src/com/android/documentsui/dirlist/Model.java - platform/packages/apps/DocumentsUI - Gitiles

 /*
  * 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.SORT_ORDER_DISPLAY_NAME;
 import static com.android.documentsui.State.SORT_ORDER_LAST_MODIFIED;
 import static com.android.documentsui.State.SORT_ORDER_SIZE;
 import static com.android.documentsui.model.DocumentInfo.getCursorLong;
 import static com.android.documentsui.model.DocumentInfo.getCursorString;
 import static com.android.internal.util.Preconditions.checkNotNull;

 import android.content.ContentProviderClient;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.database.Cursor;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.os.Looper;
 import android.provider.DocumentsContract;
 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;
 import com.android.documentsui.DirectoryResult;
 import com.android.documentsui.DocumentsApplication;
 import com.android.documentsui.RootCursorWrapper;
 import com.android.documentsui.dirlist.MultiSelectManager.Selection;
 import com.android.documentsui.model.DocumentInfo;

 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 /**
  * The data model for the current loaded directory.
  */
 @VisibleForTesting
 public class Model implements SiblingProvider {
     private static final String TAG = "Model";

     private Context mContext;
     private boolean mIsLoading;
     private List<UpdateListener> mUpdateListeners = new ArrayList<>();
     @Nullable private Cursor mCursor;
     private int mCursorCount;
     /** Maps Model ID to cursor positions, for looking up items by Model ID. */
     private Map<String, Integer> mPositions = new HashMap<>();
     /**
      * A sorted array of model IDs for the files currently in the Model.  Sort order is determined
      * by {@link #mSortOrder}
      */
     private List<String> mIds = new ArrayList<>();
     private int mSortOrder = SORT_ORDER_DISPLAY_NAME;

     @Nullable String info;
     @Nullable String error;

     Model(Context context, RecyclerView.Adapter<?> viewAdapter) {
         mContext = context;
     }

     /**
      * Generates a Model ID for a cursor entry that refers to a document. The Model ID is a unique
      * string that can be used to identify the document referred to by the cursor.
      *
      * @param c A cursor that refers to a document.
      */
     private static String createModelId(Cursor c) {
         // TODO: Maybe more efficient to use just the document ID, in cases where there is only one
         // authority (which should be the majority of cases).
         return getCursorString(c, RootCursorWrapper.COLUMN_AUTHORITY) +
                 "|" + getCursorString(c, Document.COLUMN_DOCUMENT_ID);
     }

     private void notifyUpdateListeners() {
         for (UpdateListener listener: mUpdateListeners) {
             listener.onModelUpdate(this);
         }
     }

     private void notifyUpdateListeners(Exception e) {
         for (UpdateListener listener: mUpdateListeners) {
             listener.onModelUpdateFailed(e);
         }
     }

     void update(DirectoryResult result) {
         if (DEBUG) Log.i(TAG, "Updating model with new result set.");

         if (result == null) {
             mCursor = null;
             mCursorCount = 0;
             mIds.clear();
             mPositions.clear();
             info = null;
             error = null;
             mIsLoading = false;
             notifyUpdateListeners();
             return;
         }

         if (result.exception != null) {
             Log.e(TAG, "Error while loading directory contents", result.exception);
             notifyUpdateListeners(result.exception);
             return;
         }

         mCursor = result.cursor;
         mCursorCount = mCursor.getCount();
         mSortOrder = result.sortOrder;

         updateModelData();

         final Bundle extras = mCursor.getExtras();
         if (extras != null) {
             info = extras.getString(DocumentsContract.EXTRA_INFO);
             error = extras.getString(DocumentsContract.EXTRA_ERROR);
             mIsLoading = extras.getBoolean(DocumentsContract.EXTRA_LOADING, false);
         }

         notifyUpdateListeners();
     }

     @VisibleForTesting
     int getItemCount() {
         return mCursorCount;
     }

     /**
      * Scan over the incoming cursor data, generate Model IDs for each row, and sort the IDs
      * according to the current sort order.
      */
     private void updateModelData() {
         int[] positions = new int[mCursorCount];
         mIds.clear();
         String[] strings = null;
         long[] longs = null;

         switch (mSortOrder) {
             case SORT_ORDER_DISPLAY_NAME:
                 strings = new String[mCursorCount];
                 break;
             case SORT_ORDER_LAST_MODIFIED:
             case SORT_ORDER_SIZE:
                 longs = new long[mCursorCount];
                 break;
         }

         mCursor.moveToPosition(-1);
         for (int pos = 0; pos < mCursorCount; ++pos) {
             mCursor.moveToNext();
             positions[pos] = pos;
             mIds.add(createModelId(mCursor));

             switch(mSortOrder) {
                 case SORT_ORDER_DISPLAY_NAME:
                     final String mimeType = getCursorString(mCursor, Document.COLUMN_MIME_TYPE);
                     final String displayName = getCursorString(
                             mCursor, Document.COLUMN_DISPLAY_NAME);
                     if (Document.MIME_TYPE_DIR.equals(mimeType)) {
                         strings[pos] = DocumentInfo.DIR_PREFIX + displayName;
                     } else {
                         strings[pos] = displayName;
                     }
                     break;
                 case SORT_ORDER_LAST_MODIFIED:
                     longs[pos] = getCursorLong(mCursor, Document.COLUMN_LAST_MODIFIED);
                     break;
                 case SORT_ORDER_SIZE:
                     longs[pos] = getCursorLong(mCursor, Document.COLUMN_SIZE);
                     break;
             }
         }

         switch (mSortOrder) {
             case SORT_ORDER_DISPLAY_NAME:
                 binarySort(positions, strings, mIds);
                 break;
             case SORT_ORDER_LAST_MODIFIED:
             case SORT_ORDER_SIZE:
                 binarySort(positions, longs, mIds);
                 break;
         }

         // Populate the positions.
         mPositions.clear();
         for (int i = 0; i < mCursorCount; ++i) {
             mPositions.put(mIds.get(i), positions[i]);
         }
     }

     /**
      * Borrowed from TimSort.binarySort(), but modified to sort three-column data set.
      */
     private static void binarySort(int[] positions, String[] strings, List<String> ids) {
         final int count = positions.length;
         for (int start = 1; start < count; start++) {
             final int pivotPosition = positions[start];
             final String pivotValue = strings[start];
             final String pivotId = ids.get(start);

             int left = 0;
             int right = start;

             while (left < right) {
                 int mid = (left + right) >>> 1;

                 final String lhs = pivotValue;
                 final String rhs = strings[mid];
                 final int compare = DocumentInfo.compareToIgnoreCaseNullable(lhs, rhs);

                 if (compare < 0) {
                     right = mid;
                 } else {
                     left = mid + 1;
                 }
             }

             int n = start - left;
             switch (n) {
                 case 2:
                     positions[left + 2] = positions[left + 1];
                     strings[left + 2] = strings[left + 1];
                     ids.set(left + 2, ids.get(left + 1));
                 case 1:
                     positions[left + 1] = positions[left];
                     strings[left + 1] = strings[left];
                     ids.set(left + 1, ids.get(left));
                     break;
                 default:
                     System.arraycopy(positions, left, positions, left + 1, n);
                     System.arraycopy(strings, left, strings, left + 1, n);
                     for (int i = n; i >= 1; --i) {
                         ids.set(left + i, ids.get(left + i - 1));
                     }
             }

             positions[left] = pivotPosition;
             strings[left] = pivotValue;
             ids.set(left, pivotId);
         }
     }

     /**
      * Borrowed from TimSort.binarySort(), but modified to sort three-column data set.
      */
    private static void binarySort(int[] positions, long[] longs, List<String> ids) {
         final int count = positions.length;
         for (int start = 1; start < count; start++) {
             final int pivotPosition = positions[start];
             final long pivotValue = longs[start];
             final String pivotId = ids.get(start);

             int left = 0;
             int right = start;

             while (left < right) {
                 int mid = (left + right) >>> 1;

                 final long lhs = pivotValue;
                 final long rhs = longs[mid];
                 // Sort in descending numerical order. This matches legacy behaviour, which yields
                 // largest or most recent items on top.
                 final int compare = -Long.compare(lhs, rhs);

                 if (compare < 0) {
                     right = mid;
                 } else {
                     left = mid + 1;
                 }
             }

             int n = start - left;
             switch (n) {
                 case 2:
                     positions[left + 2] = positions[left + 1];
                     longs[left + 2] = longs[left + 1];
                     ids.set(left + 2, ids.get(left + 1));
                 case 1:
                     positions[left + 1] = positions[left];
                     longs[left + 1] = longs[left];
                     ids.set(left + 1, ids.get(left));
                     break;
                 default:
                     System.arraycopy(positions, left, positions, left + 1, n);
                     System.arraycopy(longs, left, longs, left + 1, n);
                     for (int i = n; i >= 1; --i) {
                         ids.set(left + i, ids.get(left + i - 1));
                     }
             }

             positions[left] = pivotPosition;
             longs[left] = pivotValue;
             ids.set(left, pivotId);
         }
     }

     @Nullable Cursor getItem(String modelId) {
         Integer pos = mPositions.get(modelId);
         if (pos != null) {
             mCursor.moveToPosition(pos);
             return mCursor;
         }
         return null;
     }

     boolean isEmpty() {
         return mCursorCount == 0;
     }

     boolean isLoading() {
         return mIsLoading;
     }

     List<DocumentInfo> getDocuments(Selection items) {
         final int size = (items != null) ? items.size() : 0;

         final List<DocumentInfo> docs =  new ArrayList<>(size);
         for (String modelId: items.getAll()) {
             final Cursor cursor = getItem(modelId);
             checkNotNull(cursor, "Cursor cannot be null.");
             final DocumentInfo doc = DocumentInfo.fromDirectoryCursor(cursor);
             docs.add(doc);
         }
         return docs;
     }

     @Override
     public Cursor getCursor() {
         if (Looper.myLooper() != Looper.getMainLooper()) {
             throw new IllegalStateException("Can't call getCursor from non-main thread.");
         }
         return mCursor;
     }

     public void delete(Selection selected, DeletionListener listener) {
         final ContentResolver resolver = mContext.getContentResolver();
         new DeleteFilesTask(resolver, listener).execute(selected);
     }

     /**
      * A Task which collects the DocumentInfo for documents that have been marked for deletion,
      * and actually deletes them.
      */
     private class DeleteFilesTask extends AsyncTask<Selection, Void, Void> {
         private ContentResolver mResolver;
         private DeletionListener mListener;
         private boolean mHadTrouble;

         /**
          * @param resolver A ContentResolver for performing the actual file deletions.
          * @param errorCallback A Runnable that is executed in the event that one or more errors
          *     occurred while copying files.  Execution will occur on the UI thread.
          */
         public DeleteFilesTask(ContentResolver resolver, DeletionListener listener) {
             mResolver = resolver;
             mListener = listener;
         }

         @Override
         protected Void doInBackground(Selection... selected) {
             List<DocumentInfo> toDelete = getDocuments(selected[0]);
             mHadTrouble = false;

             for (DocumentInfo doc : toDelete) {
                 if (!doc.isDeleteSupported()) {
                     Log.w(TAG, doc + " could not be deleted.  Skipping...");
                     mHadTrouble = true;
                     continue;
                 }

                 ContentProviderClient client = null;
                 try {
                     if (DEBUG) Log.d(TAG, "Deleting: " + doc.displayName);
                     client = DocumentsApplication.acquireUnstableProviderOrThrow(
                         mResolver, doc.derivedUri.getAuthority());
                     DocumentsContract.deleteDocument(client, doc.derivedUri);
                 } catch (Exception e) {
                     Log.w(TAG, "Failed to delete " + doc, e);
                     mHadTrouble = true;
                 } finally {
                     ContentProviderClient.releaseQuietly(client);
                 }
             }

             return null;
         }

         @Override
         protected void onPostExecute(Void _) {
             if (mHadTrouble) {
                 // TODO show which files failed? b/23720103
                 mListener.onError();
                 if (DEBUG) Log.d(TAG, "Deletion task completed.  Some deletions failed.");
             } else {
                 if (DEBUG) Log.d(TAG, "Deletion task completed successfully.");
             }

             mListener.onCompletion();
         }
     }

     static class DeletionListener {
         /**
          * Called when deletion has completed (regardless of whether an error occurred).
          */
         void onCompletion() {}

         /**
          * Called at the end of a deletion operation that produced one or more errors.
          */
         void onError() {}
     }

     void addUpdateListener(UpdateListener listener) {
         mUpdateListeners.add(listener);
     }

     static interface UpdateListener {
         /**
          * Called when a successful update has occurred.
          */
         void onModelUpdate(Model model);

         /**
          * Called when an update has been attempted but failed.
          */
         void onModelUpdateFailed(Exception e);
     }

     /**
      * @return An ordered array of model IDs representing the documents in the model. It is sorted
      *         according to the current sort order, which was set by the last model update.
      */
     public List<String> getModelIds() {
         return mIds;
     }
 }
	/*
	* 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.SORT_ORDER_DISPLAY_NAME;
	import static com.android.documentsui.State.SORT_ORDER_LAST_MODIFIED;
	import static com.android.documentsui.State.SORT_ORDER_SIZE;
	import static com.android.documentsui.model.DocumentInfo.getCursorLong;
	import static com.android.documentsui.model.DocumentInfo.getCursorString;
	import static com.android.internal.util.Preconditions.checkNotNull;

	import android.content.ContentProviderClient;
	import android.content.ContentResolver;
	import android.content.Context;
	import android.database.Cursor;
	import android.os.AsyncTask;
	import android.os.Bundle;
	import android.os.Looper;
	import android.provider.DocumentsContract;
	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;
	import com.android.documentsui.DirectoryResult;
	import com.android.documentsui.DocumentsApplication;
	import com.android.documentsui.RootCursorWrapper;
	import com.android.documentsui.dirlist.MultiSelectManager.Selection;
	import com.android.documentsui.model.DocumentInfo;

	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;

	/**
	* The data model for the current loaded directory.
	*/
	@VisibleForTesting
	public class Model implements SiblingProvider {
	private static final String TAG = "Model";

	private Context mContext;
	private boolean mIsLoading;
	private List<UpdateListener> mUpdateListeners = new ArrayList<>();
	@Nullable private Cursor mCursor;
	private int mCursorCount;
	/** Maps Model ID to cursor positions, for looking up items by Model ID. */
	private Map<String, Integer> mPositions = new HashMap<>();
	/**
	* A sorted array of model IDs for the files currently in the Model. Sort order is determined
	* by {@link #mSortOrder}
	*/
	private List<String> mIds = new ArrayList<>();
	private int mSortOrder = SORT_ORDER_DISPLAY_NAME;

	@Nullable String info;
	@Nullable String error;

	Model(Context context, RecyclerView.Adapter<?> viewAdapter) {
	mContext = context;
	}

	/**
	* Generates a Model ID for a cursor entry that refers to a document. The Model ID is a unique
	* string that can be used to identify the document referred to by the cursor.
	*
	* @param c A cursor that refers to a document.
	*/
	private static String createModelId(Cursor c) {
	// TODO: Maybe more efficient to use just the document ID, in cases where there is only one
	// authority (which should be the majority of cases).
	return getCursorString(c, RootCursorWrapper.COLUMN_AUTHORITY) +
	"\|" + getCursorString(c, Document.COLUMN_DOCUMENT_ID);
	}

	private void notifyUpdateListeners() {
	for (UpdateListener listener: mUpdateListeners) {
	listener.onModelUpdate(this);
	}
	}

	private void notifyUpdateListeners(Exception e) {
	for (UpdateListener listener: mUpdateListeners) {
	listener.onModelUpdateFailed(e);
	}
	}

	void update(DirectoryResult result) {
	if (DEBUG) Log.i(TAG, "Updating model with new result set.");

	if (result == null) {
	mCursor = null;
	mCursorCount = 0;
	mIds.clear();
	mPositions.clear();
	info = null;
	error = null;
	mIsLoading = false;
	notifyUpdateListeners();
	return;
	}

	if (result.exception != null) {
	Log.e(TAG, "Error while loading directory contents", result.exception);
	notifyUpdateListeners(result.exception);
	return;
	}

	mCursor = result.cursor;
	mCursorCount = mCursor.getCount();
	mSortOrder = result.sortOrder;

	updateModelData();

	final Bundle extras = mCursor.getExtras();
	if (extras != null) {
	info = extras.getString(DocumentsContract.EXTRA_INFO);
	error = extras.getString(DocumentsContract.EXTRA_ERROR);
	mIsLoading = extras.getBoolean(DocumentsContract.EXTRA_LOADING, false);
	}

	notifyUpdateListeners();
	}

	@VisibleForTesting
	int getItemCount() {
	return mCursorCount;
	}

	/**
	* Scan over the incoming cursor data, generate Model IDs for each row, and sort the IDs
	* according to the current sort order.
	*/
	private void updateModelData() {
	int[] positions = new int[mCursorCount];
	mIds.clear();
	String[] strings = null;
	long[] longs = null;

	switch (mSortOrder) {
	case SORT_ORDER_DISPLAY_NAME:
	strings = new String[mCursorCount];
	break;
	case SORT_ORDER_LAST_MODIFIED:
	case SORT_ORDER_SIZE:
	longs = new long[mCursorCount];
	break;
	}

	mCursor.moveToPosition(-1);
	for (int pos = 0; pos < mCursorCount; ++pos) {
	mCursor.moveToNext();
	positions[pos] = pos;
	mIds.add(createModelId(mCursor));

	switch(mSortOrder) {
	case SORT_ORDER_DISPLAY_NAME:
	final String mimeType = getCursorString(mCursor, Document.COLUMN_MIME_TYPE);
	final String displayName = getCursorString(
	mCursor, Document.COLUMN_DISPLAY_NAME);
	if (Document.MIME_TYPE_DIR.equals(mimeType)) {
	strings[pos] = DocumentInfo.DIR_PREFIX + displayName;
	} else {
	strings[pos] = displayName;
	}
	break;
	case SORT_ORDER_LAST_MODIFIED:
	longs[pos] = getCursorLong(mCursor, Document.COLUMN_LAST_MODIFIED);
	break;
	case SORT_ORDER_SIZE:
	longs[pos] = getCursorLong(mCursor, Document.COLUMN_SIZE);
	break;
	}
	}

	switch (mSortOrder) {
	case SORT_ORDER_DISPLAY_NAME:
	binarySort(positions, strings, mIds);
	break;
	case SORT_ORDER_LAST_MODIFIED:
	case SORT_ORDER_SIZE:
	binarySort(positions, longs, mIds);
	break;
	}

	// Populate the positions.
	mPositions.clear();
	for (int i = 0; i < mCursorCount; ++i) {
	mPositions.put(mIds.get(i), positions[i]);
	}
	}

	/**
	* Borrowed from TimSort.binarySort(), but modified to sort three-column data set.
	*/
	private static void binarySort(int[] positions, String[] strings, List<String> ids) {
	final int count = positions.length;
	for (int start = 1; start < count; start++) {
	final int pivotPosition = positions[start];
	final String pivotValue = strings[start];
	final String pivotId = ids.get(start);

	int left = 0;
	int right = start;

	while (left < right) {
	int mid = (left + right) >>> 1;

	final String lhs = pivotValue;
	final String rhs = strings[mid];
	final int compare = DocumentInfo.compareToIgnoreCaseNullable(lhs, rhs);

	if (compare < 0) {
	right = mid;
	} else {
	left = mid + 1;
	}
	}

	int n = start - left;
	switch (n) {
	case 2:
	positions[left + 2] = positions[left + 1];
	strings[left + 2] = strings[left + 1];
	ids.set(left + 2, ids.get(left + 1));
	case 1:
	positions[left + 1] = positions[left];
	strings[left + 1] = strings[left];
	ids.set(left + 1, ids.get(left));
	break;
	default:
	System.arraycopy(positions, left, positions, left + 1, n);
	System.arraycopy(strings, left, strings, left + 1, n);
	for (int i = n; i >= 1; --i) {
	ids.set(left + i, ids.get(left + i - 1));
	}
	}

	positions[left] = pivotPosition;
	strings[left] = pivotValue;
	ids.set(left, pivotId);
	}
	}

	/**
	* Borrowed from TimSort.binarySort(), but modified to sort three-column data set.
	*/
	private static void binarySort(int[] positions, long[] longs, List<String> ids) {
	final int count = positions.length;
	for (int start = 1; start < count; start++) {
	final int pivotPosition = positions[start];
	final long pivotValue = longs[start];
	final String pivotId = ids.get(start);

	int left = 0;
	int right = start;

	while (left < right) {
	int mid = (left + right) >>> 1;

	final long lhs = pivotValue;
	final long rhs = longs[mid];
	// Sort in descending numerical order. This matches legacy behaviour, which yields
	// largest or most recent items on top.
	final int compare = -Long.compare(lhs, rhs);

	if (compare < 0) {
	right = mid;
	} else {
	left = mid + 1;
	}
	}

	int n = start - left;
	switch (n) {
	case 2:
	positions[left + 2] = positions[left + 1];
	longs[left + 2] = longs[left + 1];
	ids.set(left + 2, ids.get(left + 1));
	case 1:
	positions[left + 1] = positions[left];
	longs[left + 1] = longs[left];
	ids.set(left + 1, ids.get(left));
	break;
	default:
	System.arraycopy(positions, left, positions, left + 1, n);
	System.arraycopy(longs, left, longs, left + 1, n);
	for (int i = n; i >= 1; --i) {
	ids.set(left + i, ids.get(left + i - 1));
	}
	}

	positions[left] = pivotPosition;
	longs[left] = pivotValue;
	ids.set(left, pivotId);
	}
	}

	@Nullable Cursor getItem(String modelId) {
	Integer pos = mPositions.get(modelId);
	if (pos != null) {
	mCursor.moveToPosition(pos);
	return mCursor;
	}
	return null;
	}

	boolean isEmpty() {
	return mCursorCount == 0;
	}

	boolean isLoading() {
	return mIsLoading;
	}

	List<DocumentInfo> getDocuments(Selection items) {
	final int size = (items != null) ? items.size() : 0;

	final List<DocumentInfo> docs = new ArrayList<>(size);
	for (String modelId: items.getAll()) {
	final Cursor cursor = getItem(modelId);
	checkNotNull(cursor, "Cursor cannot be null.");
	final DocumentInfo doc = DocumentInfo.fromDirectoryCursor(cursor);
	docs.add(doc);
	}
	return docs;
	}

	@Override
	public Cursor getCursor() {
	if (Looper.myLooper() != Looper.getMainLooper()) {
	throw new IllegalStateException("Can't call getCursor from non-main thread.");
	}
	return mCursor;
	}

	public void delete(Selection selected, DeletionListener listener) {
	final ContentResolver resolver = mContext.getContentResolver();
	new DeleteFilesTask(resolver, listener).execute(selected);
	}

	/**
	* A Task which collects the DocumentInfo for documents that have been marked for deletion,
	* and actually deletes them.
	*/
	private class DeleteFilesTask extends AsyncTask<Selection, Void, Void> {
	private ContentResolver mResolver;
	private DeletionListener mListener;
	private boolean mHadTrouble;

	/**
	* @param resolver A ContentResolver for performing the actual file deletions.
	* @param errorCallback A Runnable that is executed in the event that one or more errors
	* occurred while copying files. Execution will occur on the UI thread.
	*/
	public DeleteFilesTask(ContentResolver resolver, DeletionListener listener) {
	mResolver = resolver;
	mListener = listener;
	}

	@Override
	protected Void doInBackground(Selection... selected) {
	List<DocumentInfo> toDelete = getDocuments(selected[0]);
	mHadTrouble = false;

	for (DocumentInfo doc : toDelete) {
	if (!doc.isDeleteSupported()) {
	Log.w(TAG, doc + " could not be deleted. Skipping...");
	mHadTrouble = true;
	continue;
	}

	ContentProviderClient client = null;
	try {
	if (DEBUG) Log.d(TAG, "Deleting: " + doc.displayName);
	client = DocumentsApplication.acquireUnstableProviderOrThrow(
	mResolver, doc.derivedUri.getAuthority());
	DocumentsContract.deleteDocument(client, doc.derivedUri);
	} catch (Exception e) {
	Log.w(TAG, "Failed to delete " + doc, e);
	mHadTrouble = true;
	} finally {
	ContentProviderClient.releaseQuietly(client);
	}
	}

	return null;
	}

	@Override
	protected void onPostExecute(Void _) {
	if (mHadTrouble) {
	// TODO show which files failed? b/23720103
	mListener.onError();
	if (DEBUG) Log.d(TAG, "Deletion task completed. Some deletions failed.");
	} else {
	if (DEBUG) Log.d(TAG, "Deletion task completed successfully.");
	}

	mListener.onCompletion();
	}
	}

	static class DeletionListener {
	/**
	* Called when deletion has completed (regardless of whether an error occurred).
	*/
	void onCompletion() {}

	/**
	* Called at the end of a deletion operation that produced one or more errors.
	*/
	void onError() {}
	}

	void addUpdateListener(UpdateListener listener) {
	mUpdateListeners.add(listener);
	}

	static interface UpdateListener {
	/**
	* Called when a successful update has occurred.
	*/
	void onModelUpdate(Model model);

	/**
	* Called when an update has been attempted but failed.
	*/
	void onModelUpdateFailed(Exception e);
	}

	/**
	* @return An ordered array of model IDs representing the documents in the model. It is sorted
	* according to the current sort order, which was set by the last model update.
	*/
	public List<String> getModelIds() {
	return mIds;
	}
	}