Bug 1359363 - Apply diffutil to search list updates for smoother ui experience.;r=petru

Differential Revision: https://phabricator.services.mozilla.com/D37733

--HG--
extra : moz-landing-system : lando

mobile/android/base/java/org/mozilla/gecko/preferences/SearchPreferenceCategory.java

@@ -5,22 +5,26 @@
 package org.mozilla.gecko.preferences;
 
 import android.content.Context;
-import android.preference.Preference;
+import android.support.annotation.Nullable;
+import android.support.v7.util.DiffUtil;
+import android.support.v7.util.ListUpdateCallback;
 import android.util.AttributeSet;
-import android.util.Log;
 
 import org.mozilla.gecko.EventDispatcher;
-import org.mozilla.gecko.GeckoAppShell;
 import org.mozilla.gecko.Telemetry;
 import org.mozilla.gecko.TelemetryContract;
 import org.mozilla.gecko.TelemetryContract.Method;
+import org.mozilla.gecko.search.SearchEngineDiffCallback;
 import org.mozilla.gecko.util.BundleEventListener;
 import org.mozilla.gecko.util.EventCallback;
 import org.mozilla.gecko.util.GeckoBundle;
-import org.mozilla.gecko.util.ThreadUtils;
 
-public class SearchPreferenceCategory extends CustomListCategory implements BundleEventListener {
+import java.util.ArrayList;
+import java.util.List;
+
+public class SearchPreferenceCategory extends CustomListCategory implements BundleEventListener, ListUpdateCallback {
     public static final String LOGTAG = "SearchPrefCategory";
+    private List<SearchEnginePreference> enginesList = new ArrayList<>();
 
     public SearchPreferenceCategory(Context context) {
         super(context);
@@ -74,44 +78,65 @@ public class SearchPreferenceCategory extends CustomListCategory implements Bund
     public void handleMessage(final String event, final GeckoBundle data,
                               final EventCallback callback) {
         if (event.equals("SearchEngines:Data")) {
-            // Parse engines array from bundle.
-            final GeckoBundle[] engines = data.getBundleArray("searchEngines");
+            // Parse engines array from bundle into ArrayList.
+            GeckoBundle[] engines = data.getBundleArray("searchEngines");
+            List<SearchEnginePreference> newEngineList = new ArrayList<>();
 
-            // Clear the preferences category from this thread.
-            this.removeAll();
-
-            // Create an element in this PreferenceCategory for each engine.
-            for (int i = 0; i < engines.length; i++) {
-                final GeckoBundle engine = engines[i];
-                final SearchEnginePreference enginePreference =
+            for (GeckoBundle engine: engines) {
+                SearchEnginePreference enginePreference =
                         new SearchEnginePreference(getContext(), this);
                 enginePreference.setSearchEngineFromBundle(engine);
-                enginePreference.setOnPreferenceClickListener(new OnPreferenceClickListener() {
-                    @Override
-                    public boolean onPreferenceClick(Preference preference) {
-                        SearchEnginePreference sPref = (SearchEnginePreference) preference;
-                        // Display the configuration dialog associated with the tapped engine.
-                        sPref.showDialog();
-                        return true;
-                    }
+                enginePreference.setOnPreferenceClickListener(preference -> {
+                    SearchEnginePreference sPref = (SearchEnginePreference) preference;
+                    // Display the configuration dialog associated with the tapped engine.
+                    sPref.showDialog();
+                    return true;
                 });
 
-                addPreference(enginePreference);
+                newEngineList.add(enginePreference);
+            }
 
-                if (i != 0) {
-                    continue;
-                }
+            DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(new SearchEngineDiffCallback(enginesList, newEngineList));
+            enginesList = newEngineList;
+            diffResult.dispatchUpdatesTo(this);
+        }
+    }
 
-                // The first element in the array is the default engine.
-                // We set this here, not in setSearchEngineFromBundle, because it allows us to
-                // keep a reference  to the default engine to use when the AlertDialog
-                // callbacks are used.
-                enginePreference.setIsDefault(true);
-                mDefaultReference = enginePreference;
+    @Override
+    public void onInserted(int pos, int count) {
+        for (int ix = pos; ix < (pos + count); ++ix) {
+
+            addPreference(enginesList.get(ix));
+
+            // The first element in the array is the default engine.
+            // We set this here, not in setSearchEngineFromBundle, because it allows us to
+            // keep a reference  to the default engine to use when the AlertDialog
+            // callbacks are used.
+            if (ix == 0) {
+                enginesList.get(ix).setIsDefault(true);
+                mDefaultReference = enginesList.get(ix);
             }
         }
     }
 
+
+    // The onRemoved, onMoved and onChanged entries are not used here as the list is never reordered
+    // by the clicking of the completion checkbox preference which activates this code.
+    @Override
+    public void onRemoved(int pos, int count) {
+
+    }
+
+    @Override
+    public void onMoved(int i, int i1) {
+
+    }
+
+    @Override
+    public void onChanged(int i, int i1, @Nullable Object o) {
+
+    }
+
     /**
      * Helper method to send a particular event string to Gecko with an associated engine name.
      * @param event The type of event to send.

mobile/android/base/java/org/mozilla/gecko/search/SearchEngineDiffCallback.java

@@ -0,0 +1,57 @@
+/* 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.gecko.search;
+
+import android.support.annotation.Nullable;
+import android.support.v7.util.DiffUtil;
+
+import org.mozilla.gecko.preferences.SearchEnginePreference;
+
+import java.util.List;
+/**
+ * SearchEngineDiffCallback.java - class used by diffutils to maintain List differential array.
+ * @author  Brad Arant
+ * @version
+ * @see SearchPreferenceCategory
+ */
+public class SearchEngineDiffCallback extends DiffUtil.Callback {
+
+    private List<SearchEnginePreference> oldList;
+    private List<SearchEnginePreference> newList;
+
+    public SearchEngineDiffCallback(List<SearchEnginePreference> oldList, List<SearchEnginePreference> 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) {
+        return oldList.get(oldItemPosition).getIdentifier().equals(newList.get(newItemPosition).getIdentifier());
+    }
+
+    @Override
+    public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
+        if (oldList.get(oldItemPosition).getTitle() != newList.get(newItemPosition).getTitle()) {
+            return false;
+        }
+        return oldList.get(oldItemPosition).getIdentifier().equals(newList.get(newItemPosition).getIdentifier());
+    }
+
+    @Nullable
+    @Override
+    public Object getChangePayload(int oldItemPosition, int newItemPosition) {
+        return super.getChangePayload(oldItemPosition, newItemPosition);
+    }
+}