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 · 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 <T> Gson.convertToJsonString(t: T): String {
    return toJson(t).toString()
}

fun <T> Gson.convertToModel(jsonString: String, cls: Class<T>): T? {
    return try {
        fromJson(jsonString, cls)
    } catch (e: Exception) {
        null
    }
}

inline fun <reified T> Gson.fromJson(json: String) = this.fromJson<T>(json, object: TypeToken<T>() {}.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<ArrayList<YourModelClassName>>(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

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

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

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

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

If I read the JSONArray constructors correctly  you can build them from any Collection  arrayList is a subclass of Collection  like so   ArrayList lt String gt  list   new ArrayList lt String gt     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

[android] convert ArrayList<MyCustomClass> to JSONArray

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