Remove flicker when multiple apps are added/removed/updated on widget tray

Bug: 36718342

1.The flicker was also happening partially because notifyWidgetProviderChanged
callback also made the entire widget list to update in addition to
packageManager update.

2. Now that adapter calls notifyItemInserted, Removed, the recycler
view uses it's internal animation to elegantly move items or insert
them. (added benefit!)

3. Added tests for WidgetsListAdapterTest

$ adb shell am instrument -w -e class com.android.launcher3.widget.WidgetsListAdapterTest com.google.android.apps.nexuslauncher.tests/android.support.test.runner.AndroidJUnitRunner

com.android.launcher3.widget.WidgetsListAdapterTest:.

Time: 0.337

OK (6 test)

Change-Id: I0818d546532631bf889fae560118decff64ec5a4
Signed-off-by: Hyunyoung Song <hyunyoungs@google.com>

src/com/android/launcher3/widget/WidgetsDiffReporter.java

@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2017 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.launcher3.widget;
+
+import android.util.Log;
+
+import com.android.launcher3.IconCache;
+import com.android.launcher3.model.PackageItemInfo;
+import com.android.launcher3.widget.WidgetsListAdapter.WidgetListRowEntryComparator;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+
+/**
+ * Do diff on widget's tray list items and call the {@link NotifyListener} methods accordingly.
+ */
+public class WidgetsDiffReporter {
+    private final boolean DEBUG = true;
+    private final String TAG = "WidgetsDiffReporter";
+    private final IconCache mIconCache;
+    private NotifyListener mListener;
+
+    public interface NotifyListener {
+        void notifyDataSetChanged();
+        void notifyItemChanged(int index);
+        void notifyItemInserted(int index);
+        void notifyItemRemoved(int index);
+    }
+
+    public WidgetsDiffReporter(IconCache iconCache) {
+        mIconCache = iconCache;
+    }
+
+    public void setListener(NotifyListener listener) {
+        mListener = listener;
+    }
+
+    public void process(ArrayList<WidgetListRowEntry> currentEntries,
+            ArrayList<WidgetListRowEntry> newEntries, WidgetListRowEntryComparator comparator) {
+        if (DEBUG) {
+            Log.d(TAG, "process oldEntries#=" + currentEntries.size()
+                    + " newEntries#=" + newEntries.size());
+        }
+        if (currentEntries.size() == 0 && newEntries.size() > 0) {
+            currentEntries.addAll(newEntries);
+            mListener.notifyDataSetChanged();
+            return;
+        }
+        ArrayList<WidgetListRowEntry> orgEntries =
+                (ArrayList<WidgetListRowEntry>) currentEntries.clone();
+        Iterator<WidgetListRowEntry> orgIter = orgEntries.iterator();
+        Iterator<WidgetListRowEntry> newIter = newEntries.iterator();
+
+        WidgetListRowEntry orgRowEntry = orgIter.next();
+        WidgetListRowEntry newRowEntry = newIter.next();
+
+        do {
+            int diff = comparePackageName(orgRowEntry, newRowEntry, comparator);
+            if (DEBUG) {
+                Log.d(TAG, String.format("diff=%d orgRowEntry (%s) newRowEntry (%s)",
+                        diff, orgRowEntry != null? orgRowEntry.toString() : null,
+                        newRowEntry != null? newRowEntry.toString() : null));
+            }
+            int index = -1;
+            if (diff < 0) {
+                index = currentEntries.indexOf(orgRowEntry);
+                mListener.notifyItemRemoved(index);
+                if (DEBUG) {
+                    Log.d(TAG, String.format("notifyItemRemoved called (%d)%s", index,
+                            orgRowEntry.titleSectionName));
+                }
+                currentEntries.remove(index);
+                orgRowEntry = orgIter.hasNext() ? orgIter.next() : null;
+            } else if (diff > 0) {
+                index = orgRowEntry != null? currentEntries.indexOf(orgRowEntry):
+                        currentEntries.size();
+                currentEntries.add(index, newRowEntry);
+                newRowEntry = newIter.hasNext() ? newIter.next() : null;
+                mListener.notifyItemInserted(index);
+                if (DEBUG) {
+                    Log.d(TAG, String.format("notifyItemInserted called (%d)%s", index,
+                            newRowEntry.titleSectionName));
+                }
+            } else {
+                // same package name but,
+                // did the icon, title, etc, change?
+                // or did the widget size and desc, span, etc change?
+                if (!isSamePackageItemInfo(orgRowEntry.pkgItem, newRowEntry.pkgItem) ||
+                        !orgRowEntry.widgets.equals(newRowEntry.widgets)) {
+                    index = currentEntries.indexOf(orgRowEntry);
+                    currentEntries.set(index, newRowEntry);
+                    mListener.notifyItemChanged(index);
+                    if (DEBUG) {
+                        Log.d(TAG, String.format("notifyItemChanged called (%d)%s", index,
+                                newRowEntry.titleSectionName));
+                    }
+                }
+                orgRowEntry = orgIter.hasNext() ? orgIter.next() : null;
+                newRowEntry = newIter.hasNext() ? newIter.next() : null;
+            }
+        } while(orgRowEntry != null || newRowEntry != null);
+    }
+
+    /**
+     * Compare package name using the same comparator as in {@link WidgetsListAdapter}.
+     * Also handle null row pointers.
+     */
+    private int comparePackageName(WidgetListRowEntry curRow, WidgetListRowEntry newRow,
+            WidgetListRowEntryComparator comparator) {
+        if (curRow == null && newRow == null) {
+            throw new IllegalStateException("Cannot compare PackageItemInfo if both rows are null.");
+        }
+
+        if (curRow == null && newRow != null) {
+            return 1; // new row needs to be inserted
+        } else if (curRow != null && newRow == null) {
+            return -1; // old row needs to be deleted
+        }
+        return comparator.compare(curRow, newRow);
+    }
+
+    private boolean isSamePackageItemInfo(PackageItemInfo curInfo, PackageItemInfo newInfo) {
+        return curInfo.iconBitmap.equals(newInfo.iconBitmap) &&
+                !mIconCache.isDefaultIcon(curInfo.iconBitmap, curInfo.user);
+    }
+}