For #18521 - Added scroll to current tab (#19021)

* For #18521 - Added scroll to current tab

* For #18521 - Addressed comments

app/src/main/java/org/mozilla/fenix/tabstray/TabsTrayFragment.kt

@@ -276,7 +276,8 @@ class TabsTrayFragment : AppCompatDialogFragment(), TabsTrayInteractor {
                 store,
                 browserInteractor,
                 syncedTabsTrayInteractor,
-                trayInteractor
+                trayInteractor,
+                requireComponents.core.store
             )
             isUserInputEnabled = false
         }

app/src/main/java/org/mozilla/fenix/tabstray/TrayPagerAdapter.kt

@@ -8,13 +8,17 @@ import android.content.Context
 import android.view.LayoutInflater
 import android.view.ViewGroup
 import androidx.recyclerview.widget.RecyclerView
+import mozilla.components.browser.state.selector.normalTabs
+import mozilla.components.browser.state.selector.privateTabs
+import mozilla.components.browser.state.selector.selectedTab
+import mozilla.components.browser.state.store.BrowserStore
+import mozilla.components.feature.syncedtabs.view.SyncedTabsView
+import org.mozilla.fenix.sync.SyncedTabsAdapter
 import org.mozilla.fenix.tabstray.browser.BrowserTabsAdapter
 import org.mozilla.fenix.tabstray.browser.BrowserTrayInteractor
 import org.mozilla.fenix.tabstray.viewholders.AbstractTrayViewHolder
 import org.mozilla.fenix.tabstray.viewholders.NormalBrowserTabViewHolder
 import org.mozilla.fenix.tabstray.viewholders.PrivateBrowserTabViewHolder
-import mozilla.components.feature.syncedtabs.view.SyncedTabsView
-import org.mozilla.fenix.sync.SyncedTabsAdapter
 import org.mozilla.fenix.tabstray.viewholders.SyncedTabViewHolder
 
 class TrayPagerAdapter(
@@ -22,7 +26,8 @@ class TrayPagerAdapter(
     private val store: TabsTrayStore,
     private val browserInteractor: BrowserTrayInteractor,
     private val syncedTabsInteractor: SyncedTabsView.Listener,
-    private val interactor: TabsTrayInteractor
+    private val interactor: TabsTrayInteractor,
+    private val browserStore: BrowserStore
 ) : RecyclerView.Adapter<AbstractTrayViewHolder>() {
 
     private val normalAdapter by lazy { BrowserTabsAdapter(context, browserInteractor, store) }
@@ -32,21 +37,31 @@ class TrayPagerAdapter(
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AbstractTrayViewHolder {
         val itemView = LayoutInflater.from(parent.context).inflate(viewType, parent, false)
 
+        val selectedTab = browserStore.state.selectedTab
+
         return when (viewType) {
-            NormalBrowserTabViewHolder.LAYOUT_ID -> NormalBrowserTabViewHolder(
-                itemView,
-                store,
-                interactor
-            )
-            PrivateBrowserTabViewHolder.LAYOUT_ID -> PrivateBrowserTabViewHolder(
-                itemView,
-                store,
-                interactor
-            )
-            SyncedTabViewHolder.LAYOUT_ID -> SyncedTabViewHolder(
-                itemView,
-                syncedTabsInteractor
-            )
+            NormalBrowserTabViewHolder.LAYOUT_ID -> {
+                NormalBrowserTabViewHolder(
+                    itemView,
+                    store,
+                    interactor,
+                    browserStore.state.normalTabs.indexOf(selectedTab)
+                )
+            }
+            PrivateBrowserTabViewHolder.LAYOUT_ID -> {
+                PrivateBrowserTabViewHolder(
+                    itemView,
+                    store,
+                    interactor,
+                    browserStore.state.privateTabs.indexOf(selectedTab)
+                )
+            }
+            SyncedTabViewHolder.LAYOUT_ID -> {
+                SyncedTabViewHolder(
+                    itemView,
+                    syncedTabsInteractor
+                )
+            }
             else -> throw IllegalStateException("Unknown viewType.")
         }
     }
@@ -58,7 +73,6 @@ class TrayPagerAdapter(
             POSITION_SYNCED_TABS -> syncedTabsAdapter
             else -> throw IllegalStateException("View type does not exist.")
         }
-
         viewHolder.bind(adapter, browserInteractor.getLayoutManagerForPosition(context, position))
     }
 

app/src/main/java/org/mozilla/fenix/tabstray/viewholders/BaseBrowserTabViewHolder.kt

@@ -17,8 +17,9 @@ import org.mozilla.fenix.tabstray.browser.BaseBrowserTrayList
  */
 abstract class BaseBrowserTabViewHolder(
     containerView: View,
+    tabsTrayStore: TabsTrayStore,
     interactor: TabsTrayInteractor,
-    tabsTrayStore: TabsTrayStore
+    private val currentTabIndex: Int
 ) : AbstractTrayViewHolder(containerView) {
 
     private val trayList: BaseBrowserTrayList = itemView.findViewById(R.id.tray_list_item)
@@ -33,7 +34,24 @@ abstract class BaseBrowserTabViewHolder(
         adapter: RecyclerView.Adapter<out RecyclerView.ViewHolder>,
         layoutManager: RecyclerView.LayoutManager
     ) {
+        adapter.registerAdapterDataObserver(OneTimeAdapterObserver(adapter) {
+            trayList.scrollToPosition(currentTabIndex)
+        })
+
         trayList.layoutManager = layoutManager
         trayList.adapter = adapter
     }
 }
+
+/**
+ * Observes the adapter and invokes the callback when data is first inserted.
+ */
+class OneTimeAdapterObserver(
+    private val adapter: RecyclerView.Adapter<out RecyclerView.ViewHolder>,
+    private val onAdapterReady: () -> Unit
+) : RecyclerView.AdapterDataObserver() {
+    override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
+        onAdapterReady.invoke()
+        adapter.unregisterAdapterDataObserver(this)
+    }
+}

app/src/main/java/org/mozilla/fenix/tabstray/viewholders/NormalBrowserTabViewHolder.kt

@@ -19,8 +19,14 @@ import org.mozilla.fenix.tabstray.browser.BrowserTabsAdapter
 class NormalBrowserTabViewHolder(
     containerView: View,
     private val store: TabsTrayStore,
-    interactor: TabsTrayInteractor
-) : BaseBrowserTabViewHolder(containerView, interactor, store), SelectionHolder<Tab> {
+    interactor: TabsTrayInteractor,
+    currentTabIndex: Int
+) : BaseBrowserTabViewHolder(
+    containerView,
+    store,
+    interactor,
+    currentTabIndex
+), SelectionHolder<Tab> {
 
     /**
      * Holds the list of selected tabs.

app/src/main/java/org/mozilla/fenix/tabstray/viewholders/PrivateBrowserTabViewHolder.kt

@@ -15,8 +15,14 @@ import org.mozilla.fenix.tabstray.TabsTrayStore
 class PrivateBrowserTabViewHolder(
     containerView: View,
     store: TabsTrayStore,
-    interactor: TabsTrayInteractor
-) : BaseBrowserTabViewHolder(containerView, interactor, store) {
+    interactor: TabsTrayInteractor,
+    currentTabIndex: Int
+) : BaseBrowserTabViewHolder(
+    containerView,
+    store,
+    interactor,
+    currentTabIndex
+) {
     companion object {
         const val LAYOUT_ID = R.layout.private_browser_tray_list
     }