I am trying to fetch data from an API but unable to get because of this length error. "The property 'length' can't be unconditionally accessed because the receiver can be 'null'.\nTry making the access conditional (using '?.') or adding a null check to the target ('!').",

When i put null check it is giving the error below: The getter 'length' isn't defined for the type 'Object'. Try importing the library that defines 'length', correcting the name to the name of an existing getter, or defining a getter or field named 'length'.

Here is the Code :

import 'package:flutter/material.dart';

import 'package:http/http.dart' as http;

class api extends StatefulWidget {
  const api({Key? key}) : super(key: key);

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

class _apiState extends State<api> {
  getuser() async {
    var users = [];
    var response =
        await http.get(Uri.https('jsonplaceholder.typicode.com', 'users'));
    var jsonData = jsonDecode(response.body);

    for (var i in jsonData) {
      UserModel user = UserModel(i['name'], i['username'], i['email']);
      users.add(user);
    }
    return users;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder(
          future: getuser(),
          builder: (context, snapshot) {
            if (snapshot.data != null) {
              return Container(
                child: Text("Nothing in API"),
              );
            } else
              return ListView.builder(
                  itemCount: snapshot.data.length,
                  itemBuilder: (context, i) {
                    return ListTile(
                      title: Text((snapshot.data as dynamic)[i].name),
                    );
                  });
          }),
    );
  }
}

class UserModel {
  var name;
  var username;
  var email;

  UserModel(this.name, this.username, this.email);
}

Error in line 39

CodePudding user response：

The error is in the if (snapshot.data != null) condition. If the content returned by your API is not null, then you display a Text widget which says se opposite. So your ListView is called only when snapshot.data is null. Try replacing it with if (snapshot.data == null) and you should be fine.

CodePudding user response：

The best way to Handle that:

FutureBuilder<List<YourObject>>(
          future: yourFuture,
          builder: (context, snapshot) {

            if(!snapshot.hasData ){
              return const Text("Nothing in API");
            }
            final list = snapshot.data;

            if(list!.isEmpty){
              return const Text("Nothing in API");
            }

            return ListView.builder(
                itemCount: list.length,
                itemBuilder: (context, i) {
                  return ListTile(
                    title: Text(list[i].name),
                  );
                });

          }
        )

CodePudding user response：

Resolved the Error by adding AsyncSnapshot before snapshot in FutureBuilder-builder and also replacing the line from if (snapshot.data != null) to if (snapshot.data == null).

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

class api extends StatefulWidget {
  const api({Key? key}) : super(key: key);

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

class _apiState extends State<api> {
  getuser() async {
    var users = [];
    var response =
        await http.get(Uri.https('jsonplaceholder.typicode.com', 'users'));
    var jsonData = jsonDecode(response.body);

    for (var i in jsonData) {
      UserModel user = UserModel(i['name'], i['username'], i['email']);
      users.add(user);
    }
    return users;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder(
          future: getuser(),
          builder: (context,AsyncSnapshot snapshot) {
            if (snapshot.data == null) {
              return Container(
                child: Text("Nothing in API"),
              );
            } 
            else return ListView.builder(
                  itemCount: snapshot.data.length,
                  itemBuilder: (context, i) {
                    return ListTile(
                      title: Text(snapshot.data[i].name),
                      subtitle: Text(snapshot.data[i].username),
                    );
                  });
          }),
    );
  }
}

class UserModel {
  var name;
  var username;
  var email;

  UserModel(this.name, this.username, this.email);
}