How can I fix "Future isn't a type" error in flutter?

Question

I'm trying to store app data of my flutter application in the database, but the complier keeps showing "Future isn't a type" for async func and underlines in red. I've tried removing .analysis-driver as well, but that doesn't help. How can I fix it ?

Code:

import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
import 'package:path/path.dart';
import 'dart:io';

class Db_Help{

  static final _db_name="Work_tasks.db";
  static final _db_version=1;
  static final table="Work Table";

  static final task_id="ID";
  static final task="Task";
  static final bool_check="Value";

  static Database _database;

  Db_Help._private_cons();
  static final Db_Help instance=Db_Help._private_cons();

  _initDatabase() async{
    Directory docu_dir=await getApplicationDocumentsDirectory();
    String path=join(docu_dir.path,_db_name);

    return await openDatabase(path, version: _db_version, onCreate: _onCreate);
  }

  Future<Database> get database async{

    if(_database!=null)
      return _database;

    _database=await _initDatabase();
    return _database;

  }

  Future _onCreate(Database db, int version) async{
    await db.execute('''
    CREATE TABLE $table (
    $task_id INTEGER PRIMARY KEY,
    $task TEXT NOT NULL,
    $bool_check INTEGER)
    ''');
  }

  Future<int> insert(Map<String,dynamic> row) async{
    Database db= await instance.database;
    return await db.insert(table, row);
  }

 }

Answer 1

Faced this problem yesterday. Tried a couple of suggestions for fixing this error and today it worked by doing the following:

1. Update your SDK version in your pubspec.yaml to at least 2.7.0 (Before that my sdk version was 2.2.0 and I think that caused the error. At least 2.7.0 worked for me).

   environment:
     sdk: ">=2.7.0 <3.0.0"
   

2. Run flutter clean

3. Go to File -> Invalidate Caches/Restart and select "Invalidate Caches and Restart"

Answer 2

In my case I was missing a function name, and it gave error in many positions in many files. For example, instead of:

Future<bool> myFunction (int parm1)

accidentally deleted the function name, so the result was:

Future<bool> (int parm1)

This gave problem in many files of the project, giving the error "Future isn't a type". In the errors list, there was also the error of the missing function name, so correcting that one all other errors disappeared.