CODEWITHSUNDEEP
flutterdart
Amal yosri
Amal yosri

Reputation: 105

The operator '<' can't be unconditionally invoked because the receiver can be 'null'. Try adding a null check to the target ('!')

my code:

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main(){
runApp(myapp());
}
info(a){
  return a;
}
class myapp extends StatelessWidget{
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(   
    home: homepage(),
    
    );
  }
  
}

class homepage extends StatefulWidget{
  @override
  _homePage createState()=>_homePage() ;

}

class _homePage extends State<homepage>{
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
   return StreamBuilder(stream:Stream.periodic(Duration(seconds: 3),(a)=>a) ,
   builder: (ctx,  snapshot){
    
     return Scaffold(
       appBar: AppBar(title: Text(         
         (snapshot.hasData && snapshot.data < 10)?"${snapshot.data}":"demo"),
         ),
       body:  Center(
         child:  snapshot .connectionState==ConnectionState.waiting?CircularProgressIndicator():Text("done"),
       ),
     );
   },);
  }
}

i have a error :

The operator '<' can't be unconditionally invoked because the receiver can be 'null'. Try adding a null check to the target ('!').

when i change snapshot.hasData && snapshot.data < 10 to snapshot.hasData && snapshot.data! < 10

or snapshot.hasData && snapshot!.data < 10

the error does not solve

dose anyone know the solution?

Upvotes: 0

Views: 2257

Answers (1)

Adelina
Adelina

Reputation: 11881

You are getting this error because null safety is turned on. So either turn it off https://dart.dev/null-safety/unsound-null-safety

Or

    return StreamBuilder<int?>( # add type 
      stream: Stream.periodic(Duration(seconds: 3), (a) => a),
      builder: (ctx, snapshot) {
        return Scaffold(
          appBar: AppBar(
            title: Text((snapshot.hasData && snapshot.data! < 10) # add bang operator
                ? "${snapshot.data}"
                : "demo"),
          ),

Upvotes: 1

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