mobile application development – android –lecture 2€¦ · android –lecture 2 mtat.03.262...

Mobile Application Development –

Android – Lecture 2Android – Lecture 2

MTAT.03.262

Satish [email protected]

Android Lecture 1- recap

• What is Android

• How to develop Android applications

• Constructing the UI

– Resources– Resources

– Views & Layouts

– Adapters

– Events

• Run, debug & test the applications

11/24/2011 Satish Srirama 2/55

Outline

• Basic application components

• Location based services

• Mobile Cloud research


Basic Application Components

• Activities

– UI component

– Typically corresponding to one screen.

• BroadcastReceivers

– Respond to broadcast Intents.

• Services

– Faceless tasks that run in the background.

• ContentProviders

– Enable applications to share data.


Activities

• Typically correspond to one screen in a UI

• But, they can:

– be faceless

– be in a floating window– be in a floating window

– return a value

• For more info

http://developer.android.com/guide/topics/fu

ndamentals/activities.html


Intents

• Unique concept in Android

• Mobile applications mostly run in their sandboxes

• Applications are isolated from each other

• Intents support interactions among the application componentsapplication components– Components can be of any application in the device

– Android does not distinguish third party applications and native applications

• Activities, services, and broadcast receivers — are all activated through Intent messages


Working with Intents

• Declare your intention that an Activity or

Service be started to perform an action

• Broadcast that an event/action has occurred

• System matches Intent with Activity that can • System matches Intent with Activity that can

best provide that service

• Activities and BroadcastReceivers describe

what Intents they can service in their

IntentFilters (via AndroidManifest.xml)


Using intents to launch activities

• Explicitly starting new ActivitiesIntent intent = new Intent(this, MyOtherActivity.class);

startActivity(intent);

• The new activity is started and no connection with the current activity

• The new activity is started and no connection with the current activity

• To get the response back from the sub-Activityprivate static final int SHOW_SUBACTIVITY = 1;

StartActivityForResult(intent, SHOW_SUBACTIVITY);

• The response is sent back assetResult(Activity.RESULT_OK, resultIntent);


Intent Object

• Contains information of interest to the component that receives the intent

– Action to be taken

• ACTION_CALL - Initiate a phone call

• ACTION_BATTERY_LOW - A warning that the battery is low• ACTION_BATTERY_LOW - A warning that the battery is low

– The URI of the data to be acted on• Uri uri = Uri.parse(“content://contact/people”);

• plus information of interest to the Android system

– Category of component that should handle the intent

• CATEGORY_BROWSABLE - The target activity can safely be invoked by the browser


Implicit intents and late runtime

binding

• The implicit Intents are mentioned in the

Android Manifest file


Intent resolution in Android

• Android puts together a list of Intent Filters

• Input Filters that do not match the action or

category are removed from the list

• Each part of the Intent’s data URI is compared • Each part of the Intent’s data URI is compared

to the Intent Filters data tag

• If more than one component is resolved, they

are offered to the user to select


BroadcastReceivers

• Used for system level message-passing

mechanism

• Components designed to respond to

broadcast Intentsbroadcast Intents

• Think of them as a way to respond to external

notifications or alarms

• Applications can invent and broadcast their

own Intents as well


Using BroadcastReceivers

• Intent intent = new Intent(NEW_LIFEFORM_DETECTED)

intent.putExtra(“lifeformName”, lifeformType);

intent.putExtra(“longitute”, cuttentLongitude);

Intent.putExtra(“latitude”, cuttentLatitude);

sendBroadcast(intent);

• public class LifeformDetectedBroadcastReceiver extends • public class LifeformDetectedBroadcastReceiver extends BroadcastReceiver{

@Override

public void onReceive(Context context, Intent intent)

{ Uri data = intent.getData();

String type = intent.getStringExtra(“lifeformName”);

…

}

}


Using BroadcastReceivers - continued

• Register the BroadcastReceiver in manifest


Content Providers

• Enables sharing of data across applications

– Examples: address book, photo gallery, etc.

• Provides uniform APIs for:

– querying (returns a Cursor)– querying (returns a Cursor)

– delete, update, and insert rows

• Content is represented by URI and MIME type


Content Provider Basics

• All content providers implement a common interface for querying the provider and returning results– Also support adding, altering, and deleting data

• ContentResolver object from the application context provides access to the content provider– ContentResolver cr = getContentResolver();– ContentResolver cr = getContentResolver();

• Content providers expose their data as a simple table on a database model– Each row is a record and each column is data of a particular type

and meaning

– Every record includes a numeric _ID field that uniquely identifies the record within the table


URIs of Content Providers

• Each content provider exposes a public URI

• A content provider that controls multiple tables exposes a separate URI for each one

• Example:

• <provider android:name=".TransportationProvider"android:authorities="com.example.transportatio

nprovider". . . >

11/24/2011 Satish Srirama

http://developer.android.com/guide/topics/providers/content-providers.html

17/55

Querying a Content Provider

• To query a content provider you need

– The URI that identifies the provider

– The names of the data fields you want to receive

– The data types for those fields

• The querying returns a object• The querying returns a Cursor object

• You can query either way

– ContentResolver.query() or Activity.managedQuery()

– Second one is better as it causes the activity to manage the life cycle of the Cursor


Querying a Content Provider -

continued

• Make the queryCursor managedCursor = managedQuery(

android.provider.Contacts.People.CONTENT_URI, //URI

projection, // Which columns to return null, // Which rows to return (all rows)null, // Which rows to return (all rows)null, // Selection arguments (none)People.NAME + " ASC“ // Put the results in ascending order by name

);

SELECT ename from employee WHERE ename='value1' OR ename='value2'


Reading retrieved data

People.NAME + " ASC");


Modifying the data

• Modifying Data– Adding records

ContentValues values = new ContentValues();values.put(People.NAME, “Satish Srirama");

…

Uri uri = getContentResolver().insert(People.CONTENT_URI, getContentResolver().insert(People.CONTENT_URI, values);

– Adding new values

– Deleting a record

ContentResolver.delete()

• More info http://developer.android.com/guide/topics/providers/content-providers.html


Contact picker

• Demo & Exercise

– How to pick contacts from the device using

content provider

– Expose with Intent– Expose with Intent

– Using SimpleCursorAdapter for list

http://thinkandroid.wordpress.com/2010/01/09/si

mplecursoradapters-and-listviews/


Storage of data with Android

• We can put data into a preferences file.

• We can put data into a ‘normal’ file.

• We can send data across the network to a

serviceservice

• We can use a local database on the handset

– We have seen the content providers

– We can also use SQLite db


Preference files

• They are a light-weight option

• Call Context.getSharedPreferences() to read and write values as key-value pairs.

• Use Activity.getPreferences() with no • Use Activity.getPreferences() with no name to keep them private to the calling activity

• These are not sharable across applications

– you expose them as a ‘content provider’

• Used to store the state of an application


Files in Android

• We can write larger data to file

• You can only access files available to the application– res/raw/mydata

• Reading data from a file• Reading data from a file

– Context.openFileInput() – Returns

FileInputStream object

• Writing to a file

– Context.openFileOutput() - Returns a FileOutputStream object


Persisting data to a db

• Android API uses the built-in SQLite db

• Each db is private to the application

– You can expose the db as a content provider

• Creating a Content Provider -• Creating a Content Provider -

http://developer.android.com/guide/topics/providers/c

ontent-providers.html

• All databases, SQLite and others, are stored on

the device in /data/data/package_name/databases


Services

• Faceless components that run in the background– Example: music player, network downlaod, etc.

• Can run in your own process or separate process

• They can perform long-running operations in the backgroundbackground– They have higher priority than the background activities

• So safe from the runtime memory management

• A service can essentially take two forms– Started - startService() - run in the background indefinitely,

even if the component that started it is destroyed

– Bound – An application component binds to the service by calling bindService()


Services - continued

• Explicitly starting new ServiceIntent intent = new Intent(this,

HelloService.class);

startService(intent);

• Services also have their life cycles managed• Services also have their life cycles managed

• You can also start java threads in Services

http://developer.android.com/guide/topics/fun

damentals/services.html


Homework

• Extend the contact picker to save the state

– Also replace the TextView with ListView

• Extend the todo list to store values in SQLite

DBDB


Location Based Services

• We have discussed them extensively in

Lecture 2

• Google Maps API is widely used on the web

for LBSfor LBS

• The Android SDK provides support for easily

integrating the Google Maps API

– Applications require a Map API Key in order to use

Google Maps


Keys

• Apps must be signed in order to deploy them

on a device

• Eclipse automatically creates a signed

debug.keystore that is used when launching debug.keystore that is used when launching

our app from Eclipse

• In order to deploy our app to the public, we

must create a signed keystore


http://developer.android.com/guide/publishing/app-signing.html#ExportWizard

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Google Maps API key

• Find your keystore

• Get your certificate fingerprintkeytool -list -alias satish –keystore

c:\Users\..\.keystore

• Register your certificate with Google

http://code.google.com/android/maps-api-

signup.html

• You see the description of a key and an

example MapView


Using Google Maps

• Configuration

– Maps require the Google API as the project build target

– AndroidManifest.xml– AndroidManifest.xml<uses-library android:name="com.google.android.maps”/>

<uses-permissionandroid:name="android.permission.INTERNET"/>

• Create a MapView in a MapActivity


http://code.google.com/android/add-ons/google-apis/maps-overview.html

33/55

Working with MapView

• Contains a map

– Map tile retrieval and caching is all done

automatically

• Includes pan• Includes pan

• Includes zoom setBuiltInZoomControls(true);

• You can set modesetSatellite(true);

setTraffic(true);

setStreetView(true);


MapController

• You can pan and zoom the map

MapView myMap = (MapView)findViewById(R.id.myMap);

MapController mapController = MapController mapController = myMap.getController();

mapController.setZoom(1); //widest zoom/far away

…

mapController.setZoom(21); //narrowest zoom/close in

mapController.zoomIn(); //one level

mapController.zoomOut(); //one level


GeoPoint

• You can move to a particular point

MapView myMap = (MapView)findViewById(R.id.myMap);

MapController mapController = myMap.getController();myMap.getController();

Double lat = 37.123456 * 1E6;

Double long = -122.123456 * 1E6;

GeoPoint point = new GeoPoint(lat.intValue(), long.intValue());

mapController.setCenter(point); //jump to point

…

mapController.animateTo(point); //smooth transition to point


Getting access to a location

• LocationManager locationManager;

String context = Context.LOCATION_SERVICE;

locationManager = (LocationManager) getSystemService(context);

String provider = LocationManager.GPS_PROVIDER;LocationManager.GPS_PROVIDER;

Location currentLocation = locationManager.getLastKnownLocation(provi

der);

double lat = location.getLatitude();

double lng = location.getLongitude();


Reverse Geocoding

• Finding address from longitude/latitude

location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

double lat = location.getLatitude();double lat = location.getLatitude();

double lng = location.getLongitude();

Geocoder gc = new Geocoder(this, Locale.getDefault());

List<Address> addresses = null;

try {

addresses = gc.getFromLocation(lat, lng, 10);

} catch (IOException e) {}


Forward Geocoding

• Find longitude/latitude (and more) from address

Geocoder gc = new Geocoder(this, Locale.US);

List<Address> addresses = null;

try {try {

addresses = gc.getFromLocationName( “123 Main St., Newton, Kansas”, 10);

} catch (IOException e) {}

double lat = addresses.get(0).getLatitude();

String zip = addresses.get(0).getPostalCode();


You can set the criteria

• Criteria criteria = new Criteria();

criteria.setAccuracy(Criteria.ACCURACY_FINE);

criteria.setAltitudeRequired(false);

criteria.setBearingRequired(false);

criteria.setCostAllowed(true);criteria.setCostAllowed(true);

criteria.setPowerRequirement(Criteria.POWER_LOW);

String bestProvider = locationManager.getBestProvider (criteria, true);


Notify changes in location

• LocationListener locationListener = new LocationListener() {

public void onLocationChanged(Location location) {

// Called when a new location is found by the network location provider.

updateWithNewLocation(location);

}

…

};

locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);


Exercise

• Demo– Creating a .apk file

– Getting the map key

– Creating a MapView

– Display - where am I–

– Home work• Make my current location to map center

• Work with Map overlay

• Put an overlay where I am

• Put some points of interest

• BONUS - Come with some interesting idea of using the maps (with implementation) – 5 points each for max 5 persons


MOBILE CLOUD RESEARCH

11/24/2011 Satish Srirama 43

What is Cloud Computing?

• Computing as a utility– Utility services e.g. water, electricity, gas etc

– Consumers pay based on their usage

• Cloud Computing characteristics – Illusion of infinite resources– Illusion of infinite resources

– No up-front cost

– Fine-grained billing (e.g. hourly)

• Gartner: “Cloud computing is a style of computing where massively scalable IT-related capabilities are provided ‘as a service’ across the Internet to multiple external customers”

Satish Srirama11/24/2011 44/55

Mobile Cloud Services

• Efficiently utilizing cloud resources in

increasing the scope of mobile applications

• Some of the process intensive services• Some of the process intensive services

– Processing sensor information

– Face recognition

– Processing videos


CroudSTag – Scenario

• CroudSTag takes the pictures/videos from the cloud and tries to recognize people

– Pictures/Videos are actually taken by the phone

– Processes the videos

– Recognizes people using facial recognition technologies– Recognizes people using facial recognition technologies

• Reports the user a list of people recognized in the pictures

• The user decides whether to add them or not to the social group

• The people selected by the user receive a message in Facebook inviting them to join the social group


Screenshots

Used cloud services

Facial Recognition

Process

Taking picture/video

using the camera

Selecting CloudMain Menu

Send Asynchronous

Notification and Results

Storage Services

1.

2.

3.

Facebook

Login


Send invitation to the

social group

Selecting people

Selecting Cloud

Facebook

Authentication

Start Process

4.

5.

6.

7.

8.

9.

Send next

invitation

Back to Menu

47/55

Technological Choices - Problems

• Cloud Interoperability– Data and application integration

– Several and different API for each service and vendor

• Invocation of resource intensive tasks from phonesphones– Time and resource consuming task

• Mobile platform integration with cloud services– Android

– iOS

– Windows Phone 7


Mobile Cloud Middleware (MCM)


MCM – enables

• Interoperability between different Cloud

Services (IaaS, SaaS, PaaS) and Providers

(Amazon, Eucalyptus, etc)

• Bringing the benefits of the Cloud to the • Bringing the benefits of the Cloud to the

Mobile Domain

• Composition of different Cloud Services

• Asynchronous communication between the

device and MCM


Technological Choices – Asynchronous

Notification

• Via third party services

– Apple Push Notification Service (APNS)

– Android Cloud to Device Messaging Framework (C2DM)

– Microsoft Push Notification Service (MPN)– Microsoft Push Notification Service (MPN)

• Mobile Host [Srirama et al, 2006]

– Providing web services from smart phones

– MCM can directly send the response back to the device

– Support for Android, iOS and J2ME


How you can contribute?

• Several open Bachelor/Master theses

http://ds.cs.ut.ee/theses

• Your course projects can be extended to

thesestheses

• All new interesting ideas are welcome

• Good students always have paid positions

– Contact srirama AT ut.ee


Reminder

• Finish the homework and all the exercises

discussed in the lecture

• Send by mail to me

– Put cc to [email protected]– Put cc to [email protected]

• Deadline for homework 29th November 2011


Preliminary presentation of projects

• Next week , Thursday 1st December 2011

• Each group gives a talk of 15 - 20 min– Explain the problem in your words

– Make use of slides

– How you are addressing them– How you are addressing them

– How far you have reached

– Do you see any problems

– What is the contribution from individuals

• If you have preliminary demonstration then it is very good – Take additional 5 min


References

• Android developers

http://developer.android.com/

• Books

– “Professional Android 2 Application – “Professional Android 2 Application

Development”, By Reto Meier


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