Kotlin Code of the Main Activity for the Counter App Tutorial on the SSaurel's Blog

MainActivity.kt

package com.ssaurel.kotlincounter

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

  var id = 0

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

    value.setText("" + id)

    plusBtn.setOnClickListener {
      value.setText("" + ++id)
    }

    minusBtn.setOnClickListener {
      value.setText("" + --id)
    }
  }
}