Blinking elements when fragment resumes

[strangel3t]

I followed the Databinding example and noticed that everytime I leave the fragment and return to it, the elements inside oneadapter redraw. Is this expected or did I miss something?

[idanatz]

This kind of behavior should not happen but, without seeing the entire implementation of your fragment and data management there is no way of telling what's wrong.

• when you leave the fragment and return to it, the fragment view is re-created?
• where are you populating your data?
• is the adapter being created again when returning to the fragment? or using the previous adapter with old data
• are you models implementing Diffable in a correct way for the DiffUtils to work in case the data is already there and re-assigned? There are at least 10 more questions to try and understand the situation.

If you can post all the relevant code or even better upload a minimal project with the behavior above so I can resolve it if needed.

[strangel3t]

Thanks for the quick reply, with a custom adapter it works as usual, so I don't think it's a problem related to the Fragment lifecycle, here is the sample code:

Model ->

data class ResultItem(
    override val uniqueIdentifier: Long,
    val label: String,
    val iconTint: Int
) : Parcelable, Diffable {

    override fun areContentTheSame(other: Any): Boolean {
         return other is ResultItem && label == other.label
    }
}

Module->

class CheckmarkResultModule(parent: Fragment) :
    ItemModule<ResultItem>() {
    init {
        config {
            layoutResource = R.layout.item_checkmark_result
        }
        onBind { model, viewBinder, _ ->
            viewBinder.dataBinding?.run {
                setVariable(BR.resultModel, model)
                lifecycleOwner = parent.viewLifecycleOwner
                executePendingBindings()
            }
        }
    }
}

Fragment logic->

class PlanInformationFragment : BaseFragment(R.layout.fragment_plan_information) {

    private val args: PlanInformationFragmentArgs by navArgs()

    private val binding by viewBinding(FragmentPlanInformationBinding::bind)

    private lateinit var testItems: List<ResultItem>

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val planInformationArray =
            requireContext().resources.getStringArray(R.array.plan_information)
        testItems = planInformationArray.mapIndexed { index, string ->
            ResultItem(index.toLong(), string, R.color.orange)
        }
        return super.onCreateView(inflater, container, savedInstanceState)
    }

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

        with(binding) {
             with(resultsList) {
                OneAdapter(this) { itemModules += CheckmarkResultModule(this@PlanInformationFragment) }.apply {
                    setItems(testItems)
                }
            }

            choosePlan.setOnClickListener {
                safeNavigation(
                    directions = PlanInformationFragmentDirections.actionOpenPlanDetails()
                )
            }
        }
    }
}

checkmark_result.xml ->

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <variable
            name="resultModel"
            type="com.example.ResultItem" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <ImageView
            android:id="@+id/checkmark"
            android:layout_width="24dp"
            android:layout_height="24dp"
            android:importantForAccessibility="no"
            android:src="@drawable/ic_check"
            android:layout_marginTop="4dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="@id/label"
            app:tint="@color/light_green" />

        <TextView
            android:id="@+id/label"
            style="@style/OnboardingResult"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="10dp"
            android:text="@{resultModel.label}"
            app:layout_constraintStart_toEndOf="@id/checkmark"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            tools:text="@tools:sample/lorem" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

Fragment layout ->

<androidx.constraintlayout.widget.ConstraintLayout android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/resultsList"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
        app:layout_constraintTop_toTopOf="parent"
        tools:itemCount="3"
        tools:listitem="@layout/item_checkmark_result" />

    <Button
        android:id="@+id/choosePlan"
        style="@style/ButtonAction.Orange"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="42dp"
        android:text="@string/onboarding_your_program_choose_plan"
        app:layout_constraintTop_toBottomOf="@id/resultsList" />

</androidx.constraintlayout.widget.ConstraintLayout>

Navigation for the choosePlan button

    <fragment
        android:id="@+id/plan_information"
        android:name="com.example.PlanInformationFragment"
        android:label=""
        tools:layout="@layout/fragment_plan_information">

        <argument
            android:name="title"
            app:argType="reference" />

        <action
            android:id="@+id/action_open_plan_details"
            app:destination="@id/plan_details"/>
    </fragment>

Navigation code:

fun Fragment.safeNavigation(directions: NavDirections) {
    NavHostFragment.findNavController(this).currentDestination?.getAction(directions.actionId)
        ?.apply {
            findNavController().navigate(directions)
        }
}

[strangel3t]

Checking your suggestions I think it's caused by Fragment being recreated during onbackpress on navigation architecture by default. Because you process stuff on background it's noticeable the redrawing, while a normal adapter just makes it look like it was preserved.

I'll see what I can do about that. Thanks

[strangel3t]

If someone is having a similar issue check this link: https://stackoverflow.com/questions/54581071/fragments-destroyed-recreated-with-jetpacks-android-navigation-components

[idanatz]

Thanks for the information 👍🏼