Btukfyl

As next week will have importat launch for Rust 2018 and Flutter 1.0, I thought to build an app using Rust for the business logic and Flutter for the user interface, that can run at both Android and iOS, I built one and tested it at Android and it is working fine.

I just wonder how to measure the performance and compare it with native Android/iOS app.

The app flow is:

1. Main is in Flutter, that is calling native function through platform_channel
   


2. The native function is calling rust library through JNI (JNI wrapper is required to be call the rust library)

The structure is as below:

The code used is:

main.dart:

import 'dart:async';

import 'package:flutter/material.dart';

import 'package:flutter/services.dart';



void main() => runApp(MyApp());



class MyApp extends StatelessWidget {

  @override

  Widget build(BuildContext context) {

    return MaterialApp(

      title: 'Flutter Demo',

      theme: ThemeData(

        primarySwatch: Colors.blue,

      ),

      home: MyHomePage(title: 'Flutter Demo Home Page'),

    );

  }

}



class MyHomePage extends StatefulWidget {

  MyHomePage({Key key, this.title}) : super(key: key);



  final String title;



  @override

  _MyHomePageState createState() => _MyHomePageState();

}



class _MyHomePageState extends State<MyHomePage> {

  static const platform = const MethodChannel('samples.flutter.io/battery');



  String _batteryLevel = 'Unknown battery level.';



  Future<void> _getBatteryLevel() async {

    String batteryLevel;

    try {

      final String hello = await platform.invokeMethod('getText');

      final int result = await platform.invokeMethod('getBatteryLevel');



      batteryLevel = '$hello Battery level at $result %.';

    } on PlatformException catch (e) {

      batteryLevel = "Failed to get battery level: '${e.message}'.";

    }



    setState(() {

      _batteryLevel = batteryLevel;

    });

  }



  @override

  Widget build(BuildContext context) {

    return Material(

      child: Center(

        child: Column(

          mainAxisAlignment: MainAxisAlignment.spaceEvenly,

          children: [

            RaisedButton(

              child: Text('Get Battery Level'),

              onPressed: _getBatteryLevel,

            ),

            Text(_batteryLevel),

          ],

        ),

      ),

    );

  }

}

JNI wrapper - RustGreetings.kt

package com.mozilla.greetings



class RustGreetings {

    companion object {

        init {

            System.loadLibrary("greetings")

        }

    }



    private external fun greeting(pattern: String): String



    fun sayHello(to: String): String = greeting(to)

}

And the Main Android activity is:

package com.example.batterylevel



import android.os.Bundle

import io.flutter.app.FlutterActivity

import io.flutter.plugins.GeneratedPluginRegistrant

import io.flutter.plugin.common.MethodChannel



import android.content.Context

import android.content.ContextWrapper

import android.content.Intent

import android.content.IntentFilter

import android.os.BatteryManager

import android.os.Build.VERSION

import android.os.Build.VERSION_CODES



import lib.Library

import com.mozilla.greetings.RustGreetings



class MainActivity: FlutterActivity() {

  private val CHANNEL = "samples.flutter.io/battery"



  override fun onCreate(savedInstanceState: Bundle?) {

    super.onCreate(savedInstanceState)

    GeneratedPluginRegistrant.registerWith(this)



    MethodChannel(flutterView, CHANNEL).setMethodCallHandler { call, result ->

      if (call.method == "getText") {

        result.success(getText())

      } else if (call.method == "getBatteryLevel") {

       // result.success(getText())

        val batteryLevel = getBatteryLevel()



        if (batteryLevel != -1) {

          result.success(batteryLevel)

        } else {

          result.error("UNAVAILABLE", "Battery level not available.", null)

        }

      }

      else {



        result.notImplemented()

      }

    }

  }



  private fun getBatteryLevel(): Int {

    val batteryLevel: Int

    if (VERSION.SDK_INT >= VERSION_CODES.LOLLIPOP) {

      val batteryManager = getSystemService(Context.BATTERY_SERVICE) as BatteryManager

      batteryLevel = batteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)

    } else {

      val intent = ContextWrapper(applicationContext).registerReceiver(null, IntentFilter(Intent.ACTION_BATTERY_CHANGED))

      batteryLevel = intent!!.getIntExtra(BatteryManager.EXTRA_LEVEL, -1) * 100 / intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1)

    }

    return batteryLevel

  }



  private fun getText(): String {

    val x = Library().someLibraryMethod()

    val g = RustGreetings()

    val r = g.sayHello("My $x Rust")

    return r

  }

}

In the Android gradle.build I just added the below, as I'm interested to check also the impact of adding kotlin JVM library and getting it interacted with the Rust library within the mobile application:

dependencies {

    implementation(files("src/main/libs/lib.jar"))

}

My question is:
How can check the performance and impact of each process when it is executed or called by another process