Override Back pressed

  private var doubleBackToExitPressedOnce = false
    override fun onBackPressed() {
        if (doubleBackToExitPressedOnce) {
            //TODO showDialog
            return
        }

        this.doubleBackToExitPressedOnce = true
        Toast.makeText(this, resources.getString(R.string.exit_toast), Toast.LENGTH_SHORT).show()

        Handler().postDelayed({ doubleBackToExitPressedOnce = false }, 2000)
    }