Mobile Computing

Mobile Computing Lecture#08 IntentFilters & BroadcastReceivers

Lecture Contents • IntentFilters for Plug-ins/Extensibility • Annonymous Actions to Applications • Intents to BroadcastEvents • Listening for Broadcasts • BroadcastReceivers • BroadcastReceivers in Code • BroadcastReceivers in XML • Native AndroidBroadcast Actions

Broadcasting • System level message sending mechanism • Structured message sending across applications • Intents can be used to send messages across applications via sendBroadcast() method • Broadcast intents extend the event driven approach (all applications on a system may behave like event handlers) • Applications registered to handle an event can react to that event without causing any change in event generating application

Broadcasting an Event Two step process:::: • Build the intent for Broadcast • Broadcast the built intent

Android Code public static final String new_life_appeared = “com.test.lives.NEW_LIFE”; Intent intent = new Intent(new_life_appeared); intent.putExtra(“type”, “human_life”); intent.putExtra(“where”, “unknown_location”); …….. …….. sendBroadcast(intent);

Listening for Broadcasts • BroadcastReceiver is a instance of a class that has registered itself as receiver for a particular broadcast event • For a class to work as a BroadcastRegister, it must register itself as BroadcastReceiver • Two methods to register:: • Register in manifest • Register in code

Listening for Broadcasts • While registering as a BroadcastReceiver a class must specify the intent-filter to describe which event this class is listening for

Creating a BroadcastReceiver public class MyBroadcastReceiver extends BroadcastReceiver{ public void onReceive(Context c, Intent intent){ //Some code to handle the event }//End of onReceive } //End of MyBroadcastReceiver • onReceive() function is called automatically when event-generated is matched with the one described in intent-filter tag.

onReceive() example public void onReceive(Context context, Intent intent){ Uri data = intent.getData(); String type = intent.getStringExtra(“type”); …… …… Typically launch some activity/service to perform some action based on the intent received. }

BroadcastReceiver in XML <receiver android:name=“com.test.MyBroadcastReceiver”> <intent-filter> <action android:name=“…….”> ………………….. </intent-filter> </receiver> • Receiver registered in xml (manifest) will always be active (even if application is not running/application is in background)

Receiver Example Code public void onReceive(Context context, Intent intent){ Bundle extras = intent.getExtras(); if (extras != null) { String state = extras.getString(TelephonyManager.EXTRA_STATE); if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)) { String phoneNumber = extras.getString(TelephonyManager.EXTRA_INCOMING_NUMBER); Log.i(tag+":Number", phoneNumber); } } }

Receiver Example Manifest <receiver android:name="com.braodcast.receiver.MyPhoneReceiver"> <intent-filter> <action android:name="android.intent.action.PHONE_STATE"> </action> </intent-filter> </receiver>

Registering Receiver in Code IntentFilter filter = new IntentFilter(string-event); MyBroadcastReceiver receiver = new MyBroadcastReceiver(); registerReceiver(receiver, filter);

Unregister a Receiver unregisterReceiver(receiver);

Dynamic Receiver A receiver can register as a receiver for any global event for a particular period of time and later can unregister when span of interest is gone. • Listening for outgoing calls during office-hours • When phone screen is turned on/off during night • ……………

Native Android Broadcast Events

Pending Intents • The PendingIntent class provides a mechanism for creating Intents that can be fired by another applicationat a later time. • A Pending Intent is commonly used to package an Intent that will be fired in response to a future event, such as a widget View being clicked or a Notification being selected from the notification panel. • PendingIntent class offers static methods to construct Pending Intents used to start an Activity, start a Service, or broadcast an Intent.

Pending Intents // Start an Activity Intent startIntent = new Intent(this, OtherActivity.class); PendingIntent.getActivity(this, 0, startIntent , 0); // Broadcast an Intent Intent broadcastIntent = new Intent(NEW_LIFEFORM_DETECTED); PendingIntent.getBroadcast(this, 0, broadcastIntent, 0);

Pending Intent It is a token that you give to a foreign application (e.g. Notification Manager, Alarm Manager, Home Screen AppWidget Manager, or other 3rd party applications), which allows a foreign application to use your application's permissions to execute a predefined piece of code.

Pending Intent If you give the foreign application an Intent, and that application sends/broadcasts the Intent you gave, they will execute the Intent with their own permissions. But if you instead give the foreign application a Pending Intent you created using your own permission, that application will execute the contained Intent using your application's permission.

Pending Intent Example (Main.xml) <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=… android:orientation="vertical“ android:layout_width="fill_parent“ android:layout_height="fill_parent"> <EditText android:layout_height="wrap_content" android:id="@+id/time" android:layout_width="wrap_content" android:hint="Number of seconds" android:inputType="numberDecimal"/> <Button android:text="Start Counter" android:id="@+id/ok" android:onClick="startAlert" android:layout_width="wrap_content" android:layout_height="wrap_content” /> </LinearLayout>

Pending Intent Example (TimerReceiver.java) public class TimerReceiver extends BroadcastReceiver { public void onReceive(Context context, Intent intent){ Toast.makeText(context, “Your time is up", Toast.LENGTH_LONG).show(); // Vibrate the mobile phone Vibrator vibrator = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE); vibrator.vibrate(2000); } }

Pending Intent Example (Main.java) public class Main extends Activity { EditText time; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); }

Pending Intent Example (Manifest) <receiver android:name=".TimerReceiver"> </receiver> <uses-permission android:name="android.permission.VIBRATE"> </uses-permission>

Mobile Computing