Android ICC Part II

1. Android ICC Part II Inter-component communication

2. Broadcast Receivers • BRs are app components that receive intents sent from the system and/or other apps • A BR has to register with the Activity Manager and Package Manager • Registration can be done through the • The manifest file • Programmatically

3. BR registration within Manifest <receiver android:name=''MsgListener'' > <intent-filter> <action android:name=''pacman.intent.action.BROADCAST'' /> </intent-filter> </receiver>

4. BR registration within Manifest <receiver android:name=''MsgListener'' > <intent-filter> <action android:name=''pacman.intent.action.BROADCAST'' /> </intent-filter> </receiver> Class responsible for processing the Intent Filter to specify what intents to receive

5. BR program. registration IntentFilter filter = new IntentFilter(); filter.addAction(``pacman.intent.action.BROADCAST’’); receiver = new BroadcastReceiver() f //@Override public void onReceive(Context context, Intent intent) { System.out.println(``message receivednn''); } }; registerReceiver(receiver, filter);

6. BR program. registration Filter to specify what intents to receive IntentFilter filter = new IntentFilter(); filter.addAction(``pacman.intent.action.BROADCAST’’); receiver = new BroadcastReceiver() f //@Override public void onReceive(Context context, Intent intent) { System.out.println(``message receivednn''); } }; registerReceiver(receiver, filter); Action performed when the intent is received Registration of the BR and filter

7. Registering Broadcast Receivers • When BRs are registered programmatically generate REGISTER_RECEIVER_TRANSACTION ioctl to AM via Binder • Registration through manifest does not generate any transactions

8. Broadcasting Intents • To broadcast an intent the sendBroadcast API should be used • Generates a BROADCAST_INTENT_TRANSACTION ioctl to AM through the Binder Intent intent = new Intent(``pacman.intent.action.BROADCAST''); intent.putExtra(``message'',''Wake up.''); sendBroadcast(intent);

9. Content Providers • CPs are the components in an app responsible for storing data • CPs must be declared in the manifest file using the <provider> tag • CPs are accessed by URI: • content://<authority>/<resource>

10. Content Providers • Access to a CP is handled by the AM • Ioctlwith GET_CONTENT_PROVIDER_TRANSACTION • Specifying the authority • The AM finds the suitable CP and sends back a handler to communicate directly with the CP • Then the app can send URI along with the requested operations: • QUERY_T, GET_TYPE_T, INSERT_T, DELETE_T, UPDATE_T, BULK_INSERT_T, OPEN_FILE_T, OPEN_ASSET_FILE_T

11. Service Manager • The Service Manager is a special system service to keep track of the services available in a device • An app that wants to provider a service to others can publish its service through the SM • Communication to SM is done through Binder

12. Service Manager Commands • The SM accepts the following commands: • publish: takes two arguments – service name and address. This is used for publishing a service within the SM • get/check: take one argument – service name. The SM returns a address of the service in the form of a handler • list: this lists the service names registered with the SM

13. Service Manager in Action

14. Service Manager ioctl ioctl on /dev/binder with BINDER_WRITE_READ cmd:BC_TRANSACTION: target name = android.os.IServiceManager code = SVC_MGR_GET_SERVICE service name = isms

15. Final Thoughts • Android ICC is both very powerful and flexible • High-level API for dynamic interaction between apps • Discovery of functionality on the fly • If not protected properly it can lead to serious consequences

16. Questions?