Storing multiple instances of Arraylist<LatLng> to shared preferences

Question

Currently I have an app that tracks user location and draws the route by using polylines and map markers, I need to add the arraylist that contains the LatLng coordinates to another array list that stores all routes, i.e the latlng arraylist is one route, so i need to store all routes in one arraylist and store that in shared preferences so i can load all the routes the user has taken to a map. What I have so far stores just one route to the shared preferences and overwrites it every time a new route is added.

Here is what i have so far, these 2 classes save the latlng data

public void addToJSONArray(JSONArray array, LatLng item) throws Exception {

    JSONObject data = new JSONObject();
    data.put("latitude", item.latitude);
    data.put("longitude", item.longitude);

    array.put(data);


}


  public void saveJourney(Context context, JSONArray saveData) {
    SharedPreferences storeAllRoutes = context.getSharedPreferences("STORED_ROUTES", context.MODE_PRIVATE);

    Editor editor = storeAllRoutes.edit();
    editor.putString("saveData",saveData.toString());
    editor.commit();

}

and these 2 classes retrieve the data

public JSONArray getData(Context context) throws Exception{
    SharedPreferences storeAllRoutes = context.getSharedPreferences("STORED_ROUTES", context.MODE_PRIVATE);

    if(storeAllRoutes.contains("saveData")) {
        return new JSONArray(storeAllRoutes.getString("saveData", ""));
    } else {
        return new JSONArray();
    }
}

public void parseJSONArray(JSONArray array) throws Exception {

    for(int i = 0; i < array.length(); ++i) {
        JSONObject item1 = array.getJSONObject(i);


        LatLng location = new LatLng(item1.getDouble("latitude"), item1.getDouble("longitude"));



        mMap.addMarker(new MarkerOptions().position(location).title("Start"));

    }

}

Answer 1

Okay so I managed to do it using shared preferences, the code is a little messy and I dont know how inefficient it is for the operation of the device but here goes

To store the multiple routes i use these 2 classes

public void addToJSONArray(JSONArray array, LatLng item) throws Exception {

    JSONObject data = new JSONObject();
    data.put("latitude", item.latitude);
    data.put("longitude", item.longitude);

    array.put(data);


}

public void saveJourney(Context context, JSONArray saveData) {
    SharedPreferences storeAllRoutes = context.getSharedPreferences("STORED_ROUTES", context.MODE_PRIVATE);
    SharedPreferences numberOfRoutes = context.getSharedPreferences("NUM_ROUTES", context.MODE_PRIVATE);
    Editor editor = storeAllRoutes.edit();
    Editor numEdit = numberOfRoutes.edit();


        i = numberOfRoutes.getInt("numOfRoutes",0);
        editor.putString("saveData"+i,saveData.toString());
        i++;
        numEdit.putInt("numOfRoutes",i);
        editor.commit();
        numEdit.commit();
        Toast.makeText(getApplicationContext(), "Journey Saved",
                Toast.LENGTH_SHORT).show();

}

Then to retrieve the data I used

public JSONArray getData(Context context, int i) throws Exception {
    SharedPreferences storeAllRoutes = context.getSharedPreferences("STORED_ROUTES", context.MODE_PRIVATE);
    SharedPreferences numberOfRoutes = context.getSharedPreferences("NUM_ROUTES", context.MODE_PRIVATE);


    if (numberOfRoutes.contains("numOfRoutes")&&i>0) {


            return new JSONArray(storeAllRoutes.getString("saveData" + i, ""));


    } else {


        return new JSONArray();
    }

}


public void parseJSONArray(JSONArray array) throws Exception {

    for (int i = 0; i < array.length(); ++i) {
        JSONObject item1 = array.getJSONObject(i);


        LatLng location = new LatLng(item1.getDouble("latitude"), item1.getDouble("longitude"));


        mMap.addMarker(new MarkerOptions().position(location).title("Start"));

    }

}

I call the retrieve methods in the onCreate method using:

SharedPreferences numberOfRoutes = this.getSharedPreferences("NUM_ROUTES", this.MODE_PRIVATE);

    try {
        if (numberOfRoutes.contains("numOfRoutes")&&numberOfRoutes.getInt("numOfRoutes",0)>0) {
            for(int i = 1;i<numberOfRoutes.getInt("numOfRoutes",0)+1;i++ )
            {
                allRoutes = getData(this,i);
                parseJSONArray(allRoutes);
            }

        }
        else{
            Toast.makeText(getApplicationContext(), "No routes exist",
                    Toast.LENGTH_SHORT).show();

        }

    } catch (Exception e) {
        e.printStackTrace();
    }

Answer 2

Why do you want it in shared preferences? Why not save it as a (list of) serialized objects, as described in this answer. I believe latlng is not serializable (as it is final), but you can fix it like this similar case:

public class TaxiRouteData implements Serializable{


private double startlat;
private double startlong;
private double endlat;
private double endlong;



public TaxiRouteData() {
}

public TaxiRouteData(LatLng startlocation, LatLng endlocation) {
    this.startlat = startlocation.latitude;
    this.startlong = startlocation.longitude;
    this.endlat = endlocation.latitude;
    this.endlong = endlocation.longitude;    }

public LatLng getStartlocation() {
    return  new LatLng(startlat,startlong);
}

public void setStartlocation(LatLng startlocation) {
    this.startlat = startlocation.latitude;
    this.startlong = startlocation.longitude;
}

public LatLng getEndlocation() {
    return  new LatLng(endlat,endlong);
}

public void setEndlocation(LatLng endlocation) {
    this.endlat = endlocation.latitude;
    this.endlong = endlocation.longitude;     }

This class is serializable and holds some (in this case only 2, start and end) LatLng points, in a similar setup you can use it to serialize and save arrays or lists of LatLng,

Answer 3

You could also make use of JSON format. Simply parse your collection into JSON formatted string, save this string in preferences.

But generaly speaking I would suggest using SQLIte aswell. Would be easier to manage your colelction for you.

Answer 4

Instead of using preferences you can use Sqlite database. But if you insist on using SharedPreferences then I don't think you have much choice as you can only store boolean, float, int, long, String or StringSet. The only possible way I see is that you concatenate all of the values with your own separator.