Flutter Right way of fetching Data - flutter

Question

I'm new to flutter and I'm currently trying to learn about fetching data
The Data might look something like this:
Data:
-- User1
---- User1Ticket1
-------- Title_text
-------- Title_picture
---- User1Ticket2
-- User2
---- User2Ticket1
---- User2Ticket2
I manage to fetch the data from RTDB and set it into a variable, The problem is I cannot useeach of the data because when I want to get the key of User1 and user2.. The data will covered in a double braces like this:
AllofUsersTicketId: [[user1Ticket1],[user2Ticket1],[user2Ticket2]]
How to fix this ? Here's my code, the allSolversPowId[j] is always null because there are braces wrapping each of them:
List solversId = powData.keys.toList();
List allSolversPowId = [];
for(int i =0; i < solversId.length; i++){
allSolversPowId.add(powData[solversId[i]].keys.toList());
}
for(int i = 0; i < solversId.length; i++) {
for (int j = 0; j < allSolversPowId.length; j++) {
calledWidget.add(
ReusablePositionWidget(
onTap: (){},
child: Column(
children: [
Text(
powData[solversId[i]][allSolversPowId[j]]['pow_text']
)
],
)
)
);
}

Answer 1

Try this,
By this way you will be able to access the element you need.
allSolversPowId[j][0]
Because,
[[user1Ticket1],[user2Ticket1],[user2Ticket2]] is a List of List.
Change the loop to something like this,
for(int i = 0; i < solversId.length; i++) {
for (int j = 0; j < allSolversPowId[i].length; j++) {
calledWidget.add(
ReusablePositionWidget(
onTap: (){},
child: Column(
children: [
Text(
powData[solversId[i]][allSolversPowId[i][j]]['pow_text']
)
],
)
)
);
}