issue with geting all data from sqflite database - flutter

Question

i have been trying to get all my data from a sqflite database, when i try to get a single data, this works totally fine:
Future<dynamic> getUser() async {
final db = await database;
var res = await db.query("files");
if (res.length == 0) {
return null;
} else {
var resMap = res[0];
return resMap;
}
}
but when i try to get all data using a for loop like the example below, i get an error
Future<dynamic> getUser() async {
final db = await database;
var res = await db.query("files");
var resMap;
var count = res.length;
if (count != 0) {
for (int i = 0; i < count; i++) {
resMap.add(res[i]);
}
}
return resMap;
}
the error says:
The method 'forEach' was called on null.
Receiver: null
Tried calling: forEach(Closure: (dynamic, dynamic) => Null)
i understand that it says that I've got no data,
and i also tried to remove the if statement, but still no luck!

Answer 1

change this method:
EDIT
Future<List<Map>> getUser() async {
final db = await database;
var res = await db.query("files");
List<Map> resMap = [];
if (res != null res.length > 0) {
for (int i = 0; i < count; i++) {
resMap.add(res[i]);
}
return resMap;
} else
{
return null;
}
}

Answer 2

try this in you widget
List<Map> newUser = [];
#override
void initState() {
super.initState();
getUser();
}
getUser() async {
final _userData = await DBProvider.db.getUser();
if(_userData != null ){
setState(() {
newUser = _userData;
});
} else{
setState(() {
newUser =[];
});
}
}