Load up-to-date thumbnail if the cached one is out of date.

Bug: 28557412
Change-Id: Ib3ef9962249305be22b7a1e49e26350f3596e430

10 files changed, 329 insertions, 62 deletions

diff --git a/src/com/android/documentsui/ThumbnailCache.java b/src/com/android/documentsui/ThumbnailCache.java
index 25cf80604..53f5092e9 100644
--- a/src/com/android/documentsui/ThumbnailCache.java
+++ b/src/com/android/documentsui/ThumbnailCache.java
@@ -65,24 +65,19 @@ public class ThumbnailCache {
      * @return the thumbnail result
      */
     public Result getThumbnail(Uri uri, Point size) {
-        Result result = Result.obtain(Result.CACHE_MISS, null, null);
-
         TreeMap<Point, Pair<Uri, Point>> sizeMap;
         sizeMap = mSizeIndex.get(uri);
         if (sizeMap == null || sizeMap.isEmpty()) {
             // There is not any thumbnail for this uri.
-            return result;
+            return Result.obtainMiss();
         }
 
         // Look for thumbnail of the same size.
         Pair<Uri, Point> cacheKey = sizeMap.get(size);
         if (cacheKey != null) {
-            Bitmap thumbnail = mCache.get(cacheKey);
-            if (thumbnail != null) {
-                result.mStatus = Result.CACHE_HIT_EXACT;
-                result.mThumbnail = thumbnail;
-                result.mSize = size;
-                return result;
+            Entry entry = mCache.get(cacheKey);
+            if (entry != null) {
+                return Result.obtain(Result.CACHE_HIT_EXACT, size, entry);
             }
         }
 
@@ -92,12 +87,9 @@ public class ThumbnailCache {
             cacheKey = sizeMap.get(otherSize);
 
             if (cacheKey != null) {
-                Bitmap thumbnail = mCache.get(cacheKey);
-                if (thumbnail != null) {
-                    result.mStatus = Result.CACHE_HIT_LARGER;
-                    result.mThumbnail = thumbnail;
-                    result.mSize = otherSize;
-                    return result;
+                Entry entry = mCache.get(cacheKey);
+                if (entry != null) {
+                    return Result.obtain(Result.CACHE_HIT_LARGER, otherSize, entry);
                 }
             }
         }
@@ -108,21 +100,18 @@ public class ThumbnailCache {
             cacheKey = sizeMap.get(otherSize);
 
             if (cacheKey != null) {
-                Bitmap thumbnail = mCache.get(cacheKey);
-                if (thumbnail != null) {
-                    result.mStatus = Result.CACHE_HIT_SMALLER;
-                    result.mThumbnail = thumbnail;
-                    result.mSize = otherSize;
-                    return result;
+                Entry entry = mCache.get(cacheKey);
+                if (entry != null) {
+                    return Result.obtain(Result.CACHE_HIT_SMALLER, otherSize, entry);
                 }
             }
         }
 
         // Cache miss.
-        return result;
+        return Result.obtainMiss();
     }
 
-    public void putThumbnail(Uri uri, Point size, Bitmap thumbnail) {
+    public void putThumbnail(Uri uri, Point size, Bitmap thumbnail, long lastModified) {
         Pair<Uri, Point> cacheKey = Pair.create(uri, size);
 
         TreeMap<Point, Pair<Uri, Point>> sizeMap;
@@ -134,17 +123,28 @@ public class ThumbnailCache {
             }
         }
 
-        mCache.put(cacheKey, thumbnail);
+        Entry entry = new Entry(thumbnail, lastModified);
+        mCache.put(cacheKey, entry);
         synchronized (sizeMap) {
             sizeMap.put(size, cacheKey);
         }
     }
 
+    private void removeKey(Uri uri, Point size) {
+        TreeMap<Point, Pair<Uri, Point>> sizeMap;
+        synchronized (mSizeIndex) {
+            sizeMap = mSizeIndex.get(uri);
+        }
+
+        // LruCache tells us to remove a key, which should exist, so sizeMap can't be null.
+        assert (sizeMap != null);
+        synchronized (sizeMap) {
+            sizeMap.remove(size);
+        }
+    }
+
     public void onTrimMemory(int level) {
         if (level >= ComponentCallbacks2.TRIM_MEMORY_MODERATE) {
-            synchronized (mSizeIndex) {
-                mSizeIndex.clear();
-            }
             mCache.evictAll();
         } else if (level >= ComponentCallbacks2.TRIM_MEMORY_BACKGROUND) {
             mCache.trimToSize(mCache.size() / 2);
@@ -159,7 +159,6 @@ public class ThumbnailCache {
         @Retention(RetentionPolicy.SOURCE)
         @IntDef({CACHE_MISS, CACHE_HIT_EXACT, CACHE_HIT_SMALLER, CACHE_HIT_LARGER})
         @interface Status {}
-
         /**
          * Indicates there is no thumbnail for the requested uri. The thumbnail will be null.
          */
@@ -182,30 +181,38 @@ public class ThumbnailCache {
         private static final Pools.SimplePool<Result> sPool = new Pools.SimplePool<>(1);
 
         private @Status int mStatus;
-
         private @Nullable Bitmap mThumbnail;
-
         private @Nullable Point mSize;
+        private long mLastModified;
+
+        private static Result obtainMiss() {
+            return obtain(CACHE_MISS, null, null, 0);
+        }
+
+        private static Result obtain(@Status int status, Point size, Entry entry) {
+            return obtain(status, entry.mThumbnail, size, entry.mLastModified);
+        }
 
         private static Result obtain(@Status int status, @Nullable Bitmap thumbnail,
-                @Nullable Point size) {
+                @Nullable Point size, long lastModified) {
             Result instance = sPool.acquire();
             instance = (instance != null ? instance : new Result());
 
             instance.mStatus = status;
             instance.mThumbnail = thumbnail;
             instance.mSize = size;
+            instance.mLastModified = lastModified;
 
             return instance;
         }
 
-        private Result() {
-        }
+        private Result() {}
 
         public void recycle() {
             mStatus = -1;
             mThumbnail = null;
             mSize = null;
+            mLastModified = -1;
 
             boolean released = sPool.release(this);
             // This assert is used to guarantee we won't generate too many instances that can't be
@@ -228,6 +235,10 @@ public class ThumbnailCache {
             return mSize;
         }
 
+        public long getLastModified() {
+            return mLastModified;
+        }
+
         public boolean isHit() {
             return (mStatus != CACHE_MISS);
         }
@@ -237,14 +248,33 @@ public class ThumbnailCache {
         }
     }
 
-    private static final class Cache extends LruCache<Pair<Uri, Point>, Bitmap> {
+    private static final class Entry {
+        private final Bitmap mThumbnail;
+        private final long mLastModified;
+
+        private Entry(Bitmap thumbnail, long lastModified) {
+            mThumbnail = thumbnail;
+            mLastModified = lastModified;
+        }
+    }
+
+    private final class Cache extends LruCache<Pair<Uri, Point>, Entry> {
+
         private Cache(int maxSizeBytes) {
             super(maxSizeBytes);
         }
 
         @Override
-        protected int sizeOf(Pair<Uri, Point> key, Bitmap value) {
-            return value.getByteCount();
+        protected int sizeOf(Pair<Uri, Point> key, Entry value) {
+            return value.mThumbnail.getByteCount();
+        }
+
+        @Override
+        protected void entryRemoved(
+                boolean evicted, Pair<Uri, Point> key, Entry oldValue, Entry newValue) {
+            if (newValue == null) {
+                removeKey(key.first, key.second);
+            }
         }
     }
 
diff --git a/src/com/android/documentsui/dirlist/GridDocumentHolder.java b/src/com/android/documentsui/dirlist/GridDocumentHolder.java
index 8b1025718..7ba4bddbe 100644
--- a/src/com/android/documentsui/dirlist/GridDocumentHolder.java
+++ b/src/com/android/documentsui/dirlist/GridDocumentHolder.java
@@ -135,7 +135,8 @@ final class GridDocumentHolder extends DocumentHolder {
         mIconThumb.setAlpha(0f);
 
         final Uri uri = DocumentsContract.buildDocumentUri(docAuthority, docId);
-        mIconHelper.load(uri, docMimeType, docFlags, docIcon, mIconThumb, mIconMimeLg, mIconMimeSm);
+        mIconHelper.load(uri, docMimeType, docFlags, docIcon, docLastModified, mIconThumb,
+                mIconMimeLg, mIconMimeSm);
 
         if (mHideTitles) {
             mTitle.setVisibility(View.GONE);
diff --git a/src/com/android/documentsui/dirlist/IconHelper.java b/src/com/android/documentsui/dirlist/IconHelper.java
index d1f792e89..78257bd12 100644
--- a/src/com/android/documentsui/dirlist/IconHelper.java
+++ b/src/com/android/documentsui/dirlist/IconHelper.java
@@ -143,6 +143,7 @@ public class IconHelper {
         private final ImageView mIconMime;
         private final ImageView mIconThumb;
         private final Point mThumbSize;
+        private final long mLastModified;
 
         // A callback to apply animation to image views after the thumbnail is loaded.
         private final BiConsumer<View, View> mImageAnimator;
@@ -150,12 +151,13 @@ public class IconHelper {
         private final CancellationSignal mSignal;
 
         public LoaderTask(Uri uri, ImageView iconMime, ImageView iconThumb,
-                Point thumbSize, BiConsumer<View, View> animator) {
+                Point thumbSize, long lastModified, BiConsumer<View, View> animator) {
             mUri = uri;
             mIconMime = iconMime;
             mIconThumb = iconThumb;
             mThumbSize = thumbSize;
             mImageAnimator = animator;
+            mLastModified = lastModified;
             mSignal = new CancellationSignal();
             if (DEBUG) Log.d(TAG, "Starting icon loader task for " + mUri);
         }
@@ -184,7 +186,7 @@ public class IconHelper {
                 result = DocumentsContract.getDocumentThumbnail(client, mUri, mThumbSize, mSignal);
                 if (result != null) {
                     final ThumbnailCache cache = DocumentsApplication.getThumbnailCache(context);
-                    cache.putThumbnail(mUri, mThumbSize, result);
+                    cache.putThumbnail(mUri, mThumbSize, result, mLastModified);
                 }
             } catch (Exception e) {
                 if (!(e instanceof OperationCanceledException)) {
@@ -216,12 +218,13 @@ public class IconHelper {
      * @param mimeType The mime type of the file being represented.
      * @param docFlags Flags for the file being represented.
      * @param docIcon Custom icon (if any) for the file being requested.
+     * @param docLastModified the last modified value of the file being requested.
      * @param iconThumb The itemview's thumbnail icon.
      * @param iconMime The itemview's mime icon. Hidden when iconThumb is shown.
      * @param subIconMime The second itemview's mime icon. Always visible.
      * @return
      */
-    public void load(Uri uri, String mimeType, int docFlags, int docIcon,
+    public void load(Uri uri, String mimeType, int docFlags, int docIcon, long docLastModified,
             ImageView iconThumb, ImageView iconMime, @Nullable ImageView subIconMime) {
         boolean loadedThumbnail = false;
 
@@ -232,7 +235,8 @@ public class IconHelper {
                 || MimePredicate.mimeMatches(MimePredicate.VISUAL_MIMES, mimeType);
         final boolean showThumbnail = supportsThumbnail && allowThumbnail && mThumbnailsEnabled;
         if (showThumbnail) {
-            loadedThumbnail = loadThumbnail(uri, docAuthority, iconThumb, iconMime);
+            loadedThumbnail =
+                loadThumbnail(uri, docAuthority, docLastModified, iconThumb, iconMime);
         }
 
         final Drawable mimeIcon = getDocumentIcon(mContext, docAuthority,
@@ -250,18 +254,21 @@ public class IconHelper {
         }
     }
 
-    private boolean loadThumbnail(Uri uri, String docAuthority, ImageView iconThumb,
-            ImageView iconMime) {
+    private boolean loadThumbnail(Uri uri, String docAuthority, long docLastModified,
+            ImageView iconThumb, ImageView iconMime) {
         final Result result = mThumbnailCache.getThumbnail(uri, mCurrentSize);
 
         final Bitmap cachedThumbnail = result.getThumbnail();
         iconThumb.setImageBitmap(cachedThumbnail);
 
-        if (!result.isExactHit()) {
+        boolean stale = (docLastModified > result.getLastModified());
+        if (DEBUG) Log.d(TAG, String.format("Load thumbnail for %s, got result %d and stale %b.",
+                uri.toString(), result.getStatus(), stale));
+        if (!result.isExactHit() || stale) {
             final BiConsumer<View, View> animator =
                     (cachedThumbnail == null ? ANIM_FADE_IN : ANIM_NO_OP);
-            final LoaderTask task =
-                    new LoaderTask(uri, iconMime, iconThumb, mCurrentSize, animator);
+            final LoaderTask task = new LoaderTask(uri, iconMime, iconThumb, mCurrentSize,
+                    docLastModified, animator);
 
             iconThumb.setTag(task);
 
diff --git a/src/com/android/documentsui/dirlist/ListDocumentHolder.java b/src/com/android/documentsui/dirlist/ListDocumentHolder.java
index 98916a15a..e88be0cfe 100644
--- a/src/com/android/documentsui/dirlist/ListDocumentHolder.java
+++ b/src/com/android/documentsui/dirlist/ListDocumentHolder.java
@@ -133,7 +133,8 @@ final class ListDocumentHolder extends DocumentHolder {
         mIconThumb.setAlpha(0f);
 
         final Uri uri = DocumentsContract.buildDocumentUri(docAuthority, docId);
-        mIconHelper.load(uri, docMimeType, docFlags, docIcon, mIconThumb, mIconMime, null);
+        mIconHelper.load(uri, docMimeType, docFlags, docIcon, docLastModified, mIconThumb,
+                mIconMime, null);
 
         mTitle.setText(docDisplayName, TextView.BufferType.SPANNABLE);
         mTitle.setVisibility(View.VISIBLE);
diff --git a/tests/src/com/android/documentsui/ItemDragListenerTest.java b/tests/src/com/android/documentsui/ItemDragListenerTest.java
index 645fd785d..924c99bc6 100644
--- a/tests/src/com/android/documentsui/ItemDragListenerTest.java
+++ b/tests/src/com/android/documentsui/ItemDragListenerTest.java
@@ -30,7 +30,7 @@ import android.view.View;
 import com.android.documentsui.testing.ClipDatas;
 import com.android.documentsui.testing.DragEvents;
 import com.android.documentsui.testing.TestTimer;
-import com.android.documentsui.testing.TestViews;
+import com.android.documentsui.testing.Views;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -53,7 +53,7 @@ public class ItemDragListenerTest {
 
     @Before
     public void setUp() {
-        mTestView = TestViews.createTestView();
+        mTestView = Views.createTestView();
 
         mTestTimer = new TestTimer();
         mTestDragHost = new TestDragHost();
diff --git a/tests/src/com/android/documentsui/ThumbnailCacheTest.java b/tests/src/com/android/documentsui/ThumbnailCacheTest.java
new file mode 100644
index 000000000..dda491847
--- /dev/null
+++ b/tests/src/com/android/documentsui/ThumbnailCacheTest.java
@@ -0,0 +1,202 @@
+/*
+ * Copyright (C) 2016 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.documentsui;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+import android.content.ComponentCallbacks2;
+import android.graphics.Bitmap;
+import android.graphics.Point;
+import android.net.Uri;
+import android.support.test.filters.SmallTest;
+import android.support.test.runner.AndroidJUnit4;
+
+import com.android.documentsui.ThumbnailCache.Result;
+import com.android.documentsui.testing.Bitmaps;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class ThumbnailCacheTest {
+
+    private static final Uri URI_0 = Uri.parse("content://authority/document/0");
+    private static final Uri URI_1 = Uri.parse("content://authority/document/1");
+
+    private static final Point SMALL_SIZE = new Point(1, 1);
+    private static final Point MID_SIZE = new Point(2, 2);
+    private static final Point LARGE_SIZE = new Point(3, 3);
+
+    private static final Bitmap SMALL_BITMAP = Bitmaps.createTestBitmap(1, 1);
+    private static final Bitmap MIDSIZE_BITMAP = Bitmaps.createTestBitmap(2, 2);
+    private static final Bitmap LARGE_BITMAP = Bitmaps.createTestBitmap(3, 3);
+
+    private static final long LAST_MODIFIED = 100;
+
+    private static final int CACHE_SIZE_LIMIT =
+            MIDSIZE_BITMAP.getByteCount() + LARGE_BITMAP.getByteCount();
+
+    private ThumbnailCache mCache;
+
+    @Before
+    public void setUp() {
+        mCache = new ThumbnailCache(CACHE_SIZE_LIMIT);
+    }
+
+    @Test
+    public void testMiss() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+
+        Result result = mCache.getThumbnail(URI_1, MID_SIZE);
+
+        assertMiss(result);
+    }
+
+    @Test
+    public void testHit_Exact() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+
+        Result result = mCache.getThumbnail(URI_0, MID_SIZE);
+
+        assertHitExact(result);
+        assertSame(MIDSIZE_BITMAP, result.getThumbnail());
+    }
+
+    @Test
+    public void testHit_Smaller() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+
+        Result result = mCache.getThumbnail(URI_0, LARGE_SIZE);
+
+        assertHitSmaller(result);
+        assertSame(MIDSIZE_BITMAP, result.getThumbnail());
+    }
+
+    @Test
+    public void testHit_Larger() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+
+        Result result = mCache.getThumbnail(URI_0, SMALL_SIZE);
+
+        assertHitLarger(result);
+        assertSame(MIDSIZE_BITMAP, result.getThumbnail());
+    }
+
+    @Test
+    public void testHit_Larger_HasBothSize() {
+        mCache.putThumbnail(URI_0, LARGE_SIZE, LARGE_BITMAP, LAST_MODIFIED);
+        mCache.putThumbnail(URI_0, SMALL_SIZE, SMALL_BITMAP, LAST_MODIFIED);
+
+        Result result = mCache.getThumbnail(URI_0, MID_SIZE);
+
+        assertHitLarger(result);
+        assertSame(LARGE_BITMAP, result.getThumbnail());
+    }
+
+    @Test
+    public void testHit_Exact_MultiplePut() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+
+        Bitmap localBitmap = Bitmaps.createTestBitmap(MID_SIZE.x, MID_SIZE.y);
+        long localLastModified = LAST_MODIFIED + 100;
+        mCache.putThumbnail(URI_0, MID_SIZE, localBitmap, localLastModified);
+
+        Result result = mCache.getThumbnail(URI_0, MID_SIZE);
+
+        assertHitExact(result);
+        assertSame(localBitmap, result.getThumbnail());
+    }
+
+    @Test
+    public void testHit_EqualLastModified() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+
+        Result result = mCache.getThumbnail(URI_0, MID_SIZE);
+
+        assertEquals(LAST_MODIFIED, result.getLastModified());
+    }
+
+    @Test
+    public void testEvictOldest_SizeExceeded() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+        mCache.putThumbnail(URI_1, SMALL_SIZE, SMALL_BITMAP, LAST_MODIFIED);
+        mCache.putThumbnail(URI_1, LARGE_SIZE, LARGE_BITMAP, LAST_MODIFIED);
+
+        Result result = mCache.getThumbnail(URI_0, MID_SIZE);
+
+        assertMiss(result);
+    }
+
+    @Test
+    public void testCacheShrink_OnTrimMemory_Moderate() {
+        mCache.putThumbnail(URI_0, MID_SIZE, MIDSIZE_BITMAP, LAST_MODIFIED);
+        mCache.putThumbnail(URI_0, SMALL_SIZE, SMALL_BITMAP, LAST_MODIFIED);
+        mCache.putThumbnail(URI_0, LARGE_SIZE, LARGE_BITMAP, LAST_MODIFIED);
+
+        mCache.onTrimMemory(ComponentCallbacks2.TRIM_MEMORY_MODERATE);
+
+        Result result = mCache.getThumbnail(URI_0, MID_SIZE);
+        assertMiss(result);
+    }
+
+    @Test
+    public void testCacheShrink_OnTrimMemory_Background() {
+        mCache.putThumbnail(URI_0, LARGE_SIZE, LARGE_BITMAP, LAST_MODIFIED);
+        mCache.putThumbnail(URI_0, SMALL_SIZE, SMALL_BITMAP, LAST_MODIFIED);
+
+        mCache.onTrimMemory(ComponentCallbacks2.TRIM_MEMORY_BACKGROUND);
+
+        // Math here (size of each pixel omitted):
+        // Limit = midSize + largeSize = 2 * 2 + 3 * 3 = 13, so after all putThumbnail the cache is
+        // full.
+        //
+        // HalfLimit = Limit / 2 = 5. After evicting largeSize bitmap, cache size decreases to 4,
+        // which is smaller than 5. Then smallSize bitmap remains.
+        Result result = mCache.getThumbnail(URI_0, MID_SIZE);
+        assertHitSmaller(result);
+        assertSame(SMALL_BITMAP, result.getThumbnail());
+    }
+
+    private static void assertMiss(Result result) {
+        assertEquals(Result.CACHE_MISS, result.getStatus());
+        assertFalse(result.isExactHit());
+        assertFalse(result.isHit());
+    }
+
+    private static void assertHitExact(Result result) {
+        assertEquals(Result.CACHE_HIT_EXACT, result.getStatus());
+        assertTrue(result.isExactHit());
+        assertTrue(result.isHit());
+    }
+
+    private static void assertHitSmaller(Result result) {
+        assertEquals(Result.CACHE_HIT_SMALLER, result.getStatus());
+        assertFalse(result.isExactHit());
+        assertTrue(result.isHit());
+    }
+
+    private static void assertHitLarger(Result result) {
+        assertEquals(Result.CACHE_HIT_LARGER, result.getStatus());
+        assertFalse(result.isExactHit());
+        assertTrue(result.isHit());
+    }
+}
diff --git a/tests/src/com/android/documentsui/testing/Bitmaps.java b/tests/src/com/android/documentsui/testing/Bitmaps.java
new file mode 100644
index 000000000..1b94b15eb
--- /dev/null
+++ b/tests/src/com/android/documentsui/testing/Bitmaps.java
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2016 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.documentsui.testing;
+
+import android.graphics.Bitmap;
+
+public final class Bitmaps {
+
+    private Bitmaps() {}
+
+    public static Bitmap createTestBitmap(int width, int height) {
+        final Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+
+        return bitmap;
+    }
+
+}
diff --git a/tests/src/com/android/documentsui/testing/ClipDatas.java b/tests/src/com/android/documentsui/testing/ClipDatas.java
index 6536fb9d2..525a02e4f 100644
--- a/tests/src/com/android/documentsui/testing/ClipDatas.java
+++ b/tests/src/com/android/documentsui/testing/ClipDatas.java
@@ -20,14 +20,14 @@ import android.content.ClipData;
 
 import org.mockito.Mockito;
 
-/**
- * Test support for working with {@link ClipData} instances.
- */
 public final class ClipDatas {
 
+    private ClipDatas() {}
+
     public static ClipData createTestClipData() {
-        ClipData data = Mockito.mock(ClipData.class);
+        final ClipData data = Mockito.mock(ClipData.class);
 
         return data;
     }
+
 }
diff --git a/tests/src/com/android/documentsui/testing/DragEvents.java b/tests/src/com/android/documentsui/testing/DragEvents.java
index e835cafb3..1a009a44c 100644
--- a/tests/src/com/android/documentsui/testing/DragEvents.java
+++ b/tests/src/com/android/documentsui/testing/DragEvents.java
@@ -21,9 +21,6 @@ import android.view.DragEvent;
 
 import org.mockito.Mockito;
 
-/**
- * Test support for working with {@link DragEvents} instances.
- */
 public final class DragEvents {
 
     private DragEvents() {}
@@ -41,4 +38,5 @@ public final class DragEvents {
 
         return dropEvent;
     }
+
 }
diff --git a/tests/src/com/android/documentsui/testing/TestViews.java b/tests/src/com/android/documentsui/testing/Views.java
index dd2bfec98..15aa01b3e 100644
--- a/tests/src/com/android/documentsui/testing/TestViews.java
+++ b/tests/src/com/android/documentsui/testing/Views.java
@@ -20,15 +20,12 @@ import android.view.View;
 
 import org.mockito.Mockito;
 
-/**
- * Test support for working with {@link TestViews} instances.
- */
-public final class TestViews {
+public final class Views {
 
-    private TestViews() {}
+    private Views() {}
 
     public static View createTestView() {
-        View view = Mockito.mock(View.class);
+        final View view = Mockito.mock(View.class);
         Mockito.doCallRealMethod().when(view).setTag(Mockito.anyInt(), Mockito.any());
         Mockito.doCallRealMethod().when(view).getTag(Mockito.anyInt());