Merge "Move Adapters to their own classes."
diff --git a/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java b/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java
index 0d5e34e..13cfbe4 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/dirlist/DirectoryFragment.java
@@ -53,6 +53,7 @@
 import android.support.annotation.Nullable;
 import android.support.design.widget.Snackbar;
 import android.support.v7.widget.GridLayoutManager;
+import android.support.v7.widget.GridLayoutManager.SpanSizeLookup;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.RecyclerView.LayoutManager;
@@ -99,18 +100,17 @@
 import com.android.documentsui.model.DocumentInfo;
 import com.android.documentsui.model.DocumentStack;
 import com.android.documentsui.model.RootInfo;
+
 import com.google.common.collect.Lists;
-import com.google.common.collect.Sets;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import java.util.Set;
 
 /**
  * Display the documents inside a single directory.
  */
-public class DirectoryFragment extends Fragment {
+public class DirectoryFragment extends Fragment implements DocumentsAdapter.Environment {
 
     public static final int TYPE_NORMAL = 1;
     public static final int TYPE_SEARCH = 2;
@@ -126,7 +126,7 @@
     private static final String TAG = "DirectoryFragment";
 
     private static final int LOADER_ID = 42;
-    private static final boolean DEBUG_ENABLE_DND = true;
+    static final boolean DEBUG_ENABLE_DND = true;
 
     private static final String EXTRA_TYPE = "type";
     private static final String EXTRA_ROOT = "root";
@@ -289,7 +289,11 @@
         final RootInfo root = getArguments().getParcelable(EXTRA_ROOT);
         final DocumentInfo doc = getArguments().getParcelable(EXTRA_DOC);
 
-        mAdapter = new DocumentsAdapter();
+        mIconHelper = new IconHelper(context, state.derivedMode);
+
+        mAdapter = new SectionBreakDocumentsAdapterWrapper(
+                this, new ModelBackedDocumentsAdapter(this, mIconHelper));
+
         mRecView.setAdapter(mAdapter);
 
         GestureDetector.SimpleOnGestureListener listener =
@@ -333,7 +337,7 @@
                     : MultiSelectManager.MODE_SINGLE);
         mSelectionManager.addCallback(new SelectionModeListener());
 
-        mModel = new Model(context, mAdapter);
+        mModel = new Model(context);
         mModel.addUpdateListener(mAdapter);
         mModel.addUpdateListener(mModelUpdateListener);
 
@@ -343,8 +347,6 @@
         mTuner = FragmentTuner.pick(state);
         mClipper = new DocumentClipper(context);
 
-        mIconHelper = new IconHelper(context, state.derivedMode);
-
         boolean hideGridTitles;
         if (mType == TYPE_RECENT_OPEN) {
             // Hide titles when showing recents for picking images/videos
@@ -574,7 +576,10 @@
             case MODE_GRID:
                 if (mGridLayout == null) {
                     mGridLayout = new GridLayoutManager(getContext(), mColumnCount);
-                    mGridLayout.setSpanSizeLookup(mAdapter.createSpanSizeLookup());
+                    SpanSizeLookup lookup = mAdapter.createSpanSizeLookup();
+                    if (lookup != null) {
+                        mGridLayout.setSpanSizeLookup(lookup);
+                    }
                 }
                 layout = mGridLayout;
                 break;
@@ -609,6 +614,11 @@
         return columnCount;
     }
 
+    @Override
+    public int getColumnCount() {
+        return mColumnCount;
+    }
+
     /**
      * Manages the integration between our ActionMode and MultiSelectManager, initiating
      * ActionMode when there is a selection, canceling it when there is no selection,
@@ -893,10 +903,34 @@
         }.execute(selected);
     }
 
-    private State getDisplayState() {
+    @Override
+    public void initDocumentHolder(DocumentHolder holder) {
+        holder.addClickListener(mItemClickListener);
+        holder.addOnKeyListener(mSelectionManager);
+    }
+
+    @Override
+    public void onBindDocumentHolder(DocumentHolder holder, Cursor cursor) {
+        if (DEBUG_ENABLE_DND) {
+            setupDragAndDropOnDocumentView(holder.itemView, cursor);
+        }
+    }
+
+    @Override
+    public State getDisplayState() {
         return ((BaseActivity) getActivity()).getDisplayState();
     }
 
+    @Override
+    public Model getModel() {
+        return mModel;
+    }
+
+    @Override
+    public boolean isDocumentEnabled(String docMimeType, int docFlags) {
+        return mTuner.isDocumentEnabled(docMimeType, docFlags);
+    }
+
     void showEmptyView() {
         mEmptyView.setVisibility(View.VISIBLE);
         mRecView.setVisibility(View.GONE);
@@ -920,240 +954,6 @@
         mRecView.setVisibility(View.VISIBLE);
     }
 
-    final class DocumentsAdapter
-            extends RecyclerView.Adapter<DocumentHolder>
-            implements Model.UpdateListener {
-
-        private static final String TAG = "DocumentsAdapter";
-        public static final int ITEM_TYPE_LAYOUT_DIVIDER = 0;
-        public static final int ITEM_TYPE_DOCUMENT = 1;
-        public static final int ITEM_TYPE_DIRECTORY = 2;
-
-        /**
-         * An ordered list of model IDs. This is the data structure that determines what shows up in
-         * the UI, and where.
-         */
-        private List<String> mModelIds = new ArrayList<>();
-
-        // The list is divided into two segments - directories, and everything else. Record the
-        // position where the transition happens.
-        private int mDividerPosition;
-
-        public GridLayoutManager.SpanSizeLookup createSpanSizeLookup() {
-            return new GridLayoutManager.SpanSizeLookup() {
-                @Override
-                public int getSpanSize(int position) {
-                    // Make layout whitespace span the grid. This has the effect of breaking
-                    // grid rows whenever layout whitespace is encountered.
-                    if (getItemViewType(position) == ITEM_TYPE_LAYOUT_DIVIDER) {
-                        return mColumnCount;
-                    } else {
-                        return 1;
-                    }
-                }
-            };
-        }
-
-        @Override
-        public DocumentHolder onCreateViewHolder(ViewGroup parent, int viewType) {
-            if (viewType == ITEM_TYPE_LAYOUT_DIVIDER) {
-                return new EmptyDocumentHolder(getContext());
-            };
-
-            DocumentHolder holder = null;
-            final State state = getDisplayState();
-            switch (state.derivedMode) {
-                case MODE_GRID:
-                    switch (viewType) {
-                        case ITEM_TYPE_DIRECTORY:
-                            holder = new GridDirectoryHolder(getContext(), parent);
-                            break;
-                        case ITEM_TYPE_DOCUMENT:
-                            holder = new GridDocumentHolder(getContext(), parent, mIconHelper);
-                            break;
-                        default:
-                            throw new IllegalStateException("Unsupported layout type.");
-                    }
-                    break;
-                case MODE_LIST:
-                    holder = new ListDocumentHolder(getContext(), parent, mIconHelper);
-                    break;
-                case MODE_UNKNOWN:
-                default:
-                    throw new IllegalStateException("Unsupported layout mode.");
-            }
-
-            holder.addClickListener(mItemClickListener);
-            holder.addOnKeyListener(mSelectionManager);
-            return holder;
-        }
-
-        /**
-         * Deal with selection changed events by using a custom ItemAnimator that just changes the
-         * background color.  This works around focus issues (otherwise items lose focus when their
-         * selection state changes) but also optimizes change animations for selection.
-         */
-        @Override
-        public void onBindViewHolder(DocumentHolder holder, int position, List<Object> payload) {
-            if (holder.getItemViewType() == ITEM_TYPE_LAYOUT_DIVIDER) {
-                // Whitespace items are hidden elements with no data to bind.
-                return;
-            }
-
-            final View itemView = holder.itemView;
-
-            if (payload.contains(MultiSelectManager.SELECTION_CHANGED_MARKER)) {
-                final boolean selected = isSelected(mModelIds.get(position));
-                itemView.setActivated(selected);
-                return;
-            } else {
-                onBindViewHolder(holder, position);
-            }
-        }
-
-        @Override
-        public void onBindViewHolder(DocumentHolder holder, int position) {
-            if (holder.getItemViewType() == ITEM_TYPE_LAYOUT_DIVIDER) {
-                // Whitespace items are hidden elements with no data to bind.
-                return;
-            }
-
-            String modelId = mModelIds.get(position);
-            Cursor cursor = mModel.getItem(modelId);
-            holder.bind(cursor, modelId, getDisplayState());
-
-            final String docMimeType = getCursorString(cursor, Document.COLUMN_MIME_TYPE);
-            final int docFlags = getCursorInt(cursor, Document.COLUMN_FLAGS);
-
-            holder.setSelected(isSelected(modelId));
-            holder.setEnabled(mTuner.isDocumentEnabled(docMimeType, docFlags));
-            if (DEBUG_ENABLE_DND) {
-                setupDragAndDropOnDocumentView(holder.itemView, cursor);
-            }
-        }
-
-        @Override
-        public int getItemCount() {
-            return mModelIds.size();
-        }
-
-        @Override
-        public void onModelUpdate(Model model) {
-            mModelIds = Lists.newArrayList(model.getModelIds());
-            // Start the divider at the end. That way if the code below encounters no documents
-            // (i.e. in a directory containing only directories), the divider is placed at the end
-            // of the list, as expected.
-            mDividerPosition = mModelIds.size();
-
-            // Walk down the list of IDs till we encounter something that's not a directory, and
-            // insert a whitespace element - this introduces a visual break in the grid between
-            // folders and documents.
-            // TODO: This code makes assumptions about the model, namely, that it performs a
-            // bucketed sort where directories will always be ordered before other files.  CBB.
-            for (int i = 0; i < mModelIds.size(); ++i) {
-                final String mimeType = getCursorString(
-                        model.getItem(mModelIds.get(i)), Document.COLUMN_MIME_TYPE);
-                if (!Document.MIME_TYPE_DIR.equals(mimeType)) {
-                    mDividerPosition = i;
-                    break;
-                }
-            }
-
-            mModelIds.add(mDividerPosition, null);
-        }
-
-        @Override
-        public void onModelUpdateFailed(Exception e) {
-            if (DEBUG) Log.d(TAG, "onModelUpdateFailed called ");
-            mModelIds.clear();
-        }
-
-        /**
-         * @return The model ID of the item at the given adapter position.
-         */
-        public String getModelId(int adapterPosition) {
-            return mModelIds.get(adapterPosition);
-        }
-
-        /**
-         * Hides a set of items from the associated RecyclerView.
-         *
-         * @param ids The Model IDs of the items to hide.
-         * @return A SparseArray that maps the hidden IDs to their old positions. This can be used
-         *         to {@link #unhide} the items if necessary.
-         */
-        public SparseArray<String> hide(String... ids) {
-            Set<String> toHide = Sets.newHashSet(ids);
-
-            // Proceed backwards through the list of items, because each removal causes the
-            // positions of all subsequent items to change.
-            SparseArray<String> hiddenItems = new SparseArray<>();
-            for (int i = mModelIds.size() - 1; i >= 0; --i) {
-                String id = mModelIds.get(i);
-                if (toHide.contains(id)) {
-                    hiddenItems.put(i, mModelIds.remove(i));
-                    notifyItemRemoved(i);
-                }
-            }
-
-            return hiddenItems;
-        }
-
-        /**
-         * Unhides a set of previously hidden items.
-         *
-         * @param ids A sparse array of IDs from a previous call to {@link #hide}.
-         */
-        public void unhide(SparseArray<String> ids) {
-            // Proceed backwards through the list of items, because each addition causes the
-            // positions of all subsequent items to change.
-            for (int i = ids.size() - 1; i >= 0; --i) {
-                int pos = ids.keyAt(i);
-                String id = ids.get(pos);
-                mModelIds.add(pos, id);
-                notifyItemInserted(pos);
-            }
-        }
-
-        /**
-         * Returns a list of model IDs of items currently in the adapter. Excludes items that are
-         * currently hidden (see {@link #hide(String...)}).
-         *
-         * @return A list of Model IDs.
-         */
-        public List<String> getModelIds() {
-            return mModelIds;
-        }
-
-        @Override
-        public int getItemViewType(int position) {
-            if (position < mDividerPosition) {
-                return ITEM_TYPE_DIRECTORY;
-            } else if (position == mDividerPosition) {
-                return ITEM_TYPE_LAYOUT_DIVIDER;
-            } else {
-                return ITEM_TYPE_DOCUMENT;
-            }
-        }
-
-        /**
-         * Triggers item-change notifications by stable ID. Passing an unrecognized ID will result
-         * in a warning in logcat, but no other error.
-         *
-         * @param id
-         * @param selectionChangedMarker
-         */
-        public void notifyItemChanged(String id, String selectionChangedMarker) {
-            int position = mModelIds.indexOf(id);
-
-            if (position >= 0) {
-                notifyItemChanged(position, selectionChangedMarker);
-            } else {
-                Log.w(TAG, "Item change notification received for unknown item: " + id);
-            }
-        }
-    }
-
     private String findCommonMimeType(List<String> mimeTypes) {
         String[] commonType = mimeTypes.get(0).split("/");
         if (commonType.length != 2) {
@@ -1504,7 +1304,8 @@
         abstract void onDocumentsReady(List<DocumentInfo> docs);
     }
 
-    boolean isSelected(String modelId) {
+    @Override
+    public boolean isSelected(String modelId) {
         return mSelectionManager.getSelection().contains(modelId);
     }
 
@@ -1520,7 +1321,7 @@
         }
     }
 
-    private class ModelUpdateListener implements Model.UpdateListener {
+    private final class ModelUpdateListener implements Model.UpdateListener {
         @Override
         public void onModelUpdate(Model model) {
             if (model.info != null || model.error != null) {
diff --git a/packages/DocumentsUI/src/com/android/documentsui/dirlist/DocumentsAdapter.java b/packages/DocumentsUI/src/com/android/documentsui/dirlist/DocumentsAdapter.java
new file mode 100644
index 0000000..2001b29
--- /dev/null
+++ b/packages/DocumentsUI/src/com/android/documentsui/dirlist/DocumentsAdapter.java
@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2015 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.dirlist;
+
+import static com.android.documentsui.model.DocumentInfo.getCursorString;
+
+import android.content.Context;
+import android.database.Cursor;
+import android.provider.DocumentsContract.Document;
+import android.support.v7.widget.GridLayoutManager;
+import android.support.v7.widget.RecyclerView;
+import android.util.SparseArray;
+
+import com.android.documentsui.State;
+
+import java.nio.channels.UnsupportedAddressTypeException;
+import java.util.List;
+
+/**
+ * DocumentsAdapter provides glue between a directory Model, and RecylcerView. We've
+ * abstracted this a bit in order to decompose some specialized support
+ * for adding dummy layout objects (@see SectionBreakDocumentsAdapter). Handling of the
+ * dummy layout objects was error prone when interspersed with the core mode / adapter code.
+ *
+ * @see ModelBackedDocumentsAdapter
+ * @see SectionBreakDocumentsAdapter
+ */
+abstract class DocumentsAdapter
+        extends RecyclerView.Adapter<DocumentHolder>
+        implements Model.UpdateListener {
+
+    // Payloads for notifyItemChange to distinguish between selection and other events.
+    static final String SELECTION_CHANGED_MARKER = "Selection-Changed";
+
+    /**
+     * Returns a list of model IDs of items currently in the adapter. Excludes items that are
+     * currently hidden (see {@link #hide(String...)}).
+     *
+     * @return A list of Model IDs.
+     */
+    abstract List<String> getModelIds();
+
+    /**
+     * Triggers item-change notifications by stable ID (as opposed to position).
+     * Passing an unrecognized ID will result in a warning in logcat, but no other error.
+     */
+    abstract void notifyItemSelectionChanged(String id);
+
+    /**
+     * @return The model ID of the item at the given adapter position.
+     */
+    abstract String getModelId(int position);
+
+    /**
+     * Hides a set of items from the associated RecyclerView.
+     *
+     * @param ids The Model IDs of the items to hide.
+     * @return A SparseArray that maps the hidden IDs to their old positions. This can be used
+     *         to {@link #unhide} the items if necessary.
+     */
+    abstract public SparseArray<String> hide(String... ids);
+
+    /**
+     * Unhides a set of previously hidden items.
+     *
+     * @param ids A sparse array of IDs from a previous call to {@link #hide}.
+     */
+    abstract void unhide(SparseArray<String> ids);
+
+    /**
+     * Returns a class that yields the span size for a particular element. This is
+     * primarily useful in {@link SectionBreakDocumentsAdapterWrapper} where
+     * we adjust sizes.
+     */
+    GridLayoutManager.SpanSizeLookup createSpanSizeLookup() {
+        throw new UnsupportedAddressTypeException();
+    }
+
+    static boolean isDirectory(Cursor cursor) {
+        final String mimeType = getCursorString(cursor, Document.COLUMN_MIME_TYPE);
+        return Document.MIME_TYPE_DIR.equals(mimeType);
+    }
+
+    boolean isDirectory(Model model, int position) {
+        String modelId = getModelIds().get(position);
+        Cursor cursor = model.getItem(modelId);
+        return isDirectory(cursor);
+    }
+
+    /**
+     * Environmental access for View adapter implementations.
+     */
+    interface Environment {
+        Context getContext();
+        int getColumnCount();
+        State getDisplayState();
+        boolean isSelected(String id);
+        Model getModel();
+        boolean isDocumentEnabled(String mimeType, int flags);
+        void initDocumentHolder(DocumentHolder holder);
+        void onBindDocumentHolder(DocumentHolder holder, Cursor cursor);
+    }
+}
diff --git a/packages/DocumentsUI/src/com/android/documentsui/dirlist/Model.java b/packages/DocumentsUI/src/com/android/documentsui/dirlist/Model.java
index bea38c6..864f405 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/dirlist/Model.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/dirlist/Model.java
@@ -35,7 +35,6 @@
 import android.provider.DocumentsContract.Document;
 import android.support.annotation.Nullable;
 import android.support.annotation.VisibleForTesting;
-import android.support.v7.widget.RecyclerView;
 import android.util.Log;
 
 import com.android.documentsui.BaseActivity.SiblingProvider;
@@ -74,7 +73,7 @@
     @Nullable String info;
     @Nullable String error;
 
-    Model(Context context, RecyclerView.Adapter<?> viewAdapter) {
+    Model(Context context) {
         mContext = context;
     }
 
diff --git a/packages/DocumentsUI/src/com/android/documentsui/dirlist/ModelBackedDocumentsAdapter.java b/packages/DocumentsUI/src/com/android/documentsui/dirlist/ModelBackedDocumentsAdapter.java
new file mode 100644
index 0000000..bb0d729
--- /dev/null
+++ b/packages/DocumentsUI/src/com/android/documentsui/dirlist/ModelBackedDocumentsAdapter.java
@@ -0,0 +1,223 @@
+/*
+ * Copyright (C) 2015 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.dirlist;
+
+import static com.android.documentsui.Shared.DEBUG;
+import static com.android.documentsui.State.MODE_GRID;
+import static com.android.documentsui.State.MODE_LIST;
+import static com.android.documentsui.State.MODE_UNKNOWN;
+import static com.android.documentsui.model.DocumentInfo.getCursorInt;
+import static com.android.documentsui.model.DocumentInfo.getCursorString;
+
+import android.database.Cursor;
+import android.provider.DocumentsContract.Document;
+import android.support.v7.widget.GridLayoutManager;
+import android.util.Log;
+import android.util.SparseArray;
+import android.view.ViewGroup;
+
+import com.android.documentsui.State;
+
+import com.google.common.collect.Sets;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Adapts from dirlist.Model to something RecyclerView understands.
+ */
+final class ModelBackedDocumentsAdapter extends DocumentsAdapter {
+
+    private static final String TAG = "ModelBackedDocumentsAdapter";
+    public static final int ITEM_TYPE_DOCUMENT = 1;
+    public static final int ITEM_TYPE_DIRECTORY = 2;
+
+    // Provides access to information needed when creating and view holders. This
+    // isn't an ideal pattern (more transitive dependency stuff) but good enough for now.
+    private final Environment mEnv;
+    private final IconHelper mIconHelper;  // a transitive dependency of the holders.
+
+    /**
+     * An ordered list of model IDs. This is the data structure that determines what shows up in
+     * the UI, and where.
+     */
+    private List<String> mModelIds = new ArrayList<>();
+
+    // List of files that have been deleted. Some transient directory updates
+    // may happen while files are being deleted. During this time we don't
+    // want once-hidden files to be re-shown. We only remove
+    // items from this list when we get a model update where the model
+    // does not contain a corresponding id. This ensures hidden entries
+    // don't momentarily re-appear if we get intermediate updates from
+    // the file system.
+    private Set<String> mHiddenIds = new HashSet<>();
+
+    public ModelBackedDocumentsAdapter(Environment env, IconHelper iconHelper) {
+        mEnv = env;
+        mIconHelper = iconHelper;
+    }
+
+    @Override
+    public DocumentHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+        DocumentHolder holder = null;
+        final State state = mEnv.getDisplayState();
+        switch (state.derivedMode) {
+            case MODE_GRID:
+                switch (viewType) {
+                    case ITEM_TYPE_DIRECTORY:
+                        holder = new GridDirectoryHolder(mEnv.getContext(), parent);
+                        break;
+                    case ITEM_TYPE_DOCUMENT:
+                        holder = new GridDocumentHolder(mEnv.getContext(), parent, mIconHelper);
+                        break;
+                    default:
+                        throw new IllegalStateException("Unsupported layout type.");
+                }
+                break;
+            case MODE_LIST:
+                holder = new ListDocumentHolder(mEnv.getContext(), parent, mIconHelper);
+                break;
+            case MODE_UNKNOWN:
+            default:
+                throw new IllegalStateException("Unsupported layout mode.");
+        }
+
+        mEnv.initDocumentHolder(holder);
+        return holder;
+    }
+
+    @Override
+    public void onBindViewHolder(DocumentHolder holder, int position, List<Object> payload) {
+        if (payload.contains(SELECTION_CHANGED_MARKER)) {
+            final boolean selected = mEnv.isSelected(mModelIds.get(position));
+            holder.setSelected(selected);
+        } else {
+            onBindViewHolder(holder, position);
+        }
+    }
+
+    @Override
+    public void onBindViewHolder(DocumentHolder holder, int position) {
+        String modelId = mModelIds.get(position);
+        Cursor cursor = mEnv.getModel().getItem(modelId);
+        holder.bind(cursor, modelId, mEnv.getDisplayState());
+
+        final String docMimeType = getCursorString(cursor, Document.COLUMN_MIME_TYPE);
+        final int docFlags = getCursorInt(cursor, Document.COLUMN_FLAGS);
+
+        holder.setSelected(mEnv.isSelected(modelId));
+        holder.setEnabled(mEnv.isDocumentEnabled(docMimeType, docFlags));
+
+        mEnv.onBindDocumentHolder(holder, cursor);
+    }
+
+    @Override
+    public int getItemCount() {
+        return mModelIds.size();
+    }
+
+    @Override
+    public void onModelUpdate(Model model) {
+        if (DEBUG && mHiddenIds.size() > 0) {
+            Log.d(TAG, "Updating model with hidden ids: " + mHiddenIds);
+        }
+
+        List<String> modelIds = model.getModelIds();
+        mModelIds = new ArrayList<>(modelIds.size());
+        for (String id : modelIds) {
+            if (!mHiddenIds.contains(id)) {
+                mModelIds.add(id);
+            } else {
+                if (DEBUG) Log.d(TAG, "Omitting hidden id from model during update: " + id);
+            }
+        }
+
+        // Finally remove any hidden ids that aren't present in the model.
+        // This assumes that model updates represent a complete set of files.
+        mHiddenIds.retainAll(mModelIds);
+    }
+
+    @Override
+    public void onModelUpdateFailed(Exception e) {
+        Log.w(TAG, "Model update failed.", e);
+        mModelIds.clear();
+    }
+
+    @Override
+    public String getModelId(int adapterPosition) {
+        return mModelIds.get(adapterPosition);
+    }
+
+    @Override
+    public SparseArray<String> hide(String... ids) {
+        if (DEBUG) Log.d(TAG, "Hiding ids: " + ids);
+        Set<String> toHide = Sets.newHashSet(ids);
+
+        // Proceed backwards through the list of items, because each removal causes the
+        // positions of all subsequent items to change.
+        SparseArray<String> hiddenItems = new SparseArray<>();
+        for (int i = mModelIds.size() - 1; i >= 0; --i) {
+            String id = mModelIds.get(i);
+            if (toHide.contains(id)) {
+                mHiddenIds.add(id);
+                hiddenItems.put(i, mModelIds.remove(i));
+                notifyItemRemoved(i);
+            }
+        }
+
+        return hiddenItems;
+    }
+
+    @Override
+    public void unhide(SparseArray<String> ids) {
+        if (DEBUG) Log.d(TAG, "Un-iding ids: " + ids);
+        // Proceed backwards through the list of items, because each addition causes the
+        // positions of all subsequent items to change.
+        for (int i = ids.size() - 1; i >= 0; --i) {
+            int pos = ids.keyAt(i);
+            String id = ids.get(pos);
+            mHiddenIds.remove(id);
+            mModelIds.add(pos, id);
+            notifyItemInserted(pos);
+        }
+    }
+
+    @Override
+    public List<String> getModelIds() {
+        return mModelIds;
+    }
+
+    @Override
+    public int getItemViewType(int position) {
+        return isDirectory(mEnv.getModel(), position)
+                ? ITEM_TYPE_DIRECTORY
+                : ITEM_TYPE_DOCUMENT;
+    }
+
+    @Override
+    public void notifyItemSelectionChanged(String id) {
+        int position = mModelIds.indexOf(id);
+
+        if (position >= 0) {
+            notifyItemChanged(position, SELECTION_CHANGED_MARKER);
+        } else {
+            Log.w(TAG, "Item change notification received for unknown item: " + id);
+        }
+    }
+}
diff --git a/packages/DocumentsUI/src/com/android/documentsui/dirlist/MultiSelectManager.java b/packages/DocumentsUI/src/com/android/documentsui/dirlist/MultiSelectManager.java
index e47af67..4b3bf1e 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/dirlist/MultiSelectManager.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/dirlist/MultiSelectManager.java
@@ -75,9 +75,6 @@
 
     private boolean mSingleSelect;
 
-    // Payloads for notifyItemChange to distinguish between selection and other events.
-    public static final String SELECTION_CHANGED_MARKER = "Selection-Changed";
-
     @Nullable private BandController mBandManager;
 
     /**
@@ -339,7 +336,10 @@
             if (DEBUG) Log.d(TAG, "Ignoring toggle for element with no position.");
             return;
         }
-        toggleSelection(mEnvironment.getModelIdFromAdapterPosition(position));
+        String id = mEnvironment.getModelIdFromAdapterPosition(position);
+        if (id != null) {
+            toggleSelection(id);
+        }
     }
 
     /**
@@ -348,6 +348,7 @@
      * @param modelId
      */
     public void toggleSelection(String modelId) {
+        checkNotNull(modelId);
         boolean changed = false;
         if (mSelection.contains(modelId)) {
             changed = attemptDeselect(modelId);
@@ -405,6 +406,10 @@
         checkState(end >= begin);
         for (int i = begin; i <= end; i++) {
             String id = mEnvironment.getModelIdFromAdapterPosition(i);
+            if (id == null) {
+                continue;
+            }
+
             if (selected) {
                 boolean canSelect = notifyBeforeItemStateChange(id, true);
                 if (canSelect) {
@@ -436,6 +441,7 @@
      * @return True if the update was applied.
      */
     private boolean attemptDeselect(String id) {
+        checkArgument(id != null);
         if (notifyBeforeItemStateChange(id, false)) {
             mSelection.remove(id);
             notifyItemStateChanged(id, false);
@@ -462,6 +468,7 @@
      * (identified by {@code position}) changes.
      */
     private void notifyItemStateChanged(String id, boolean selected) {
+        checkArgument(id != null);
         int lastListener = mCallbacks.size() - 1;
         for (int i = lastListener; i > -1; i--) {
             mCallbacks.get(i).onItemStateChanged(id, selected);
@@ -613,7 +620,7 @@
          * @param id
          * @return true if the position is currently selected.
          */
-        public boolean contains(String id) {
+        public boolean contains(@Nullable String id) {
             return mTotalSelection.contains(id);
         }
 
@@ -804,7 +811,12 @@
         int getChildCount();
         int getVisibleChildCount();
         void focusItem(int position);
-        String getModelIdFromAdapterPosition(int position);
+        /**
+         * Returns null if non-useful item.
+         * @param position
+         * @return
+         */
+        @Nullable String getModelIdFromAdapterPosition(int position);
         int getItemCount();
         List<String> getModelIds();
         void notifyItemChanged(String id);
@@ -818,11 +830,11 @@
         private final Drawable mBand;
 
         private boolean mIsOverlayShown = false;
-        private DirectoryFragment.DocumentsAdapter mAdapter;
+        private DocumentsAdapter mAdapter;
 
         RuntimeSelectionEnvironment(RecyclerView rv) {
             mView = rv;
-            mAdapter = (DirectoryFragment.DocumentsAdapter) rv.getAdapter();
+            mAdapter = (DocumentsAdapter) rv.getAdapter();
             mBand = mView.getContext().getTheme().getDrawable(R.drawable.band_select_overlay);
         }
 
@@ -841,7 +853,7 @@
         }
 
         @Override
-        public String getModelIdFromAdapterPosition(int position) {
+        public @Nullable String getModelIdFromAdapterPosition(int position) {
             return mAdapter.getModelId(position);
         }
 
@@ -964,7 +976,7 @@
 
         @Override
         public void notifyItemChanged(String id) {
-            mAdapter.notifyItemChanged(id, SELECTION_CHANGED_MARKER);
+            mAdapter.notifyItemSelectionChanged(id);
         }
 
         @Override
diff --git a/packages/DocumentsUI/src/com/android/documentsui/dirlist/SectionBreakDocumentsAdapterWrapper.java b/packages/DocumentsUI/src/com/android/documentsui/dirlist/SectionBreakDocumentsAdapterWrapper.java
new file mode 100644
index 0000000..ae6ada9
--- /dev/null
+++ b/packages/DocumentsUI/src/com/android/documentsui/dirlist/SectionBreakDocumentsAdapterWrapper.java
@@ -0,0 +1,211 @@
+/*
+ * Copyright (C) 2015 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.dirlist;
+
+import static com.android.internal.util.Preconditions.checkArgument;
+
+import android.support.v7.widget.GridLayoutManager;
+import android.support.v7.widget.RecyclerView.AdapterDataObserver;
+import android.util.SparseArray;
+import android.view.ViewGroup;
+
+import java.util.List;
+
+/**
+ * Adapter wrapper that inserts a sort of line break item between directories and regular files.
+ * Only needs to be used in GRID mode...at this time.
+ */
+final class SectionBreakDocumentsAdapterWrapper extends DocumentsAdapter {
+
+    private static final String TAG = "SectionBreakDocumentsAdapterWrapper";
+    private static final int ITEM_TYPE_SECTION_BREAK = Integer.MAX_VALUE;
+
+    private final Environment mEnv;
+    private final DocumentsAdapter mDelegate;
+
+    private int mBreakPosition = -1;
+
+    SectionBreakDocumentsAdapterWrapper(Environment environment, DocumentsAdapter delegate) {
+        mEnv = environment;
+        mDelegate = delegate;
+
+        // Events and information flows two ways between recycler view and adapter.
+        // So we need to listen to events on our delegate and forward them
+        // to our listeners with a corrected position.
+        AdapterDataObserver adapterDataObserver = new AdapterDataObserver() {
+            public void onChanged() {
+                throw new UnsupportedOperationException();
+            }
+
+            public void onItemRangeChanged(int positionStart, int itemCount) {
+                checkArgument(itemCount == 1);
+            }
+
+            public void onItemRangeInserted(int positionStart, int itemCount) {
+                checkArgument(itemCount == 1);
+                if (positionStart < mBreakPosition) {
+                    mBreakPosition++;
+                }
+                notifyItemRangeInserted(toViewPosition(positionStart), itemCount);
+            }
+
+            public void onItemRangeRemoved(int positionStart, int itemCount) {
+                checkArgument(itemCount == 1);
+                if (positionStart < mBreakPosition) {
+                    mBreakPosition--;
+                }
+                notifyItemRangeRemoved(toViewPosition(positionStart), itemCount);
+            }
+
+            public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
+                throw new UnsupportedOperationException();
+            }
+        };
+
+        mDelegate.registerAdapterDataObserver(adapterDataObserver);
+    }
+
+    public GridLayoutManager.SpanSizeLookup createSpanSizeLookup() {
+        return new GridLayoutManager.SpanSizeLookup() {
+            @Override
+            public int getSpanSize(int position) {
+                // Make layout whitespace span the grid. This has the effect of breaking
+                // grid rows whenever layout whitespace is encountered.
+                if (getItemViewType(position) == ITEM_TYPE_SECTION_BREAK) {
+                    return mEnv.getColumnCount();
+                } else {
+                    return 1;
+                }
+            }
+        };
+    }
+
+    @Override
+    public DocumentHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+        if (viewType == ITEM_TYPE_SECTION_BREAK) {
+            return new EmptyDocumentHolder(mEnv.getContext());
+        } else {
+            return mDelegate.createViewHolder(parent, viewType);
+        }
+    }
+
+    @Override
+    public void onBindViewHolder(DocumentHolder holder, int p, List<Object> payload) {
+        if (holder.getItemViewType() != ITEM_TYPE_SECTION_BREAK) {
+            mDelegate.onBindViewHolder(holder, toDelegatePosition(p), payload);
+        }
+    }
+
+    @Override
+    public void onBindViewHolder(DocumentHolder holder, int p) {
+        if (holder.getItemViewType() != ITEM_TYPE_SECTION_BREAK) {
+            mDelegate.onBindViewHolder(holder, toDelegatePosition(p));
+        }
+    }
+
+    @Override
+    public int getItemCount() {
+        return mBreakPosition == -1
+                ? mDelegate.getItemCount()
+                : mDelegate.getItemCount() + 1;
+    }
+
+    @Override
+    public void onModelUpdate(Model model) {
+        mDelegate.onModelUpdate(model);
+        mBreakPosition = -1;
+
+        // Walk down the list of IDs till we encounter something that's not a directory, and
+        // insert a whitespace element - this introduces a visual break in the grid between
+        // folders and documents.
+        // TODO: This code makes assumptions about the model, namely, that it performs a
+        // bucketed sort where directories will always be ordered before other files. CBB.
+        List<String> modelIds = mDelegate.getModelIds();
+        for (int i = 0; i < modelIds.size(); i++) {
+            if (!isDirectory(model, i)) {
+                mBreakPosition = i;
+                break;
+            }
+        }
+    }
+
+    @Override
+    public void onModelUpdateFailed(Exception e) {
+        mDelegate.onModelUpdateFailed(e);
+    }
+
+    @Override
+    public int getItemViewType(int p) {
+        if (p == mBreakPosition) {
+            return ITEM_TYPE_SECTION_BREAK;
+        } else {
+            return mDelegate.getItemViewType(toDelegatePosition(p));
+        }
+    }
+
+    /**
+     * Returns the position of an item in the delegate, adjusting
+     * values that are greater than the break position.
+     *
+     * @param p Position within the view
+     * @return Position within the delegate
+     */
+    private int toDelegatePosition(int p) {
+        return (mBreakPosition != -1 && p > mBreakPosition) ? p - 1 : p;
+    }
+
+    /**
+     * Returns the position of an item in the view, adjusting
+     * values that are greater than the break position.
+     *
+     * @param p Position within the delegate
+     * @return Position within the view
+     */
+    private int toViewPosition(int p) {
+        // If position is greater than or equal to the break, increase by one.
+        return (mBreakPosition != -1 && p >= mBreakPosition) ? p + 1 : p;
+    }
+
+    @Override
+    public SparseArray<String> hide(String... ids) {
+        // NOTE: We hear about these changes and adjust break position
+        // in our AdapterDataObserver.
+        return mDelegate.hide(ids);
+    }
+
+    @Override
+    void unhide(SparseArray<String> ids) {
+        // NOTE: We hear about these changes and adjust break position
+        // in our AdapterDataObserver.
+        mDelegate.unhide(ids);
+    }
+
+    @Override
+    List<String> getModelIds() {
+        return mDelegate.getModelIds();
+    }
+
+    @Override
+    String getModelId(int p) {
+        return (p == mBreakPosition) ? null : mDelegate.getModelId(toDelegatePosition(p));
+    }
+
+    @Override
+    public void notifyItemSelectionChanged(String id) {
+        mDelegate.notifyItemSelectionChanged(id);
+    }
+}
diff --git a/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/ModelBackedDocumentsAdapterTest.java b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/ModelBackedDocumentsAdapterTest.java
new file mode 100644
index 0000000..92668a8
--- /dev/null
+++ b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/ModelBackedDocumentsAdapterTest.java
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2015 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.dirlist;
+
+import android.content.Context;
+import android.database.Cursor;
+import android.support.v7.widget.RecyclerView;
+import android.test.AndroidTestCase;
+import android.test.suitebuilder.annotation.SmallTest;
+import android.view.ViewGroup;
+
+import com.android.documentsui.State;
+
+import java.util.List;
+
+@SmallTest
+public class ModelBackedDocumentsAdapterTest extends AndroidTestCase {
+
+    private static final String AUTHORITY = "test_authority";
+    private static final String[] NAMES = new String[] {
+            "4",
+            "foo",
+            "1",
+            "bar",
+            "*(Ljifl;a",
+            "0",
+            "baz",
+            "2",
+            "3",
+            "%$%VD"
+    };
+
+    private TestModel model;
+    private ModelBackedDocumentsAdapter adapter;
+
+    public void setUp() {
+
+        final Context testContext = TestContext.createStorageTestContext(getContext(), AUTHORITY);
+        model = new TestModel(testContext, AUTHORITY);
+        model.update(NAMES);
+
+        DocumentsAdapter.Environment env = new TestEnvironment(testContext);
+
+        adapter = new ModelBackedDocumentsAdapter(
+                env, new IconHelper(testContext, State.MODE_GRID));
+        adapter.onModelUpdate(model);
+    }
+
+    // Tests that the item count is correct.
+    public void testItemCount() {
+        assertEquals(model.getItemCount(), adapter.getItemCount());
+    }
+
+    // Tests that the item count is correct.
+    public void testHide_ItemCount() {
+        List<String> ids = model.getModelIds();
+        adapter.hide(ids.get(0), ids.get(1));
+        assertEquals(model.getItemCount() - 2, adapter.getItemCount());
+    }
+
+    private final class TestEnvironment implements DocumentsAdapter.Environment {
+        private final Context testContext;
+
+        private TestEnvironment(Context testContext) {
+            this.testContext = testContext;
+        }
+
+        @Override
+        public boolean isSelected(String id) {
+            return false;
+        }
+
+        @Override
+        public boolean isDocumentEnabled(String mimeType, int flags) {
+            return true;
+        }
+
+        @Override
+        public void initDocumentHolder(DocumentHolder holder) {}
+
+        @Override
+        public Model getModel() {
+            return model;
+        }
+
+        @Override
+        public State getDisplayState() {
+            return null;
+        }
+
+        @Override
+        public Context getContext() {
+            return testContext;
+        }
+
+        @Override
+        public int getColumnCount() {
+            return 4;
+        }
+
+        @Override
+        public void onBindDocumentHolder(DocumentHolder holder, Cursor cursor) {}
+    }
+
+    private static class DummyListener implements Model.UpdateListener {
+        public void onModelUpdate(Model model) {}
+        public void onModelUpdateFailed(Exception e) {}
+    }
+
+    private static class DummyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
+        public int getItemCount() { return 0; }
+        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {}
+        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+            return null;
+        }
+    }
+}
diff --git a/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/ModelTest.java b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/ModelTest.java
index 121eb41..bed7c9c 100644
--- a/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/ModelTest.java
+++ b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/ModelTest.java
@@ -21,16 +21,10 @@
 import android.content.ContextWrapper;
 import android.database.Cursor;
 import android.database.MatrixCursor;
-import android.net.Uri;
-import android.os.Bundle;
-import android.provider.DocumentsContract;
 import android.provider.DocumentsContract.Document;
-import android.support.v7.widget.RecyclerView;
 import android.test.AndroidTestCase;
-import android.test.mock.MockContentProvider;
 import android.test.mock.MockContentResolver;
 import android.test.suitebuilder.annotation.SmallTest;
-import android.view.ViewGroup;
 
 import com.android.documentsui.DirectoryResult;
 import com.android.documentsui.RootCursorWrapper;
@@ -49,6 +43,7 @@
 
     private static final int ITEM_COUNT = 10;
     private static final String AUTHORITY = "test_authority";
+
     private static final String[] COLUMNS = new String[]{
         RootCursorWrapper.COLUMN_AUTHORITY,
         Document.COLUMN_DOCUMENT_ID,
@@ -57,23 +52,24 @@
         Document.COLUMN_SIZE,
         Document.COLUMN_MIME_TYPE
     };
-    private static Cursor cursor;
 
+    private static final String[] NAMES = new String[] {
+            "4",
+            "foo",
+            "1",
+            "bar",
+            "*(Ljifl;a",
+            "0",
+            "baz",
+            "2",
+            "3",
+            "%$%VD"
+        };
+
+    private Cursor cursor;
     private Context context;
     private Model model;
     private TestContentProvider provider;
-    private static final String[] NAMES = new String[] {
-        "4",
-        "foo",
-        "1",
-        "bar",
-        "*(Ljifl;a",
-        "0",
-        "baz",
-        "2",
-        "3",
-        "%$%VD"
-    };
 
     public void setUp() {
         setupTestContext();
@@ -97,7 +93,7 @@
         r.cursor = cursor;
 
         // Instantiate the model with a dummy view adapter and listener that (for now) do nothing.
-        model = new Model(context, new DummyAdapter());
+        model = new Model(context);
         model.addUpdateListener(new DummyListener());
         model.update(r);
     }
@@ -326,32 +322,4 @@
         public void onModelUpdate(Model model) {}
         public void onModelUpdateFailed(Exception e) {}
     }
-
-    private static class DummyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
-        public int getItemCount() { return 0; }
-        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {}
-        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
-            return null;
-        }
-    }
-
-    private static class TestContentProvider extends MockContentProvider {
-        List<Uri> mDeleted = new ArrayList<>();
-
-        @Override
-        public Bundle call(String method, String arg, Bundle extras) {
-            // Intercept and log delete method calls.
-            if (DocumentsContract.METHOD_DELETE_DOCUMENT.equals(method)) {
-                final Uri documentUri = extras.getParcelable(DocumentsContract.EXTRA_URI);
-                mDeleted.add(documentUri);
-                return new Bundle();
-            } else {
-                return super.call(method, arg, extras);
-            }
-        }
-
-        public void assertWasDeleted(DocumentInfo doc) {
-            assertTrue(mDeleted.contains(doc.derivedUri));
-        }
-    }
 }
diff --git a/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestContentProvider.java b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestContentProvider.java
new file mode 100644
index 0000000..c8d424f
--- /dev/null
+++ b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestContentProvider.java
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2015 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.dirlist;
+
+import android.net.Uri;
+import android.os.Bundle;
+import android.provider.DocumentsContract;
+import android.test.mock.MockContentProvider;
+
+import com.android.documentsui.model.DocumentInfo;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A very simple test double for ContentProvider. Useful in this package only.
+ */
+class TestContentProvider extends MockContentProvider {
+    List<Uri> mDeleted = new ArrayList<>();
+
+    @Override
+    public Bundle call(String method, String arg, Bundle extras) {
+        // Intercept and log delete method calls.
+        if (DocumentsContract.METHOD_DELETE_DOCUMENT.equals(method)) {
+            final Uri documentUri = extras.getParcelable(DocumentsContract.EXTRA_URI);
+            mDeleted.add(documentUri);
+            return new Bundle();
+        } else {
+            return super.call(method, arg, extras);
+        }
+    }
+
+    public void assertWasDeleted(DocumentInfo doc) {
+        ModelTest.assertTrue(mDeleted.contains(doc.derivedUri));
+    }
+}
\ No newline at end of file
diff --git a/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestContext.java b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestContext.java
new file mode 100644
index 0000000..714062d
--- /dev/null
+++ b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestContext.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2015 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.dirlist;
+
+import android.content.ContentResolver;
+import android.content.Context;
+import android.content.ContextWrapper;
+import android.test.mock.MockContentResolver;
+
+public final class TestContext {
+
+    /**
+     * Returns a Context configured with test provider for authority.
+     */
+    static Context createStorageTestContext(Context context, String authority) {
+        final MockContentResolver testResolver = new MockContentResolver();
+        TestContentProvider provider = new TestContentProvider();
+        testResolver.addProvider(authority, provider);
+
+        return new ContextWrapper(context) {
+            @Override
+            public ContentResolver getContentResolver() {
+                return testResolver;
+            }
+        };
+    }
+}
diff --git a/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestModel.java b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestModel.java
new file mode 100644
index 0000000..f861c73
--- /dev/null
+++ b/packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestModel.java
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2015 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.dirlist;
+
+import android.content.Context;
+import android.database.MatrixCursor;
+import android.provider.DocumentsContract.Document;
+
+import com.android.documentsui.DirectoryResult;
+import com.android.documentsui.RootCursorWrapper;
+import com.android.documentsui.dirlist.MultiSelectManager.Selection;
+
+import java.util.Random;
+import java.util.Set;
+
+public class TestModel extends Model {
+
+    private static final String[] COLUMNS = new String[]{
+        RootCursorWrapper.COLUMN_AUTHORITY,
+        Document.COLUMN_DOCUMENT_ID,
+        Document.COLUMN_FLAGS,
+        Document.COLUMN_DISPLAY_NAME,
+        Document.COLUMN_SIZE,
+        Document.COLUMN_MIME_TYPE
+    };
+
+    private final String mAuthority;
+    private Set<String> mDeleted;
+
+    /**
+     * Creates a new context. context must be configured with provider for authority.
+     * @see TestContext#createStorageTestContext(Context, String).
+     */
+    public TestModel(Context context, String authority) {
+        super(context);
+        mAuthority = authority;
+    }
+
+    void update(String... names) {
+        Random rand = new Random();
+
+        MatrixCursor c = new MatrixCursor(COLUMNS);
+        for (int i = 0; i < names.length; i++) {
+            MatrixCursor.RowBuilder row = c.newRow();
+            row.add(RootCursorWrapper.COLUMN_AUTHORITY, mAuthority);
+            row.add(Document.COLUMN_DOCUMENT_ID, Integer.toString(i));
+            row.add(Document.COLUMN_FLAGS, Document.FLAG_SUPPORTS_DELETE);
+            // Generate random document names and sizes. This forces the model's internal sort code
+            // to actually do something.
+            row.add(Document.COLUMN_DISPLAY_NAME, names[i]);
+            row.add(Document.COLUMN_SIZE, rand.nextInt());
+        }
+
+        DirectoryResult r = new DirectoryResult();
+        r.cursor = c;
+        update(r);
+    }
+
+    @Override
+    public void delete(Selection selected, DeletionListener listener) {
+        for (String id : selected.getAll()) {
+            mDeleted.add(id);
+        }
+        listener.onCompletion();
+    }
+}