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:

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:

tamtom · Accepted Answer · 2019-05-18T23:30:46.550

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

I swear I tried this LOL, but now it works so no complains on my side, Thank you very much! — ofir2471, May 18 '19 at 23:34

score 0 · Answer 2 · answered May 18 '19 at 23:18

Take a look at architicture components, yuo can also achieve that in the old way Android - save/restore fragment state When a fragment isnt viewable its paused or might even be destroyed use bundle to perserve data. What you are trying to acheive could be done using two containers but you really shouldn't

Move between fragments without recreation- Kotlin

2 Answers2