AndroidMainActivity.scala

package com.biznet

import android.app.Activity
import android.os.Bundle
import android.support.v7.widget.{LinearLayoutManager, RecyclerView}
import android.util.Log
import android.view.{LayoutInflater, View, ViewGroup}
import android.widget.TextView
import okhttp3.MultipartBody
import retrofit2.converter.gson.GsonConverterFactory
import retrofit2.{Call, Callback, Response, Retrofit}
import retrofit2.http._

class MainActivity extends Activity {
  case class User(val name:String)
  trait OnlineService{
    @GET("user")
    def getUsers():Call[Array[User]]
  }

    override def onCreate(savedInstanceState: Bundle): Unit = {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main)

      var theRecyclerView= findViewById(R.id.theRecycler).asInstanceOf[RecyclerView]
      var theUserList:List[User] = List.empty[User]
      theRecyclerView.setLayoutManager(new LinearLayoutManager(this))
      theRecyclerView.setAdapter(new MyAdapter(theUserList))

      var retrofit:Retrofit = new Retrofit.Builder()
        .baseUrl("http://10.0.2.2:8080")
        .addConverterFactory(GsonConverterFactory.create())
        .build()
      var service:OnlineService = retrofit.create(classOf[OnlineService])
      var call:Call[Array[User]]=service.getUsers()
      call.enqueue(new Callback[Array[User]]{
        override def onFailure(call: Call[Array[User]], t: Throwable): Unit = {}

        override def onResponse(call: Call[Array[User]], response: Response[Array[User]]): Unit = {
          if(response.isSuccessful){
           var theRes:Array[User] = response.body()
            theUserList = theRes.toList

            theRecyclerView.setAdapter(new MyAdapter(theUserList))
            theRecyclerView.getAdapter.notifyDataSetChanged()
          }
        }
      })
      
    }

  class MyViewHolder(v:View) extends RecyclerView.ViewHolder(v){
      var theUser:TextView = v.findViewById(R.id.oneUser).asInstanceOf[TextView]
  }

  class MyAdapter(val userList:List[User]=List(User("one"),User("two"),User("three"))) extends RecyclerView.Adapter[MyViewHolder]{
    override def getItemCount: Int = userList.length

    override def onBindViewHolder(vh: MyViewHolder, i: Int): Unit = {
      var theText = vh.theUser.asInstanceOf[TextView]
      theText.setText(userList(i).name)
    }

    override def onCreateViewHolder(viewGroup: ViewGroup, i: Int): MyViewHolder = {
      var layoutIn:View= LayoutInflater.from(getApplicationContext).inflate(R.layout.one_user,viewGroup, false)
      new MyViewHolder(layoutIn)
    }
  }
}

build.sbt

name := "matrix"

version := "1.0"

scalaVersion := "2.12.3"

resolvers += Resolver.bintrayRepo("hseeberger", "maven")

libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-http" % "10.0.9",
  "com.typesafe.akka" %% "akka-http-testkit" % "10.0.9" % Test
)

// https://mvnrepository.com/artifact/org.neo4j/neo4j
libraryDependencies += "org.neo4j" % "neo4j" % "3.2.2"

// https://mvnrepository.com/artifact/org.neo4j.driver/neo4j-java-driver
libraryDependencies += "org.neo4j.driver" % "neo4j-java-driver" % "1.4.2"

libraryDependencies ++= List(
  "de.heikoseeberger" %% "akka-http-circe" % "1.17.0"
)
val circeVersion = "0.8.0"

libraryDependencies ++= Seq(
  "io.circe" %% "circe-core",
  "io.circe" %% "circe-generic",
  "io.circe" %% "circe-parser",
  "io.circe" %% "circe-optics"
).map(_ % circeVersion)

addCompilerPlugin(
  "org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full
)

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <android.support.v7.widget.RecyclerView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/theRecycler"
    >

    </android.support.v7.widget.RecyclerView>
</LinearLayout>

MyServer.scala

import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import io.circe.syntax._
import akka.stream.ActorMaterializer
import akka.http.scaladsl.server.Directives._
import org.neo4j.driver.v1.{AuthTokens, GraphDatabase}
import de.heikoseeberger.akkahttpcirce. FailFastCirceSupport

import scala.io.StdIn


object MyServer extends FailFastCirceSupport{
  
  case class User(name:String)

  def main(args:Array[String]): Unit = {
    implicit val system = ActorSystem("mike-actors")
    implicit val materializer = ActorMaterializer()
    implicit val executionContext = system.dispatcher

    val driver = GraphDatabase.driver("bolt://localhost/7687", AuthTokens.basic("neo4j", "myNeo4j"))
    val session = driver.session
    val script = s"MATCH (n:Person) RETURN n LIMIT 25"
    var result = session.run(script)

    var myUsers: List[User] = List.empty[User]

    while(result.hasNext){
      var row = result.next().get(0).get("name").asString()
      myUsers=User(row)::myUsers
    }
    
    val theRoute = path("user") {
      get {
        complete(myUsers.asJson)
      }
    }


    val bindingFuture = Http().bindAndHandle(theRoute, "localhost", 8080)
    println("ze server iz running")
    StdIn.readLine()

    bindingFuture.flatMap(_.unbind()).onComplete(_ => system.terminate())

  }
}

one_user.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content">
    <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/oneUser"
    />

</LinearLayout>