Tuesday, June 28, 2011

Developing Mobile Learning Applications for Android using Web Services

The evolution of today's mobile devices increases the number of mobile applications devel-
oped, and among them the mobile learning applications. Mobile hardware and software plat-
forms allow running of faster and richer applications. This paper presents the main steps in
development of a distributed mobile learning application for Android. The client application
communicates with the server using Web services. The prototype developed includes the test-
ing module.
Keywords: Mobile Application, Android Operating System, Web Service
Mobile learning applications are devel-
oped using various technologies and plat-
forms. Each implementation has specific cha-
racteristics in terms of user interface and con-
tent and influences the development process.
A mobile learning system consists at least of
the following components:
 Mobile learning device;
 Mobile learning software;
 Mobile learning content.
The software required for mobile learning
process is a simple mobile Web browser or a
dedicated application, that can be standalone
or a client application.
The students' actions within an m-learning
system are to [2]:
 Take online course;
 Take exams;
 Send feedback;
 Send homework, projects.
The trainers involved in e-learning solutions,
including m-learning, are to:
 Deal with content management;
 Prepare tests;
 Assess tests, homework, projects taken
by students;
 Send feedback;
 Communicate with students (forums, e-
mails and other type of messaging).
One of most used architecture for mobile
learning applications is Web based due to
well known technologies that are used.
Usually, standalone mobile applications need
that all the mobile learning content to be
stored within the mobile device.
Distributed mobile learning applications (in-
cluding Web based) load and use the content
when they need it.
Distributed platforms have a similar architec-
ture as Web-based platforms, but the client
application is a rich application and not a
simple mobile Web browser and the server is
also different.
The advantages of using this platform are:
 Rich user interface;
 Support for multimedia content;
 E-learning content can be easily updated
on the server;
There are also some disadvantages:
 The user need to install and setup the
client application;
 The user have to learn how to use the ap-
 Possible additional costs for traffic usage.
The development of distributed mobile learn-
ing applications involves the following steps:
 Project Management;
 Analysis;
 Design;
 Implementation;
 Testing.
The steps are applied to software develop-
ment and to mobile content.
The application development consider the re-
sults obtained in [5] and [6] related to the
quality of mobile applications and systems.
Figure 1 depicts the components involved in
a distributed mobile learning system.
In addition to mobile learning content, there
Informatica Economică vol. 14, no. 3/2010
are databases used to manage users, messag-
es and other settings. Data stored in databas-
es is accessed from dedicated servers.
The mobile learning application, developed
for Android based devices, has the following
 Courses;
 Quizzes;
 Final and partial tests;
 Messaging.
In order to administrate the system, specia-
lized modules are developed to provide:
 User control;
 Content management;
 Courses;
 Tests;
 Marks.
The modules are written independently, and
they share the common data. Each module
has an associated screen and they are
launched from a main screen.
The communication between client and serv-
er is based on Web services. XML Web ser-
vices have many advantages for developers
and for users: they use simple protocols and
the implementation of the services and
clients is easier than other methods.
The prototype developed up to now imple-
ments the quizzes module.
2 Android Platform
2.1 Android Operating System
Android operating system is a project in-
itiated by Google through the Open Handset
Alliance, which includes over 30 companies
in ICT. Android platform is an open source
project, allowing its amendment by any man-
ufacturer of mobile devices.
Figure 2 depicts the architecture of Android
operating system.
The operating system is based on Linux ker-
nel version 2.6.x, that is a monolithic kernel.
The kernel includes drivers for the mobile
device hardware: screen, keyboard, camera,
USB, Bluetooth etc. Kernel provides inter-
face hardware and memory management,
processes and other resources.
Informatica Economică vol. 14, no. 3/2010
Applications and Widgets each application running in a separate thread.
Application Programming Interface 2.2 Android Application Development
                                 Android applications are developed using
                                one or more basic components [3], [4]:
                                activities (Activity base class),
                                 services (base class Services),
                                  content providers (ContentProvider
                                  base class)
                                  components that receive and act on mes-
                                  sages sent to all applications (the base
                                 class BroadcastReceiver)
                                 messages (class Intent)
                                 A particular importance in application devel-
                                opment is the resources that enable separa-
                               tion of interface code.
                              Activities represent the screen associated to
                             an application. An application can have one
                            or more activities.
                           Services are routines that run in parallel with
                          the main thread and do not have GUI. They
                         allow the development of actions in the
                        background without blocking the main thread
                       execution and interaction with such applica-
                     Content providers are used for sharing data
                    between applications. Data sharing is done
                   through files, databases or other means. An
                  alternative to content providers is the use of
                 communication between processes.
                Applications can respond to the occurrence
               of events in the system by using classes de-
              rived from BroadcastReceiver. They do
             not GUI and an application can have several
            components of this type.
           In order to activate components like activi-
          ties, asynchronous messages encapsulated in
         objects of Intent type are used.
        Android applications are developed mainly
       using Eclipse IDE with Android Develop-
      ment Tools (ADT) plug-in. Android SDK
     and emulators are necessary for application
Android runtime
Linux Kernel and Drivers
Fig. 2. Android Architecture
Native libraries on the next level are depen-
dent on hardware architecture of the mobile
device. These libraries include support for
2D and 3D graphics (Single, OpenGL ES),
multimedia, security, storage, browsing
(WebKit) and standard C library [8].
Android applications are developed using Ja-
va programming language. Applications re-
quire an environment to manage their life-
cycle. This includes a Java virtual machine
(called Dalvik virtual machine) and Java
class libraries that provide basic support for
applications (collections, input/output opera-
tions management etc.). Android applications
are not compatible with Java ME or Java SE.
The applications are optimized for mobile
devices constraints.
The application programming interface al-
lows accessing a framework that includes
components used by all Android applica-
tions. The application framework includes
components for Android application man-
agement (installation, execution), windows
management and user interface graphical,
event handling etc.
Application level includes pre-installed ap-
plications (contact management, phone, ca-
lendar, Internet browser) and user applica-
tions. Applications are based on Java tech-
nologies and use classes provided through
application programming interface. In addi-
tion, there is the possibility to use native
functions in programs written in C/C++ pro-
gramming language through NDK (Native
Development Kit).
Widgets unlike applications, occupies only
part of the main display screen and asso-
ciated (Home).
Android operating system is multitasking,
3 Graphical User Interface
The prototype developed consists of three ac-
 Test selection;
 Question and answers;
 Answers list.
Informatica Economică vol. 14, no. 3/2010
The interface is simple and intuitive, without
any graphics and drawings. That will reduce
the amount of memory required by the appli-
cation and reduces the time of development.
Future versions will include de redesigned
and friendlier user interface. The application
targets the mobile devices with touch screen,
but is not limited to.
The main screen for the quizzes module is
presented in Figure 3. The associated activity
is ActTeste and is declared as the main activi-
ty in AndroidManifest.xml configuration file.
When the application is launched, the list of
tests is automatically loaded in this screen.
The list is an object of ListView type.
The description of list elements is defined in
a resource file based on XML. For the exam-
ple from Figure 3 the following structure was
used for each list element:
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
Manifest.xml, a runtime exception will occur
when the code is executed.
All the available tests are loaded from a da-
tabase stored on the server side. A dedicated
Web service method is used for this initial
The main menu includes items that allow to:
 Login/Logout the application;
 Exit the application;
 View application version.
The main menu options are added when
onCreateOptionsMenu method is called:
public boolean
onCreateOptionsMenu(Menu menu)
menu.add(0, LOGIN, 0, "Login");
menu.add(0, LOGOUT, 1, "Logout");
menu.add(0,IESIRE, 2,"Iesire");
menu.add(0,DESPRE, 3,"Despre");
return true;
Fig. 3. Test selection screen on an Android
In order to start a new activity, an Intent in-
stance is used. All activities need to be de-
clared in AndroidManifest.xml file:
<activity android:name=".ActTeste" />
<activity android:name=".ActIntreb"/>
<activity android:name=".ActRasp"/>
If the activities are not declared in Android-
When the user selects a menu item
onOptionsItemSelected function is called.
For example, when user want to exit from the
application, the code associated with IESIRE
label is executed:
public boolean onOptionsItemSelected
(MenuItem item)
switch (item.getItemId())
case IESIRE:
Informatica Economică vol. 14, no. 3/2010
return true;
The following code is used to show the activ-
ity associated with questions and answers,
View.OnItemClickListener interface:
return false;
public void onItemClick(AdapterView<?> parent, View item, int position,
long id)
Intent intent = new Intent(ActTeste.this, ActIntreb.class);
//add parameters
intent.putExtra("idTest", position + 1);
//launch selected test
When the user selects a test from the list, the
screen associated to the first question will be
shown. Figure 4 illustrate the graphical inter-
face associated to the question window.
public boolean onPrepareOptionsMe-
nu(Menu menu)
if (idIntrebareCurenta ==
ActIntreb.INAINTE, false);
ActIntreb.INAINTE, true);
In order to pass complex objects from an ac-
tivity to another, they have to implement the
interface android.os.Parcelable through
the methods describeContents and writeTo-
For example, the class Intrebare, that
represents a question, implements the write-
ToParcel method in this way:
dest, int flags)
Fig. 4. Question screen as shown on an An-
droid device
The questions have only one correct answer.
The student can navigate sequentially from
one question to another. Some menu items
are disabled for the first or the last question:
The class must include a static field named
ble.Creator<Intrebare> CREATOR =
Informatica Economică vol. 14, no. 3/2010
used when Intrebare objects are created using
this method.
At the end, the student can review the an-
swers and send them to the server in order to
monitor the progress.
The student has the possibility to review the
answers and to calculate her or his score.
Because the answers are stored in a HashMap
and the questions need to be shown sorted by
question code, the class Intrebare imple-
ments the Comparable<Intrebare> inter-
4 Web Services
The Web service used by this application has
been developed using Microsoft .NET tech-
nologies. The Web service provides several
Web methods that are used by this mobile
learning application.
The use of Web services provide a very flex-
ible way for client applications that can be
developed on almost any mobile or desktop
The GetNumarIntrebariTest method re-
turns the number of questions of a given test
identified through a code. The number of
questions is taken from the database.
If an exception occurs, the method will return
a negative value.
The following code is an example of a me-
thod used in this Web service:
Fig. 5. Answers verification lists as shown on
an Android device
public int GetNumarIntrebariTest(int idTest)
OleDbConnection conn = new OleDbConnection(connString +
Context.Request.PhysicalApplicationPath + dbString);
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = conn;
cmd.CommandText = "SELECT COUNT(*) FROM Grile WHERE id_test = " +
int nrIntrebari = -1;
nrIntrebari = (int)cmd.ExecuteScalar();
catch (Exception ex)
nrIntrebari = -1;
Informatica Economică vol. 14, no. 3/2010
return nrIntrebari;
The Web services are consumed using a
third-party library distributed as free source
optimized for Android.
The libraries need to be added to the project
in order to be used. This library is based on
the SOAP architecture and there is no need to
generate a proxy/stub to call Web services
A SOAP envelope is created using the Soap-
SerializationEnvelope class (specifying
the SOAP version) and the request details are
added to the envelope body (using SoapOb-
ject class).
The HttpTransportSE class is used to make
the actual call of the Web service method, the
envelope being passed as parameter. The re-
sult is retrieving from the response part of the
The getIntrebare function is used to access
the Web service and to call a specific method
used to get the specified question. The func-
tion's source code is:
public static Intrebare getIntrebare(int idTest, int idIntrebare)
Intrebare intrebare = new Intrebare();
SoapObject request = new SoapObject(NAMESPACE, GET_INTREBARE);
// add paramaters and values
request.addProperty("idTest", idTest);
request.addProperty("idIntrebare", idIntrebare);
SoapSerializationEnvelope envelope =
new SoapSerializationEnvelope(SoapEnvelope.VER11);
envelope.dotNet = true;
HttpTransportSE androidHttpTransport =
new HttpTransportSE(URL_WS);
androidHttpTransport.call(NAMESPACE + GET_INTREBARE, envelope);
SoapObject result = (SoapObject) envelope.getResponse();
//question initialization
SoapObject variante = (SoapObject) result.getProperty("Var");
for (int i = 0; i < Intrebare.VARIANTE; i++)
catch (Exception e)
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intrebare = null;
return intrebare;
return intrebare;
It is very important to send the right parame-
ters to the methods. In this example, the pa-
rameters used in these calls are initialized as
 NAMESPACE = "http://tempuri.org/";
– Web service namespace; in this exam-
ple the default namespace is used
Web service URL
 GET_INTREBARE = "GetIntrebare"; –
Web service method name
 idTest, idIntrebare – the parameters
used by GetIntrebare method
Using wrong values for these parameters will
lead to Web service method call to fail.
All the functions used to access the Web ser-
vice are included in a class, in order to be ac-
cessible from anywhere within the package.
This is an example of this Web method
intrebare = AccesSW.getIntrebare
(idTest, idIntrebareCurenta);
In order to use Web services the application
needs special permission. Permissions are
stored in AndroidManifest.xml file. For this
mobile application, the following line has to
be added:
In this prototype, all data is stored in memo-
ry, during program execution. All loaded
questions and given answers are saved in or-
der to reduce costs related to data transfer
through wireless networks:
Vector<Intrebare> intrebari = new Vector<Intrebare>();
Hashtable<Intrebare, Raspuns> raspunsuri = new Hashtable<Intrebare,
For the future versions the following me-
thods will be taken into account:
 Local files;
 Property files;
 Local databases.
5 Security Issues
The security of distributed mobile learning
applications is very important and challeng-
ing compared with stand alone applications.
There are several areas where the security re-
quirements are high and they need special at-
Table 1 presents some security concerns re-
garding the mobile learning solutions, based
on [7].
Table 1. Security concerns of m-learning applications
Security requirements
Online exams
Content management
Feedback management (forums) Low-Medium
Homework/Projects Assessment High
User management
These issues can be managed using several
methods and techniques like:
Informatica Economică vol. 14, no. 3/2010
 different authentication levels;
 password management;
 data encryption;
 location services.
Each of actions from Table 1 requires a cer-
tain degree of security, depending on the im-
portance and data sensitivity.
The databases with tests, marks and users
contain sensitive data and they need a special
The security requirements for examinations,
homework/project assessment and user man-
agement are very high due to the importance
of data and information they use.
Quizzes and content management have me-
dium security requirements, because the data
manipulated is less sensitive.
Feedback management and messaging for
these systems does not use sensitive data.
The minimum requirement is to use authenti-
cation through users and passwords.
Wireless data communication can be easily
monitored, so high security need to be as-
sured by using specific standards.
Application testing has to include several se-
curity tests.
6 Conclusions and Future Work
The development of mobile applications is
not an easy task. There is a variety of plat-
forms and technologies to choose from. Mo-
bile devices resources are limited. User expe-
rience with mobile devices and software is
Using Web services for mobile learning ap-
plications helps the process of development
by providing a standardized way of commu-
nication between mobile clients and servers.
There are also drawbacks that need to be re-
duced or eliminated:
 data volume (optimization);
 security (discover and eliminate security
 data serialization for custom and complex
objects (refactoring).
Regarding the presented mobile application,
the following development directions are
 new functionalities,
 interface improvement,
Courses and Tests modules implementa-
 user management,
 modules integration,
in order to provide a basis for an working m-
learning application.
This prototype is a part of an m-learning sys-
tem that will also be developed for other mo-
bile platforms in order to cover a wide area
of mobile devices and users.
This work was supported by CNCSIS –
UEFISCSU, project number PNII – IDEI
2637/2008, project title: Project management
methodologies for the development of mobile
applications in the educational system.
[1] D. S. Metcalf II and J. M. De Marco,
mLearning: Mobile Learning and Perfor-
mance in the Palm of Your Hand, HRD
Press, Inc., 2006.
[2] P. Pocatilu, F. Alecu and M. Vetrici,
Measuring the Efficiency of Cloud Com-
puting for E-learning Systems, WSEAS
1, Volume 9, January 2010, pp. 42-51.
[3] E. Burnette, Hello, Android: Introducing
Google’s Mobile Development Platform,
2nd Edition, The Pragmatic Bookshelf,
[4] R. Meier, Professional Android 2 Appli-
cation Development, Wiley Publishing,
Inc., 2010.
[5] C. Ciurea, "A Metrics Approach for Col-
laborative Systems," Informatica Econo-
mica, vol. 13, no. 2/2009, pp. 41-49.
[6] C. Boja, L Batagan, “Analysis of M-
Learning Applications Quality,” WSEAS
4, Vol. 8, May 2009, ISSN 1109-2750,
pp. 767-777.
[7] F. Alecu, P. Pocatilu and S. Capisizu,
WiMAX Security Issues in E-Learning
Systems, Proc. of 2nd International Con-
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of Information Technology and Commu-
nication Security, Bucharest, November
2009, pp. 45-52.
Informatica Economică vol. 14, no. 3/2010
[8] The Developer's Guide | Android Develop-
tml (March 2010).
Paul POCATILU graduated the Faculty of Cybernetics, Statistics and Eco-
nomic Informatics in 1998. He achieved the PhD in Economics in 2003 with
thesis on Software Testing Cost Assessment Models. He has published as au-
thor and co-author over 45 articles in journals and over 40 articles on national
and international conferences. He is author and co-author of 10 books, (Soft-
ware Testing Costs, and Object Oriented Software Testing are two of them).
He is associate professor in the Department of Economic Informatics of the
Academy of Economic Studies, Bucharest. He teaches courses, seminars and laboratories on
Mobile Devices Programming, Economic Informatics, Computer Programming and Project
Management to graduate and postgraduate students. His current research areas are software
testing, software quality, project management, and mobile application development.

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