Adding a utility class to cache views at an activity level

Bug: 122345781
Change-Id: I9a939e0b19c06c1089c1ceb515f8b97fb5dbb49e

src/com/android/launcher3/util/ViewCache.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2019 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.util;
+
+import android.content.Context;
+import android.util.SparseArray;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+/**
+ * Utility class to cache views at an activity level
+ */
+public class ViewCache {
+
+    protected final SparseArray<CacheEntry> mCache = new SparseArray();
+
+    public void setCacheSize(int layoutId, int size) {
+        mCache.put(layoutId, new CacheEntry(size));
+    }
+
+    public <T extends View> T getView(int layoutId, Context context, ViewGroup parent) {
+        CacheEntry entry = mCache.get(layoutId);
+        if (entry == null) {
+            entry = new CacheEntry(1);
+            mCache.put(layoutId, entry);
+        }
+
+        if (entry.mCurrentSize > 0) {
+            entry.mCurrentSize --;
+            T result = (T) entry.mViews[entry.mCurrentSize];
+            entry.mViews[entry.mCurrentSize] = null;
+            return result;
+        }
+
+        return (T) LayoutInflater.from(context).inflate(layoutId, parent, false);
+    }
+
+    public void recycleView(int layoutId, View view) {
+        CacheEntry entry = mCache.get(layoutId);
+        if (entry != null && entry.mCurrentSize < entry.mMaxSize) {
+            entry.mViews[entry.mCurrentSize] = view;
+            entry.mCurrentSize++;
+        }
+    }
+
+    private static class CacheEntry {
+
+        final int mMaxSize;
+        final View[] mViews;
+
+        int mCurrentSize;
+
+        public CacheEntry(int maxSize) {
+            mMaxSize = maxSize;
+            mViews = new View[maxSize];
+            mCurrentSize = 0;
+        }
+    }
+}