Android - Cannot Retrieve Data From Firebase

I am drawing a route between two markers, and I want to save that route. To do that I saved the ArrayList containing the lat and lng in the Firebase database. But I am having probl

Solution 1:

Your code is almost right, but I think it's the saving of the data that's letting it down. When you load the data back from the database you're marshalling the data into a Route instance:

Route route = dataSnapshot.getValue(Route.class);

This will expect a locations node under each child to match setLocations(ArrayList<Location>) in your POJO class. Instead, the data it retrieves is the ArrayList directly.

When saving your location list, you'll need to arrange the structure such that the list of locations are stored under $schoolName/routes/$routeId/locations:

So, when saving your route point data, you'll need to do:

database.child(schoolName).child("routes").child(routeId).child("locations").setValue(points);

An easy way to think of this would be: if the Route also had a name field (setName(String)) then the database may also have $schoolName/routes/$routeId/name in the same place as the locations value.

Alternatively, when saving to the database, you could convert your points variable to a Route instance and then push that directly to $schoolName/routes/$routeId instead, which will ensure that it's stored correctly.

Solution 2:

Try this

final HashMap<Integer,HashMap<String,Double>> positions = new HashMap<>();
    userRef.child(sharedPreferences.getString("school", null)).child("routes").child(sh.getString("key",null)).addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        publicvoid onDataChange(DataSnapshot dataSnapshot) {
            int i=0;
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                HashMap<String,Double> position = new HashMap<String, Double>();
                position.put("lat",Double.parseDouble(postSnapshot.child("latitude").getValue().toString()));
                position.put("lng",Double.parseDouble(postSnapshot.child("longitude").getValue().toString()));
                positions.put(i++,position);
            }

        }

You can access the values stored in positions variable as

 positions.get(index).get("lat");
 positions.get(index).get("lng");