I am trying to show list of messages with different types of ViewHolders i.e. Text, ImageText, Video etc. I get a list of these objects from API somewhat in this format:
{
"message":"success",
"total_pages":273,
"current_page":1,
"page_size":10,
"notifications":[
{
"id":4214,
"notification_message":"test notification 1",
"meta_data":{
"messageId":"19819189",
"viewHolderType":"textOnly",
"body":{
"time":"10-06-21T02:31:29,573",
"type":"notification",
"title":"Hi, Welcome to the NT experience",
"description":"This is the welcome message",
"read":true
}
}
},
{
"id":9811,
"notification_message":"test vss notification",
"meta_data":{
"messageId":"2657652",
"viewHolderType":"textWithImage",
"body":{
"time":"11-06-21T02:31:29,573",
"type":"promotions",
"title":"Your Package - Premium",
"description":"Thank you for subscribing to the package. Your subscription entitles you to Premium 365 Days Plan (worth $76.61)",
"headerImage":"www.someurl.com/image.jpg",
"read":true
}
}
}
]
}
Now I have to parse this list from network module for client module which will use only the objects inside meta_data. To that end I have created following classes:
open class BaseMessageListItem
internal data class MessageListResponse(
#field:SerializedName("current_page")
val current_page: Int,
#field:SerializedName("notifications")
val notifications: List<MessageListItem>,
#field:SerializedName("message")
val message: String,
#field:SerializedName("page_size")
val page_size: Int,
#field:SerializedName("total_page")
val total_page: Int
)
internal data class MessageListItem(
#field:SerializedName(“id”)
val id: String,
#field:SerializedName("notification_message")
val notification_message: String,
#field:SerializedName("meta_data")
val meta_data: MessageListMetaDataItem,
)
internal data class MessageListMetaDataItem(
#field:SerializedName("messageId")
val messageId: String = "",
#field:SerializedName("viewHolderType")
val viewHolderType: String = "",
#field:SerializedName("body")
val body: BaseMessageListItem = BaseMessageListItem()
)
internal data class ImageMessageListItem(
#field:SerializedName("description")
val description: String,
#field:SerializedName("headerImage")
val headerImage: String,
#field:SerializedName("read")
val read: Boolean,
#field:SerializedName("time")
val time: String,
#field:SerializedName("title")
val title: String,
#field:SerializedName("type")
val type: String
): BaseMessageListItem()
internal data class TextMessageListItem(
#field:SerializedName("description")
val description: String,
#field:SerializedName("read")
val read: Boolean,
#field:SerializedName("time")
val time: String,
#field:SerializedName("title")
val title: String,
#field:SerializedName("type")
val type: String
): BaseMessageListItem()
The notifications>meta_data>body can be polymorphic. I have set of classes (for ImageItem, ImageWithTextItem, VideoItem etc) which extend to BaseMessageListItem.
private var runtimeTypeAdapterFactory: RuntimeTypeAdapterFactory<BaseMessageListItem> = RuntimeTypeAdapterFactory
.of(BaseMessageListItem::class.java, "viewHolderType")
.registerSubtype(ImageMessageListItem::class.java, MessageListItemTypes.TEXT_WITH_IMAGE.value)
.registerSubtype(TextMessageListItem::class.java, MessageListItemTypes.TEXT_ONLY.value)
private var gson: Gson = GsonBuilder()
.registerTypeAdapterFactory(runtimeTypeAdapterFactory)
.create()
I tried parsing it using viewHolderType in RuntimeTypeAdapterFactory but since it's not a property of BaseMessageListItem, it is not able to parse it.
Any one has any experience dealing with this type of JSON, please do share any pointers.
RuntimeTypeAdapterFactory requires the viewHolderType field to be put right into the body objects. In order to fix this, you have
either patch RuntimeTypeAdapterFactory (it is not even published as a compiled JAR, but rather still retains in the public repository as source code free to modify), or fix your class hierarchy to lift up the missing field because it can only work with fields on the same nest level.
internal var gson: Gson = GsonBuilder()
.registerTypeAdapterFactory(
RuntimeTypeAdapterFactory.of(BaseMessageListMetaDataItem::class.java, "viewHolderType")
.registerSubtype(TextWithImageMessageListMetaDataItem::class.java, "textWithImage")
.registerSubtype(TextOnlyMessageListMetaDataItem::class.java, "textOnly")
)
.create()
internal data class MessageListItem(
#field:SerializedName("meta_data")
val metaData: BaseMessageListMetaDataItem<*>?,
)
internal abstract class BaseMessageListMetaDataItem<out T>(
#field:SerializedName("viewHolderType")
val viewHolderType: String?,
#field:SerializedName("body")
val body: T?
) where T : BaseMessageListMetaDataItem.Body {
internal abstract class Body
}
internal class TextOnlyMessageListMetaDataItem
: BaseMessageListMetaDataItem<TextOnlyMessageListMetaDataItem.Body>(null, null) {
internal data class Body(
#field:SerializedName("title")
val title: String?
) : BaseMessageListMetaDataItem.Body()
}
internal class TextWithImageMessageListMetaDataItem
: BaseMessageListMetaDataItem<TextWithImageMessageListMetaDataItem.Body>(null, null) {
internal data class Body(
#field:SerializedName("title")
val title: String?,
#field:SerializedName("headerImage")
val headerImage: String?
) : BaseMessageListMetaDataItem.Body()
}
I might be understanding you wrong, but I would like to suggest a different approach. I am assuming you would like to assign to get a ViewHolder type directly from what you get in your API response.
There are two approaches I would like to suggest:
First, if it is possible to get the API response modified, I would suggest to change viewHolderType from a String to an Int so as you can be clear with your mapping and then you can directly compare it.
Second what I would suggest is to keep another key in your data class which sets value as per the viewHolderType it receives which would be something of as follows.
internal data class MessageListMetaDataItem(
#field:SerializedName("messageId")
val messageId: String = "",
#field:SerializedName("viewHolderType")
val viewHolderType: String = "",
#field:SerializedName("body")
val body: BaseMessageListItem = BaseMessageListItem()
) {
val viewHolderMapping: Int
get() = when(viewHolderType){
"textOnly" -> MessageListItemTypes.TEXT_ONLY
"textWithImage" -> MessageListItemTypes.TEXT_WITH_IMAGE
else -> MessageListItemTypes.UNKNOWN_TYPE
}
}
I have project with android app that fetch post from wordpress rest api
some field that i take is like this list.
[
{
"id": 43600,
"date": "2020-09-07T19:52:47",
"title": {
"rendered": "Video: .... "
},
"content": {
"rendered": "<div class=\"wp-block-embed__wrapper\"></div>",
"protected": false
},
"author": 31,
"featured_media": 43601,
"categories": [
788,
2760
]
}
]
Already read :
https://developer.android.com/training/data-storage/room
How to parse data of WordPress REST API using Retrofit and GSON?
Wordpress API - How to loop through a JSON Array of objects in Android/Java
Android Kotlin parsing nested JSON
Parse Json to Primative Array Kotlin
the closest answer but mostly in converter
Android Room Database: How to handle Arraylist in an Entity?
https://medium.com/#gilesjeremydev/room-through-a-complete-example-ce5c9ed417ba
I tried to save it into local storage with room in single entity. But based on google doc, it would seperate into 2 entities tied with annotation #relation
#Entity(tableName = "post")
data class SomePost(
#PrimaryKey
#field:SerializedName("id")
val id: Int,
#field:SerializedName("date")
val date: String,
#Embedded
#field:SerializedName("title")
val title: PostTitle,
#Embedded
#field:SerializedName("content")
val content: PostContent,
#field:SerializedName("featured_media")
val imageId: Int,
#field:SerializedName("author")
val author: Int
)
#Entity
data class PostCategories(
#PrimaryKey(autoGenerate = true)
val id: Int,
#field:SerializedName("categories")
val postCategories: Int
)
data class SomePostRelationship (
#Embedded
var post: SomePost? = null,
#Relation(
parentColumn = "id",
entityColumn = "categories"
)
var categories: List<PostCategories>? = null
)
interface PostService {
companion object {
const val ENDPOINT = "https://example.com/wp-json/"
}
// Posts
#GET("wp/v2/posts/")
suspend fun getPostAll(
#Query("page") page: Int? = null,
#Query("per_page") perPage: Int? = null,
#Query("search") search: String? = null,
#Query("order") order: String? = null
): Response<List<somePost>>
The problem is data class PostCategories.
My question is how to serialization json array into entity data class of categories for android room.
if there already answer or same question hope can link to it.
After tried some variation.
I decided to used converter and combine it in on dataclass for now.
#Entity(tableName = "post")
data class SomePost(
...
#field:SerializedName("categories")
var categories: ArrayList<Int>? = null,
...
)
class Converters {
...
#TypeConverter
fun listToInt(value: ArrayList<Int>?): String? {
return Gson().toJson(value)
}
#TypeConverter
fun intToList(value: String?): ArrayList<Int>? {
val type = object : TypeToken<ArrayList<Int>?>() {}.type
return Gson().fromJson(value, type)
}
}
I'm trying to use moshi with my Android project, but I am running into some problems.
Here is a stripped down sample JSON
{
"data": [
{
"label": "May",
"schedule_items": [
{
"type": "event",
"item": {
"foo": "bar",
"some_prop": 1
},
"schedule_item_groups": [
{
"label": "Friday May 4th",
"schedule_items": [
{
"type": "check_in",
"item": {
"a_different_prop": 15
},
"schedule_item_groups": null
},
{
"type": "game",
"item": {
"yet_another_different_prop": 3598
},
"schedule_item_groups": null
}
]
}
]
}
]
}
]
}
As you can see, it is a list of ScheduleGroups, and within that object you have a label and schedule_items. Which is an array of ScheduleItem with 3 fields:
type: String label to identify which type of Item this is
item: Can be of class Event, Game, and CheckIn
schedule_item_groups: A ScheduleGroup which is a list of more -
ScheduleItems
So the first problem is a ScheduleGroup has a list of ScheduleItems and each item can have it's own list of ScheduleGroup containing more items.
The second problem is the item field, it needs to be instantiated as one of three classes: Event, Game, CheckIn.
I've been working at it for awhile, and so far I can only get one working at a time, but not both.
Here are the data classes (I have only included one of the Item classes):
data class ScheduleGroup(
val label: String,
val schedule_items: List<ScheduleItem<Any>>
)
data class ScheduleItem<out T>(
val type: String,
val schedule_item_groups: List<ScheduleGroup>
val item: T
) {
abstract class Item
}
data class Event(
val some_prop: Int,
val foo: String
) : ScheduleItem.Item()
This is how I got the dynamic Generic class Item to work:
#FromJson
fun fromJson(map: Map<*, *>): ScheduleItem<Any> {
val moshi: Moshi = Moshi.Builder().build()
val type: String = map["type"] as String
val itemJson = moshi.adapter(Map::class.java).toJson(map["item"] as Map<*, *>)
val item = when (type) {
EventType.EVENT -> moshi.adapter(Event::class.java).fromJson(itemJson)
EventType.GAME -> moshi.adapter(Game::class.java).fromJson(itemJson)
EventType.CHECK_IN, EventType.CHECK_OUT ->
moshi.adapter(CheckIn::class.java).fromJson(itemJson)
else -> throw Error("Unknown type was found $type")
}
val scheduleGroupType = Types.newParameterizedType(List::class.java, ScheduleGroup::class.java)
#Suppress("UNCHECKED_CAST")
val scheduleGroupJson = moshi.adapter<List<ScheduleGroup>>(scheduleGroupType)
.toJson(map["schedule_item_groups"] as List<ScheduleGroup>?)
val list: List<ScheduleGroup>? = moshi
.adapter<List<ScheduleGroup>>(scheduleGroupType).fromJson(scheduleGroupJson)
return ScheduleItem(type, list ?: listOf(), item)
}
It will correctly create the right Item class, but when I try to add the List<ScheduleGroup> I get errors, and no matter what I do I cannot seem to get both to work.
Edit:
I Have updated the code to show what I'm using to try and deserialize the schedule_item_groups which is a List<ScheduleGroup>.
I get an error: (This is a different error than I got before...)
com.squareup.moshi.JsonDataException: java.lang.IllegalArgumentException: Can not set final java.lang.String field com.roomroster.mobile_android.data.api.schedule.models.ScheduleGroup.label to com.squareup.moshi.LinkedHashTreeMap at $.data[0].schedule_items[1]
I figured this out awhile ago, but I guess I can post what I did in case it will help anyone in the future.
First I created a temporary intermediatry class, to hold the data before the generic data was made.
data class ScheduleItem<T>(
val date: Date,
val type: String,
var scheduleGroups: List<ScheduleGroup> = listOf(),
var item: T
) {
data class ScheduleItemJson(
val date: Date,
val type: String,
val schedule_item_groups: List<ScheduleGroup>? = listOf(),
val item: Any
)
}
Then in the adapter
#FromJson fun fromJson(item: ScheduleItem.ScheduleItemJson): ScheduleItem<Any> {
val moshi: Moshi = Moshi.Builder().build()
val json = moshi.adapter(Map::class.java).toJson(item.item as Map<*, *>)
return ScheduleItem(
item.date,
item.type,
item.schedule_item_groups ?: listOf(),
when (item.type) {
ItemType.GAME -> moshi.adapter(GameItem::class.java).fromJson(json)
ItemType.EVENT -> moshi.adapter(EventItem::class.java).fromJson(json)
ItemType.CHECK_IN, ItemType.CHECK_OUT ->
moshi.adapter(ReservationItem::class.java)
.fromJson(json).apply { this!!.type = item.type }
else -> ScheduleItem.NullItem()
}!!
)
}
The when statement is what creates the <T : Item> and passes it to the ScheduleItem constructor.
Recently I went through similar problem, I made use of sealed class and JsonAdapter to build models dynamically.
I posted my answer in another post, see https://stackoverflow.com/a/56897476/5584709
I'm receiving a quite deep JSON object string from a service which I must parse to a JSON object and then map it to classes.
How can I transform a JSON string to object in Kotlin?
After that the mapping to the respective classes, I was using StdDeserializer from Jackson. The problem arises at the moment the object had properties that also had to be deserialized into classes. I was not able to get the object mapper, at least I didn't know how, inside another deserializer.
Preferably, natively, I'm trying to reduce the number of dependencies I need so if the answer is only for JSON manipulation and parsing it'd be enough.
There is no question that the future of parsing in Kotlin will be with kotlinx.serialization. It is part of Kotlin libraries. Version kotlinx.serialization 1.0 is finally released
https://github.com/Kotlin/kotlinx.serialization
import kotlinx.serialization.*
import kotlinx.serialization.json.JSON
#Serializable
data class MyModel(val a: Int, #Optional val b: String = "42")
fun main(args: Array<String>) {
// serializing objects
val jsonData = JSON.stringify(MyModel.serializer(), MyModel(42))
println(jsonData) // {"a": 42, "b": "42"}
// serializing lists
val jsonList = JSON.stringify(MyModel.serializer().list, listOf(MyModel(42)))
println(jsonList) // [{"a": 42, "b": "42"}]
// parsing data back
val obj = JSON.parse(MyModel.serializer(), """{"a":42}""")
println(obj) // MyModel(a=42, b="42")
}
You can use this library https://github.com/cbeust/klaxon
Klaxon is a lightweight library to parse JSON in Kotlin.
Without external library (on Android)
To parse this:
val jsonString = """
{
"type":"Foo",
"data":[
{
"id":1,
"title":"Hello"
},
{
"id":2,
"title":"World"
}
]
}
"""
Use these classes:
import org.json.JSONObject
class Response(json: String) : JSONObject(json) {
val type: String? = this.optString("type")
val data = this.optJSONArray("data")
?.let { 0.until(it.length()).map { i -> it.optJSONObject(i) } } // returns an array of JSONObject
?.map { Foo(it.toString()) } // transforms each JSONObject of the array into Foo
}
class Foo(json: String) : JSONObject(json) {
val id = this.optInt("id")
val title: String? = this.optString("title")
}
Usage:
val foos = Response(jsonString)
You can use Gson .
Example
Step 1
Add compile
compile 'com.google.code.gson:gson:2.8.2'
Step 2
Convert json to Kotlin Bean(use JsonToKotlinClass)
Like this
Json data
{
"timestamp": "2018-02-13 15:45:45",
"code": "OK",
"message": "user info",
"path": "/user/info",
"data": {
"userId": 8,
"avatar": "/uploads/image/20180115/1516009286213053126.jpeg",
"nickname": "",
"gender": 0,
"birthday": 1525968000000,
"age": 0,
"province": "",
"city": "",
"district": "",
"workStatus": "Student",
"userType": 0
},
"errorDetail": null
}
Kotlin Bean
class MineUserEntity {
data class MineUserInfo(
val timestamp: String,
val code: String,
val message: String,
val path: String,
val data: Data,
val errorDetail: Any
)
data class Data(
val userId: Int,
val avatar: String,
val nickname: String,
val gender: Int,
val birthday: Long,
val age: Int,
val province: String,
val city: String,
val district: String,
val workStatus: String,
val userType: Int
)
}
Step 3
Use Gson
var gson = Gson()
var mMineUserEntity = gson?.fromJson(response, MineUserEntity.MineUserInfo::class.java)
Not sure if this is what you need but this is how I did it.
Using import org.json.JSONObject :
val jsonObj = JSONObject(json.substring(json.indexOf("{"), json.lastIndexOf("}") + 1))
val foodJson = jsonObj.getJSONArray("Foods")
for (i in 0..foodJson!!.length() - 1) {
val categories = FoodCategoryObject()
val name = foodJson.getJSONObject(i).getString("FoodName")
categories.name = name
}
Here's a sample of the json :
{"Foods": [{"FoodName": "Apples","Weight": "110" } ]}
I personally use the Jackson module for Kotlin that you can find here: jackson-module-kotlin.
implementation "com.fasterxml.jackson.module:jackson-module-kotlin:$version"
As an example, here is the code to parse the JSON of the Path of Exile skilltree which is quite heavy (84k lines when formatted) :
Kotlin code:
package util
import com.fasterxml.jackson.databind.DeserializationFeature
import com.fasterxml.jackson.module.kotlin.*
import java.io.File
data class SkillTreeData( val characterData: Map<String, CharacterData>, val groups: Map<String, Group>, val root: Root,
val nodes: List<Node>, val extraImages: Map<String, ExtraImage>, val min_x: Double,
val min_y: Double, val max_x: Double, val max_y: Double,
val assets: Map<String, Map<String, String>>, val constants: Constants, val imageRoot: String,
val skillSprites: SkillSprites, val imageZoomLevels: List<Int> )
data class CharacterData( val base_str: Int, val base_dex: Int, val base_int: Int )
data class Group( val x: Double, val y: Double, val oo: Map<String, Boolean>?, val n: List<Int> )
data class Root( val g: Int, val o: Int, val oidx: Int, val sa: Int, val da: Int, val ia: Int, val out: List<Int> )
data class Node( val id: Int, val icon: String, val ks: Boolean, val not: Boolean, val dn: String, val m: Boolean,
val isJewelSocket: Boolean, val isMultipleChoice: Boolean, val isMultipleChoiceOption: Boolean,
val passivePointsGranted: Int, val flavourText: List<String>?, val ascendancyName: String?,
val isAscendancyStart: Boolean?, val reminderText: List<String>?, val spc: List<Int>, val sd: List<String>,
val g: Int, val o: Int, val oidx: Int, val sa: Int, val da: Int, val ia: Int, val out: List<Int> )
data class ExtraImage( val x: Double, val y: Double, val image: String )
data class Constants( val classes: Map<String, Int>, val characterAttributes: Map<String, Int>,
val PSSCentreInnerRadius: Int )
data class SubSpriteCoords( val x: Int, val y: Int, val w: Int, val h: Int )
data class Sprite( val filename: String, val coords: Map<String, SubSpriteCoords> )
data class SkillSprites( val normalActive: List<Sprite>, val notableActive: List<Sprite>,
val keystoneActive: List<Sprite>, val normalInactive: List<Sprite>,
val notableInactive: List<Sprite>, val keystoneInactive: List<Sprite>,
val mastery: List<Sprite> )
private fun convert( jsonFile: File ) {
val mapper = jacksonObjectMapper()
mapper.configure( DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT, true )
val skillTreeData = mapper.readValue<SkillTreeData>( jsonFile )
println("Conversion finished !")
}
fun main( args : Array<String> ) {
val jsonFile: File = File( """rawSkilltree.json""" )
convert( jsonFile )
JSON (not-formatted): http://filebin.ca/3B3reNQf3KXJ/rawSkilltree.json
Given your description, I believe it matches your needs.
GSON is a good choice for Android and Web platform to parse JSON in a Kotlin project. This library is developed by Google.
https://github.com/google/gson
1. First, add GSON to your project:
dependencies {
implementation 'com.google.code.gson:gson:2.8.9'
}
2. Now you need to convert your JSON to Kotlin Data class:
Copy your JSON and go to this(https://json2kt.com) website and paste your JSON to Input Json box. Write package(ex: com.example.appName) and Class name(ex: UserData) in proper box. This site will show live preview of your data class below and also you can download all classes at once in a zip file.
After downloading all classes extract the zip file & place them into your project.
3. Now Parse like below:
val myJson = """
{
"user_name": "john123",
"email": "john#example.com",
"name": "John Doe"
}
""".trimIndent()
val gson = Gson()
var mUser = gson.fromJson(myJson, UserData::class.java)
println(mUser.userName)
Done :)
This uses kotlinx.serialization like Elisha's answer. Meanwhile the project is past version 1.0 so the API has changed. Note that e.g. JSON.parse was renamed to Json.decodeFromString. Also it is imported in gradle differently starting in Kotlin 1.4.0:
dependencies {
implementation "org.jetbrains.kotlinx:kotlinx-serialization-json:1.2.0"
}
apply plugin: 'kotlinx-serialization'
Example usage:
import kotlinx.serialization.Serializable
import kotlinx.serialization.json.Json
import kotlinx.serialization.decodeFromString
import kotlinx.serialization.encodeToString
#Serializable
data class Point(val x: Int, val y: Int)
val pt = Json.decodeFromString<Point>("""{"y": 1, "x": 2}""")
val str = Json.encodeToString(pt) // type can be inferred!
val ilist = Json.decodeFromString<List<Int>>("[-1, -2]")
val ptlist = Json.decodeFromString<List<Point>>(
"""[{"x": 3, "y": 4}, {"x": 5, "y": 6}]"""
)
You can use nullable types (T?) for both nullable and optional fields:
#Serializable
data class Point2(val x: Int, val y: Int? = null)
val nlist = Json.decodeFromString<List<Point2>>(
"""[{"x": 7}, {"x": 8, "y": null}, {"x": 9, "y": 0}]"""
)
Kotlin's data class is a class that mainly holds data and has members, .toString() and other methods (e.g. destructuring declarations) automatically defined.
To convert JSON to Kotlin use http://www.json2kotlin.com/
Also you can use Android Studio plugin. File > Settings, select Plugins in left tree, press "Browse repositories...", search "JsonToKotlinClass", select it and click green button "Install".
After AS restart you can use it. You can create a class with File > New > JSON To Kotlin Class (JsonToKotlinClass). Another way is to press Alt + K.
Then you will see a dialog to paste JSON.
In 2018 I had to add package com.my.package_name at the beginning of a class.
First of all.
You can use JSON to Kotlin Data class converter plugin in Android Studio for JSON mapping to POJO classes (kotlin data class).
This plugin will annotate your Kotlin data class according to JSON.
Then you can use GSON converter to convert JSON to Kotlin.
Follow this Complete tutorial:
Kotlin Android JSON Parsing Tutorial
If you want to parse json manually.
val **sampleJson** = """
[
{
"userId": 1,
"id": 1,
"title": "sunt aut facere repellat provident occaecati excepturi optio
reprehenderit",
"body": "quia et suscipit\nsuscipit recusandae consequuntur expedita"
}]
"""
Code to Parse above JSON Array and its object at index 0.
var jsonArray = JSONArray(sampleJson)
for (jsonIndex in 0..(jsonArray.length() - 1)) {
Log.d("JSON", jsonArray.getJSONObject(jsonIndex).getString("title"))
}
Kotlin Serialization
Kotlin specific library by JetBrains for all supported platforms – Android, JVM, JavaScript, Native.
https://github.com/Kotlin/kotlinx.serialization
Moshi
Moshi is a JSON library for Android and Java by Square.
https://github.com/square/moshi
Jackson
https://github.com/FasterXML/jackson
Gson
Most popular but almost deprecated.
https://github.com/google/gson
JSON to Java
http://www.jsonschema2pojo.org/
JSON to Kotlin
IntelliJ plugin - https://plugins.jetbrains.com/plugin/9960-json-to-kotlin-class-jsontokotlinclass-
Parse JSON string to Kotlin object
As others recommend, Gson library is the simplest way!
If the File is in the Asset folder you can do like this, first add
dependencies {
implementation 'com.google.code.gson:gson:2.9.0'
}
then get a file from Asset:
jsonString = context.assets.open(fileName).bufferedReader().use { it.readText() }
then use Gson :
val gson = Gson()
val listPersonType = object : TypeToken<List<Person>>() {}.type
var persons: List<Person> = gson.fromJson(jsonFileString, listPersonType)
persons.forEachIndexed { idx, person -> Log.i("data", "> Item $idx:\n$person") }
Where Person is a Model/Data class, like this
data class Person(val name: String, val age: Int, val messages: List) {
}
If you prefer parsing JSON to JavaScript-like constructs making use of Kotlin syntax, I recommend JSONKraken, of which I am the author.
You can do things like:
val json: JsonValue = JsonKraken.deserialize("""{"getting":{"started":"Hello World"}}""")
println(JsonKraken.serialize(json)) //prints: {"getting":{"started":"Hello World"}}
println(json["getting"]["started"].cast<String>()) //prints: Hello World
Suggestions and opinions on the matter are much apreciated!
I created a simple Extention function to convert JSON string to model class
inline fun <reified T: Any> String.toKotlinObject(): T =
Gson().fromJson(this, T::class.java)
Usage method
stringJson.toKotlinObject<MyModelClass>()
http://www.jsonschema2pojo.org/
Hi you can use this website to convert json to pojo.
control+Alt+shift+k
After that you can manualy convert that model class to kotlin model class. with the help of above shortcut.
Seems like Kotlin does not have any built-in method as in many cases it just imports and implements some tools from Java. After trying lots of packages, finally this one worked reasonably. This fastjson from alibaba, which is very easy to use. Inside build gradle dependencies:
implementation 'com.alibaba:fastjson:1.1.67.android'
Inside your Kotlin code:
import com.alibaba.fastjson.JSON
var jsonDecodedMap: Map<String, String> =
JSON.parse(yourStringValueHere) as Map<String, String>;
Download the source of deme from here(Json parsing in android kotlin)
Add this dependency:
compile 'com.squareup.okhttp3:okhttp:3.8.1'
Call api function:
fun run(url: String) {
dialog.show()
val request = Request.Builder()
.url(url)
.build()
client.newCall(request).enqueue(object : Callback {
override fun onFailure(call: Call, e: IOException) {
dialog.dismiss()
}
override fun onResponse(call: Call, response: Response) {
var str_response = response.body()!!.string()
val json_contact:JSONObject = JSONObject(str_response)
var jsonarray_contacts:JSONArray= json_contact.getJSONArray("contacts")
var i:Int = 0
var size:Int = jsonarray_contacts.length()
al_details= ArrayList();
for (i in 0.. size-1) {
var json_objectdetail:JSONObject=jsonarray_contacts.getJSONObject(i)
var model:Model= Model();
model.id=json_objectdetail.getString("id")
model.name=json_objectdetail.getString("name")
model.email=json_objectdetail.getString("email")
model.address=json_objectdetail.getString("address")
model.gender=json_objectdetail.getString("gender")
al_details.add(model)
}
runOnUiThread {
//stuff that updates ui
val obj_adapter : CustomAdapter
obj_adapter = CustomAdapter(applicationContext,al_details)
lv_details.adapter=obj_adapter
}
dialog.dismiss()
}
})