Move between fragments without recreation- Kotlin

Question

I'm trying to move between two fragments without recreation of them so the data in the previous fragment won't disappear.

I tried to look over the internet for answers and tried for hours but without success. I looked at those links:

• link 1
• link 2
• link 3- android developer site

After show() and hide() I also tried the AddToBackStack() but yet no success

• link 4

class MainActivity : AppCompatActivity(){

    private val onNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
        @Override
        when (item.itemId) {
            R.id.navigation_home -> {
                //replaceFragment(SignInFragment())
                supportFragmentManager.beginTransaction().hide(AllEventsFragment()).commit()
                supportFragmentManager.beginTransaction().show(SignInFragment()).commit()
                return@OnNavigationItemSelectedListener true
            }
            R.id.navigation_events -> {
                //replaceFragment(AllEventsFragment())
                supportFragmentManager.beginTransaction().hide(SignInFragment()).commit()
                supportFragmentManager.beginTransaction().show(AllEventsFragment()).commit()
                if (currentUser.isNotEmpty()) {
                    updateRecyclerView()
                    sign_in_error?.visibility = View.INVISIBLE
                }
                return@OnNavigationItemSelectedListener true
            }
        }
        return@OnNavigationItemSelectedListener false
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        supportFragmentManager.beginTransaction().add(R.id.activity_main, AllEventsFragment(), "2").commit()
        supportFragmentManager.beginTransaction().add(R.id.activity_main, SignInFragment(), "1").commit()
        val navView: BottomNavigationView = findViewById(R.id.nav_view)
        navView.setOnNavigationItemSelectedListener(onNavigationItemSelectedListener)
        personInEvent = false
    }

The result is overlapping fragments without an option to really navigate between them. I really tried everything I know there are some answers over the internet but none of them helped me fix my issue. I would really appreciate some help with this frustrating issue.

Before navigation:

After navigation:

Answer 1

supportFragmentManager.beginTransaction().hide(AllEventsFragment()).commit()

your recreating your fragments every time! calling AllEventsFragment() is equivelant to new AllEventsFragment()

you need to instantiate them first for example, your code needs to be like this,

    val fragment1: Fragment = SignInFragment()
    val fragment2: Fragment = AllEventsFragment()
    var active = fragment1

      override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            supportFragmentManager.beginTransaction().add(R.id.activity_main,fragment2 , "2").commit()
            supportFragmentManager.beginTransaction().add(R.id.activity_main, fragment1, "1").commit()
            val navView: BottomNavigationView = findViewById(R.id.nav_view)
            navView.setOnNavigationItemSelectedListener(onNavigationItemSelectedListener)
            personInEvent = false
        }

inside your listener

    R.id.navigation_home -> {
                 supportFragmentManager.beginTransaction().beginTransaction().hide(active).show(fragment1).commit();
                    active = fragment1;
                return@OnNavigationItemSelectedListener true
            }
 R.id.navigation_events -> {
                //replaceFragment(AllEventsFragment())
                supportFragmentManager.beginTransaction().beginTransaction().hide(active).show(fragment2).commit();
active = fragment2
)

    //handle rest of the cases