(context).pushNamed("/Gif");
,
title: Text(
"شائع",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.gif,
color: Colors.white,
),
),
//----------------favourite-------------------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.of(context).pushNamed('/favourite');
,
title: Text(
"المفضلة",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.favorite_border,
color: Colors.white,
),
),
//--------------profile---------------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.of(context).pushNamed('/profile');
,
title: Text(
"الصفحة الشخصية",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.person_pin_circle,
color: Colors.white,
),
),
//---------------settings-------------
SizedBox(
height: 7,
),
ListTile(
onTap: () ,
title: Text(
"الاعدادات",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.settings,
color: Colors.white,
),
),
//-----------------login--------------
SizedBox(
height: 7,
),
ListTile(
onTap: ()
Navigator.of(context).pushNamed("/singin");
,
title: Text(
"تسجيل خروج",
style: TextStyle(
color: Colors.white,
),
),
leading: Icon(
Icons.settings_backup_restore,
color: Colors.white,
),
),
],
),
),
),
),
),
body: GridView.builder(
shrinkWrap: true,
scrollDirection: Axis.vertical,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 3, crossAxisSpacing: 3, mainAxisSpacing: 3),
itemCount: dataa.length,
itemBuilder: (BuildContext context,int index)
return gridItem(dataa[index].name,
dataa[index].image,dataa[index].items);
));
Widget gridItem(String text, String photo, String item)
return Stack(
children: <Widget>[
Container(
height: 150,
width: 150,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(60),
image:
DecorationImage(image: AssetImage(photo), fit: BoxFit.cover),
color: Colors.red),
child: Align(
alignment: Alignment.center,
child: Padding(
padding: const EdgeInsets.only(top: 25),
child: Column(
children: <Widget>[
Text(
text,
style: TextStyle(
color: Colors.white,
),
),
Text(
item,
style: TextStyle(
color: Colors.white,
),
),
],
),
),
),
)
],
);
【问题讨论】：
【参考方案1】：我不确定，但它看起来像是代码中的错误。
class _CategoriesPageState extends State<CategoriesPage>
MainModel model = MainModel(); <--- this one
应该是：
CategoryListModel model = new CategoryListModel();
【讨论】：
不，Dart 2 doesn't requirenew
我不是在谈论 new 关键字。 OP 正在实例化错误的类。【参考方案2】：
我认为问题在于您没有在构造 CategoryListModel 时实例化 dataa，这意味着它为空（根据错误猜测，对 Dart 不太熟悉）。所以在请求响应中设置 dataa 之前，这一行：
temCount: dataa.length,
在 null 上调用 .length。
相反，我建议将dataa 实例化为一个空数组，如下所示：
// ...
Category category = Category();
dataa = [];
// ...
【讨论】：
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