{"reference":
    [
     {"ref_no":"11111111111111","Name":"Faisal"},

     {"ref_no":"22222222222222","Name":"Salman"},

     {"ref_no":"33333333333333","Name":"Asim"},

     {"ref_no":"44444444444444","Name":"Asad"},

     {"ref_no":"55555555555555","Name":"Mateen"},

     {"ref_no":"66666666666666","Name":"Omar"},

     {"ref_no":"77777777777777","Name":"Usama"}

     ]}

Spinner dd_ref, dd_m_type,dd_site_status, dd_pole_type;
String refr_no, meter_type, latitude, longitude, site_status, comm_status, pole_type;
ArrayList<String> refList, m_type_List, site_status_List, pole_type_List;

 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

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

 public void loadData() throws JSONException {

//////////////// Below method is for reference number call
    JSONArray RefjsonArray;
    JSONObject Ref_obj;
    refList = new ArrayList<String>();

   try
   {
       Ref_obj = new JSONObject(loadRefJSONFromAssest());
       RefjsonArray = Ref_obj.getJSONArray("reference");


       for(int i = 0; i<RefjsonArray.length();i++)
       {
           Ref_obj = RefjsonArray.getJSONObject(i);
           Log.d("Details-->", Ref_obj.getString("ref_no"));
           String ref = Ref_obj.getString("ref_no");


           refList.add(ref);
       }
       refList.add(0,"Select a reference number");


   } catch (JSONException e)
   {
       e.printStackTrace();
   }
    dd_ref = (Spinner)findViewById(R.id.dd_ref);

    dd_ref.setAdapter(new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_dropdown_item, refList));


    dd_ref.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

                refr_no = String.valueOf(refList.get(position));
                //text_pos.setText("Hi " + refr_no);

           // Log.d(" out ",refr_no);

        }
        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });//// end reference spinner
///////// start of method meter type dropdown
    JSONArray m_type_Array;
    JSONObject m_type_obj;
    m_type_List = new ArrayList<String>();

    try{
        m_type_obj = new JSONObject(loadMeterTypeJSONFromAssest());

        m_type_Array = m_type_obj.getJSONArray("meter");

        for(int i = 0; i<m_type_Array.length(); i++)
        {
            m_type_obj = m_type_Array.getJSONObject(i);
            Log.d("Details-->", m_type_obj.getString("m_type"));

            String m_type = m_type_obj.getString("m_type");

            m_type_List.add(m_type);
        }
        m_type_List.add(0,"Select Meter Type");
    }catch (JSONException e)
    {
        e.printStackTrace();
    }

    dd_m_type = (Spinner)findViewById(R.id.dd_m_type);

    dd_m_type.setAdapter(new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_dropdown_item, m_type_List));

    dd_ref.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

            meter_type = String.valueOf(m_type_List.get(position));

        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });// end dropdown meter type
}

  ////// method for loading meter type data
public String loadMeterTypeJSONFromAssest() {

    String json = " ";

    try{
        InputStream is = getAssets().open("meter.json");

        int size = is.available();

        byte[] buffer = new byte[size];

        is.read(buffer);
        is.close();

        json = new String(buffer, "UTF-8");
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }

    return json;



}

//// load reference # data
public String loadRefJSONFromAssest() {

    String json = " ";

    try{
        InputStream is = getAssets().open("ref.json");

        int size = is.available();

        byte[] buffer = new byte[size];

        is.read(buffer);
        is.close();

        json = new String(buffer, "UTF-8");
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }

    return json;


}

java.lang.ArrayIndexOutOfBoundsException: length=12; index=-1
at java.util.ArrayList.get(ArrayList.java:310)
at com.example.accurat.application.MainActivity$2.onItemSelected(MainActivity.java:131)
at android.widget.AdapterView.fireOnSelected(AdapterView.java:931)
at android.widget.AdapterView.dispatchOnItemSelected(AdapterView.java:920)
at android.widget.AdapterView.-wrap1(AdapterView.java)
at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:890)
at android.os.Handler.handleCallback(Handler.java:746)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5491)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)