SMS

1. SMS

2. SMS • Short Message Service • Primarily text messages between mobile phones • First one sent December 3, 1982 • “Merry Christmas” • In 2008 • Approximately 2.5 billion active users • Over 4.1 trillion messages sent • Average cost to users: 0.11USD • Average cost to providers: less than 0.01USD

3. Components of SMS in Android • Manifest file • Permissions • Intent filter • Classes within android.telephony package • android.telephony.SmsManager class • android.telephony.SmsMessageclass • android.content.BroadcastReceiver • No Listeners

4. Manifest file

5. Permissions • uses-permission tags • children of manifest tag • often placed above application tag <uses-permission android:name="android.permission.SEND_SMS"/> provides ability to send messages <uses-permission android:name="android.permission.RECEIVE_SMS"/> provides ability to receive messages

6. Intent filter • receiver, intent-filter, and action tags • receiver is child of application tag • intent-filter is child of receiver tag • action is child of intent-filter tag • intent-filter ‘filters’ all possible components that can be received and delivers only those specified • name attribute must be set to the name of class that will be receiving messages • class must be a subclass of BroadcastReceiver <receiver android:name=“.MyBroadcastReceiver"> <intent-filter> <action android:name="android.provider.Telephony.SMS_RECEIVED" /> </intent-filter> </receiver>

7. SmsManager class

8. SmsManager • Concrete class • Manages SMS activities • Needed to send a message • not needed to receive • Not instantiated directly • instantiated through the SmsManagergetDefault() method SmsManagersm = SmsManager.getDefault();

9. SmsManager • important methods • getDefault • returns an instance of SmsManager • sendTextMessage (5 parameters) • String indicating destination (i.e. a phone number) • String indicating the source (i.e. a phone number) • String holding the message • 2 PendingIntents • Used when multiple apps are communicating with each other • PendingIntents are Intents that can be handed to other apps with your apps permissions • Here used to pass additional information, or to verify successful communication • 1st Intent done when message sent, 2nd when message received • only first and third arguments are required – others can be null

10. Sample code • Sending a message //sendTo is a String holding the phone number //message is a String holding the text messageSmsManagersm = SmsManager.getDefault(); sm.sendTextMessage(sendTo, null, message, null, null); • To send a message, only an SmsManager is needed • BroadcastReceiver and SmsMessage are not used

11. SmsMessage class

12. SmsMessage class • Concrete class • Used in conjunction with a BroadcastReceiver to receive messages • Represents a specific message • Contains: • sender’s phone • message • other information (timestamp, whether or not the message was sent from e-mail, etc.)

13. SmsMessage class • important methods • createFromPDU() • creates an SmsMessage from a PDU obtained from the BroadcastReceiver • PDU – protocol data unit (any transferrable entity) • in our case a message • in other network apps may be an address, packet, etc. • getOriginatingAddress() • returns phone number of sender as a String • getMessageBody() • returns message as a String

14. BroadcastReceiver class

15. BroadcastReceiver class • Concrete class • Receives incoming messages • messages are stored in an Intent created by the transmitter • to obtain SmsMessage – override onReceive method in BroadcastReceiver class: • getExtras() method in the Intent class returns a Bundle • get(“pdus”) method in the Bundle class returns an Object • must be cast to an Object[] • SmsMessage now created via createFromPdu method • use first element in object array, cast to a byte[]

16. Sample code – receiving a message public class MyBroadcastReceiver extends BroadcastReceiver { public void onReceive(Context context, Intent i) { Bundle b = i.getExtras(); SmsMessagemsg = null; String phone = new String(); String message = new String(); if (b != null) { if (b.get("pdus") instanceof Object[]) { Object[] pdus = (Object[])b.get("pdus"); //Large message may be broken up in parts //iterate thru pdus array if necessary msg = SmsMessage.createFromPdu((byte[])pdus[0]); phone = msg.getOriginatingAddress(); message = msg.getMessageBody(); //Code handling the phone and message goes here } } } }

17. Consequences of not having a Listener

18. Listening for events • Historically 2 approaches • Providing a Listener interface • Preferred approach • OnClickListener • LocationListener • SensorEventListener • etc. • Providing the event producer with a handle to the listening object

19. Sample code – providing a handle to the Listener • In the event producing class private static MyListener observer; public static final void setObserver(MyListener observer) { MyBroadcastReceiver.observer = observer; } • In the listener (in onCreate()) MyBroadcastReceiver.setObserver(this);

20. Application Structure

21. Application Structure • In the ‘Listening’ class • In our case this is the main Activity • ‘this’ is past into the ‘setObserver’ method of the BroadcastReceiver subclass • if messages can be sent, there is functionality to send a message using an instance of SmsManager • e.g. this method might be tied to a button via onClick • if messages can be received, there is functionality that handles the actual message • placed in TextView, stored in db, etc. • this method typically called from receiver class • can also be called from listening class if needed

22. Application Structure • In the BroadcastReceiver subclass • static class variable with the type of the ‘Listening’ class • in our case, an instance of the main Activity • variable typically called ‘observer’ • static method to initialize this instance • argument is an instance of the ‘Listening’ class • method typically called ‘setObserver’ • onReceive method is overridden • signature: public void onReceive (Context c, Intent i) • SmsMessage is instantiated via createFromPdu class method in SmsMessage class • Pertinent information is obtained and sent back to the observer to handle accordingly