jSON data error Unity3d

Hey there!

I'm currently busy with a project in Unity. For this project, I need to use and work with json data.

This is the json file: { "exerciseFrame":{ "currentFrameRate":115.003, "gestures":[

       ],
       "hands":[
          {
             "direction":[
                -0.21788,
                0.396045,
                -0.892007
             ],
             "id":67,
             "palmNormal":[
                -0.207517,
                -0.911865,
                -0.354174
             ],
             "palmPosition":[
                76.5549,
                114.137,
                5.89759
             ],
             "palmVelocity":[
                11.5489,
                -12.4382,
                30.413
             ],
             "r":[
                [
                   0.985174,
                   0.0992006,
                   -0.139971
                ],
                [
                   -0.110688,
                   0.990883,
                   -0.0768105
                ],
                [
                   0.131075,
                   0.0911648,
                   0.987172
                ]
             ],
             "s":0.877737,
             "sphereCenter":[
                53.6198,
                53.1508,
                -39.351
             ],
             "sphereRadius":91.0197,
             "stabilizedPalmPosition":[
                74.1678,
                112.23,
                3.77527
             ],
             "t":[
                -20.2956,
                10.8737,
                19.0197
             ],
             "timeVisible":3.23297
          }
       ],
       "id":470433,
       "interactionBox":{
          "center":[
             0,
             189,
             0
          ],
          "size":[
             209.24,
             209.24,
             146.232
          ]
       },
       "pointables":[
          {
             "direction":[
                -0.204191,
                -0.171441,
                -0.963802
             ],
             "handId":67,
             "id":83,
             "length":79.2433,
             "stabilizedTipPosition":[
                54.4213,
                125.134,
                -95.3633
             ],
             "timeVisible":1.79999,
             "tipPosition":[
                58.1631,
                128.283,
                -96.3226
             ],
             "tipVelocity":[
                11.7388,
                -0.426162,
                2.39705
             ],
             "tool":false,
             "touchDistance":0.16562,
             "touchZone":"hovering"
          },
          {
             "direction":[
                -0.128641,
                0.0244301,
                -0.99139
             ],
             "handId":67,
             "id":25,
             "length":73.593,
             "stabilizedTipPosition":[
                84.4969,
                125.889,
                -91.8182
             ],
             "timeVisible":1.40869,
             "tipPosition":[
                88.0132,
                128.67,
                -92.9798
             ],
             "tipVelocity":[
                9.78409,
                -4.46077,
                -10.2516
             ],
             "tool":false,
             "touchDistance":0.0726596,
             "touchZone":"hovering"
          },
          {
             "direction":[
                -0.231257,
                -0.0952694,
                -0.968217
             ],
             "handId":67,
             "id":62,
             "length":65.8749,
             "stabilizedTipPosition":[
                27.6915,
                127.768,
                -78.6761
             ],
             "timeVisible":0.913038,
             "tipPosition":[
                30.0744,
                130.094,
                -78.9935
             ],
             "tipVelocity":[
                11.5967,
                -2.61466,
                -3.92538
             ],
             "tool":false,
             "touchDistance":0.123818,
             "touchZone":"hovering"
          },
          {
             "direction":[
                -0.0484869,
                0.109018,
                -0.992857
             ],
             "handId":67,
             "id":73,
             "length":46.8336,
             "stabilizedTipPosition":[
                115.627,
                114.182,
                -61.4815
             ],
             "timeVisible":0.739126,
             "tipPosition":[
                118.889,
                116.921,
                -62.7602
             ],
             "tipVelocity":[
                2.0058,
                -14.1922,
                26.0571
             ],
             "tool":false,
             "touchDistance":0.308196,
             "touchZone":"hovering"
          },
          {
             "direction":[
                -0.757118,
                0.0997547,
                -0.645617
             ],
             "handId":67,
             "id":37,
             "length":47.2933,
             "stabilizedTipPosition":[
                -13.0828,
                113.28,
                3.91602
             ],
             "timeVisible":0.913038,
             "tipPosition":[
                -10.3237,
                117.652,
                2.30821
             ],
             "tipVelocity":[
                9.14501,
                5.11948,
                -3.45668
             ],
             "tool":false,
             "touchDistance":0.0164196,
             "touchZone":"hovering"
          }
       ],
       "r":[
          [
             0.564536,
             0.157925,
             -0.81016
          ],
          [
             0.200296,
             -0.978399,
             -0.0511501
          ],
          [
             -0.800738,
             -0.133395,
             -0.583973
          ]
       ],
       "s":-443.531,
       "t":[
          22821.5,
          -11650.1,
          -3347.64
       ],
       "timestamp":5463086706
    }}

I have loaded it into unity with the following script (according this tutorial http://www.paultondeur.com/2010/03/23/tutorial-loading-and-parsing-external-xml-and-json-files-with-unity-part-2-json/)

 using UnityEngine;
 using LitJson;
 using System;
 using System.Collections;
 
 public class LoadJSON : MonoBehaviour
 {    
     IEnumerator Start()
     {
 
         //Load JSON data from a URL
         string url = "http://localhost/project/application/exercise.json";
         WWW www = new WWW(url);
         
         //Load the data and yield (wait) till it's ready before we continue executing the rest of this method.
         yield return www;
         if (www.error == null)
         {        
             //Process exercises found in JSON file            
             ProcessExercises(www.data);
         }
         else
         {
             Debug.Log("ERROR: " + www.error);
         }
 
     }
    
     private void ProcessExercises(string jsonString)
     {
         Debug.Log (jsonString);
         JsonData jsonExercise = JsonMapper.ToObject(jsonString); // convert json data to object. 
         Exercise exercise;
         
         for(int i = 0; i<jsonExercise["exerciseFrame"].Count; i++) // for each exerciseFrame data in the .json file 
         {    
             Debug.Log(jsonExercise["exerciseFrame"].Count); 
         }
     }
     private void loadExercise(){
     }
     
 
 }

It goes according to plan up until the line that is supposed to convert the json data to an object:

     JsonData jsonExercise = JsonMapper.ToObject(jsonString); // convert json data to object. 

I get the following error and I have no idea what is going wrong. Because jsonString is a string with data.

 ArgumentNullException: Argument cannot be null.
 Parameter name: key
 System.Collections.Generic.Dictionary`2[System.String,LitJson.PropertyMetadata].ContainsKey (System.String key) (at /Applications/buildAgent/work/c514da0c8183631c/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:458)
 LitJson.JsonMapper.ReadValue (System.Type inst_type, LitJson.JsonReader reader)
 LitJson.JsonMapper.ReadValue (System.Type inst_type, LitJson.JsonReader reader)
 LitJson.JsonMapper.ReadValue (System.Type inst_type, LitJson.JsonReader reader)
 LitJson.JsonMapper.ReadValue (System.Type inst_type, LitJson.JsonReader reader)
 LitJson.JsonMapper.ToObject[JsonData] (System.String json)
 LoadJSON.ProcessExercises (System.String jsonString) (at Assets/Scripts/JSON/LoadJSON.cs:32)
 LoadJSON+<Start>c__Iterator1.MoveNext () (at Assets/Scripts/JSON/LoadJSON.cs:20)

I really hope someone here can help me out. Thanks a lot for your time!