Merge changes from topic "2020-09-14-spans" into rvc-qpr-dev

* changes:
  Fix span computation
  Integrate the list limit updates

4 files changed, 180 insertions, 35 deletions

diff --git a/src/com/android/car/media/BrowseViewController.java b/src/com/android/car/media/BrowseViewController.java
index 5f7be28..cd67f71 100644
--- a/src/com/android/car/media/BrowseViewController.java
+++ b/src/com/android/car/media/BrowseViewController.java
@@ -20,7 +20,6 @@ import static com.android.car.arch.common.LiveDataFunctions.ifThenElse;
 
 import android.car.content.pm.CarPackageManager;
 import android.content.Context;
-import android.content.res.Resources;
 import android.os.Handler;
 import android.text.TextUtils;
 import android.util.Log;
@@ -41,6 +40,7 @@ import androidx.recyclerview.widget.RecyclerView;
 import com.android.car.apps.common.util.ViewUtils;
 import com.android.car.arch.common.FutureData;
 import com.android.car.media.browse.BrowseAdapter;
+import com.android.car.media.browse.LimitedBrowseAdapter;
 import com.android.car.media.common.GridSpacingItemDecoration;
 import com.android.car.media.common.MediaItemMetadata;
 import com.android.car.media.common.browse.BrowsedMediaItems;
@@ -48,7 +48,6 @@ import com.android.car.media.common.browse.MediaBrowserViewModel;
 import com.android.car.media.common.source.MediaSource;
 import com.android.car.media.widgets.AppBarController;
 import com.android.car.ui.FocusArea;
-import com.android.car.ui.recyclerview.DelegatingContentLimitingAdapter;
 import com.android.car.ui.baselayout.Insets;
 import com.android.car.ui.toolbar.Toolbar;
 import com.android.car.uxr.LifeCycleObserverUxrContentLimiter;
@@ -58,8 +57,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 import java.util.Stack;
-import java.util.function.Predicate;
-import java.util.stream.Collectors;
 
 /**
  * A view controller that implements the content forward browsing experience.
@@ -81,9 +78,7 @@ public class BrowseViewController extends ViewControllerBase {
     private final RecyclerView mBrowseList;
     private final ImageView mErrorIcon;
     private final TextView mMessage;
-    private final DelegatingContentLimitingAdapter mLimitedBrowseAdapter;
-    private final BrowseAdapter mBrowseAdapter;
-    private int mMaxSpanSize = 1;
+    private final LimitedBrowseAdapter mLimitedBrowseAdapter;
     private String mSearchQuery;
     private final int mFadeDuration;
     private final int mLoadingIndicatorDelay;
@@ -240,7 +235,7 @@ public class BrowseViewController extends ViewControllerBase {
             updateTabs((mediaSource != null) ? null : new ArrayList<>());
         }
 
-        mBrowseAdapter.submitItems(null, null);
+        mLimitedBrowseAdapter.submitItems(null, null);
         stopLoadingIndicator();
         ViewUtils.hideViewAnimated(mErrorIcon, mFadeDuration);
         ViewUtils.hideViewAnimated(mMessage, mFadeDuration);
@@ -294,16 +289,10 @@ public class BrowseViewController extends ViewControllerBase {
         mBrowseList.addItemDecoration(new GridSpacingItemDecoration(
                 activity.getResources().getDimensionPixelSize(R.dimen.grid_item_spacing)));
 
-        mBrowseAdapter = new BrowseAdapter(mBrowseList.getContext());
-        mBrowseAdapter.registerObserver(mBrowseAdapterObserver);
-        mLimitedBrowseAdapter = new DelegatingContentLimitingAdapter(mBrowseAdapter,
-                R.id.browse_list_uxr_config);
-        mBrowseList.setAdapter(mLimitedBrowseAdapter);
-
         GridLayoutManager manager = (GridLayoutManager) mBrowseList.getLayoutManager();
-        mMaxSpanSize = manager.getSpanCount();
-        manager.setSpanSizeLookup(mSpanSizeLookup);
-
+        mLimitedBrowseAdapter = new LimitedBrowseAdapter(
+                new BrowseAdapter(mBrowseList.getContext()), manager, mBrowseAdapterObserver);
+        mBrowseList.setAdapter(mLimitedBrowseAdapter);
 
         mUxrContentLimiter = new LifeCycleObserverUxrContentLimiter(
                 new UxrContentLimiterImpl(activity, R.xml.uxr_config));
@@ -311,9 +300,9 @@ public class BrowseViewController extends ViewControllerBase {
         activity.getLifecycle().addObserver(mUxrContentLimiter);
 
         mMediaBrowserViewModel.rootBrowsableHint().observe(activity,
-                mBrowseAdapter::setRootBrowsableViewType);
+                hint -> mLimitedBrowseAdapter.getBrowseAdapter().setRootBrowsableViewType(hint));
         mMediaBrowserViewModel.rootPlayableHint().observe(activity,
-                mBrowseAdapter::setRootPlayableViewType);
+                hint -> mLimitedBrowseAdapter.getBrowseAdapter().setRootPlayableViewType(hint));
         LiveData<FutureData<List<MediaItemMetadata>>> mediaItems = ifThenElse(mShowSearchResults,
                 mMediaBrowserViewModel.getSearchedMediaItems(),
                 mMediaBrowserViewModel.getBrowsedMediaItems());
@@ -359,19 +348,6 @@ public class BrowseViewController extends ViewControllerBase {
         }
     };
 
-    private final GridLayoutManager.SpanSizeLookup mSpanSizeLookup =
-            new GridLayoutManager.SpanSizeLookup() {
-        @Override
-        public int getSpanSize(int position) {
-            if (mLimitedBrowseAdapter.getItemViewType(position) ==
-                    mLimitedBrowseAdapter.getScrollingLimitedMessageViewType()) {
-                return mMaxSpanSize;
-            }
-
-            return mBrowseAdapter.getSpanSize(position, mMaxSpanSize);
-        }
-    };
-
     boolean onBackPressed() {
         boolean success = navigateBack();
         if (!success && (mIsSearchController)) {
@@ -579,7 +555,7 @@ public class BrowseViewController extends ViewControllerBase {
             ViewUtils.hideViewAnimated(mMessage, 0);
             // TODO(b/139759881) build a jank-free animation of the transition.
             mBrowseList.setAlpha(0f);
-            mBrowseAdapter.submitItems(null, null);
+            mLimitedBrowseAdapter.submitItems(null, null);
 
             if (forRoot) {
                 if (Log.isLoggable(TAG, Log.INFO)) {
@@ -605,7 +581,7 @@ public class BrowseViewController extends ViewControllerBase {
             mCallbacks.onRootLoaded();
             updateTabs(items != null ? items : new ArrayList<>());
         } else {
-            mBrowseAdapter.submitItems(getCurrentMediaItem(), items);
+            mLimitedBrowseAdapter.submitItems(getCurrentMediaItem(), items);
         }
 
         int duration = forRoot ? 0 : mFadeDuration;
diff --git a/src/com/android/car/media/browse/BrowseAdapter.java b/src/com/android/car/media/browse/BrowseAdapter.java
index 1d8ccb6..abf770d 100644
--- a/src/com/android/car/media/browse/BrowseAdapter.java
+++ b/src/com/android/car/media/browse/BrowseAdapter.java
@@ -51,6 +51,17 @@ import java.util.function.Consumer;
  */
 public class BrowseAdapter extends ListAdapter<BrowseViewData, BrowseViewHolder> {
     private static final String TAG = "BrowseAdapter";
+
+    /**
+     * Listens to the list data changes.
+     */
+    public interface OnListChangedListener {
+        /**
+         * Called when {@link #onCurrentListChanged(List, List)} is called.
+         */
+        void onListChanged(List<BrowseViewData> previousList, List<BrowseViewData> currentList);
+    }
+
     @NonNull
     private final Context mContext;
     @NonNull
@@ -63,6 +74,8 @@ public class BrowseAdapter extends ListAdapter<BrowseViewData, BrowseViewHolder>
     private BrowseItemViewType mRootBrowsableViewType = BrowseItemViewType.LIST_ITEM;
     private BrowseItemViewType mRootPlayableViewType = BrowseItemViewType.LIST_ITEM;
 
+    private OnListChangedListener mOnListChangedListener;
+
     private static final DiffUtil.ItemCallback<BrowseViewData> DIFF_CALLBACK =
             new DiffUtil.ItemCallback<BrowseViewData>() {
                 @Override
@@ -145,6 +158,13 @@ public class BrowseAdapter extends ListAdapter<BrowseViewData, BrowseViewHolder>
         return viewType.getSpanSize(maxSpanSize);
     }
 
+    /**
+     * Sets a listener to listen for the list data changes.
+     */
+    public void setOnListChangedListener(OnListChangedListener onListChangedListener) {
+        mOnListChangedListener = onListChangedListener;
+    }
+
     @NonNull
     @Override
     public BrowseViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
@@ -176,6 +196,15 @@ public class BrowseAdapter extends ListAdapter<BrowseViewData, BrowseViewHolder>
         return getItem(position).mViewType.ordinal();
     }
 
+    @Override
+    public void onCurrentListChanged(@NonNull List<BrowseViewData> previousList,
+            @NonNull List<BrowseViewData> currentList) {
+        super.onCurrentListChanged(previousList, currentList);
+        if (mOnListChangedListener != null) {
+            mOnListChangedListener.onListChanged(previousList, currentList);
+        }
+    }
+
     public void submitItems(@Nullable MediaItemMetadata parentItem,
             @Nullable List<MediaItemMetadata> children) {
         mParentMediaItem = parentItem;
diff --git a/src/com/android/car/media/browse/BrowseViewHolder.java b/src/com/android/car/media/browse/BrowseViewHolder.java
index aa4449f..d30166e 100644
--- a/src/com/android/car/media/browse/BrowseViewHolder.java
+++ b/src/com/android/car/media/browse/BrowseViewHolder.java
@@ -34,7 +34,7 @@ import com.android.car.media.common.MediaItemMetadata;
 /**
  * Generic {@link RecyclerView.ViewHolder} to use for all views in the {@link BrowseAdapter}
  */
-class BrowseViewHolder extends RecyclerView.ViewHolder {
+public class BrowseViewHolder extends RecyclerView.ViewHolder {
     private final TextView mTitle;
     private final TextView mSubtitle;
     private final ImageView mAlbumArt;
diff --git a/src/com/android/car/media/browse/LimitedBrowseAdapter.java b/src/com/android/car/media/browse/LimitedBrowseAdapter.java
new file mode 100644
index 0000000..bbca980
--- /dev/null
+++ b/src/com/android/car/media/browse/LimitedBrowseAdapter.java
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2020 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.car.media.browse;
+
+import androidx.annotation.Nullable;
+import androidx.recyclerview.widget.GridLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+import com.android.car.media.R;
+import com.android.car.media.common.MediaItemMetadata;
+import com.android.car.ui.recyclerview.DelegatingContentLimitingAdapter;
+
+import java.util.List;
+
+/**
+ * Provides list limiting functionality to {@link BrowseAdapter}.
+ */
+public class LimitedBrowseAdapter extends DelegatingContentLimitingAdapter<BrowseViewHolder> {
+
+    private final BrowseAdapter mBrowseAdapter;
+    private final GridLayoutManager mLayoutManager;
+    private final int mMaxSpanSize;
+
+    @Nullable private String mAnchorId;
+
+    public LimitedBrowseAdapter(BrowseAdapter browseAdapter, GridLayoutManager manager,
+            BrowseAdapter.Observer browseAdapterObserver) {
+        super(browseAdapter, R.id.browse_list_uxr_config);
+
+        mBrowseAdapter = browseAdapter;
+        mLayoutManager = manager;
+        mMaxSpanSize = manager.getSpanCount();
+
+        mLayoutManager.setSpanSizeLookup(mSpanSizeLookup);
+        mBrowseAdapter.registerObserver(browseAdapterObserver);
+        mBrowseAdapter.setOnListChangedListener(((previousList, currentList) -> {
+            updateUnderlyingDataChanged(currentList.size(), validateAnchor());
+        }));
+    }
+
+    private final GridLayoutManager.SpanSizeLookup mSpanSizeLookup =
+            new GridLayoutManager.SpanSizeLookup() {
+                @Override
+                public int getSpanSize(int position) {
+                    if (getItemViewType(position) == getScrollingLimitedMessageViewType()) {
+                        return mMaxSpanSize;
+                    }
+
+                    int itemIndex = positionToIndex(position);
+                    return mBrowseAdapter.getSpanSize(itemIndex, mMaxSpanSize);
+                }
+            };
+
+    public BrowseAdapter getBrowseAdapter() {
+        return mBrowseAdapter;
+    }
+
+    /**
+     * @see BrowseAdapter#submitItems(MediaItemMetadata, List)
+     */
+    public void submitItems(@Nullable MediaItemMetadata parentItem,
+            @Nullable List<MediaItemMetadata> items) {
+        mBrowseAdapter.submitItems(parentItem, items);
+
+        if (items == null) {
+            updateUnderlyingDataChanged(0, 0);
+            return;
+        }
+        // We can't take any action with the new items as they must first go through the
+        // AsyncListDiffer of ListAdapter. This is handled in the OnListChangedListener.
+    }
+
+    private int validateAnchor() {
+        if (mAnchorId == null) {
+            return 0;
+        }
+
+        List<BrowseViewData> items = mBrowseAdapter.getCurrentList();
+        for (int i = 0; i < items.size(); i++) {
+            MediaItemMetadata mediaItem = items.get(i).mMediaItem;
+            if (mediaItem != null && mAnchorId.equals(mediaItem.getId())) {
+                return i;
+            }
+        }
+
+        // The anchor isn't present in the new list, reset it.
+        mAnchorId = null;
+        return 0;
+    }
+
+
+    @Override
+    public int computeAnchorIndexWhenRestricting() {
+        List<BrowseViewData> items = mBrowseAdapter.getCurrentList();
+        if (items.size() <= 0) {
+            mAnchorId = null;
+            return 0;
+        }
+
+        int anchorIndex = (getFirstVisibleItemPosition() + getLastVisibleItemPosition()) / 2;
+        if (0 <= anchorIndex && anchorIndex < items.size()) {
+            MediaItemMetadata mediaItem = items.get(anchorIndex).mMediaItem;
+            mAnchorId = mediaItem != null ? mediaItem.getId() : null;
+            return anchorIndex;
+        } else {
+            mAnchorId = null;
+            return 0;
+        }
+    }
+
+    private int getFirstVisibleItemPosition() {
+        int firstItem = mLayoutManager.findFirstCompletelyVisibleItemPosition();
+        if (firstItem == RecyclerView.NO_POSITION) {
+            firstItem = mLayoutManager.findFirstVisibleItemPosition();
+        }
+        return firstItem;
+    }
+
+    private int getLastVisibleItemPosition() {
+        int lastItem = mLayoutManager.findLastCompletelyVisibleItemPosition();
+        if (lastItem == RecyclerView.NO_POSITION) {
+            lastItem = mLayoutManager.findLastVisibleItemPosition();
+        }
+        return lastItem;
+    }
+}