From 3dcfed376140565a7995b222df648086d29cc41c Mon Sep 17 00:00:00 2001
From: Amaan Marfatia <amaan.marfatia@match.com>
Date: Fri, 20 Mar 2020 12:03:45 -0400
Subject: [PATCH] AboutPageAdapter doesn't use notifyDataSetChanged()

We make the AboutPageAdapter inherit from a ListAdapter so that we don't use notifyDataSetChanged().
---
 .../fenix/settings/about/AboutFragment.kt     |  2 +-
 .../fenix/settings/about/AboutPageAdapter.kt  | 34 +++++++++----------
 .../settings/about/AboutPageAdapterTest.kt    | 20 ++---------
 3 files changed, 21 insertions(+), 35 deletions(-)

diff --git a/app/src/main/java/org/mozilla/fenix/settings/about/AboutFragment.kt b/app/src/main/java/org/mozilla/fenix/settings/about/AboutFragment.kt
index 4109e3f95..66cda3490 100644
--- a/app/src/main/java/org/mozilla/fenix/settings/about/AboutFragment.kt
+++ b/app/src/main/java/org/mozilla/fenix/settings/about/AboutFragment.kt
@@ -64,7 +64,7 @@ class AboutFragment : Fragment(), AboutPageListener {
         }
 
         populateAboutHeader()
-        aboutPageAdapter.updateData(populateAboutList())
+        aboutPageAdapter.submitList(populateAboutList())
     }
 
     private fun populateAboutHeader() {
diff --git a/app/src/main/java/org/mozilla/fenix/settings/about/AboutPageAdapter.kt b/app/src/main/java/org/mozilla/fenix/settings/about/AboutPageAdapter.kt
index 3e38e04ac..e4b418dd7 100644
--- a/app/src/main/java/org/mozilla/fenix/settings/about/AboutPageAdapter.kt
+++ b/app/src/main/java/org/mozilla/fenix/settings/about/AboutPageAdapter.kt
@@ -6,33 +6,33 @@ package org.mozilla.fenix.settings.about
 
 import android.view.LayoutInflater
 import android.view.ViewGroup
-import androidx.annotation.VisibleForTesting
-import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
 import org.mozilla.fenix.settings.about.viewholders.AboutItemViewHolder
 
-class AboutPageAdapter(private val listener: AboutPageListener) : RecyclerView.Adapter<AboutItemViewHolder>() {
-
-    @VisibleForTesting
-    var aboutList: List<AboutPageItem>? = null
-
-    fun updateData(items: List<AboutPageItem>) {
-        this.aboutList = items
-        notifyDataSetChanged()
-    }
+class AboutPageAdapter(private val listener: AboutPageListener) :
+    ListAdapter<AboutPageItem, AboutItemViewHolder>(DiffCallback) {
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AboutItemViewHolder {
         val view = LayoutInflater.from(parent.context)
             .inflate(AboutItemViewHolder.LAYOUT_ID, parent, false)
-
         return AboutItemViewHolder(view, listener)
     }
 
-    override fun getItemCount(): Int = aboutList?.size ?: 0
-
     override fun onBindViewHolder(holder: AboutItemViewHolder, position: Int) {
-        (aboutList?.get(position) as AboutPageItem.Item).also {
-            holder.bind(it)
-        }
+        holder.bind(getItem(position) as AboutPageItem.Item)
+    }
+
+    private object DiffCallback : DiffUtil.ItemCallback<AboutPageItem>() {
+
+        override fun areItemsTheSame(oldItem: AboutPageItem, newItem: AboutPageItem) =
+            oldItem === newItem
+
+        override fun areContentsTheSame(oldItem: AboutPageItem, newItem: AboutPageItem) =
+            when (oldItem) {
+                is AboutPageItem.Item ->
+                    newItem is AboutPageItem.Item && oldItem.title == newItem.title
+            }
     }
 }
 
diff --git a/app/src/test/java/org/mozilla/fenix/settings/about/AboutPageAdapterTest.kt b/app/src/test/java/org/mozilla/fenix/settings/about/AboutPageAdapterTest.kt
index fa693550e..a15c2a494 100644
--- a/app/src/test/java/org/mozilla/fenix/settings/about/AboutPageAdapterTest.kt
+++ b/app/src/test/java/org/mozilla/fenix/settings/about/AboutPageAdapterTest.kt
@@ -38,20 +38,6 @@ class AboutPageAdapterTest {
         )
     private val listener: AboutPageListener = mockk(relaxed = true)
 
-    @Test
-    fun `updateData should set the new data and call notifyDataSetChanged()`() {
-        val adapter = spyk(AboutPageAdapter(listener), recordPrivateCalls = true)
-        every { adapter.notifyDataSetChanged() } just Runs
-
-        adapter.updateData(aboutList)
-
-        // Wasn't able to test in verify block the 'adapter.aboutList' setter from the updateData method
-        assertThat(adapter.aboutList).isEqualTo(aboutList)
-        verify {
-            adapter.notifyDataSetChanged()
-        }
-    }
-
     @Test
     fun `getItemCount on a default instantiated Adapter should return 0`() {
         val adapter = AboutPageAdapter(listener)
@@ -63,7 +49,7 @@ class AboutPageAdapterTest {
     fun `getItemCount after updateData() call should return the correct list size`() {
         val adapter = AboutPageAdapter(listener)
 
-        adapter.updateData(aboutList)
+        adapter.submitList(aboutList)
 
         assertThat(adapter.itemCount).isEqualTo(2)
     }
@@ -93,9 +79,9 @@ class AboutPageAdapterTest {
         } returns viewHolder
         every { viewHolder.bind(any()) } just Runs
 
-        adapter.updateData(aboutList)
+        adapter.submitList(aboutList)
         adapter.bindViewHolder(viewHolder, 1)
 
-        verify { viewHolder.bind(adapter.aboutList?.get(1) as AboutPageItem.Item) }
+        verify { viewHolder.bind(aboutList[1] as AboutPageItem.Item) }
     }
 }