How to get the first object in an JSONObject without knowing the name?

Question

I've a JSONObject that contains other objects:

{
"1" : {
        "state": [],
        "hue": 224
      }
"2" : {
        "state": [],
        "hue": 224
      }
"3" : {
        "state": [],
        "hue": 224
      }
}

It's the response from the Philips Hue Brigde JSON that contains all the connected lights. I use Volley for the http connection. I created a Light class where I store the data like state, hue, bri etc. I fill the Light class by using of a for loop in the onResponse from Volley:

for (int i = 0; i <= response.length(); i++) {
     JSONObject lightObject = response.getJSONObject(String.valueOf(i)); 
     System.out.println("OBJECT " + lightObject);

     // Use try/catch because of empty or unknown key
                try {
                    description = lightObject.getString("type");
                } catch (Exception e) {}
                try {
                    bri = lightObjectState.getInt("bri");
                } catch (Exception e) {}

                try {
                    sat = lightObjectState.getInt("sat");
                } catch (Exception e) {}

                try {
                    hue = lightObjectState.getInt("hue");
                } catch (Exception e) {}

     Light light = new Light(String.valueOf(i),lightObject.getString("name"), description, on, bri, sat, hue);
     mLightList.add(light);
     mLightAdapter.notifyDataSetChanged();

}

The problem with the for loop is that, when the Light id starts with greater then zero, it will crash my Android app, because there is no value of 0 . My question is how I can get the first object of the response without knowing the key name that contains the object with all the properties of one light, so when the JSONObject looks like below, the app will not crash, but just display light 4 till 6:

{
"4" : {
        "state": [],
        "hue": 224
      }
"5" : {
        "state": [],
        "hue": 224
      }
"6" : {
        "state": [],
        "hue": 224
      }
}

If there are any questions left, please let me know. Thanks.

Answer 1

    // use keys() iterator, you don't need to know what keys are there/missing
    Iterator<String> iter = response.keys();
    while (iter.hasNext()) {
        String key = iter.next();
        JSONObject lightObject = response.getJSONObject(key); 
        System.out.println("key: " + key + ", OBJECT " + lightObject);

        // you can check if the object has a key before you access it
        if (lightObject.has("bri")) {
            bri = lightObject.getInt("bri");
        }

        if (lightObject.has("sat")) {
            sat = lightObject.getInt("sat");
        }

        if (lightObject.has("hue")) {
            hue = lightObject.getInt("hue");
        }

        if (lightObject.has("name")) {
            name = lightObject.getString("name")
        }

        Light light = new Light(key, name, description, on, bri, sat, hue);
        mLightList.add(light);
    }

    mLightAdapter.notifyDataSetChanged();

Answer 2

try with object key:

 Iterator<String> keys = jsonObject.keys();
 if( keys.hasNext() ){
     String key = (String)keys.next(); // First key in your json object
  }

Answer 3

Let's say you have a class called Bulb

public class Bulb {

    int[] state;
    int hue;

}

Then you can use a JSON serializer like GSON

And then you can map your response to in a Map ( like HashMap ) like this

Type typeOfHashMap = new TypeToken<Map<String, Bulb>>() { }.getType();

Map<String,Bulb> bulbMap = gson.fromJson(json, typeOfHashMap); 

And then you can iterate over the map with keys like so

Iterator bulbIterator = bulbMap.entrySet().iterator();

  while (bulbIterator.hasNext()) {

    Map.Entry pair = (Map.Entry)bulbIterator.next();

    String pKey = (String) pair.getKey();

    Bulb bulb = (Bulb) pair.getValue();

    // Do something here with the bulb
}