Kotlin MainActivity to start walkbase SDK (android project in a flutter project)

MainActivity.kt

package com.dansmy.walkbase_start

import android.content.Intent
import android.content.pm.PackageManager
import android.net.Uri
import android.os.Build
import android.os.Bundle
import android.provider.Settings
import android.support.annotation.RequiresApi
import android.support.design.widget.Snackbar
import android.support.v4.app.ActivityCompat
import android.support.v4.content.ContextCompat;
import android.view.View
import com.walkbase.sdk.WalkbaseManager
import io.flutter.Log

import io.flutter.app.FlutterActivity
import io.flutter.plugins.GeneratedPluginRegistrant

class MainActivity: FlutterActivity(), ActivityCompat.OnRequestPermissionsResultCallback {
  private val PERMISSIONS_REQUEST_CODE = 1234 // Arbitrary Number
  private val apiKey = "your apiKey"
  private val TAG = "MainActivity"

  // Create an instance of WalkbaseManager
  private lateinit var walkbaseManager: WalkbaseManager

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    GeneratedPluginRegistrant.registerWith(this)

    // Initialize the WalkbaseManager
    walkbaseManager = WalkbaseManager(this)

    // Verify that we have the required fine location permissions before proceeding.
    // It's the developers responsibility to confirm this
    if (!havePermissions()) {
      Log.i(TAG, "Requesting permissions needed for this app.")
      requestPermissions()
    } else {
      walkbaseManager.startWithApiKey(apiKey)
    }
  }

  override fun onResume() {
    super.onResume()

    // Call this when the Activity Resumes
    walkbaseManager.onResume()
  }

  override fun onStop() {
    super.onStop()

    // Call this when the Activity Stops
    walkbaseManager.onStop()
  }

  /**
   * havePermissions checks if the user has granted permissions to ACCESS FINE LOCATION
   * Returns a boolean
   */
  private fun havePermissions(): Boolean {
    return ContextCompat.checkSelfPermission(this,
            android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
  }

  // Request location permissions
  private fun requestPermissions() {
    ActivityCompat.requestPermissions(this,
            arrayOf(android.Manifest.permission.ACCESS_FINE_LOCATION), PERMISSIONS_REQUEST_CODE)
  }

  private fun showLinkToSettingsSnackbar() {
    Snackbar.make(this.flutterView,
            "Permission denied",
            Snackbar.LENGTH_INDEFINITE)
            .setAction("Permission settings", View.OnClickListener {
              // Build intent that displays the App settings screen.
              val intent = Intent()
              intent.action = Settings.ACTION_APPLICATION_DETAILS_SETTINGS
              val uri = Uri.fromParts("package",
                      BuildConfig.APPLICATION_ID, null)
              intent.data = uri
              intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK
              startActivity(intent)
            }).show()
  }

  // Show a dialog to request location permissionse
  private fun showRequestPermissionsSnackbar() {
    Snackbar.make(this.flutterView, "We need permissions to access your location",
            Snackbar.LENGTH_INDEFINITE)
            .setAction("Ok", View.OnClickListener {
              // Request permission.
              ActivityCompat.requestPermissions(this@MainActivity,
                      arrayOf(android.Manifest.permission.ACCESS_FINE_LOCATION),
                      PERMISSIONS_REQUEST_CODE)
            }).show()
  }

  @RequiresApi(api = Build.VERSION_CODES.M)
  override fun onRequestPermissionsResult(requestCode: Int,
                                          permissions: Array<String>, grantResults: IntArray) {
    if (requestCode != PERMISSIONS_REQUEST_CODE) {
      return
    }

    for (i in permissions.indices) {
      val permission = permissions[i]
      if (grantResults[i] == PackageManager.PERMISSION_DENIED) {
        if (shouldShowRequestPermissionRationale(permission)) {
          Log.i(TAG, "Permission denied without 'NEVER ASK AGAIN': " + permission)
          showRequestPermissionsSnackbar()
        } else {
          Log.i(TAG, "Permission denied with 'NEVER ASK AGAIN': " + permission)
          showLinkToSettingsSnackbar()
        }
      } else {
        Log.i(TAG, "Permission granted, starting the Walkbase SDK")

        // When we have verified the user has granted permission we can start the SDK.
        walkbaseManager.startWithApiKey(apiKey)
      }
    }
  }
}

The following dependencies must be added to make the Walkbase SDK work properly:

org.jetbrains.anko:anko-commons:0.10.4
com.squareup.okhttp3:okhttp:4.2.2
com.squareup.okhttp3:logging-interceptor:4.2.2
com.squareup.retrofit2:retrofit:2.6.2
com.squareup.retrofit2:converter-gson:2.6.2
com.google.code.gson:gson:2.8.0
com.google.android.gms:play-services-nearby:12.0.1
com.google.android.gms:play-services-location:12.0.1