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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"}  
        ]  
}  
{"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:



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.javatpoint.com.kotlinjsonparsing.MainActivity">  
  
    < ListView  
        android:id="@+id/listView"  
        android:layout_width="match_parent"  
        android:layout_height="match_parent">  
  
    < /ListView>  
  
< /android.support.constraint.ConstraintLayout>  
< ?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.javatpoint.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.


compile 'com.squareup.okhttp3:okhttp:3.8.1'  
compile 'com.squareup.okhttp3:okhttp:3.8.1'

Model.kt


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


package example.javatpoint.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()  
}  
package example.javatpoint.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>  
< ?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.javatpoint.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  
    }  
}  
package example.javatpoint.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.javatpoint.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  
            }  
        })  
    }  
}  
package example.javatpoint.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.


< uses-permission android:name="android.permission.INTERNET"/>  
< uses-permission android:name="android.permission.INTERNET"/>

Output:



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Hi I am Pluto.