put adds the list as an element to the JSONArray. Thats not what you want. You want your JSONArray to represent the list.
JSONArray offers a constructor for that:
val jsonArray = JSONArray(listOf(1, 2, 3))
But there is a much easier way. You don't need to worry about single properties. Just pass the whole POJO.
Let's say you have this:
class QuoteData(val id: Int, val quoteId: Int, travellerId: Int?)
class TravelerData(val userQuoteTravellers: List<QuoteData>)
val travelerData = TravelerData(listOf(QuoteData(1354, 546, null)))
You just have to pass travelerData to the JSONArray constructor:
val travelerDataJson = JSONArray(travelerData)
and it will be represented like this:
Answer from Willi Mentzel on Stack Overflow"userQuoteTravellers": [ { "id": 1354, "quoteId": 526, "travellerId": null } ]
Top answer 1 of 5
6
put adds the list as an element to the JSONArray. Thats not what you want. You want your JSONArray to represent the list.
JSONArray offers a constructor for that:
val jsonArray = JSONArray(listOf(1, 2, 3))
But there is a much easier way. You don't need to worry about single properties. Just pass the whole POJO.
Let's say you have this:
class QuoteData(val id: Int, val quoteId: Int, travellerId: Int?)
class TravelerData(val userQuoteTravellers: List<QuoteData>)
val travelerData = TravelerData(listOf(QuoteData(1354, 546, null)))
You just have to pass travelerData to the JSONArray constructor:
val travelerDataJson = JSONArray(travelerData)
and it will be represented like this:
"userQuoteTravellers": [ { "id": 1354, "quoteId": 526, "travellerId": null } ]
2 of 5
6
With Dependencies
Add to your gradle:
implementation 'com.squareup.retrofit2:converter-gson:2.3.0'
Convert ArrayList to JsonArray
val jsonElements = (JsonArray) new Gson().toJsonTree(itemsArrayList)
Without Dependencies
val jsonElements = JSONArray(itemsArrayList)
Top answer 1 of 9
138
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
2 of 9
77
Use Gson library to convert ArrayList to JsonArray.
Gson gson = new GsonBuilder().create();
JsonArray myCustomArray = gson.toJsonTree(myCustomList).getAsJsonArray();
android - How to add ArrayList to JsonObject in Kotlin - Stack Overflow
PaymentDetails class data class PaymentDetails( val type:String, val bank: String, val branch: String, val account_no: String, val cheque_date:String, val return_type:Boolean, val cheque_no:String... More on stackoverflow.com
how to parse JSONArray to List<CustomObject> ?
I'm trying without success to serialize JSONArray to local variable List of CustomObjects, when CustomObject class is Serializable, i reread all the q&a, all the documents, I can not unders... More on github.com
14
July 22, 2018android - Converting JSONarray to ArrayList - Stack Overflow
I am downloading a JSON string and converting it to JSONArray. Im putting it into a listview and need to be able to delete from that listview later, and since JSONArray has no .remove method (Thanks More on stackoverflow.com
android - Can't convert JSONArray into a list (Kotlin) - Stack Overflow
Communities for your favorite technologies. Explore all Collectives ยท Stack Overflow for Teams is now called Stack Internal. Bring the best of human thought and AI automation together at your work More on stackoverflow.com
Kotlin
kotlinlang.org โบ api โบ kotlinx.serialization โบ kotlinx-serialization-json โบ kotlinx.serialization.json โบ -json-array
JsonArray | kotlinx.serialization โ Kotlin Programming Language
Class representing JSON array, consisting of indexed values, where value is arbitrary JsonElement ยท Since this class also implements List interface, you can use traditional methods like List.get or List.getOrNull to obtain Json elements
CopyProgramming
copyprogramming.com โบ howto โบ how-to-convert-arraylist-to-jsonarray-in-kotlin
Android: Converting ArrayList to JSONArray() using Kotlin
May 7, 2023 - ... You have initialized a jsonObject ... converting ArrayList to JSON and post to a url, You could try something like that: 1) Build the JSON object ArrayList<Beacon> arrayL = new ArrayList<>(); JSONArray mJSONArray = new...
Android Developers
developer.android.com โบ api reference โบ jsonarray
JSONArray | API reference | Android Developers
Skip to main content ยท English ยท Deutsch ยท Espaรฑol โ Amรฉrica Latina ยท Franรงais ยท Indonesia ยท Polski ยท Portuguรชs โ Brasil ยท Tiรชฬng Viรชฬฃt ยท ไธญๆ โ ็ฎไฝ
Top answer 1 of 2
4
Gson().toJson(myList) returns a String.
You should build a JSONArray and add its elements. Then add this true array. This just works:
JsonArray array = new JsonArray();
array.add("test1");
array.add("test2");
JsonObject object = new JsonObject();
object.add("arr", array);
You also seam to be messing up JSON and GSON objects. Here I just used Gson objects.
2 of 2
3
as @shkschneider pointed gson.toJson() returns string value and you are adding that string directly to your json object, You need to convert it to json array and then add it.
JSONArray jsArray = new JSONArray(Gson().toJson(myList))
var obj2 = JSONObject(obj.get("reciptDetail").toString())
obj2.remove("payment_details")
obj2.put("payment_details",jsArray)
Log.e("cash Object", obj2.toString())
GitHub
github.com โบ Kotlin โบ kotlinx.serialization โบ issues โบ 179
how to parse JSONArray to List<CustomObject> ? ยท Issue #179 ยท Kotlin/kotlinx.serialization
July 22, 2018 - I'm trying without success to serialize JSONArray to local variable List of CustomObjects, when CustomObject class is Serializable, i reread all the q&a, all the documents, I can not unders...
Author ย xdma
Top answer 1 of 16
204
ArrayList<String> listdata = new ArrayList<String>();
JSONArray jArray = (JSONArray)jsonObject;
if (jArray != null) {
for (int i=0;i<jArray.length();i++){
listdata.add(jArray.getString(i));
}
}
2 of 16
85
I've done it using Gson (by Google).
Add the following line to your module's build.gradle:
dependencies {
// ...
// Note that `compile` will be deprecated. Use `implementation` instead.
// See https://stackoverflow.com/a/44409111 for more info
implementation 'com.google.code.gson:gson:2.8.2'
}
JSON string:
private String jsonString = "[\n" +
" {\n" +
" \"id\": \"c200\",\n" +
" \"name\": \"Ravi Tamada\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c201\",\n" +
" \"name\": \"Johnny Depp\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c202\",\n" +
" \"name\": \"Leonardo Dicaprio\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c203\",\n" +
" \"name\": \"John Wayne\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c204\",\n" +
" \"name\": \"Angelina Jolie\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"female\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c205\",\n" +
" \"name\": \"Dido\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"female\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c206\",\n" +
" \"name\": \"Adele\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"female\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c207\",\n" +
" \"name\": \"Hugh Jackman\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c208\",\n" +
" \"name\": \"Will Smith\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c209\",\n" +
" \"name\": \"Clint Eastwood\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c2010\",\n" +
" \"name\": \"Barack Obama\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c2011\",\n" +
" \"name\": \"Kate Winslet\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"female\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" },\n" +
" {\n" +
" \"id\": \"c2012\",\n" +
" \"name\": \"Eminem\",\n" +
" \"email\": \"[email protected]\",\n" +
" \"address\": \"xx-xx-xxxx,x - street, x - country\",\n" +
" \"gender\" : \"male\",\n" +
" \"phone\": {\n" +
" \"mobile\": \"+91 0000000000\",\n" +
" \"home\": \"00 000000\",\n" +
" \"office\": \"00 000000\"\n" +
" }\n" +
" }\n" +
" ]";
ContactModel.java:
public class ContactModel {
public String id;
public String name;
public String email;
}
Code for converting a JSON string to ArrayList<Model>:
Note: You have to import java.lang.reflect.Type;:
// Top of file
import java.lang.reflect.Type;
// ...
private void parseJSON() {
Gson gson = new Gson();
Type type = new TypeToken<List<ContactModel>>(){}.getType();
List<ContactModel> contactList = gson.fromJson(jsonString, type);
for (ContactModel contact : contactList){
Log.i("Contact Details", contact.id + "-" + contact.name + "-" + contact.email);
}
}
Hope this will help you.
Baeldung
baeldung.com โบ home โบ kotlin โบ kotlin collections โบ parsing json arrays in kotlin with gson
Parsing JSON Arrays in Kotlin with Gson | Baeldung on Kotlin
March 19, 2024 - In this tutorial, weโll explore how to serialize and deserialize JSON arrays with Kotlin using Gson. In the context of Google Gson, serialization is a mechanism for converting the state of an object into a JSON representation.
Top answer 1 of 2
6
This can be done without GSON or any other third party library:
@Throws(JSONException::class)
fun JSONObject.toMap(): Map<String, Any> {
val map = mutableMapOf<String, Any>()
val keysItr: Iterator<String> = this.keys()
while (keysItr.hasNext()) {
val key = keysItr.next()
var value: Any = this.get(key)
when (value) {
is JSONArray -> value = value.toList()
is JSONObject -> value = value.toMap()
}
map[key] = value
}
return map
}
@Throws(JSONException::class)
fun JSONArray.toList(): List<Any> {
val list = mutableListOf<Any>()
for (i in 0 until this.length()) {
var value: Any = this[i]
when (value) {
is JSONArray -> value = value.toList()
is JSONObject -> value = value.toMap()
}
list.add(value)
}
return list
}
Usage to convert JSONArray to List:
val jsonArray = JSONArray(jsonArrStr)
val list = jsonArray.toList()
Usage to convert JSONObject to Map:
val jsonObject = JSONObject(jsonObjStr)
val map = jsonObject.toMap()
More info is here
2 of 2
0
Use this code:
import com.google.gson.annotations.SerializedName
import com.google.gson.Gson
data class Array(
@SerializedName("message")
var message: String,
@SerializedName("name")
var name: String,
@SerializedName("creation")
var creation: String
)
data class Example(
@SerializedName("array")
var array: List<Array>? = null
)
private fun fromJson(json:String):Example{
return Gson().fromJson<Example>(json, Example::class.java)
}
PS: I made it with this site:http://www.jsonschema2pojo.org/
Kotlin Discussions
discuss.kotlinlang.org โบ javascript
Arraylist from json can not be iterated - JavaScript
August 12, 2017 - i created a ArrayList with PersonDto objects and transform it to a json string on the server to send it to the client. in the client i try to parse this string back to the ArrayList of PersonDto objects but only get an Array back val listPerson = JSON.parse (data...
Top answer 1 of 3
27
[{
"description":"My expense to others",
"items":["aaa","bbb"],
"name":"My Expense"
},
{
"description":"My expense to others","
items":["aaa","bbb"],
"name":"My Expense"
}]
Kotlin Code
val gson = GsonBuilder().create()
val Model= gson.fromJson(body,Array<GroupModel>::class.java).toList()
Gradle
implementation 'com.google.code.gson:gson:2.8.5'
2 of 3
17
I have found a solution that is actually working on Android with Kotlin for parsing JSON arrays of a given class. The solution of @Aravindraj didn't really work for me.
val fileData = "your_json_string"
val gson = GsonBuilder().create()
val packagesArray = gson.fromJson(fileData , Array<YourClass>::class.java).toList()
So basically, you only need to provide a class (YourClass in the example) and the JSON string. GSON will figure out the rest.
The Gradle dependency is:
implementation 'com.google.code.gson:gson:2.8.6'
Codexpedia
codexpedia.com โบ home โบ kotlin โบ kotlin converting jsonarray to arraylist with extension functions
Kotlin converting JSONArray to ArrayList with extension functions - Codexpedia
March 24, 2022 - Convert string list from JSONArray to ArrayList fun JSONArray.toArrayList(): ArrayList { val list = arrayListOf() for (i in 0 until this.length()) { list.add(this.getString(i)) } return list } val messages = JSONArray("['aaa','bbb','ccc']") messages.toArrayList() Remove a string from JSONArray ...
Stack Overflow
stackoverflow.com โบ questions โบ 52486898 โบ transforming-a-jsonobject-to-jsonarray-in-kotlin
arrays - Transforming a JSONObject to JSONArray in Kotlin - Stack Overflow
Kotlin code private fun loadRecyclerViewData() { val request = Request.Builder().url(URL_Json).build() val client = OkHttpClient() client.newCall(request).enqueue(object: Callback{ ...
TutorialsPoint
tutorialspoint.com โบ how-to-convert-arraylist-to-string-using-gson
How to convert ArrayList to String using GSON?
package com.example.andy.myapplication; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.widget.TextView; import android.widget.Toast; import com.google.gson.Gson; import java.util.ArrayList; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); TextView result = findViewById(R.id.result); ArrayList<String> list = new ArrayList<String>(); list.add("JAVA"); list.add("Android"); list.add("Kotlin"); list.add("C programing Language"); list.add("C plus plus"); Gson gson = new Gson(); String arrayData = gson.toJson(list); result.setText(arrayData); } }
TutorialsPoint
tutorialspoint.com โบ how-to-iterate-a-json-array-in-android-using-kotlin
How to iterate a JSON Array in Android using Kotlin?
{ super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) title = "KotlinApp" textView = findViewById(R.id.textView) val data = StringBuilder() val jsonObject = JSONObject(strJson) val jsonArray = jsonObject.optJSONArray("Employee") for (i in 0 until jsonArray.length()) { val jsonObject = jsonArray.getJSONObject(i) val id = jsonObject.optString("ID").toInt() val name = jsonObject.optString("Name") val salary = jsonObject.optString("Salary").toFloat() data.append("Employee ").append(i).append(" : ID= ") .append(id).append(" " + "Name= ") .append(name).append(" Salary= ") .append(salary).append(" ") } textView.text = data.toString() } }
Top answer 1 of 2
1
It's an ugly request, and you might be able to resolve it with an ugly solution :)
I wouldn't suggest this for anything serious, large, or anything that requires some hard and complex maintenance, but if this object will stay that simple (one int and two strings, non-nullable fields) and won't change a lot, you can do it manually:
class RailPoint(
var railPointId: Int,
var startTime: String,
var endTime: String
)
val rails = listOf(
RailPoint(1, "", "2021-10-19 07:37:19"),
RailPoint(2, "2021-10-19 07:33:37", "2021-10-19 07:35:20"),
)
fun toJson(rails: List<RailPoint>): String {
val sb = StringBuilder()
rails.forEachIndexed { index, railPoint ->
sb.append("\"railPoint[$index][railPointId]\": ${railPoint.railPointId},")
sb.append("\"railPoint[$index][startTime]\": \"${railPoint.startTime}\",")
sb.append("\"railPoint[$index][endTime]\": \"${railPoint.endTime}\",")
}
return "{ $sb }"
}
It is very dirty approach, but might be enough, as long as you don't make RailPoint more complex, especially, if you don't add members that are custom classes or collections.
(I assumed that times are Strings, but if they are not, just add some date formatting in the formula)
2 of 2
1
This can be solved by first having Gson serialize the list to a JsonArray, then combining the elements in a new JsonObject and afterwards serializing that object to JSON:
val rails: List<RailPoint> = ...
val gson = Gson()
val railsJsonList = gson.toJsonTree(rails).asJsonArray!!
val railsJsonObject = JsonObject()
// Transform elements
for (i in 0 until railsJsonList.size()) {
val railPointJson = railsJsonList[i].asJsonObject
for ((name, value) in railPointJson.entrySet()) {
railsJsonObject.add("railPoint[$i][$name]", value)
}
}
println(gson.toJson(railsJsonObject))
Reddit
reddit.com โบ r/androiddev โบ how do i save an arraylist with json?
r/androiddev on Reddit: How do I save an ArrayList<(Custom object here)> with JSON?
May 14, 2014 -
public class Semester {
private static final String JSON_ID = "id";
private static final String JSON_TITLE = "title";
private static final String JSON_CREDITS = "credits";
private static final String JSON_GPA = "gpa";
private static final String JSON_CUMULATIVECREDITS = "cumulativecredits";
private static final String JSON_CUMULATIVEGPA = "cumulativegpa";
private static final String JSON_COURSES = "courses";
private UUID id;
private String title;
private int credits;
private double GPA;
private int cumulativeCredits;
private double cumulativeGPA;private ArrayList<Course> courses;
public Semester() {
id = UUID.randomUUID();
courses = new ArrayList<Course>();
for (int i = 0; i < 6; i++) {
courses.add(new Course());
}
}
public Semester(JSONObject json) throws JSONException {
id = UUID.fromString(json.getString(JSON_ID));
title = json.getString(JSON_TITLE);
credits = json.getInt(JSON_CREDITS);
GPA = json.getDouble(JSON_GPA);
cumulativeCredits = json.getInt(JSON_CUMULATIVECREDITS);
cumulativeGPA = json.getDouble(JSON_CUMULATIVEGPA);//what do i put here?
}
public JSONObject toJSON() throws JSONException {
JSONObject json = new JSONObject();
json.put(JSON_ID, id.toString());
json.put(JSON_TITLE, title);
json.put(JSON_CREDITS, credits);
json.put(JSON_GPA, GPA);
json.put(JSON_CUMULATIVECREDITS, cumulativeCredits);
json.put(JSON_CUMULATIVEGPA, cumulativeGPA);JSONArray array = new JSONArray(courses);
json.put(JSON_COURSES, array);
return json; } .........
This is followed by a bunch of getters and setters for each private variable.
The first bolded item is the private ArrayList of a custom class that I made.
The second bolded item is what I need help with: how to retrieve the custom ArrayList just like the other variables.
Lastly, the third bolded item is my current idea of how to put an ArrayList into a JSONObject, but I don't know how to retrieve it. If there is another way, please tell me. Thank you.
Top answer 1 of 2
3
Gson gson = new Gson(); String jsonAsString = gson.toJson(arrayList); This doesn't make a JSON object, just a string in JSON format. Easier to keep up with (e.g. saving it in SharedPreferences). And to deserialize it from JSON... Type type = new TypeToken>(){}.getType(); ArrayList courses = gson.fromJson(jsonAsString, type); The GSON library is really one of the more useful tools Google has for this purpose.
2 of 2
2
use gson, it's going to make your life about 800 times easier.
Java Guides
javaguides.net โบ 2019 โบ 07 โบ convert-list-to-json-array-using-jackson.html
Convert List to JSON Array Using Jackson
July 21, 2019 - package net.javaguides.jackson; import java.util.ArrayList; import java.util.List; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.SerializationFeature; /** * Using Jackson API for list serialization and deserialization * @author ramesh fadatare * */ public class JacksonListToJson { public static void main(String[] args) throws JsonProcessingException { // Create ObjectMapper object.