src/com/android/photos/data/PhotoProvider.java - LeafOS-Project/android_packages_apps_Gallery2 - Gitiles

 /*
  * Copyright (C) 2013 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.photos.data;

 import android.content.ContentProvider;
 import android.content.ContentResolver;
 import android.content.ContentValues;
 import android.content.UriMatcher;
 import android.database.Cursor;
 import android.database.DatabaseUtils;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteOpenHelper;
 import android.database.sqlite.SQLiteStatement;
 import android.net.Uri;
 import android.os.CancellationSignal;
 import android.provider.BaseColumns;

 import java.util.ArrayList;
 import java.util.List;

 /**
  * A provider that gives access to photo and video information for media stored
  * on the server. Only media that is or will be put on the server will be
  * accessed by this provider. Use Photos.CONTENT_URI to query all photos and
  * videos. Use Albums.CONTENT_URI to query all albums. Use Metadata.CONTENT_URI
  * to query metadata about a photo or video, based on the ID of the media. Use
  * ImageCache.THUMBNAIL_CONTENT_URI, ImageCache.PREVIEW_CONTENT_URI, or
  * ImageCache.ORIGINAL_CONTENT_URI to query the path of the thumbnail, preview,
  * or original-sized image respectfully. <br/>
  * To add or update metadata, use the update function rather than insert. All
  * values for the metadata must be in the ContentValues, even if they are also
  * in the selection. The selection and selectionArgs are not used when updating
  * metadata. If the metadata values are null, the row will be deleted.
  */
 public class PhotoProvider extends ContentProvider {
     @SuppressWarnings("unused")
     private static final String TAG = PhotoProvider.class.getSimpleName();
     static final String AUTHORITY = "com.android.gallery3d.photoprovider";
     static final Uri BASE_CONTENT_URI = new Uri.Builder().scheme("content").authority(AUTHORITY)
             .build();

     /**
      * Contains columns that can be accessed via PHOTOS_CONTENT_URI.
      */
     public static interface Photos extends BaseColumns {
         /**
          * Internal database table used for basic photo information.
          */
         public static final String TABLE = "photo";
         /**
          * Content URI for basic photo and video information.
          */
         public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);
         /**
          * Identifier used on the server. Long value.
          */
         public static final String SERVER_ID = "server_id";
         /**
          * Column name for the width of the original image. Integer value.
          */
         public static final String WIDTH = "width";
         /**
          * Column name for the height of the original image. Integer value.
          */
         public static final String HEIGHT = "height";
         /**
          * Column name for the date that the original image was taken. Long
          * value indicating the milliseconds since epoch in the GMT time zone.
          */
         public static final String DATE_TAKEN = "date_taken";
         /**
          * Column name indicating the long value of the album id that this image
          * resides in. Will be NULL if it it has not been uploaded to the
          * server.
          */
         public static final String ALBUM_ID = "album_id";
         /**
          * The column name for the mime-type String.
          */
         public static final String MIME_TYPE = "mime_type";
     }

     /**
      * Contains columns and Uri for accessing album information.
      */
     public static interface Albums extends BaseColumns {
         /**
          * Internal database table used album information.
          */
         public static final String TABLE = "album";
         /**
          * Content URI for album information.
          */
         public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);
         /**
          * Parent directory or null if this is in the root.
          */
         public static final String PARENT_ID = "parent";
         /**
          * Column name for the name of the album. String value.
          */
         public static final String NAME = "name";
         /**
          * Column name for the visibility level of the album. Can be any of the
          * VISIBILITY_* values.
          */
         public static final String VISIBILITY = "visibility";
         /**
          * Column name for the server identifier for this album. NULL if the
          * server doesn't have this album yet.
          */
         public static final String SERVER_ID = "server_id";

         // Privacy values for Albums.VISIBILITY
         public static final int VISIBILITY_PRIVATE = 1;
         public static final int VISIBILITY_SHARED = 2;
         public static final int VISIBILITY_PUBLIC = 3;
     }

     /**
      * Contains columns and Uri for accessing photo and video metadata
      */
     public static interface Metadata extends BaseColumns {
         /**
          * Internal database table used metadata information.
          */
         public static final String TABLE = "metadata";
         /**
          * Content URI for photo and video metadata.
          */
         public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);
         /**
          * Foreign key to photo_id. Long value.
          */
         public static final String PHOTO_ID = "photo_id";
         /**
          * Metadata key. String value
          */
         public static final String KEY = "key";
         /**
          * Metadata value. Type is based on key.
          */
         public static final String VALUE = "value";
     }

     /**
      * Contains columns and Uri for maintaining the image cache.
      */
     public static interface ImageCache extends BaseColumns {
         /**
          * Internal database table used for the image cache
          */
         public static final String TABLE = "image_cache";

         /**
          * The image_type query parameter required for accessing a specific
          * image
          */
         public static final String IMAGE_TYPE_QUERY_PARAMETER = "image_type";

         // ImageCache.IMAGE_TYPE values
         public static final int IMAGE_TYPE_THUMBNAIL = 1;
         public static final int IMAGE_TYPE_PREVIEW = 2;
         public static final int IMAGE_TYPE_ORIGINAL = 3;

         /**
          * Content URI for retrieving image paths. The
          * IMAGE_TYPE_QUERY_PARAMETER must be used in queries.
          */
         public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);

         /**
          * Foreign key to the photos._id. Long value.
          */
         public static final String PHOTO_ID = "photos_id";
         /**
          * One of IMAGE_TYPE_* values.
          */
         public static final String IMAGE_TYPE = "image_type";
         /**
          * The String path to the image.
          */
         public static final String PATH = "path";
     };

     // SQL used within this class.
     protected static final String WHERE_ID = BaseColumns._ID + " = ?";
     protected static final String WHERE_METADATA_ID = Metadata.PHOTO_ID + " = ? AND "
             + Metadata.KEY + " = ?";

     protected static final String SELECT_ALBUM_ID = "SELECT " + Albums._ID + " FROM "
             + Albums.TABLE;
     protected static final String SELECT_PHOTO_ID = "SELECT " + Photos._ID + " FROM "
             + Photos.TABLE;
     protected static final String SELECT_PHOTO_COUNT = "SELECT COUNT(*) FROM " + Photos.TABLE;
     protected static final String DELETE_PHOTOS = "DELETE FROM " + Photos.TABLE;
     protected static final String DELETE_METADATA = "DELETE FROM " + Metadata.TABLE;
     protected static final String SELECT_METADATA_COUNT = "SELECT COUNT(*) FROM " + Metadata.TABLE;
     protected static final String WHERE = " WHERE ";
     protected static final String IN = " IN ";
     protected static final String NESTED_SELECT_START = "(";
     protected static final String NESTED_SELECT_END = ")";

     /**
      * For selecting the mime-type for an image.
      */
     private static final String[] PROJECTION_MIME_TYPE = {
         Photos.MIME_TYPE,
     };

     private SQLiteOpenHelper mOpenHelper;
     protected static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

     protected static final int MATCH_PHOTO = 1;
     protected static final int MATCH_PHOTO_ID = 2;
     protected static final int MATCH_ALBUM = 3;
     protected static final int MATCH_ALBUM_ID = 4;
     protected static final int MATCH_METADATA = 5;
     protected static final int MATCH_METADATA_ID = 6;
     protected static final int MATCH_IMAGE = 7;

     static {
         sUriMatcher.addURI(AUTHORITY, Photos.TABLE, MATCH_PHOTO);
         // match against Photos._ID
         sUriMatcher.addURI(AUTHORITY, Photos.TABLE + "/#", MATCH_PHOTO_ID);
         sUriMatcher.addURI(AUTHORITY, Albums.TABLE, MATCH_ALBUM);
         // match against Albums._ID
         sUriMatcher.addURI(AUTHORITY, Albums.TABLE + "/#", MATCH_ALBUM_ID);
         sUriMatcher.addURI(AUTHORITY, Metadata.TABLE, MATCH_METADATA);
         // match against metadata/<Metadata._ID>
         sUriMatcher.addURI(AUTHORITY, Metadata.TABLE + "/#", MATCH_METADATA_ID);
         // match against image_cache/<ImageCache.PHOTO_ID>
         sUriMatcher.addURI(AUTHORITY, ImageCache.TABLE + "/#", MATCH_IMAGE);
     }

     @Override
     public int delete(Uri uri, String selection, String[] selectionArgs) {
         int match = matchUri(uri);
         if (match == MATCH_IMAGE) {
             throw new IllegalArgumentException("Cannot delete from image cache");
         }
         selection = addIdToSelection(match, selection);
         selectionArgs = addIdToSelectionArgs(match, uri, selectionArgs);
         List<Uri> changeUris = new ArrayList<Uri>();
         int deleted = 0;
         SQLiteDatabase db = mOpenHelper.getWritableDatabase();
         db.beginTransaction();
         try {
             deleted = deleteCascade(db, match, selection, selectionArgs, changeUris, uri);
             db.setTransactionSuccessful();
         } finally {
             db.endTransaction();
         }
         for (Uri changeUri : changeUris) {
             notifyChanges(changeUri);
         }
         return deleted;
     }

     @Override
     public String getType(Uri uri) {
         Cursor cursor = query(uri, PROJECTION_MIME_TYPE, null, null, null);
         String mimeType = null;
         if (cursor.moveToNext()) {
             mimeType = cursor.getString(0);
         }
         cursor.close();
         return mimeType;
     }

     @Override
     public Uri insert(Uri uri, ContentValues values) {
         // Cannot insert into this ContentProvider
         return null;
     }

     @Override
     public boolean onCreate() {
         mOpenHelper = createDatabaseHelper();
         return true;
     }

     @Override
     public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
             String sortOrder) {
         return query(uri, projection, selection, selectionArgs, sortOrder, null);
     }

     @Override
     public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
             String sortOrder, CancellationSignal cancellationSignal) {
         int match = matchUri(uri);
         selection = addIdToSelection(match, selection);
         selectionArgs = addIdToSelectionArgs(match, uri, selectionArgs);
         String table = getTableFromMatch(match, uri);
         SQLiteDatabase db = mOpenHelper.getReadableDatabase();
         return db.query(false, table, projection, selection, selectionArgs, null, null, sortOrder,
                 null, cancellationSignal);
     }

     @Override
     public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
         int match = matchUri(uri);
         int rowsUpdated = 0;
         SQLiteDatabase db = mOpenHelper.getWritableDatabase();
         db.beginTransaction();
         try {
             if (match == MATCH_METADATA) {
                 rowsUpdated = modifyMetadata(db, values);
             } else {
                 selection = addIdToSelection(match, selection);
                 selectionArgs = addIdToSelectionArgs(match, uri, selectionArgs);
                 String table = getTableFromMatch(match, uri);
                 rowsUpdated = db.update(table, values, selection, selectionArgs);
             }
             db.setTransactionSuccessful();
         } finally {
             db.endTransaction();
         }
         notifyChanges(uri);
         return rowsUpdated;
     }

     protected static String addIdToSelection(int match, String selection) {
         String where;
         switch (match) {
             case MATCH_PHOTO_ID:
             case MATCH_ALBUM_ID:
             case MATCH_METADATA_ID:
                 where = WHERE_ID;
                 break;
             default:
                 return selection;
         }
         return DatabaseUtils.concatenateWhere(selection, where);
     }

     protected static String[] addIdToSelectionArgs(int match, Uri uri, String[] selectionArgs) {
         String[] whereArgs;
         switch (match) {
             case MATCH_PHOTO_ID:
             case MATCH_ALBUM_ID:
             case MATCH_METADATA_ID:
                 whereArgs = new String[] {
                     uri.getPathSegments().get(1),
                 };
                 break;
             default:
                 return selectionArgs;
         }
         return DatabaseUtils.appendSelectionArgs(selectionArgs, whereArgs);
     }

     protected static String[] addMetadataKeysToSelectionArgs(String[] selectionArgs, Uri uri) {
         List<String> segments = uri.getPathSegments();
         String[] additionalArgs = {
                 segments.get(1),
                 segments.get(2),
         };

         return DatabaseUtils.appendSelectionArgs(selectionArgs, additionalArgs);
     }

     protected static String getTableFromMatch(int match, Uri uri) {
         String table;
         switch (match) {
             case MATCH_PHOTO:
             case MATCH_PHOTO_ID:
                 table = Photos.TABLE;
                 break;
             case MATCH_ALBUM:
             case MATCH_ALBUM_ID:
                 table = Albums.TABLE;
                 break;
             case MATCH_METADATA:
             case MATCH_METADATA_ID:
                 table = Metadata.TABLE;
                 break;
             default:
                 throw unknownUri(uri);
         }
         return table;
     }

     protected final SQLiteOpenHelper getDatabaseHelper() {
         return mOpenHelper;
     }

     protected SQLiteOpenHelper createDatabaseHelper() {
         return new PhotoDatabase(getContext());
     }

     private int modifyMetadata(SQLiteDatabase db, ContentValues values) {
         String[] selectionArgs = {
             values.getAsString(Metadata.PHOTO_ID),
             values.getAsString(Metadata.KEY),
         };
         int rowCount;
         if (values.get(Metadata.VALUE) == null) {
             rowCount = db.delete(Metadata.TABLE, WHERE_METADATA_ID, selectionArgs);
         } else {
             rowCount = (int) DatabaseUtils.queryNumEntries(db, Metadata.TABLE, WHERE_METADATA_ID,
                     selectionArgs);
             if (rowCount > 0) {
                 db.update(Metadata.TABLE, values, WHERE_METADATA_ID, selectionArgs);
             } else {
                 db.insert(Metadata.TABLE, null, values);
                 rowCount = 1;
             }
         }
         return rowCount;
     }

     private int matchUri(Uri uri) {
         int match = sUriMatcher.match(uri);
         if (match == UriMatcher.NO_MATCH) {
             throw unknownUri(uri);
         }
         return match;
     }

     protected void notifyChanges(Uri uri) {
         ContentResolver resolver = getContext().getContentResolver();
         resolver.notifyChange(uri, null, false);
     }

     protected static IllegalArgumentException unknownUri(Uri uri) {
         return new IllegalArgumentException("Unknown Uri format: " + uri);
     }

     protected static String nestSql(String base, String columnMatch, String nested) {
         StringBuilder sql = new StringBuilder(base);
         sql.append(WHERE);
         sql.append(columnMatch);
         sql.append(IN);
         sql.append(NESTED_SELECT_START);
         sql.append(nested);
         sql.append(NESTED_SELECT_END);
         return sql.toString();
     }

     protected static String addWhere(String base, String where) {
         if (where == null || where.isEmpty()) {
             return base;
         }
         return base + WHERE + where;
     }

     protected static int deleteCascade(SQLiteDatabase db, int match, String selection,
             String[] selectionArgs, List<Uri> changeUris, Uri uri) {
         switch (match) {
             case MATCH_PHOTO:
             case MATCH_PHOTO_ID: {
                 String selectPhotoIdsSql = addWhere(SELECT_PHOTO_ID, selection);
                 deleteCascadeMetadata(db, selectPhotoIdsSql, selectionArgs, changeUris);
                 break;
             }
             case MATCH_ALBUM:
             case MATCH_ALBUM_ID: {
                 String selectAlbumIdSql = addWhere(SELECT_ALBUM_ID, selection);
                 deleteCascadePhotos(db, selectAlbumIdSql, selectionArgs, changeUris);
                 break;
             }
         }
         String table = getTableFromMatch(match, uri);
         changeUris.add(uri);
         return db.delete(table, selection, selectionArgs);
     }

     protected static void execSql(SQLiteDatabase db, String sql, String[] args) {
         if (args == null) {
             db.execSQL(sql);
         } else {
             db.execSQL(sql, args);
         }
     }

     private static void deleteCascadePhotos(SQLiteDatabase db, String albumSelect,
             String[] selectArgs, List<Uri> changeUris) {
         String selectPhotoIdSql = nestSql(SELECT_PHOTO_ID, Photos.ALBUM_ID, albumSelect);
         deleteCascadeMetadata(db, selectPhotoIdSql, selectArgs, changeUris);
         String deletePhotoSql = nestSql(DELETE_PHOTOS, Photos.ALBUM_ID, albumSelect);
         SQLiteStatement statement = db.compileStatement(deletePhotoSql);
         statement.bindAllArgsAsStrings(selectArgs);
         int deleted = statement.executeUpdateDelete();
         if (deleted > 0) {
             changeUris.add(Photos.CONTENT_URI);
         }
     }

     private static void deleteCascadeMetadata(SQLiteDatabase db, String photosSelect,
             String[] selectArgs, List<Uri> changeUris) {
         String deleteMetadataSql = nestSql(DELETE_METADATA, Metadata.PHOTO_ID, photosSelect);
         SQLiteStatement statement = db.compileStatement(deleteMetadataSql);
         statement.bindAllArgsAsStrings(selectArgs);
         int deleted = statement.executeUpdateDelete();
         if (deleted > 0) {
             changeUris.add(Metadata.CONTENT_URI);
         }
     }
 }
	/*
	* Copyright (C) 2013 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.photos.data;

	import android.content.ContentProvider;
	import android.content.ContentResolver;
	import android.content.ContentValues;
	import android.content.UriMatcher;
	import android.database.Cursor;
	import android.database.DatabaseUtils;
	import android.database.sqlite.SQLiteDatabase;
	import android.database.sqlite.SQLiteOpenHelper;
	import android.database.sqlite.SQLiteStatement;
	import android.net.Uri;
	import android.os.CancellationSignal;
	import android.provider.BaseColumns;

	import java.util.ArrayList;
	import java.util.List;

	/**
	* A provider that gives access to photo and video information for media stored
	* on the server. Only media that is or will be put on the server will be
	* accessed by this provider. Use Photos.CONTENT_URI to query all photos and
	* videos. Use Albums.CONTENT_URI to query all albums. Use Metadata.CONTENT_URI
	* to query metadata about a photo or video, based on the ID of the media. Use
	* ImageCache.THUMBNAIL_CONTENT_URI, ImageCache.PREVIEW_CONTENT_URI, or
	* ImageCache.ORIGINAL_CONTENT_URI to query the path of the thumbnail, preview,
	* or original-sized image respectfully. <br/>
	* To add or update metadata, use the update function rather than insert. All
	* values for the metadata must be in the ContentValues, even if they are also
	* in the selection. The selection and selectionArgs are not used when updating
	* metadata. If the metadata values are null, the row will be deleted.
	*/
	public class PhotoProvider extends ContentProvider {
	@SuppressWarnings("unused")
	private static final String TAG = PhotoProvider.class.getSimpleName();
	static final String AUTHORITY = "com.android.gallery3d.photoprovider";
	static final Uri BASE_CONTENT_URI = new Uri.Builder().scheme("content").authority(AUTHORITY)
	.build();

	/**
	* Contains columns that can be accessed via PHOTOS_CONTENT_URI.
	*/
	public static interface Photos extends BaseColumns {
	/**
	* Internal database table used for basic photo information.
	*/
	public static final String TABLE = "photo";
	/**
	* Content URI for basic photo and video information.
	*/
	public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);
	/**
	* Identifier used on the server. Long value.
	*/
	public static final String SERVER_ID = "server_id";
	/**
	* Column name for the width of the original image. Integer value.
	*/
	public static final String WIDTH = "width";
	/**
	* Column name for the height of the original image. Integer value.
	*/
	public static final String HEIGHT = "height";
	/**
	* Column name for the date that the original image was taken. Long
	* value indicating the milliseconds since epoch in the GMT time zone.
	*/
	public static final String DATE_TAKEN = "date_taken";
	/**
	* Column name indicating the long value of the album id that this image
	* resides in. Will be NULL if it it has not been uploaded to the
	* server.
	*/
	public static final String ALBUM_ID = "album_id";
	/**
	* The column name for the mime-type String.
	*/
	public static final String MIME_TYPE = "mime_type";
	}

	/**
	* Contains columns and Uri for accessing album information.
	*/
	public static interface Albums extends BaseColumns {
	/**
	* Internal database table used album information.
	*/
	public static final String TABLE = "album";
	/**
	* Content URI for album information.
	*/
	public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);
	/**
	* Parent directory or null if this is in the root.
	*/
	public static final String PARENT_ID = "parent";
	/**
	* Column name for the name of the album. String value.
	*/
	public static final String NAME = "name";
	/**
	* Column name for the visibility level of the album. Can be any of the
	* VISIBILITY_* values.
	*/
	public static final String VISIBILITY = "visibility";
	/**
	* Column name for the server identifier for this album. NULL if the
	* server doesn't have this album yet.
	*/
	public static final String SERVER_ID = "server_id";

	// Privacy values for Albums.VISIBILITY
	public static final int VISIBILITY_PRIVATE = 1;
	public static final int VISIBILITY_SHARED = 2;
	public static final int VISIBILITY_PUBLIC = 3;
	}

	/**
	* Contains columns and Uri for accessing photo and video metadata
	*/
	public static interface Metadata extends BaseColumns {
	/**
	* Internal database table used metadata information.
	*/
	public static final String TABLE = "metadata";
	/**
	* Content URI for photo and video metadata.
	*/
	public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);
	/**
	* Foreign key to photo_id. Long value.
	*/
	public static final String PHOTO_ID = "photo_id";
	/**
	* Metadata key. String value
	*/
	public static final String KEY = "key";
	/**
	* Metadata value. Type is based on key.
	*/
	public static final String VALUE = "value";
	}

	/**
	* Contains columns and Uri for maintaining the image cache.
	*/
	public static interface ImageCache extends BaseColumns {
	/**
	* Internal database table used for the image cache
	*/
	public static final String TABLE = "image_cache";

	/**
	* The image_type query parameter required for accessing a specific
	* image
	*/
	public static final String IMAGE_TYPE_QUERY_PARAMETER = "image_type";

	// ImageCache.IMAGE_TYPE values
	public static final int IMAGE_TYPE_THUMBNAIL = 1;
	public static final int IMAGE_TYPE_PREVIEW = 2;
	public static final int IMAGE_TYPE_ORIGINAL = 3;

	/**
	* Content URI for retrieving image paths. The
	* IMAGE_TYPE_QUERY_PARAMETER must be used in queries.
	*/
	public static final Uri CONTENT_URI = Uri.withAppendedPath(BASE_CONTENT_URI, TABLE);

	/**
	* Foreign key to the photos._id. Long value.
	*/
	public static final String PHOTO_ID = "photos_id";
	/**
	* One of IMAGE_TYPE_* values.
	*/
	public static final String IMAGE_TYPE = "image_type";
	/**
	* The String path to the image.
	*/
	public static final String PATH = "path";
	};

	// SQL used within this class.
	protected static final String WHERE_ID = BaseColumns._ID + " = ?";
	protected static final String WHERE_METADATA_ID = Metadata.PHOTO_ID + " = ? AND "
	+ Metadata.KEY + " = ?";

	protected static final String SELECT_ALBUM_ID = "SELECT " + Albums._ID + " FROM "
	+ Albums.TABLE;
	protected static final String SELECT_PHOTO_ID = "SELECT " + Photos._ID + " FROM "
	+ Photos.TABLE;
	protected static final String SELECT_PHOTO_COUNT = "SELECT COUNT(*) FROM " + Photos.TABLE;
	protected static final String DELETE_PHOTOS = "DELETE FROM " + Photos.TABLE;
	protected static final String DELETE_METADATA = "DELETE FROM " + Metadata.TABLE;
	protected static final String SELECT_METADATA_COUNT = "SELECT COUNT(*) FROM " + Metadata.TABLE;
	protected static final String WHERE = " WHERE ";
	protected static final String IN = " IN ";
	protected static final String NESTED_SELECT_START = "(";
	protected static final String NESTED_SELECT_END = ")";

	/**
	* For selecting the mime-type for an image.
	*/
	private static final String[] PROJECTION_MIME_TYPE = {
	Photos.MIME_TYPE,
	};

	private SQLiteOpenHelper mOpenHelper;
	protected static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

	protected static final int MATCH_PHOTO = 1;
	protected static final int MATCH_PHOTO_ID = 2;
	protected static final int MATCH_ALBUM = 3;
	protected static final int MATCH_ALBUM_ID = 4;
	protected static final int MATCH_METADATA = 5;
	protected static final int MATCH_METADATA_ID = 6;
	protected static final int MATCH_IMAGE = 7;

	static {
	sUriMatcher.addURI(AUTHORITY, Photos.TABLE, MATCH_PHOTO);
	// match against Photos._ID
	sUriMatcher.addURI(AUTHORITY, Photos.TABLE + "/#", MATCH_PHOTO_ID);
	sUriMatcher.addURI(AUTHORITY, Albums.TABLE, MATCH_ALBUM);
	// match against Albums._ID
	sUriMatcher.addURI(AUTHORITY, Albums.TABLE + "/#", MATCH_ALBUM_ID);
	sUriMatcher.addURI(AUTHORITY, Metadata.TABLE, MATCH_METADATA);
	// match against metadata/<Metadata._ID>
	sUriMatcher.addURI(AUTHORITY, Metadata.TABLE + "/#", MATCH_METADATA_ID);
	// match against image_cache/<ImageCache.PHOTO_ID>
	sUriMatcher.addURI(AUTHORITY, ImageCache.TABLE + "/#", MATCH_IMAGE);
	}

	@Override
	public int delete(Uri uri, String selection, String[] selectionArgs) {
	int match = matchUri(uri);
	if (match == MATCH_IMAGE) {
	throw new IllegalArgumentException("Cannot delete from image cache");
	}
	selection = addIdToSelection(match, selection);
	selectionArgs = addIdToSelectionArgs(match, uri, selectionArgs);
	List<Uri> changeUris = new ArrayList<Uri>();
	int deleted = 0;
	SQLiteDatabase db = mOpenHelper.getWritableDatabase();
	db.beginTransaction();
	try {
	deleted = deleteCascade(db, match, selection, selectionArgs, changeUris, uri);
	db.setTransactionSuccessful();
	} finally {
	db.endTransaction();
	}
	for (Uri changeUri : changeUris) {
	notifyChanges(changeUri);
	}
	return deleted;
	}

	@Override
	public String getType(Uri uri) {
	Cursor cursor = query(uri, PROJECTION_MIME_TYPE, null, null, null);
	String mimeType = null;
	if (cursor.moveToNext()) {
	mimeType = cursor.getString(0);
	}
	cursor.close();
	return mimeType;
	}

	@Override
	public Uri insert(Uri uri, ContentValues values) {
	// Cannot insert into this ContentProvider
	return null;
	}

	@Override
	public boolean onCreate() {
	mOpenHelper = createDatabaseHelper();
	return true;
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
	String sortOrder) {
	return query(uri, projection, selection, selectionArgs, sortOrder, null);
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
	String sortOrder, CancellationSignal cancellationSignal) {
	int match = matchUri(uri);
	selection = addIdToSelection(match, selection);
	selectionArgs = addIdToSelectionArgs(match, uri, selectionArgs);
	String table = getTableFromMatch(match, uri);
	SQLiteDatabase db = mOpenHelper.getReadableDatabase();
	return db.query(false, table, projection, selection, selectionArgs, null, null, sortOrder,
	null, cancellationSignal);
	}

	@Override
	public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
	int match = matchUri(uri);
	int rowsUpdated = 0;
	SQLiteDatabase db = mOpenHelper.getWritableDatabase();
	db.beginTransaction();
	try {
	if (match == MATCH_METADATA) {
	rowsUpdated = modifyMetadata(db, values);
	} else {
	selection = addIdToSelection(match, selection);
	selectionArgs = addIdToSelectionArgs(match, uri, selectionArgs);
	String table = getTableFromMatch(match, uri);
	rowsUpdated = db.update(table, values, selection, selectionArgs);
	}
	db.setTransactionSuccessful();
	} finally {
	db.endTransaction();
	}
	notifyChanges(uri);
	return rowsUpdated;
	}

	protected static String addIdToSelection(int match, String selection) {
	String where;
	switch (match) {
	case MATCH_PHOTO_ID:
	case MATCH_ALBUM_ID:
	case MATCH_METADATA_ID:
	where = WHERE_ID;
	break;
	default:
	return selection;
	}
	return DatabaseUtils.concatenateWhere(selection, where);
	}

	protected static String[] addIdToSelectionArgs(int match, Uri uri, String[] selectionArgs) {
	String[] whereArgs;
	switch (match) {
	case MATCH_PHOTO_ID:
	case MATCH_ALBUM_ID:
	case MATCH_METADATA_ID:
	whereArgs = new String[] {
	uri.getPathSegments().get(1),
	};
	break;
	default:
	return selectionArgs;
	}
	return DatabaseUtils.appendSelectionArgs(selectionArgs, whereArgs);
	}

	protected static String[] addMetadataKeysToSelectionArgs(String[] selectionArgs, Uri uri) {
	List<String> segments = uri.getPathSegments();
	String[] additionalArgs = {
	segments.get(1),
	segments.get(2),
	};

	return DatabaseUtils.appendSelectionArgs(selectionArgs, additionalArgs);
	}

	protected static String getTableFromMatch(int match, Uri uri) {
	String table;
	switch (match) {
	case MATCH_PHOTO:
	case MATCH_PHOTO_ID:
	table = Photos.TABLE;
	break;
	case MATCH_ALBUM:
	case MATCH_ALBUM_ID:
	table = Albums.TABLE;
	break;
	case MATCH_METADATA:
	case MATCH_METADATA_ID:
	table = Metadata.TABLE;
	break;
	default:
	throw unknownUri(uri);
	}
	return table;
	}

	protected final SQLiteOpenHelper getDatabaseHelper() {
	return mOpenHelper;
	}

	protected SQLiteOpenHelper createDatabaseHelper() {
	return new PhotoDatabase(getContext());
	}

	private int modifyMetadata(SQLiteDatabase db, ContentValues values) {
	String[] selectionArgs = {
	values.getAsString(Metadata.PHOTO_ID),
	values.getAsString(Metadata.KEY),
	};
	int rowCount;
	if (values.get(Metadata.VALUE) == null) {
	rowCount = db.delete(Metadata.TABLE, WHERE_METADATA_ID, selectionArgs);
	} else {
	rowCount = (int) DatabaseUtils.queryNumEntries(db, Metadata.TABLE, WHERE_METADATA_ID,
	selectionArgs);
	if (rowCount > 0) {
	db.update(Metadata.TABLE, values, WHERE_METADATA_ID, selectionArgs);
	} else {
	db.insert(Metadata.TABLE, null, values);
	rowCount = 1;
	}
	}
	return rowCount;
	}

	private int matchUri(Uri uri) {
	int match = sUriMatcher.match(uri);
	if (match == UriMatcher.NO_MATCH) {
	throw unknownUri(uri);
	}
	return match;
	}

	protected void notifyChanges(Uri uri) {
	ContentResolver resolver = getContext().getContentResolver();
	resolver.notifyChange(uri, null, false);
	}

	protected static IllegalArgumentException unknownUri(Uri uri) {
	return new IllegalArgumentException("Unknown Uri format: " + uri);
	}

	protected static String nestSql(String base, String columnMatch, String nested) {
	StringBuilder sql = new StringBuilder(base);
	sql.append(WHERE);
	sql.append(columnMatch);
	sql.append(IN);
	sql.append(NESTED_SELECT_START);
	sql.append(nested);
	sql.append(NESTED_SELECT_END);
	return sql.toString();
	}

	protected static String addWhere(String base, String where) {
	if (where == null \|\| where.isEmpty()) {
	return base;
	}
	return base + WHERE + where;
	}

	protected static int deleteCascade(SQLiteDatabase db, int match, String selection,
	String[] selectionArgs, List<Uri> changeUris, Uri uri) {
	switch (match) {
	case MATCH_PHOTO:
	case MATCH_PHOTO_ID: {
	String selectPhotoIdsSql = addWhere(SELECT_PHOTO_ID, selection);
	deleteCascadeMetadata(db, selectPhotoIdsSql, selectionArgs, changeUris);
	break;
	}
	case MATCH_ALBUM:
	case MATCH_ALBUM_ID: {
	String selectAlbumIdSql = addWhere(SELECT_ALBUM_ID, selection);
	deleteCascadePhotos(db, selectAlbumIdSql, selectionArgs, changeUris);
	break;
	}
	}
	String table = getTableFromMatch(match, uri);
	changeUris.add(uri);
	return db.delete(table, selection, selectionArgs);
	}

	protected static void execSql(SQLiteDatabase db, String sql, String[] args) {
	if (args == null) {
	db.execSQL(sql);
	} else {
	db.execSQL(sql, args);
	}
	}

	private static void deleteCascadePhotos(SQLiteDatabase db, String albumSelect,
	String[] selectArgs, List<Uri> changeUris) {
	String selectPhotoIdSql = nestSql(SELECT_PHOTO_ID, Photos.ALBUM_ID, albumSelect);
	deleteCascadeMetadata(db, selectPhotoIdSql, selectArgs, changeUris);
	String deletePhotoSql = nestSql(DELETE_PHOTOS, Photos.ALBUM_ID, albumSelect);
	SQLiteStatement statement = db.compileStatement(deletePhotoSql);
	statement.bindAllArgsAsStrings(selectArgs);
	int deleted = statement.executeUpdateDelete();
	if (deleted > 0) {
	changeUris.add(Photos.CONTENT_URI);
	}
	}

	private static void deleteCascadeMetadata(SQLiteDatabase db, String photosSelect,
	String[] selectArgs, List<Uri> changeUris) {
	String deleteMetadataSql = nestSql(DELETE_METADATA, Metadata.PHOTO_ID, photosSelect);
	SQLiteStatement statement = db.compileStatement(deleteMetadataSql);
	statement.bindAllArgsAsStrings(selectArgs);
	int deleted = statement.executeUpdateDelete();
	if (deleted > 0) {
	changeUris.add(Metadata.CONTENT_URI);
	}
	}
	}