For #8561 - Scroll to topSites on app cold start

app/src/main/java/org/mozilla/fenix/home/HomeFragment.kt

@@ -28,6 +28,7 @@ import androidx.core.content.ContextCompat
 import androidx.core.view.updateLayoutParams
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
+import androidx.fragment.app.viewModels
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleObserver
 import androidx.lifecycle.Observer
@@ -95,6 +96,10 @@ import kotlin.math.min
 @ExperimentalCoroutinesApi
 @SuppressWarnings("TooManyFunctions", "LargeClass")
 class HomeFragment : Fragment() {
+    private val homeViewModel: HomeScreenViewModel by viewModels {
+        ViewModelProvider.AndroidViewModelFactory(requireActivity().application)
+    }
+
     private val snackbarAnchorView: View?
         get() {
             return if (requireContext().settings().shouldUseBottomToolbar) {
@@ -206,7 +211,8 @@ class HomeFragment : Fragment() {
         setOffset(view)
         sessionControlView = SessionControlView(
             homeFragmentStore,
-            view.sessionControlRecyclerView, sessionControlInteractor
+            view.sessionControlRecyclerView, sessionControlInteractor,
+            homeViewModel
         )
         activity.themeManager.applyStatusBarTheme(activity)
 

app/src/main/java/org/mozilla/fenix/home/HomeScreenViewModel.kt

@@ -10,4 +10,9 @@ import androidx.lifecycle.ViewModel
 class HomeScreenViewModel : ViewModel() {
     var layoutManagerState: Parcelable? = null
     var motionLayoutProgress = 0F
+
+    /**
+     * Used to remember if we need to scroll to top of the homeFragment's recycleView (top sites) see #8561
+     * */
+    var shouldScrollToTopSites: Boolean = true
 }

app/src/main/java/org/mozilla/fenix/home/sessioncontrol/SessionControlView.kt

@@ -18,6 +18,7 @@ import mozilla.components.lib.state.ext.consumeFrom
 import org.mozilla.fenix.R
 import org.mozilla.fenix.home.HomeFragmentState
 import org.mozilla.fenix.home.HomeFragmentStore
+import org.mozilla.fenix.home.HomeScreenViewModel
 import org.mozilla.fenix.home.Mode
 import org.mozilla.fenix.home.OnboardingState
 import org.mozilla.fenix.home.Tab
@@ -163,7 +164,8 @@ private fun collectionTabItems(collection: TabCollection) = collection.tabs.mapI
 class SessionControlView(
     private val homeFragmentStore: HomeFragmentStore,
     override val containerView: View?,
-    interactor: SessionControlInteractor
+    interactor: SessionControlInteractor,
+    private var homeScreenViewModel: HomeScreenViewModel
 ) : LayoutContainer {
 
     val view: RecyclerView = containerView as RecyclerView
@@ -193,6 +195,22 @@ class SessionControlView(
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
             sessionControlAdapter.submitList(null)
         }
-        sessionControlAdapter.submitList(state.toAdapterList())
+
+        val stateAdapterList = state.toAdapterList()
+
+        if (homeScreenViewModel.shouldScrollToTopSites) {
+            sessionControlAdapter.submitList(stateAdapterList) {
+
+                val loadedTopSites = stateAdapterList.find { adapterItem ->
+                    adapterItem is AdapterItem.TopSiteList && adapterItem.topSites.isNotEmpty()
+                }
+                loadedTopSites?.run {
+                    homeScreenViewModel.shouldScrollToTopSites = false
+                    view.scrollToPosition(stateAdapterList.indexOf(this))
+                }
+            }
+        } else {
+            sessionControlAdapter.submitList(stateAdapterList)
+        }
     }
 }