favorites code: simplified

src/org/geometerplus/android/fbreader/libraryService/BookCollectionShadow.java

@@ -204,6 +204,26 @@ public class BookCollectionShadow extends AbstractBookCollection implements Serv
 		}
 	}
 
+	public synchronized boolean hasFavorites() {
+		if (myInterface != null) {
+			try {
+				return myInterface.hasFavorites();
+			} catch (RemoteException e) {
+			}
+		}
+		return false;
+	}
+
+	public synchronized boolean isFavorite(Book book) {
+		if (myInterface != null) {
+			try {
+				return myInterface.isFavorite(SerializerUtil.serialize(book));
+			} catch (RemoteException e) {
+			}
+		}
+		return false;
+	}
+
 	public synchronized void setBookFavorite(Book book, boolean favorite) {
 		if (myInterface != null) {
 			try {

src/org/geometerplus/android/fbreader/libraryService/LibraryInterface.aidl

@@ -20,6 +20,9 @@ interface LibraryInterface {
 	boolean saveBook(in String book, in boolean force);
 	void removeBook(in String book, in boolean deleteFromDisk);
 	void addBookToRecentList(in String book);
+
+	boolean hasFavorites();
+	boolean isFavorite(in String book);
 	void setBookFavorite(in String book, in boolean favorite);
 
 	TextPosition getStoredPosition(in long bookId);

src/org/geometerplus/android/fbreader/libraryService/LibraryService.java

@@ -161,6 +161,14 @@ public class LibraryService extends Service {
 			myCollection.addBookToRecentList(SerializerUtil.deserializeBook(book));
 		}
 
+		public boolean hasFavorites() {
+			return myCollection.hasFavorites();
+		}
+
+		public boolean isFavorite(String book) {
+			return myCollection.isFavorite(SerializerUtil.deserializeBook(book));
+		}
+
 		public void setBookFavorite(String book, boolean favorite) {
 			myCollection.setBookFavorite(SerializerUtil.deserializeBook(book), favorite);
 		}

src/org/geometerplus/android/fbreader/libraryService/SQLiteBooksDatabase.java

@@ -691,6 +691,25 @@ final class SQLiteBooksDatabase extends BooksDatabase {
 		return ids;
 	}
 
+	protected boolean hasFavorites() {
+		final Cursor cursor = myDatabase.rawQuery(
+			"SELECT book_id FROM Favorites LIMIT 1", null
+		);
+		boolean result = cursor.moveToNext();
+		cursor.close();
+		return result;
+	}
+
+	protected boolean isFavorite(long bookId) {
+		final Cursor cursor = myDatabase.rawQuery(
+			"SELECT book_id FROM Favorites WHERE book_id = ? LIMIT 1",
+			new String[] { String.valueOf(bookId) }
+		);
+		boolean result = cursor.moveToNext();
+		cursor.close();
+		return result;
+	}
+
 	private SQLiteStatement myAddToFavoritesStatement;
 	protected void addToFavorites(long bookId) {
 		if (myAddToFavoritesStatement == null) {