convert ArrayList MyCustomClass to JSONArray

Question

I have an ArrayList that I use within an ArrayAdapter for a ListView   I need to take the items in the list and convert them to a JSONArray to send to an API  I ve searched around  but haven t found anything that explains how this might work  any help would be appreciated   UPDATE - SOLUTION  Here is what I ended up doing to solve the issue   Object in ArrayList   public class ListItem       private long  masterId      private String  name      private long  category       public ListItem long masterId  String name  long category             masterId   masterId           name   name           category   category             public JSONObject getJSONObject             JSONObject obj   new JSONObject            try               obj put  Id    masterId               obj put  Name    name               obj put  Category    category             catch  JSONException e                trace  DefaultListItem toString JSONException    e getMessage                       return obj            Here is how I converted it   ArrayList lt ListItem gt  myCustomList           list filled with objects JSONArray jsonArray   new JSONArray    for  int i 0  i  lt  myCustomList size    i              jsonArray put myCustomList get i  getJSONObject         And the output      Name   Name 1   Id  0  Category   category 1     Name   Name 2   Id  1  Category   category 2     Name   Name 3   Id  2  Category   category 3      Hope this helps someone some day

User · Accepted Answer

If I read the JSONArray constructors correctly, you can build them from any Collection (arrayList is a subclass of Collection) like so:

ArrayList<String> list = new ArrayList<String>();
list.add("foo");
list.add("baar");
JSONArray jsArray = new JSONArray(list);

References:

jsonarray constructor: http://developer.android.com/reference/org/json/JSONArray.html#JSONArray%28java.util.Collection%29
collection: http://developer.android.com/reference/java/util/Collection.html

User · Answer

With kotlin and Gson we can do it more easily    First  add Gson dependency       implementation  com squareup retrofit2 converter-gson 2 3 0     Create a separate kotlin file  add the following methods    import com google gson Gson import com google gson reflect TypeToken  fun  lt T gt  Gson convertToJsonString t  T   String       return toJson t  toString      fun  lt T gt  Gson convertToModel jsonString  String  cls  Class lt T gt    T        return try           fromJson jsonString  cls        catch  e  Exception            null          inline fun  lt reified T gt  Gson fromJson json  String    this fromJson lt T gt  json  object  TypeToken lt T gt       type     Note  Do not add declare class  just add these methods  everything will work fine    Now to call    create a reference of gson      val gson Gson     To convert array to json string  call   val jsonString gson convertToJsonString arrayList    To  get array from json string  call   val arrayList gson fromJson lt ArrayList lt YourModelClassName gt  gt  jsonString    To convert a model to json string  call   val jsonString gson convertToJsonString model    To convert json string to model  call   val model gson convertToModel jsonString  YourModelClassName  class java

User · Answer

As somebody figures out that the OP wants to convert custom List to org json JSONArray not the com google gson JsonArray the CORRECT answer should be like this   Gson gson   new Gson     String listString   gson toJson                      targetList             new TypeToken lt ArrayList lt targetListItem gt  gt       getType       JSONArray jsonArray    new JSONArray listString

User · Answer

I know its already answered  but theres a better solution here use this code    for   Field f   context getFields            if   f getType      String class        f getType      String class                    DO String To JSON                 And so on        This way you can access variables from class without manually typing them    Faster and better    Hope this helps    Cheers   D

User · Answer

public void itemListToJsonConvert ArrayList lt HashMap lt String  String gt  gt  list             JSONObject jResult   new JSONObject      main object         JSONArray jArray   new JSONArray       ItemDetail jsonArray          for  int i   0  i  lt  list size    i                  JSONObject jGroup   new JSONObject       sub Object              try                   jGroup put  ItemMasterID   list get i  get  ItemMasterID                     jGroup put  ID   list get i  get  id                     jGroup put  Name   list get i  get  name                     jGroup put  Category   list get i  get  category                      jArray put jGroup                        itemDetail Name is JsonArray Name                 jResult put  itemDetail   jArray                   return jResult                catch  JSONException e                    e printStackTrace

User · Answer

Use Gson library to convert ArrayList to JsonArray   Gson gson   new GsonBuilder   create    JsonArray myCustomArray   gson toJsonTree myCustomList  getAsJsonArray

User · Answer

Add to your gradle    implementation  com squareup retrofit2 converter-gson 2 3 0    Convert ArrayList to JsonArray  JsonArray jsonElements    JsonArray  new Gson   toJsonTree itemsArrayList

[android] convert ArrayList<MyCustomClass> to JSONArray

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