For #10496 - Automatically scroll to the selected tab when you open the tab tray

app/src/main/java/org/mozilla/fenix/HomeActivity.kt

@@ -83,6 +83,7 @@ import org.mozilla.fenix.utils.RunWhenReadyQueue
 import mozilla.components.concept.tabstray.TabsTray
 import mozilla.components.browser.tabstray.TabsAdapter
 import mozilla.components.browser.tabstray.BrowserTabsTray
+import org.mozilla.fenix.tabtray.FenixTabsAdapter
 import org.mozilla.fenix.tabtray.TabTrayViewHolder
 
 /**
@@ -223,18 +224,12 @@ open class HomeActivity : LocaleAwareAppCompatActivity() {
             }
         }.asView()
         TabsTray::class.java.name -> {
-            val layout = LinearLayoutManager(context)
-            layout.reverseLayout = true
-            layout.stackFromEnd = true
-
-            val adapter = TabsAdapter { parentView, _ ->
-                TabTrayViewHolder(
-                    LayoutInflater.from(this).inflate(
-                        R.layout.tab_tray_item,
-                        parentView,
-                        false)
-                )
+            val layout = LinearLayoutManager(context).apply {
+                reverseLayout = true
+                stackFromEnd = true
             }
+
+            val adapter = FenixTabsAdapter(context)
             val decoration = DividerItemDecoration(
                 context,
                 DividerItemDecoration.VERTICAL

app/src/main/java/org/mozilla/fenix/tabtray/FenixTabsAdapter.kt

@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.tabtray
+
+import android.content.Context
+import android.view.LayoutInflater
+import mozilla.components.browser.tabstray.TabsAdapter
+import mozilla.components.concept.tabstray.Tabs
+import org.mozilla.fenix.R
+
+class FenixTabsAdapter(
+    context: Context
+) : TabsAdapter(
+    viewHolderProvider = { parentView, _ ->
+        TabTrayViewHolder(
+            LayoutInflater.from(context).inflate(
+                R.layout.tab_tray_item,
+                parentView,
+                false)
+        )
+    }
+) {
+    var onTabsUpdated: (() -> Unit)? = null
+
+    override fun updateTabs(tabs: Tabs) {
+        super.updateTabs(tabs)
+        onTabsUpdated?.invoke()
+    }
+}

app/src/main/java/org/mozilla/fenix/tabtray/TabTrayView.kt

@@ -57,6 +57,8 @@ class TabTrayView(
     private var tabsFeature: TabsFeature
     private var tabTrayItemMenu: TabTrayItemMenu
 
+    private var hasLoaded = false
+
     override val containerView: View?
         get() = container
 
@@ -98,8 +100,24 @@ class TabTrayView(
             { it.content.private == isPrivate },
             { })
 
+
+        val selectedBrowserTabIndex = if (isPrivate) {
+            view.context.components.core.store.state.privateTabs
+        } else {
+            view.context.components.core.store.state.normalTabs
+        }.indexOfFirst { it.id == view.context.components.core.store.state.selectedTabId }
+
+
         (view.tabsTray as? BrowserTabsTray)?.also { tray ->
             TabsTouchHelper(tray.tabsAdapter).attachToRecyclerView(tray)
+            (tray.tabsAdapter as? FenixTabsAdapter)?.also { adapter ->
+                adapter.onTabsUpdated = {
+                    if (!hasLoaded) {
+                        hasLoaded = true
+                        tray.layoutManager?.scrollToPosition(selectedBrowserTabIndex)
+                    }
+                }
+            }
         }
 
         tabTrayItemMenu = TabTrayItemMenu(view.context, { view.tab_layout.selectedTabPosition == 0 }) {