Fragment re-created on bottom navigation view item selected

Question

Following is my code for bottom navigation view item selected

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationI         


        

Answer 1

I solved this problem by adding a ViewPager to which I delegated all my navigation fragments. Its adapter (FragmentPagerAdapter) doesn't recreate the fragments instances when the user navigates through the BotoomNavigationView.

To achieve this, you have to complete 5 easy steps:

1. add a ViewPager to your layout;

2. implement its adapter:

   class YourNavigationViewPagerAdapter(fm: FragmentManager,
                                        private val param1: Int,
                                        private val param2: Int)
   
       : FragmentPagerAdapter(fm) {
   
       override fun getItem(p0: Int) = when(p0) {
           0 -> NavigationFragment1.newInstance(param1, param2)
           1 -> NavigationFragment2.newInstance(param1, param2)
           2 -> NavigationFragment3.newInstance(param1, param2)
           else -> null
       }
   
       override fun getCount() = 3
   }
   

3. don't forget to set the new adapter:

   yourViewPager.adapter = YourNavigationViewPagerAdapter(supportFragmentManager, param1, param2)
   

4. set a OnNavigationItemSelectedListener to your BottomNavigationView like the following:

   yourBottomNavigationView.setOnNavigationItemSelectedListener {
   
       when(it.itemId) {
   
           R.id.yourFirstFragmentMenuItem -> {
               yourViewPager.currentItem = 0
               true
           }
   
           R.id.yourSecondFragmentMenuItem -> {
               yourViewPager.currentItem = 1
               true
           }
   
           R.id.yourThirdFragmentMenuItem -> {
               yourViewPager.currentItem = 2
               true
           }
   
   
           else -> false
       }
   }
   

5. set a OnPageChangeListener to your ViewPager like the following:

   yourViewPager.addOnPageChangeListener(object : 
   ViewPager.OnPageChangeListener {
       override fun onPageScrollStateChanged(p0: Int) {
   
       }
   
       override fun onPageScrolled(p0: Int, p1: Float, p2: Int) {
   
       }
   
       override fun onPageSelected(p0: Int) {
           yourBottomNavigationView.menu.getItem(p0).isChecked = true
       }
   
   })
   

6. enjoy :)