Tuesday, February 5, 2019

android kotlin - Volley example

MainActivity.kt

package com.cfsuman.jetpack

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import com.android.volley.Request
import com.android.volley.Response
import com.android.volley.toolbox.JsonObjectRequest
import kotlinx.android.synthetic.main.activity_main.*
import org.json.JSONException


class MainActivity : AppCompatActivity() {

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

        // Run volley
        btn.setOnClickListener {
            val url = "http://pastebin.com/raw/2bW31yqa"
            textView.text = ""

            val jsonObjectRequest = JsonObjectRequest(
                Request.Method.GET, url, null,
                Response.Listener { response ->
                    // Process the JSON
                    try {
                        // Get the JSON array
                        val array = response.getJSONArray("students")

                        // Loop through the array elements
                        for (i in 0 until array.length()) {
                            // Get current json object
                            val student = array.getJSONObject(i)

                            // Get the current student (json object) data
                            val firstName = student.getString("firstname")
                            val lastName = student.getString("lastname")
                            val age = student.getString("age")

                            // Display the formatted json data in text view
                            textView.append("$firstName $lastName\nage : $age")
                            textView.append("\n\n")
                        }
                    } catch (e: JSONException) {
                        e.printStackTrace()
                    }
                },Response.ErrorListener { error ->
                    Log.d("error",error.toString())
                }
            )

            // Access the RequestQueue through singleton class.
            VolleySingleton.getInstance(this).addToRequestQueue(jsonObjectRequest)
        }
    }
}
VolleySingleton.kt

package com.cfsuman.jetpack

import android.content.Context
import com.android.volley.Request
import com.android.volley.RequestQueue
import com.android.volley.toolbox.Volley


class VolleySingleton constructor(context: Context) {
    companion object {
        @Volatile
        private var INSTANCE: VolleySingleton? = null
        fun getInstance(context: Context) =
            INSTANCE ?: synchronized(this) {
                INSTANCE ?: VolleySingleton(context).also {
                    INSTANCE = it
                }
            }
    }
    private val requestQueue: RequestQueue by lazy {
        // applicationContext is key, it keeps you from leaking the
        // Activity or BroadcastReceiver if someone passes one in.
        Volley.newRequestQueue(context.applicationContext)
    }
    fun <T> addToRequestQueue(req: Request<T>) {
        requestQueue.add(req)
    }
}
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/rootLayout"
        tools:context=".MainActivity"
        android:background="#fdfdfc">
    <Button
            android:text="Run Volley"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/btn"
            android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="parent"
            android:layout_marginStart="8dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            android:layout_marginEnd="8dp"/>
    <TextView
            android:text=""
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textView"
            app:layout_constraintEnd_toEndOf="parent"
            android:layout_marginEnd="16dp"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginStart="16dp"
            android:layout_marginTop="16dp"
            app:layout_constraintTop_toBottomOf="@+id/btn"
            android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium"
            android:textColor="#3F51B5"
            tools:text="TextView"
    />
</androidx.constraintlayout.widget.ConstraintLayout>
gradle dependencies

// Volley network library
implementation 'com.android.volley:volley:1.1.1'
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