Android™ Application Development - Bahar Ali Khan

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Chapter 9: Peer-to-Peer Communication 290 By extending the reach of your applications beyond the scope of the device on which they’re running, you take on additional responsibilities to ensure that your applications are well behaved, and to take all possible precautions to ensure that your applications aren’t open to exploitation by those looking to use this mechanism maliciously. Data messages are an excellent way to support multi-user applications on distributed mobile devices, thanks to the low latency and rapid response times provided by the instant messaging architecture. Transmitting Data Messages The best practice is to create custom actions to use when broadcasting an Intent to a remote device, such as the one shown in the snippet below: public static final String ACTION_OTA_ELIMINATE = “com.paad.ota_eliminate_action”; The next snippet shows how to create a simple Intent that will be packaged within a data message to transmit the above action to a remote device: Intent intent = new Intent(ACTION_OTA_ELIMINATE); As with normal broadcast Intents, you can package additional information within the Intent using the extras Bundle. These extras will be included in the Intent when it’s re-broadcast on the remote device. intent.putExtra(“long”, String.valueOf(location.getLatitude())); intent.putExtra(“lat”, String.valueOf(location.getLatitude())); intent.putExtra(“target”, “Sarah Conner”); intent.putExtra(“sender”, gTalk.getUsername()); Only String extras are currently supported in the OTA Intent broadcast mechanism. Non-string extras will be disregarded before transmission and won’t be available on the target device. Send the message using the sendDataMessage method, passing in the target username and the Intent to broadcast. The sendDataMessage is available on IM Session or Chat Session objects, as shown below: String username = “T1000@sky.net”; // Send to target user. imSession.sendDataMessage(username, intent); // Send to all chat room participants. chatSession.sendDataMessage(intent); Receiving Data Messages To listen for data messages, register a Broadcast Receiver that fi lters on the action String included in a transmitted Intent. GTalk data messages are processed as normal broadcast Intents, so they have no sender information associated when they’re received by a Broadcast Receiver. If you require such metadata, you should include them in the extras Bundle of the source Intent as was done in the code shown in the previous section.
Chapter 9: Peer-to-Peer Communication The following skeleton code shows how to register a simple Broadcast Receiver implementation that can handle the Intent transmitted in the previous example: BroadcastReceiver otaGTalkIntentReceiver = new BroadcastReceiver() { @Override public void onReceive(Context _context, Intent _intent) { if (_intent.getAction().equals(ACTION_OTA_ELIMINATE)) { String sender = _intent.getStringExtra(“sender”); String target = _intent.getStringExtra(“target”); } }; } String lat = _intent.getStringExtra(“lat”); String lng = _intent.getStringExtra(“long”); Location location = new Location(LocationManager.GPS_PROVIDER); location.setLatitude(Double.parseDouble(lat)); location.setLongitude(Double.parseDouble(lng)); // TODO: Do something with the data transmitted. IntentFilter filter = new IntentFilter(ACTION_OTA_ELIMINATE); registerReceiver(otaGTalkIntentReceiver, filter); Introducing SMS If you own a mobile phone that’s less than two decades old, chances are you’re familiar with SMS messaging. SMS (short messaging service) is now one of the most-used features on mobile phones, with many people favoring it over making phone calls. SMS technology is designed to send short text messages between mobile phones. It provides support for sending both text messages (designed to be read by people) and data messages (meant to be consumed by applications). As a mature mobile technology, there’s a lot of information out there that describes the technical details of how an SMS message is constructed and transmitted over the air. Rather than rehash that here, the following sections focus on the practicalities of sending and receiving text and data messages within Android. Using SMS in Your <strong>Application</strong> Android offers full access to SMS functionality from within your applications with the SMSManager. Using the SMS Manager, you can replace the native SMS application or create new applications that send text messages, react to incoming texts, or use SMS as a data transport layer. SMS message delivery is not timely, so SMS is not really suitable for anything that requires real-time responsiveness. That said, the widespread adoption and resiliency of SMS networks make it a particularly good tool for delivering content to non-Android users and reducing the dependency on third-party servers. 291
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Professional Android Application su
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Professional Android Application D
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Professional Android Application D
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About the Author Originally from Pe
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Acknowledgments A big thank you goe
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Contents Chapter 2: Getting Started
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Contents xii Saving and Loading Fil
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Contents Chapter 10: Accessing Andr
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Introduction Now is an exciting tim
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Introduction covered, you can move
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Introduction At http://p2p.wrox.com
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Chapter 1: Hello, Android 2 Using t
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Chapter 1: Hello, Android An Open P
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Chapter 1: Hello, Android 6 ❑ ❑
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Chapter 1: Hello, Android 8 When ma
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Chapter 1: Hello, Android 10 In mar
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Chapter 1: Hello, Android 12 Each A
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Chapter 1: Hello, Android 14 ❑ Da
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Chapter 1: Hello, Android 16 ❑ an
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Getting Started All you need to sta
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Chapter 2: Getting Started Unless o
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Installing the ADT Plug-in Install
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Chapter 2: Getting Started 3. In th
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Chapter 2: Getting Started If every
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} lp = new LinearLayout.LayoutParam
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Chapter 2: Getting Started on how t
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Chapter 2: Getting Started To start
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Ensuring a Seamless User Experience
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Figure 2-11 Chapter 2: Getting Star
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} myListView.setAdapter(aa); Chapte
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Chapter 2: Getting Started A number
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Creating Applications and Activitie
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Chapter 3: Creating Applications an
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Creating Resources Chapter 3: Creat
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❑ ❑ #ARGB #ARRGGBB Chapter 3: C
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android:startOffset=”500” andro
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Referencing Resources in Resources
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} } Chapter 3: Creating Application
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Chapter 4: Creating User Interfaces
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Chapter 5: Intents, Broadcast Recei
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Data Storage, Retrieval, and Sharin
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Chapter 6: Data Storage, Retrieval,
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} } } Chapter 6: Data Storage, Retr
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Querying Your Database Chapter 6: D
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} // Open or create the database to
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Adding, Updating, and Deleting Cont
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Maps, Geocoding, and Location-Based
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Chapter 7: Maps, Geocoding, and Loc
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400 Android, getting started Androi
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402 databases databases creating ea
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404 interapplication communication
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406 passing custom class objects pa
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408 synchronizing threads synchroni
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Android™ Application Development - Bahar Ali Khan

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