class MainActivity : AppCompatActivity(R.layout.activity_main) {
    var sharedPreferences: SharedPreferences? = null
    var sharedEditor: SharedPreferences.Editor? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        if (savedInstanceState == null) {
            sharedPreferences = getPreferences(MODE_PRIVATE)
            sharedEditor = sharedPreferences!!.edit()
            if (isFirstStart()) {
                supportFragmentManager.beginTransaction()
                    .setReorderingAllowed(true)
                    .add(R.id.fragment_container_view, FirstStartFragment::class.java, null)
                    .commit()
            } else {
                supportFragmentManager.beginTransaction()
                    .setReorderingAllowed(true)
                    .add(R.id.fragment_container_view, SecondStartFragment::class.java, null)
                    .commit()
            }
        }
    }

    private fun isFirstStart(): Boolean {
        return if (sharedPreferences!!.getBoolean("firstTime", true)) {
            sharedEditor!!.putBoolean("firstTime", false)
            sharedEditor!!.commit()
            sharedEditor!!.apply()
            true
        } else {
            false
        }
    }
}