Marker maps android dari json

 package com.example.my_pc.lokasi;

import android.content.Intent;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.maps.android.geojson.GeoJsonLayer;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, GoogleMap.OnMarkerClickListener {

    private GoogleMap mMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

        loadFile();
    }

    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;

        // Add a marker in Sydney and move the camera
        LatLng sydney = new LatLng(-6.297269, 107.067625);
        mMap.addMarker(new MarkerOptions().position(sydney).title("My Home"));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));

        // Set a listener for marker click.
        //mMap.setOnMarkerClickListener(this);
        mMap.setOnInfoWindowClickListener(new GoogleMap.OnInfoWindowClickListener() {
            @Override
            public void onInfoWindowClick(Marker marker) {
                Toast.makeText(MapsActivity.this, "Klik", Toast.LENGTH_SHORT).show();
                Log.d("Coba", "hasilnya");

                    for(int i = 0; i < 3; i++){
                        Toast.makeText(MapsActivity.this, "KE - "+i, Toast.LENGTH_SHORT).show();
                    }

            }
        });
    }

    @Override
    public boolean onMarkerClick(Marker marker) {
        Toast.makeText(MapsActivity.this, "Tes", Toast.LENGTH_SHORT).show();
        return false;
    }

    public String callfile(){
        String json = null;
        try {
            InputStream is = getAssets().open("sekolah.json");
            int size = is.available();
            byte[] buffer = new byte[size];
            is.read(buffer);
            is.close();
            json = new String(buffer, "UTF-8");

        } catch (IOException e) {
            // Should never happen!
            throw new RuntimeException(e);
        }/* catch (JSONException e) {
            e.printStackTrace();
        }*/

        return json;

    }

    public void loadFile(){
        //GeoJsonLayer layer = new GeoJsonLayer(getMap(), geoJsonData);
        JSONObject obj = null;
        try {
            obj = new JSONObject(callfile());
            JSONArray m_jArry = obj.getJSONArray("result");
            for (int i = 0; i < m_jArry.length(); i++) {
                JSONObject jo_inside = m_jArry.getJSONObject(i);
                Toast.makeText(MapsActivity.this, jo_inside.getString("nama_sekolah"), Toast.LENGTH_SHORT).show();
                Log.d("pesan", jo_inside.toString());
            }

            //Toast.makeText(MapsActivity.this, json, Toast.LENGTH_SHORT).show();

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

    }

}

saya ingin membuat marker dengan data dari json tpi knpa tidak muncul ya pas di parsenya., ada yang bisa bantu atau ada yang punya referensi? terimaksih