How to update an item stored in an ArrayList? (Android)

Question

I am fetching data from Firebase and after fetching the supposed data, I stored it on an ArrayList. So here is the sample code.

markerArray = new ArrayList<>();
Firebase ref = new Firebase(Config.FIREBASE_URL_DRIVER);
ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        if (dataSnapshot.getChildrenCount() == 0) {
            markerInfo();
        } else {
            for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                name = snapshot.child("driversName").getValue().toString().trim();
                busNum = snapshot.child("busNum").getValue().toString().trim();
                latitude = Double.valueOf(snapshot.child("latitude").getValue().toString().trim());
                longitude = Double.valueOf(snapshot.child("longitude").getValue().toString().trim());
                availableSeat = snapshot.child("availableSeat").getValue().toString().trim();
                estimatedTime = snapshot.child("estimatedTime").getValue().toString().trim();
                if ((!latitude.equals(null) || latitude.equals(0)) && (!longitude.equals(null) || longitude.equals(0)) && availableSeat.equals("") && (!estimatedTime.equals("") || estimatedTime.equals("0"))) {
                    convertLatLong();
                    getTotalPass();
                    Toast.makeText(MainMapActivity.this, currentLocation+" :currentLocation", Toast.LENGTH_SHORT).show();
                    markerArray.add(new Driver(name, totalPassenger, busNum, latitude, longitude, currentLocation, estimatedTime));
                }
            }
            Toast.makeText(MainMapActivity.this, "markerArraySize: "+markerArray.size(), Toast.LENGTH_SHORT).show();
            for (i = 0; i < markerArray.size(); i++) {
                createMarker(markerArray.get(i).getDriversName(), markerArray.get(i).getTotalPassenger(), markerArray.get(i).getBusNum(), markerArray.get(i).getLatitude(), markerArray.get(i).getLongitude(), markerArray   .get(i).getLocation(), markerArray.get(i).getEstimatedTime());
            }
        }
    }
}

I want to update my ArrayList so that whenever there are changes on the Firebase (especially the latitude and longitude) being fetched, the markers will not be redundant/multiply.

Answer 1

So what did I understand from your code is that, you want to uniquely identify the changes of the location of each driver you have there in your application.

So yes, keeping a HashMap is a nice idea as you won't have to be worried about the unique key that you're using to identify the location change of a specific driver.

But hence, I would like to suggest to keep the data fetch from your Firebase in a local sqlite database file and each time it gets updated, you can re-analyze your data to create the markers again (i.e. refreshing the markers).

For example, you can have a three tables.

• One for listing all the drivers (Primary key driver_id)
• The trips you're having. (Primary key trip_id and each row in the Trip table is associated with a driver_id)
• One for listing all the rides (this table will have all the information about each ride along with the latitude and longitude. Each update in your firebase database will have an entry here)

The tables may look like

Drivers table

driver_id - 1
name - Driver 1

driver_id - 2
name - Driver 2

Trips table

trip_id - 1
driver_id - 1

trip_id - 2 
driver_id - 1

trip_id - 3 
driver_id - 2

Rides table

trip_id - 1
driver_id - 1 
longitude - 9.4
latitude - 38
updateTime - 78783232

trip_id - 1
driver_id - 1 
longitude - 5.8
latitude - 53
updateTime - 78783242

trip_id - 1
driver_id - 1 
longitude - 78
latitude - 56
updateTime - 78783252

trip_id - 2
driver_id - 1 
longitude - 8
latitude - 77
updateTime - 78783262

Now from the Rides table you re-analyze your data each time Firebase updates the local database and redraw the markers for each driver in the map.

You can have simple sql queries to make a path the driver has travelled based on the updateTime. Sort the path points based on updateTime and remove any consecutive data which have the same longitude and latitude.

Hope that helps.

Answer 2

using set(position,data) method of arraylist to consume your demand.

 ArrayList<String> alstr = new ArrayList<>();
            alstr.add("khan");
            alstr.add("yogesh");
            alstr.add("kapil");
            alstr.add("rajoria");

            for(String str : alstr) {
                System.out.println(str);
            }
            // update value here
            alstr.set(3, "Ramveer");
            System.out.println("with Iterator");
            Iterator<String> itr = alstr.iterator();

            while (itr.hasNext()) {
                Object obj = itr.next();
                System.out.println(obj);

            }