Getting all meanings of field in ArrayList | Firebase

Question

I am using Firebase Realtime database in my Android app. How can I query field Ingridients in my database and get all meanings in ArrayList

Answer 1

Although Firebase Realtime database can store arrays, it does not support querying array members or updating single array elements. So to solve this, I recommend you an alternative database structure that looks like this:

{
  "Receptes" : {
    "Ingridients" : {
      "Carrot" : true,
      "Salt" : true,
      "Apples" : true
    },
    "Name" : "Food"
  }
}

As you can see, now the Receptes and the Ingridients are stored as a Maps and not as an arrays. And to query your database to display all ingridients, please use the following code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ingridientsRef = rootRef.child("Receptes").child("Ingridients");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String ingridient = ds.getKey();
            Log.d("TAG", ingridient);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
ingridientsRef.addListenerForSingleValueEvent(valueEventListener);

According to your comment, the database should look like this:

{
  "Receptes" : {
    "Ingridients" : {
      "IngridientIdOne" : {
        "Carrot" : true,
        "Salt" : true,
        "Apples" : true
      },
      "IngridientIdTwo" : {
        "Strawberries" : true,
        "Sugar" : true,
        "Bananas" : true
      },
    },
    "Name" : "Food"
  }
}

Answer 2

DatabaseReference recept = FirebaseDatabase.getInstance().getReference("Receptes");
DatabaseReference vegies = recept.child("Ingridients");

Check the documentation for more explanation.

You also need to add a listener

recept.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Log.i(TAG, dataSnapshot.child("Ingredients").getValue(String.class);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.w(TAG, "onCancelled", databaseError.toException());
    }
});