From d063cd539652aebd67bac674a5deff7f9e87141b Mon Sep 17 00:00:00 2001
From: Jonathan Almeida <jalmeida@mozilla.com>
Date: Tue, 15 Sep 2020 17:06:29 -0400
Subject: [PATCH] For #14230: Stop redrawing all top sites when one is removed

---
 .../sessioncontrol/SessionControlAdapter.kt   |  4 +--
 .../viewholders/TopSitePagerViewHolder.kt     |  3 ++-
 .../topsites/TopSitesPagerAdapter.kt          | 26 +++++++++----------
 3 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/SessionControlAdapter.kt b/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/SessionControlAdapter.kt
index bde850a17..dc075d3df 100644
--- a/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/SessionControlAdapter.kt
+++ b/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/SessionControlAdapter.kt
@@ -45,7 +45,7 @@ sealed class AdapterItem(@LayoutRes val viewType: Int) {
     data class TopSitePager(val topSites: List<TopSite>) : AdapterItem(TopSitePagerViewHolder.LAYOUT_ID) {
         override fun sameAs(other: AdapterItem): Boolean {
             val newTopSites = (other as? TopSitePager) ?: return false
-            return newTopSites.topSites == this.topSites
+            return newTopSites.topSites.size == this.topSites.size
         }
 
         override fun contentsSameAs(other: AdapterItem): Boolean {
@@ -53,7 +53,7 @@ sealed class AdapterItem(@LayoutRes val viewType: Int) {
             if (newTopSites.topSites.size != this.topSites.size) return false
             val newSitesSequence = newTopSites.topSites.asSequence()
             val oldTopSites = this.topSites.asSequence()
-            return newSitesSequence.zip(oldTopSites).all { (new, old) -> new.title == old.title }
+            return newSitesSequence.zip(oldTopSites).all { (new, old) -> new == old }
         }
     }
 
diff --git a/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/TopSitePagerViewHolder.kt b/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/TopSitePagerViewHolder.kt
index 06affb026..23e59a081 100644
--- a/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/TopSitePagerViewHolder.kt
+++ b/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/TopSitePagerViewHolder.kt
@@ -44,7 +44,8 @@ class TopSitePagerViewHolder(
     }
 
     fun bind(topSites: List<TopSite>) {
-        topSitesPagerAdapter.updateData(topSites)
+        val chunkedTopSites = topSites.chunked(TOP_SITES_PER_PAGE)
+        topSitesPagerAdapter.submitList(chunkedTopSites)
 
         // Don't show any page indicator if there is only 1 page.
         val numPages = if (topSites.size > TOP_SITES_PER_PAGE) {
diff --git a/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/topsites/TopSitesPagerAdapter.kt b/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/topsites/TopSitesPagerAdapter.kt
index b335e57de..e1d1d571f 100644
--- a/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/topsites/TopSitesPagerAdapter.kt
+++ b/app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/topsites/TopSitesPagerAdapter.kt
@@ -6,21 +6,16 @@ package org.mozilla.fenix.home.sessioncontrol.viewholders.topsites
 
 import android.view.LayoutInflater
 import android.view.ViewGroup
-import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
+import kotlinx.android.synthetic.main.component_top_sites.view.*
 import mozilla.components.feature.top.sites.TopSite
 import org.mozilla.fenix.home.sessioncontrol.TopSiteInteractor
 import org.mozilla.fenix.home.sessioncontrol.viewholders.TopSiteViewHolder
 
 class TopSitesPagerAdapter(
     private val interactor: TopSiteInteractor
-) : RecyclerView.Adapter<TopSiteViewHolder>() {
-
-    private var topSites: List<List<TopSite>> = listOf()
-
-    fun updateData(topSites: List<TopSite>) {
-        this.topSites = topSites.chunked(TOP_SITES_PER_PAGE)
-        notifyDataSetChanged()
-    }
+) : ListAdapter<List<TopSite>, TopSiteViewHolder>(DiffCallback) {
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TopSiteViewHolder {
         val view = LayoutInflater.from(parent.context)
@@ -29,12 +24,17 @@ class TopSitesPagerAdapter(
     }
 
     override fun onBindViewHolder(holder: TopSiteViewHolder, position: Int) {
-        holder.bind(this.topSites[position])
+        val adapter = holder.itemView.top_sites_list.adapter as TopSitesAdapter
+        adapter.submitList(getItem(position))
     }
 
-    override fun getItemCount(): Int = this.topSites.size
+    private object DiffCallback : DiffUtil.ItemCallback<List<TopSite>>() {
+        override fun areItemsTheSame(oldItem: List<TopSite>, newItem: List<TopSite>): Boolean {
+            return oldItem.size == newItem.size
+        }
 
-    companion object {
-        const val TOP_SITES_PER_PAGE = 8
+        override fun areContentsTheSame(oldItem: List<TopSite>, newItem: List<TopSite>): Boolean {
+            return newItem.zip(oldItem).all { (new, old) -> new == old }
+        }
     }
 }