[fenix] For https://github.com/mozilla-mobile/fenix/issues/18672 - Renaming a TopSite changes just the title

Previously renaming a TopSite would bind that as a new item and in such update
the entire list. This could potentially leading changes in the list and then
it's ViewPager parent's layout.

This patch switches the code to use the existing TopSitePayload and so do a
partial update of an on-screen TopSite instead of rebind it as a new item.

If a layout is requested while showing <=4 TopSites on the second page, by
having "offscreenPageLimit = 1" the biggest height of ViewPager pages is used
preventing an edgecase where the ViewPager would hide half of the items from
the first page.

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

@@ -45,6 +45,10 @@ class TopSitePagerViewHolder(
         view.top_sites_pager.apply {
             adapter = topSitesPagerAdapter
             registerOnPageChangeCallback(topSitesPageChangeCallback)
+            // Retain one more TopSites pages to ensure a new layout request will measure the first page also.
+            // Otherwise the second page with 3 TopSites will have the entire ViewPager only show
+            // the first row of TopSites, hiding half of those shown on the first page.
+            offscreenPageLimit = 1
         }
     }
 

app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/topsites/TopSiteItemViewHolder.kt

@@ -11,6 +11,7 @@ import android.view.View
 import android.widget.PopupWindow
 import androidx.appcompat.content.res.AppCompatResources.getDrawable
 import kotlinx.android.synthetic.main.top_site_item.*
+import kotlinx.android.synthetic.main.top_site_item.view.*
 import mozilla.components.browser.menu.BrowserMenuBuilder
 import mozilla.components.browser.menu.item.SimpleBrowserMenuItem
 import mozilla.components.feature.top.sites.TopSite
@@ -92,6 +93,11 @@ class TopSiteItemViewHolder(
         this.topSite = topSite
     }
 
+    fun bind(topSitePayload: TopSitesAdapter.TopSitePayload) {
+        itemView.top_site_title.text = topSitePayload.newTitle
+        topSite = topSite.copy(title = topSitePayload.newTitle)
+    }
+
     private fun onTouchEvent(
         v: View,
         event: MotionEvent,

app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/topsites/TopSitesAdapter.kt

@@ -40,7 +40,7 @@ class TopSitesAdapter(
                     holder.bind((payloads[0] as TopSite))
                 }
                 is TopSitePayload -> {
-                    holder.itemView.top_site_title.text = (payloads[0] as TopSitePayload).newTitle
+                    holder.bind(payloads[0] as TopSitePayload)
                 }
             }
         }

app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/topsites/TopSitesPagerAdapter.kt

@@ -37,7 +37,10 @@ class TopSitesPagerAdapter(
                 val adapter = holder.itemView.top_sites_list.adapter as TopSitesAdapter
                 val payload = payloads[0] as AdapterItem.TopSitePagerPayload
                 for (item in payload.changed) {
-                    adapter.notifyItemChanged(item.first % TOP_SITES_PER_PAGE, item.second)
+                    adapter.notifyItemChanged(
+                        item.first % TOP_SITES_PER_PAGE,
+                        TopSitesAdapter.TopSitePayload(item.second.title)
+                    )
                 }
             }
         }