Add DiffCallback to handle Contextual Cards update.

Use DiffCallback in ContextualCardsAdapter to only update items that
are changed instead of touching those unchanged ones.

Also fix a bug where ConditionContexualCardCard#onStart is incorrectly
skipped.

Fixes: 112245748
Bug: 118165942
Test: robotests
Change-Id: I7989d621764fe40a3fceb8c9f40baced840818ba

src/com/android/settings/homepage/ContextualCardManager.java

@@ -115,10 +115,6 @@ public class ContextualCardManager implements CardContentLoader.CardContentLoade
 
     @Override
     public void onContextualCardUpdated(Map<Integer, List<ContextualCard>> updateList) {
-        //TODO(b/112245748): Should implement a DiffCallback.
-        //Keep the old list for comparison.
-        final List<ContextualCard> prevCards = mContextualCards;
-
         final Set<Integer> cardTypes = updateList.keySet();
         //Remove the existing data that matches the certain cardType before inserting new data.
         final List<ContextualCard> cardsToKeep = mContextualCards

src/com/android/settings/homepage/ContextualCardsAdapter.java

@@ -17,11 +17,13 @@
 package com.android.settings.homepage;
 
 import android.content.Context;
+import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 
 import androidx.lifecycle.LifecycleOwner;
+import androidx.recyclerview.widget.DiffUtil;
 import androidx.recyclerview.widget.GridLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 
@@ -108,14 +110,15 @@ public class ContextualCardsAdapter extends RecyclerView.Adapter<RecyclerView.Vi
     @Override
     public void onContextualCardUpdated(Map<Integer, List<ContextualCard>> cards) {
         final List<ContextualCard> contextualCards = cards.get(ContextualCard.CardType.DEFAULT);
-        //TODO(b/112245748): Should implement a DiffCallback so we can use notifyItemChanged()
-        // instead.
         if (contextualCards == null) {
             mContextualCards.clear();
+            notifyDataSetChanged();
         } else {
+            final DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(
+                    new ContextualCardsDiffCallback(mContextualCards, contextualCards));
             mContextualCards.clear();
             mContextualCards.addAll(contextualCards);
-        }
+            diffResult.dispatchUpdatesTo(this);
-        notifyDataSetChanged();
+        }
     }
 }

src/com/android/settings/homepage/ContextualCardsDiffCallback.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.homepage;
+
+import androidx.recyclerview.widget.DiffUtil;
+
+import java.util.List;
+
+//TODO(b/117816826): add test cases for DiffUtil.
+/**
+ * A DiffCallback to calculate the difference between old and new {@link ContextualCard} List.
+ */
+public class ContextualCardsDiffCallback extends DiffUtil.Callback {
+
+    private final List<ContextualCard> mOldCards;
+    private final List<ContextualCard> mNewCards;
+
+    public ContextualCardsDiffCallback(List<ContextualCard> oldCards,
+            List<ContextualCard> newCards) {
+        mOldCards = oldCards;
+        mNewCards = newCards;
+    }
+
+    @Override
+    public int getOldListSize() {
+        return mOldCards.size();
+    }
+
+    @Override
+    public int getNewListSize() {
+        return mNewCards.size();
+    }
+
+    @Override
+    public boolean areItemsTheSame(int oldCardPosition, int newCardPosition) {
+        return mOldCards.get(oldCardPosition).getName().equals(
+                mNewCards.get(newCardPosition).getName());
+    }
+
+    @Override
+    public boolean areContentsTheSame(int oldCardPosition, int newCardPosition) {
+        return mOldCards.get(oldCardPosition).equals(mNewCards.get(newCardPosition));
+    }
+}

src/com/android/settings/homepage/conditional/ConditionContextualCardController.java

@@ -37,6 +37,8 @@ import java.util.Map;
 public class ConditionContextualCardController implements ContextualCardController,
         ConditionListener, LifecycleObserver, OnStart, OnStop {
 
+    private static final String TAG = "ConditionCtxCardCtrl";
+
     private final Context mContext;
     private final ConditionManager mConditionManager;
 

src/com/android/settings/homepage/conditional/ConditionManager.java

@@ -107,13 +107,13 @@ public class ConditionManager {
      */
     public void startMonitoringStateChange() {
         if (mIsListeningToStateChange) {
-            Log.d(TAG, "Already listening to condition state changes, skipping");
+            Log.d(TAG, "Already listening to condition state changes, skipping monitor setup");
-            return;
+        } else {
-        }
             mIsListeningToStateChange = true;
             for (ConditionalCardController controller : mCardControllers) {
                 controller.startMonitoringStateChange();
             }
+        }
         // Force a refresh on listener
         onConditionChanged();
     }

tests/robotests/src/com/android/settings/homepage/conditional/ConditionManagerTest.java

@@ -19,6 +19,8 @@ package com.android.settings.homepage.conditional;
 import static com.google.common.truth.Truth.assertThat;
 
 import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -53,7 +55,7 @@ public class ConditionManagerTest {
     public void setUp() {
         MockitoAnnotations.initMocks(this);
         mContext = RuntimeEnvironment.application;
-        mManager = new ConditionManager(mContext, mConditionListener);
+        mManager = spy(new ConditionManager(mContext, mConditionListener));
 
         assertThat(mManager.mCandidates.size()).isEqualTo(mManager.mCardControllers.size());
 
@@ -94,11 +96,13 @@ public class ConditionManagerTest {
 
     @Test
     public void startMonitoringStateChange_multipleTimes_shouldRegisterOnce() {
+        final int loopCount = 10;
+        for (int i = 0; i < loopCount; i++) {
             mManager.startMonitoringStateChange();
-        mManager.startMonitoringStateChange();
+        }
-        mManager.startMonitoringStateChange();
 
         verify(mController).startMonitoringStateChange();
+        verify(mManager, times(loopCount)).onConditionChanged();
     }
 
     @Test