The getter 'length' was called on null. fetch from api - flutter

Question

I am trying to fetch data from api its splash screen of my app I want user wait 5 second when app is launched and then go to next screen but when I tried fetch data from api I received The getter 'length' was called on null. please help me here is my code I tried resolve it number of other resources but failed to find solution that's why I am posting my question is here please check and help
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_app/main.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main() {
runApp(new MaterialApp(
home: new SplashScreen(),
debugShowCheckedModeBanner: false,
routes: <String, WidgetBuilder>{
'/MyHomePage': (BuildContext context) => new MyHomePage()
},
));
}
class SplashScreen extends StatefulWidget {
#override
_SplashScreenState createState() => new _SplashScreenState();
}
class _SplashScreenState extends State<SplashScreen> {
startTime() async {
var _duration = new Duration(seconds: 5);
return new Timer(_duration, navigationPage);
}
void navigationPage() {
Navigator.of(context).pushReplacementNamed('/MyHomePage');
}
bool _loading=true;
Map data;
List userData=null;
Future getData() async {
http.Response response = await http.get("https://livinghopemobile.com/public/api/fetch-site-settings?token=123ab_#_#AbCD");
data = json.decode(response.body);
debugPrint(response.body);
setState(() {
userData = data["data"];
_loading=false;
// print(userData[0]['title']);
});
}
#override
void initState() {
super.initState();
//startTime();
getData();
}
#override
Widget build(BuildContext context) {
return new Scaffold(
body: ListView.builder(
itemCount:userData.length,
itemBuilder: (context, index) {
return Container(
child: Image.network(userData[index]['site_logo']),
);
}
)
);
}
}
Launching lib/ui/SplashScreen.dart on iPhone 11 Pro Max in debug mode...
Running Xcode build...
Xcode build done. 23.8s
Debug service listening on ws://127.0.0.1:60469/bL7bmRYyhoc=/ws
Syncing files to device iPhone 11 Pro Max...
════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following NoSuchMethodError was thrown building SplashScreen(dirty, state: _SplashScreenState#5fa75):
The getter 'length' was called on null.
Receiver: null
Tried calling: length
The relevant error-causing widget was:
SplashScreen file:///Users/apple/livinghopev4/livinghope4ios/lib/ui/SplashScreen.dart:10:15
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
#1 _SplashScreenState.build (package:flutter_app/ui/SplashScreen.dart:61:30)
#2 StatefulElement.build (package:flutter/src/widgets/framework.dart:4612:27)
#3 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4495:15)
#4 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4667:11)
...
════════════════════════════════════════════════════════════════════════════════════════════════════
flutter: {"status":200,"message":"Data fetched successfully","data":{"id":1,"site_logo":"https:\/\/livinghopemobile.com\/public\/storage\/site_logo\/270421_122025_image.png","site_name":"Living hope","created_at":null,"updated_at":"2021-04-27T07:20:26.000000Z"}}
[VERBOSE-2:ui_dart_state.cc(186)] Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List<dynamic>'
#0 _SplashScreenState.getData.<anonymous closure> (package:flutter_app/ui/SplashScreen.dart:41:7)
#1 State.setState (package:flutter/src/widgets/framework.dart:1267:30)
#2 _SplashScreenState.getData (package:flutter_app/ui/SplashScreen.dart:40:5)
<asynchronous suspension>

Answer 1

This is because data is not type List, and userData is null hence there is no length to it when you are calling userData.length in ListView.builder.
Change null to [].
{"status":200,"message":"Data fetched successfully","data":{"id":1,"site_logo":"https:\/\/livinghopemobile.com\/public\/storage\/site_logo\/270421_122025_image.png","site_name":"Living hope","created_at":null,"updated_at":"2021-04-27T07:20:26.000000Z"}}
You could append the received data to userData, like: userData.add(data).

Answer 2

You try it:
itemCount:userData.length == null ? 0 : userData.length

Answer 3

Data is returning in Object and you are taking it as List. This is the reason you are getting the error.
Solution:
Don't use Listview.builder as api response is just an object(Map<String, dynamic>).
You can simply use
Image.network(userData['site_logo']),
and everthing will be fine.