Kotlin Android JSON Parsing using URL

JSON refers to JavaScript Object Notation, and it is a programming language. JSON is used to parse the data between the server and the client. It is minimal, textual and a subset of JavaScript. It is the alternative to XML parsing.

The advantage of JSON over XML

JSON is faster and easier than XML for AJAX applications.
Unlike XML, it is shorter and quicker to read and write.
It uses an array.

JSON Object

A JSON object contains key/value pairs like a map. The keys are strings and the values are the JSON types. A comma separates keys and values (,). The curly brace {} represents the JSON object.

Kotlin JSON Parsing using URL Example

In this example, we parse the JSON data from URL and bind them into a ListView. The JSON data contains the “id” “name” “email”.

JSON data index.html

Create a JSON file index.html.

  {“info”:[  {“name”:”Ajay”,”id”:”111″,”email”:”ajay@gmail.com”},  {“name”:”John”,”id”:”112″,”email”:”john@gmail.com”},  {“name”:”Rahul”,”id”:”113″,”email”:”rahul@gmail.com”},  {“name”:”Maich”,”id”:”114″,”email”:”maich@gmail.com”},  {“name”:”Vikash”,”id”:”115″,”email”:”vikash@gmail.com”},  {“name”:”Mayank”,”id”:”116″,”email”:”mayank@gmail.com”},  {“name”:”Prem”,”id”:”117″,”email”:”prem@gmail.com”},  {“name”:”Chandan”,”id”:”118″,”email”:”chandan@gmail.com”},  {“name”:”Soham”,”id”:”119″,”email”:”soham@gmail.com”},  {“name”:”Mukesh”,”id”:”120″,”email”:”mukesh@gmail.com”},  {“name”:”Ajad”,”id”:”121″,”email”:”ajad@gmail.com”}  ]  }  

While executing the JSON file (index.html) looks like as:

Kotlin Android JSON Parsing using URL

activity_main.xml

Add the ListView in the activity_main.xml layout file.

  <?xml version=”1.0″ encoding=”utf-8″?>  <android.support.constraint.ConstraintLayout xmlns:android=”http://schemas.android.com/apk/res/android”      xmlns:app=”http://schemas.android.com/apk/res-auto”      xmlns:tools=”http://schemas.android.com/tools”      android:layout_width=”match_parent”      android:layout_height=”match_parent”      tools:context=”example.tutoraspire.com.kotlinjsonparsing.MainActivity”>        <ListView          android:id=”@+id/listView”          android:layout_width=”match_parent”          android:layout_height=”match_parent”>        </ListView>    </android.support.constraint.ConstraintLayout>  

build.gradle

Add the following okhttp dependency in the build.gradle file.

Model.kt

Create a data model class Model.kt which includes the information String “id”, String “name” and String “email”.

  package example.tutoraspire.com.kotlinjsonparsing    public class Model{      lateinit var id:String      lateinit var name:String      lateinit var email:String        constructor(id: String,name:String,email:String) {          this.id = id          this.name = name          this.email = email      }        constructor()  }  

adapter_layout.xml

Create an adapter_layout.xml file in the layout directory which contains the row items for ListView.

  <?xml version=”1.0″ encoding=”utf-8″?>  <LinearLayout xmlns:android=”http://schemas.android.com/apk/res/android”      android:layout_width=”match_parent”      android:layout_height=”wrap_content”      android:id=”@+id/linearLayout”      android:padding=”5dp”      android:orientation=”vertical”>        <TextView          android:layout_width=”wrap_content”          android:layout_height=”wrap_content”          android:id=”@+id/tvId”          android:layout_margin=”5dp”          android:textSize=”16dp”/>      <TextView          android:layout_width=”wrap_content”          android:layout_height=”wrap_content”          android:id=”@+id/tvName”          android:textSize=”16dp”          android:layout_margin=”5dp”/>        <TextView          android:layout_width=”wrap_content”          android:layout_height=”wrap_content”          android:id=”@+id/tvEmail”          android:layout_margin=”5dp”          android:textSize=”16dp”/>    </LinearLayout>  

CustomAdapter.kt

Create a custom adapter class CustomAdapter.kt and extend BaseAdapter to handle the custom ListView.

  package example.tutoraspire.com.kotlinjsonparsing    import android.content.Context  import android.view.LayoutInflater  import android.view.View  import android.view.ViewGroup  import android.widget.BaseAdapter  import android.widget.LinearLayout  import android.widget.TextView    class CustomAdapter(context: Context,arrayListDetails:ArrayList<Model>) : BaseAdapter(){        private val layoutInflater: LayoutInflater      private val arrayListDetails:ArrayList<Model>        init {          this.layoutInflater = LayoutInflater.from(context)          this.arrayListDetails=arrayListDetails      }        override fun getCount(): Int {          return arrayListDetails.size      }        override fun getItem(position: Int): Any {          return arrayListDetails.get(position)      }        override fun getItemId(position: Int): Long {          return position.toLong()      }        override fun getView(position: Int, convertView: View?, parent: ViewGroup): View? {          val view: View?          val listRowHolder: ListRowHolder          if (convertView == null) {              view = this.layoutInflater.inflate(R.layout.adapter_layout, parent, false)              listRowHolder = ListRowHolder(view)              view.tag = listRowHolder          } else {              view = convertView              listRowHolder = view.tag as ListRowHolder          }            listRowHolder.tvName.text = arrayListDetails.get(position).name          listRowHolder.tvEmail.text = arrayListDetails.get(position).email          listRowHolder.tvId.text = arrayListDetails.get(position).id          return view      }  }    private class ListRowHolder(row: View?) {      public val tvName: TextView      public val tvEmail: TextView      public val tvId: TextView      public val linearLayout: LinearLayout        init {          this.tvId = row?.findViewById<TextView>(R.id.tvId) as TextView          this.tvName = row?.findViewById<TextView>(R.id.tvName) as TextView          this.tvEmail = row?.findViewById<TextView>(R.id.tvEmail) as TextView          this.linearLayout = row?.findViewById<LinearLayout>(R.id.linearLayout) as LinearLayout      }  }  

MainActivity.kt

Add the following code in MainActivity.kt class file. This class read the JSON data in the form of a JSON object. Using the JSON object, we read the JSON array data. The JSON data are bind in ArrayList.

  package example.tutoraspire.com.kotlinjsonparsing    import android.support.v7.app.AppCompatActivity  import android.os.Bundle  import android.view.View  import android.widget.ListView  import android.widget.ProgressBar  import okhttp3.*  import org.json.JSONArray  import org.json.JSONObject  import java.io.IOException  import kotlin.collections.ArrayList    class MainActivity : AppCompatActivity() {      lateinit var progress:ProgressBar      lateinit var listView_details: ListView      var arrayList_details:ArrayList<Model> = ArrayList();      //OkHttpClient creates connection pool between client and server      val client = OkHttpClient()      override fun onCreate(savedInstanceState: Bundle?) {          super.onCreate(savedInstanceState)          setContentView(R.layout.activity_main)          progress = findViewById(R.id.progressBar)          progress.visibility = View.VISIBLE          listView_details = findViewById<ListView>(R.id.listView) as ListView          run(“http://10.0.0.7:8080/jsondata/index.html”)      }        fun run(url: String) {          progress.visibility = View.VISIBLE          val request = Request.Builder()                  .url(url)                  .build()            client.newCall(request).enqueue(object : Callback {              override fun onFailure(call: Call, e: IOException) {                  progress.visibility = View.GONE              }                override fun onResponse(call: Call, response: Response) {                  var str_response = response.body()!!.string()                  //creating json object                  val json_contact:JSONObject = JSONObject(str_response)                  //creating json array                  var jsonarray_info:JSONArray= json_contact.getJSONArray(“info”)                  var i:Int = 0                  var size:Int = jsonarray_info.length()                  arrayList_details= ArrayList();                  for (i in 0.. size-1) {                      var json_objectdetail:JSONObject=jsonarray_info.getJSONObject(i)                      var model:Model= Model();                      model.id=json_objectdetail.getString(“id”)                      model.name=json_objectdetail.getString(“name”)                      model.email=json_objectdetail.getString(“email”)                      arrayList_details.add(model)                  }                    runOnUiThread {                      //stuff that updates ui                      val obj_adapter : CustomAdapter                      obj_adapter = CustomAdapter(applicationContext,arrayList_details)                      listView_details.adapter=obj_adapter                  }                  progress.visibility = View.GONE              }          })      }  }  

AndroidManifest.xml

Add the Internet permission in AndroidManifest.xml file.

Output:

Kotlin Android JSON Parsing using URL

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Kotlin Android JSON Parsing using URL

Kotlin Android JSON Parsing using URL

The advantage of JSON over XML

JSON Object

Kotlin JSON Parsing using URL Example

JSON data index.html

activity_main.xml

build.gradle

Model.kt

adapter_layout.xml

CustomAdapter.kt

MainActivity.kt

AndroidManifest.xml

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