Using Kotlin JSON Parsing with Listview

In this post, we’ll learn how to parse JSON data using Moshi library. 

What is Moshi?
Moshi is an open source modern JSON library for both Android and Java, for parsing JSON. It is developed by Square (Jake and Jesse).It is like other JSON parsing libraries like Retrofit, GSON etc.

Step 1 :- Adding Internet permissions to manifest.xml as Fallows in red:

 

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.ravi.jsonparseing">

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

    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:roundIcon="@mipmap/ic_launcher_round"        android:supportsRtl="true"        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest> 

Step 2 :- Adding Dependencies and Library to Gradle file(Module:app) as Fallows in red: 

 

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
android {
    compileSdkVersion 26    useLibrary  'org.apache.http.legacy'
    defaultConfig {
        applicationId "com.example.ravi.jsonparseing"        minSdkVersion 15        targetSdkVersion 26        versionCode 1        versionName "1.0"        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"    }
    buildTypes {
        release {
            minifyEnabled false            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"    implementation 'com.android.support:appcompat-v7:26.1.0'    implementation 'com.android.support.constraint:constraint-layout:1.0.2'    testImplementation 'junit:junit:4.12'    androidTestImplementation 'com.android.support.test:runner:1.0.1'    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'    compile 'com.squareup.moshi:moshi:1.5.0'}

Step 3 :- let’s create a model class add following code into it:

 

package com.example.ravi.jsonparseing

/** * Created by ravi on 11/8/17. */internal class Product {

    val productid: String? = null    val productname: String? = null    val price: String? = null    val instock: Int = 0    val offer: String? = null    val color: String? = null    val imageurl: String? = null}

Step 4 :- For JSON Data, we’ve added that Apache dependency into our gradle file. We’ll get web page content using an AsyncTask named DownloadWebPageTask in our code. 

Let’s see the code now:

import android.os.AsyncTask
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.ArrayAdapter
import android.widget.ListView
import com.squareup.moshi.Moshi
import org.apache.http.client.methods.HttpGet
import org.apache.http.impl.client.DefaultHttpClient
import java.io.BufferedReader
import java.io.InputStreamReader
import java.util.*

class MainActivity : AppCompatActivity() {

    internal var json = ""    internal lateinit var list: ArrayList<Product>
    internal lateinit var listView: ListView
    internal lateinit var myList: ArrayList<String>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        DownloadWebPageTask().execute("http://api2.mytrendin.com/json/")

    }

    private inner class DownloadWebPageTask : AsyncTask<String, Void, String>() {

        override fun doInBackground(vararg urls: String): String
        {

            var response = ""
            for (url in urls)
            {
                val client = DefaultHttpClient()

                val httpGet = HttpGet(url)


                try                {
                    val execute = client.execute(httpGet)
                    val content = execute.entity.content
                    val buffer = BufferedReader(InputStreamReader(content))

                    var s = ""
                    while (s != null)
                    {
                        s = buffer.readLine()

                        response += s
                    }

                } catch (e: Exception) { e.printStackTrace() }

            }
            return response
        }

        override fun onPostExecute(result: String) {
            json = result

            parseJSON(json)

        }
    }

    fun parseJSON(json: String) {

        Log.e("MainActivity","Result==>>"+json)


        val moshi = Moshi.Builder().build()

        val jsonAdapter = moshi.adapter<Array<Product>>(Array<Product>::class.java)


        var products: Array<Product>? = null


        myList = ArrayList<String>()


        try        {

            products = jsonAdapter.fromJson(json)


        } catch (e: Exception) {
            e.printStackTrace()
        }

        for (p in products!!)
        {

            println(p.productid + " " + p.instock + " " + p.price + " " + p.color + " " + p.productname + " " + p.offer + " " + p.imageurl)

            myList.add("ID: " + p.productid + "\n" + "In stock: " + p.instock + "\n" + "Price: " + p.price + "\n" + "Color: " + p.color + "\n" + "Product name: " + p.productname + "\n" + "Offer: " + p.offer + "\n")
        }

        list = ArrayList(Arrays.asList(*products))

        setUpListView()

    }

    fun setUpListView() {

        listView = findViewById<ListView>(R.id.listView) as ListView

        listView.adapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, myList)
    }


}

 

Step 5 :- Now run your app, and make sure you are connected to the Internet. It’ll fetch the content of web page, parse it and then display it to the list view.

Note: For more,actual Parsing is done in parseJSON() method and AsyncTask is for getting content from a web page.