Question 217009 in Flutter Question posted in
The official Flutter documentation can be found here.

Flutter – Exception handling inside FutureBuilder

import 'package:flutter/material.dart';

void main() {
  runApp(const MainApp());
}

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  Future<void> _initialize() async {
    await Future.delayed(const Duration(seconds: 2));
    try {
      throw Exception("Error");
    } catch (e) {}
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: FutureBuilder(
          future: _initialize(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.done) {
              if (snapshot.hasError) {
                return const Text(snapshot.error.toString());
              }
              return const Text("Completed");
            }
            return const CircularProgressIndicator();
          },
        ),
      ),
    );
  }
}

In this code I am trying to display the error inside the FutureBuilder. If handle the error with a try catch statement, the future is completed with no errors, but If don’t, the app crashes. How can I make the FutureBuilder aware of the error?

Tags:

2

Answers


  1. 0

    note: Future<void> is not return any value. If you still use it, the snapshot.data will always null.

    Future.builder will catch any error when the future function throw any exception.

    void main() {
  runApp(const MainApp());
}

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  Future<String> _initialize() async {
    await Future.delayed(const Duration(seconds: 2));
    try {
      // call your function here
      // for example this method will return String complete
      return Future.value("Complete");
    }  on TimeoutException catch(e) {
      throw ("Time out broo....!$e"); // you can throw custom message
      
    } catch (e) {
      rethrow; // this is will throw any error message;
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: FutureBuilder<String>(
            future: _initialize(),
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                if (snapshot.hasError) {
                  return Text(snapshot.error.toString());
                } else if (snapshot.hasData) {
                  return Text(snapshot.data!); 
                }
              }
              return const CircularProgressIndicator();
            },
          ),
        ),
      ),
    );
  }
}
    Login or Signup to reply.
  2. 0

    Try return Future.error("Error") when you catch an error.

      Future<void> _initialize() async {
    await Future.delayed(const Duration(seconds: 2));
    try {
      throw Exception("Error");
    } catch (e) {
      return Future.error("Error");
    }
  }
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search