如何防止在底部导航视图中重新创建片段？

Question

I have successfully implemented Bottom Navigation View but whenever the navigate from one fragment to another the first fragment gets completely destroyed even when i'm on the same fragment and press the menu button for it it gets destroyed

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import com.ncapdevi.fragnav.FragNavController
import com.shivam.spaced.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity(), FragNavController.RootFragmentListener {

private lateinit var binding: ActivityMainBinding
private var selectedFragment: Fragment? = null



override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding = DataBindingUtil.setContentView(this, R.layout.activity_main)


    binding.bottomNavigation.setOnNavigationItemSelectedListener { menuItem ->
        when (menuItem.itemId) {
            R.id.home_item -> {
                selectedFragment = HomeFragment()
            }
            R.id.notification_item -> {
                selectedFragment = NotificationsFragment()
            }
            R.id.camera_item -> {
                selectedFragment = CameraFragment()
            }
            R.id.settings_item -> {
                selectedFragment = SettingsFragment()
            }
        }

        selectedFragment.id
        if (selectedFragment != null) {
            supportFragmentManager.beginTransaction()
                .replace(R.id.fragment_container, selectedFragment!!).commit()
        }

        return@setOnNavigationItemSelectedListener true
    }
}

}

Answer 1

supportFragmentManager
.beginTransaction()
.add(R.id.fragment_container, selectedFragment!!)
.commit()

Transition.add function adds a fragment to a container and Transition.replace function removes the current container's fragment and add a new to it.