MainActivity.kt

class MainActivity {
  
  companion object {
        //tag for each fragment
        const val TAG_HOME = "home"
        const val TAG_SEARCH = "search"
        const val TAG_NOTIFICATION = "notification"
        const val TAG_PROFILE = "profile"
  }
  
  //fragments
  private val homeFragment : HomeFragment by lazy {
      val fr = supportFragmentManager.findFragmentByTag(TAG_HOME)
      if(fr != null)fr as HomeFragment
      else HomeFragment()
  }
  private val searchFragment  : SearchFragment by lazy {
      val fr = supportFragmentManager.findFragmentByTag(TAG_SEARCH)
      if(fr != null) fr as SearchFragment
      else SearchFragment()
  }
  private val notificationFragment : TrendingFragment by lazy {
      val fr = supportFragmentManager.findFragmentByTag(TAG_NOTIFICATION)
      if(fr != null) fr as TrendingFragment
      else TrendingFragment()
  }
  private val profileFragment : ProfileFragment by lazy {
      val fr = supportFragmentManager.findFragmentByTag(TAG_PROFILE)
      if(fr != null) fr as ProfileFragment
      else ProfileFragment.getInstance()
  }
  
  private lateinit var binding : MainActivityBinding
  
  override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this,R.layout.main_activity)
        
    }
}