Use DiffUtil with call log

app/src/main/java/dummydomain/yetanothercallblocker/CallLogItemRecyclerViewAdapter.java

@@ -1,5 +1,6 @@
 package dummydomain.yetanothercallblocker;
 
+import android.text.TextUtils;
 import android.text.format.DateUtils;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -9,8 +10,10 @@ import android.widget.TextView;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.appcompat.widget.AppCompatImageView;
+import androidx.recyclerview.widget.DiffUtil;
 import androidx.recyclerview.widget.RecyclerView;
 
+import java.util.Collections;
 import java.util.List;
 
 import dummydomain.yetanothercallblocker.data.CallLogItem;
@@ -22,12 +25,47 @@ public class CallLogItemRecyclerViewAdapter
         void onListFragmentInteraction(CallLogItem item);
     }
 
-    private final List<CallLogItem> items;
+    private static class DiffUtilCallback extends DiffUtil.Callback {
+        private List<CallLogItem> oldList;
+        private List<CallLogItem> newList;
+
+        DiffUtilCallback(List<CallLogItem> oldList, List<CallLogItem> newList) {
+            this.oldList = oldList;
+            this.newList = newList;
+        }
+
+        @Override
+        public int getOldListSize() {
+            return oldList.size();
+        }
+
+        @Override
+        public int getNewListSize() {
+            return newList.size();
+        }
+
+        @Override
+        public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
+            CallLogItem oldItem = oldList.get(oldItemPosition);
+            CallLogItem newItem = newList.get(newItemPosition);
+
+            return newItem.type == oldItem.type
+                    && TextUtils.equals(newItem.number, oldItem.number)
+                    && newItem.timestamp == oldItem.timestamp
+                    && newItem.duration == oldItem.duration;
+        }
+
+        @Override
+        public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
+            return false; // time always updates
+        }
+    }
+
     private final @Nullable OnListInteractionListener listener;
 
-    public CallLogItemRecyclerViewAdapter(List<CallLogItem> items,
-                                          @Nullable OnListInteractionListener listener) {
-        this.items = items;
+    private List<CallLogItem> items = Collections.emptyList();
+
+    public CallLogItemRecyclerViewAdapter(@Nullable OnListInteractionListener listener) {
         this.listener = listener;
     }
 
@@ -49,6 +87,15 @@ public class CallLogItemRecyclerViewAdapter
         return items.size();
     }
 
+    public void setItems(List<CallLogItem> items) {
+        DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(
+                new DiffUtilCallback(this.items, items));
+
+        this.items = items;
+
+        diffResult.dispatchUpdatesTo(this);
+    }
+
     private void onClick(int index) {
         if (index != RecyclerView.NO_POSITION && listener != null) {
             listener.onListFragmentInteraction(items.get(index));

app/src/main/java/dummydomain/yetanothercallblocker/MainActivity.java

@@ -5,6 +5,7 @@ import android.content.Intent;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.os.Handler;
+import android.os.Parcelable;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
@@ -12,13 +13,13 @@ import android.view.View;
 import androidx.annotation.NonNull;
 import androidx.appcompat.app.AlertDialog;
 import androidx.appcompat.app.AppCompatActivity;
+import androidx.recyclerview.widget.DividerItemDecoration;
 import androidx.recyclerview.widget.RecyclerView;
 
 import org.greenrobot.eventbus.EventBus;
 import org.greenrobot.eventbus.Subscribe;
 import org.greenrobot.eventbus.ThreadMode;
 
-import java.util.ArrayList;
 import java.util.List;
 
 import dummydomain.yetanothercallblocker.data.CallLogHelper;
@@ -38,7 +39,7 @@ public class MainActivity extends AppCompatActivity {
     private final UpdateScheduler updateScheduler = UpdateScheduler.get(App.getInstance());
 
     private CallLogItemRecyclerViewAdapter callLogAdapter;
-    private List<CallLogItem> callLogItems = new ArrayList<>();
+    private RecyclerView recyclerView;
 
     private AsyncTask<Void, Void, Boolean> checkMainDbTask;
     private AsyncTask<Void, Void, List<CallLogItem>> loadCallLogTask;
@@ -48,10 +49,10 @@ public class MainActivity extends AppCompatActivity {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
 
-        callLogAdapter = new CallLogItemRecyclerViewAdapter(callLogItems, this::onCallLogItemClicked);
-        RecyclerView recyclerView = findViewById(R.id.callLogList);
+        callLogAdapter = new CallLogItemRecyclerViewAdapter(this::onCallLogItemClicked);
+        recyclerView = findViewById(R.id.callLogList);
         recyclerView.setAdapter(callLogAdapter);
-        recyclerView.addItemDecoration(new CustomVerticalDivider(this));
+        recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));
     }
 
     @Override
@@ -228,9 +229,12 @@ public class MainActivity extends AppCompatActivity {
 
             @Override
             protected void onPostExecute(List<CallLogItem> items) {
-                callLogItems.clear();
-                callLogItems.addAll(items);
-                callLogAdapter.notifyDataSetChanged();
+                // workaround for auto-scrolling to first item
+                // https://stackoverflow.com/a/44053550
+                @SuppressWarnings("ConstantConditions")
+                Parcelable recyclerViewState = recyclerView.getLayoutManager().onSaveInstanceState();
+                callLogAdapter.setItems(items);
+                recyclerView.getLayoutManager().onRestoreInstanceState(recyclerViewState);
 
                 setCallLogVisibility(true);
             }