main activity of mock app

MainActivity.kt

package com.example.mock

import android.os.Bundle
import android.os.StrictMode
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import java.io.BufferedReader
import java.io.IOException
import java.io.InputStream
import java.io.InputStreamReader
import java.net.HttpURLConnection
import java.net.URL

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        disableStrictMode()
        setListener()
    }

    private fun disableStrictMode() {
        //WARNING: do not do this on real application
        val policy = StrictMode.ThreadPolicy.Builder().permitAll().build()
        StrictMode.setThreadPolicy(policy)
    }

    private fun setListener() {
        button.setOnClickListener { hello_world.text = callAPI() }
    }

    private fun callAPI(): String {
        var reader: BufferedReader? = null
        var response = ""

        try {
            val myUrl = URL("https://postman-echo.com/time/now")
            val conn: HttpURLConnection = myUrl.openConnection() as HttpURLConnection
            conn.requestMethod = "GET"
            conn.setRequestProperty("Content-Type", "application/json")
            conn.connect()
            val inputStream: InputStream = conn.getInputStream()
            reader = BufferedReader(InputStreamReader(inputStream))
            response = reader.readLine()
        } catch (e: IOException) {
            e.printStackTrace()
        } finally {
            if (reader != null) {
                try {
                    reader.close()
                } catch (e: Exception) {
                    e.printStackTrace()
                }
            }
        }

        return response
    }
}