从Firebase树获取所有密钥

Question

This is my firebase tree.

"LAMBO" : {
"LAMBO" : {
  "colour" : "blue",
  "date" : "08 04 2018",
  "doors" : "2",
  "enginesize" : "3000",
  "fuel" : "petrol",
  "lotnumber" : "99",
  "manufacturer" : "Lamborghini",
  "model" : "cuntash",
  "reg" : "LAMBO"
}
  }

"FIESTA" : {
"FIESTA" : {
  "colour" : "red",
  "date" : "08 04 2018",
  "doors" : "5",
  "enginesize" : "1300",
  "fuel" : "petrol",
  "lotnumber" : "1",
  "manufacturer" : "ford",
  "model" : "fiesta",
  "reg" : "FIESTA"
}
  }

etc etc....

as the user adds more cars to the tree obviously the list will get bigger. I want to be able to get a list of all the items in my tree. But I won't know the key name as I won't be in control of the key the user has. The Key is = to The cars Registration so is unique every time.

the way I normally access the child would be

 String lambo = datasnapshot.child("LAMBO").getValue(String.class) 

from within a ChildEventListener . But I won't know the ("KEYNAME")

I've found this snippet of code

databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
    if (dataSnapshot.exists()) {
        int i = 0;
        for(DataSnapshot d : dataSnapshot.getChildren()) {

        }
    }
}//onDataChange

@Override
public void onCancelled(DatabaseError error) {

}//onCancelled
});

I just want the Main keys in my list view ie LAMBO and FIESTA not the children from it either. any help would be appreciated and sorry for being confusing

Answer 1

You can use getKey() from DataSnapShot:

List<String> keyList = new ArrayList<>();

databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        if (dataSnapshot.exists()) {
            for(DataSnapshot ds : dataSnapshot.getChildren()) {
                keyList.add(ds.getKey());
            }
        }
    }

    @Override
    public void onCancelled(DatabaseError error) {

    }
});

Hope it helps!