will RecyclerView cause a memory leak while working with jetpack navigation?

Issue

supposeI have such a fragment.

class MyFragment : Fragment() {

    // Suppose there is a binding, which contains a recyclerView
    private var _binding: FragmentAbinding? = null
    val binding get() = _binding!!
    
    // Suppose there is a recyclerView adapter
    val adapter by lazy { MyAdapter() }

    // use navigation as router
    private val navController: NavController by lazy { findNavController() }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        _binding = FragmentAbinding.inflate(
            inflater,
            container,
            false
        )
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {

        // ...
        binding.recyclerView.adapter = adapter
        // ...
    }

    override fun onDestroyView() {
        _binding = null
    }
}

when using navController.navigate(...), MyFragment will be replaced, and _binding will be null. However, since recyclerView uses the observer mode to observe the dataset in the adapter, the adapter will hold recyclerView as its observer. After navigating to another fragment(that is, after onDestroyView()), will recyclerView actively cancel the observation of the adapter dataset, which means that adapter would not hold an instance of recyclerView?

I use method below to remove adapter dataset observers

fun RecyclerView.Adapter<*>.removeObservers() {
    var clazz: Class<*> = javaClass
    val simpleName = RecyclerView.Adapter::class.simpleName
    while (clazz.simpleName != simpleName) {
        clazz = clazz.superclass
    }
    val field = clazz.getDeclaredField("mObservable")
    field.isAccessible = true
    val observable = field[this] as Observable<*>
    observable.unregisterAll()
}

// in fragment
class MyFragment : Fragment() {

    override fun onDestroyView() {
        adapter.removeObservers()
    }
}

Solution

The adapter when called "onCreateViewHolder" uses recyclerView as a view group when you navigate with navigation your fragment just views destroyed but still its instance is alive in the backstack and your adapter is too because that is a class-level variable for solving this issue you should create adapter in view lifecycle events(onViewCreated.. onDestroyView).

Answered By - Pejman Azad