How to find JSON array present in JSON object or not android

Question

i'm working with JSON objects . it gives result like this

{
   "routes" : [
      {
         "bounds" : {
            "northeast" : {
               "lat" : 19.0759817,
               "lng" : 80.27071789999999
            },
            "southwest" : {
               "lat" : 12.5100381,
               "lng" : 72.8772599
            }
         },
         "copyrights" : "Map data ©2015 Google",
         "legs" : [
            {
               "distance" : {
                  "text" : "1,334 km",
                  "value" : 1333618
               },
               "duration" : {
                  "text" : "17 hours 43 mins",
                  "value" : 63763
               },
               "end_address" : "Mumbai, Maharashtra, India",
               "end_location" : {
                  "lat" : 19.0759817,
                  "lng" : 72.8776544
               },
               "start_address" : "Chennai, Tamil Nadu, India",
               "start_location" : {
                  "lat" : 13.0826782,
                  "lng" : 80.27071789999999
               },

so i'm retrieving following arrays routes ->legs -> distance` . with following code

        JSONArray one = reader.getJSONArray("routes");
              for ( i = 0; i < one.length(); i++) {

                 two = one.getJSONObject(i);

                 three = two.getJSONArray("legs");

                for ( j = 0; j < three.length(); j++) {

                   four = three.getJSONObject(j);
                   bounds = four.getJSONObject("distance");

                    distance[i]=bounds.getString("text");

it works fine. sometimes my JSON result is like this when wrong input.

{
   "routes" : [],
   "status" : "NOT_FOUND"
}

so when i'm search legs in this empty JSON object so my android app hangs and terminated automatically. so i should check whether legs array present in my JSON object or not . if present i will work with my code. otherwise i will just show warning messages to users.

Answer 1

you can check the length or routes arary and do your stuff if it has data in it:

JSONArray one = reader.getJSONArray("routes");
      if(one.size()>0)
    {
          for ( i = 0; i < one.length(); i++) {

             two = one.getJSONObject(i);

             three = two.getJSONArray("legs");

            for ( j = 0; j < three.length(); j++) {

               four = three.getJSONObject(j);
               bounds = four.getJSONObject("distance");

                distance[i]=bounds.getString("text");
 }}
else
 {//handle empty json array here
    }

Answer 2

JSONObject class has a method named "has"

http://developer.android.com/reference/org/json/JSONObject.html#has(java.lang.String)

Returns true if this object has a mapping for name. The mapping may be NULL.

example

if (jsonObject.has("yourkey"))
    {
        // it will return true;
    }
    else
    {
        //it will return false;
    }