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Programming Applications for Android Platform 

Posted On January 2, 2012 by Geeta Priya filed under Miscellaneous

Android breaks down the barriers to building new and innovative applications. For example, a developer can combine information from the web with data on an individual's mobile phone — such as the user's contacts, calendar, or geographic location — to provide a more relevant user experience. With Android, a developer can build an application that enables users to view the location of their friends and be alerted when they are in the vicinity giving them a chance to connect. Android provides access to a wide range of useful libraries and tools that can be used to build rich applications. For example, Android enables developers to obtain the location of the device, and allows devices to communicate with one another enabling rich peer-to-peer social applications. In addition, Android includes a full set of tools that have been built from the ground up alongside the platform providing developers with high productivity and deep insight into their applications. This article includes some of the important applications programing for Android platform .

Introduction

Android delivers a complete set of software for mobile devices: an operating system, middleware and key mobile applications. Android was built from the ground-up to enable developers to create compelling mobile applications that take full advantage of all a handset has to offer.
Android is a mobile operating system initially developed by Android Inc. Android was bought by Google in 2005. Android is based upon a modified version of the Linux kernel. Google and other members of the Open Handset Alliance collaborated on Android's development and release. The Android Open Source Project (AOSP) is tasked with the maintenance and further development of Android.

It was built to be truly open. For example, an application can call upon any of the phone's core functionality such as making calls, sending text messages, or using the camera, allowing developers to create richer and more cohesive experiences for users. Android is built on the open Linux Kernel. Furthermore, it utilizes a custom virtual machine that was designed to optimize memory and hardware resources in a mobile environment. Android is open source; it can be liberally extended to incorporate new cutting edge technologies as they emerge. The platform will continue to evolve as the developer community works together to build innovative mobile applications.

Android does not differentiate between the phone's core applications and third-party applications. They can all be built to have equal access to a phone's capabilities providing users with a broad spectrum of applications and services. With devices built on the Android Platform, users are able to fully tailor the phone to their interests. They can swap out the phone's homescreen, the style of the dialer, or any of the applications. They can even instruct their phones to use their favorite photo viewing application to handle the viewing of all photos.

The Android operating system software stack consists of Java applications running on a Java-based, object-oriented application framework on top of Java core libraries running on a Dalvik virtual machine featuring JIT compilation. Libraries written in C include the surface manager, OpenCore media framework, SQLite relational database management system, OpenGL ES 2.0 3D graphics API, WebKit layout engine, SGL graphics engine, SSL, and Bionic libc. The Android operating system consists of 12 million lines of code including 3 million lines of XML, 2.8 million lines of C, 2.1 million lines of Java, and 1.75 million lines of C++.

Android Capabilities

Handset layouts	The platform is adaptable to larger, VGA, 2D graphics library, 3D graphics library based on OpenGL ES 2.0 specifications, and traditional smartphone layouts.
Storage	SQLite, a lightweight relational database, is used for data storage purposes
Connectivity	Android supports connectivity technologies including GSM/EDGE, IDEN, CDMA, EV-DO, UMTS, Bluetooth, Wi-Fi, LTE, and WiMAX.
Messaging	SMS and MMS are available forms of messaging, including threaded text messaging and now Android Cloud to Device Messaging Framework (C2DM) is also a part of Android Push Messaging service.
Web browser	The web browser available in Android is based on the open-source WebKit layout engine, coupled with Chrome's V8 JavaScript engine. The browser scores a 93/100 on the Acid3 Test.
Java support	While most Android applications are written in Java, there is no Java Virtual Machine in the platform and Java byte code is not executed. Java classes are compiled into Dalvik executables and run on the Dalvik virtual machine. Dalvik is a specialized virtual machine designed specifically for Android and optimized for battery-powered mobile devices with limited memory and CPU. J2ME support can be provided via third-party-applications.
Media support	Android supports the following audio/video/still media formats: WebM, H.263, H.264 (in 3GP or MP4 container), MPEG-4 SP, AMR, AMR-WB (in 3GP container), AAC, HE-AAC (in MP4 or 3GP container), MP3, MIDI, Ogg Vorbis, WAV, JPEG, PNG, GIF, BMP.
Streaming media support	RTP/RTSP streaming (3GPP PSS, ISMA), HTML progressive download (HTML5 <video> tag). Adobe Flash Streaming (RTMP) and HTTP Dynamic Streaming are supported by the Flash 10.1 plugin. Apple HTTP Live Streaming is supported by RealPlayer for Mobile and planned to be supported by the operating system in Android 3.0 (Honeycomb). Microsoft Smooth Streaming is planned to be supported through the awaited port of Silverlight plugin to Android.
Additional hardware support	Android can use video/still cameras, touchscreens, GPS, accelerometers, gyroscopes, magnetometers, proximity and pressure sensors, thermometers, accelerated 2D bit blits (with hardware orientation, scaling, pixel format conversion) and accelerated 3D graphics.
Development environment	Includes a device emulator, tools for debugging, memory and performance profiling. The integrated development environment (IDE) is Eclipse (currently 3.4 or greater) using the Android Development Tools (ADT) Plugin. The programming languages are Java and C/C++.
Market	The Android Market is a catalog of applications that can be downloaded and installed to Android devices over-the-air, without the use of a PC.
Multi-touch	Android has native support for multi-touch which was initially made available in handsets such as the HTC Hero. The feature was originally disabled at the kernel level (possibly to avoid infringing Apple's patents on touch-screen technology). Google has since released an update for the Nexus One and the Motorola Droid which enables multi-touch natively.
Bluetooth	Supports A2DP, AVRCP, sending files (OPP), accessing the phone book (PBAP), voice dialing and sending contacts between phones. Keyboard, mouse and joystick (HID) support is available through manufacturer customizations and third-party applications. Full HID support is planned for Android 3.0 (Honeycomb).
Video calling	The mainstream Android version does not support video calling, but some handsets have a customized version of the operating system which supports it, either via UMTS network (like the Samsung Galaxy S) or over IP. Video calling through Google Talk is planned for Android 3.0 (Honeycomb).
Multitasking	Multitasking of applications is available.
Voice based features	Google search through Voice has been available since initial release. Voice actions for calling, texting, navigation etc. are supported on Android 2.2 onwards.
Tethering	Android supports tethering, which allows a phone to be used as a wireless/wired hotspot. Prior to Android 2.2 this was supported by third-party applications or manufacturer customizations.

Application: Programming Faster Screen Orientation Change
Android is designed to run efficiently on a wide array of devices, with very different hardware configurations. Some devices, like the T-Mobile G1, can change their hardware configuration at runtime. For instance, when you open the keyboard, the screen change from the portrait orientation to the landscape orientation.

To make Android app development easier, the Android system automatically handles configuration change events and restarts the current activity with the new configuration. This is the default behavior that lets you declare resources like layouts and drawables based on the orientation, screen size, locale, etc.
While this behavior is really powerful, since your application adapts automatically to the device's configuration at runtime, it is sometimes confusing for new Android developers, who wonder why their activity is destroyed and recreated.

Facing this "issue," some developers choose to handle configuration changes themselves which is, in general, a short-term solution that will only complicate their lives later. On the other hand, the system's automatic resource handling is a very efficient and easy way to adapt an application's user interface to various devices and devices configurations. It sometimes comes at a price, though.

When your application displays a lot of data, or data that is expensive to fetch, the automatic destruction/creation of the activities can be lead to a painful user experience. Take the example of Photostream, a simple Flickr browsing application. After you launch the application and choose a Flickr account, the application downloads a set of 6 photos (on a T-Mobile G1) from the Flickr servers and displays them on screen. To improve the user experience, the application uses slightly different layouts and drawables in portrait and landscape modes and this is what the result looks like:

Photostream lets Android take care of the configuration change when the screen is rotated. However, can you imagine how painful it would be for the user to see all the images being downloaded again? The obvious solution to this problem is to temporarily cache the images. They could be cached on the SD card (if there's one), in the Application object, in a static field, etc. None of these techniques is adapted to the current situation: why should we bother caching the images when the screen is not rotated? Fortunately for us, Android offers a great API exactly for that purpose.

The Activity class has a special method called onRetainNonConfigurationInstance(). This method can be used to pass an arbitrary object your future self and Android is smart enough to call this method only when needed. In the case of Photostream, the application used this method to pass the downloaded images to the future activity on orientation change. The implementation can be summarized like so:

@Override
  public Object onRetainNonConfigurationInstance() {
      final LoadedPhoto[] list = new LoadedPhoto[numberOfPhotos];
      keepPhotos(list);
      return list;
  }

In the new activity, in onCreate(), all you have to do to get your object back is to call getLastNonConfigurationInstance(). In Photostream, this method is invoked and if the returned value is not null, the grid is loaded with the list of photos from the previous activity:

private void loadPhotos() {
      final Object data = getLastNonConfigurationInstance();
      
      // The activity is starting for the first time, load the photos from Flickr
      if (data == null) {
          mTask = new GetPhotoListTask().execute(mCurrentPage);
      } else {
          // The activity was destroyed/created automatically, populate the grid
          // of photos with the images loaded by the previous activity
          final LoadedPhoto[] photos = (LoadedPhoto[]) data;
          for (LoadedPhoto photo : photos) {
              addPhoto(photo);
          }
      }
  }

Be very careful with the object you pass through onRetainNonConfigurationChange(), though. If the object you pass is for some reason tied to the Activity/Context, you will leak all the views and resources of the activity. This means you should never pass a View, a Drawable, an Adapter, etc. Photostream for instance extracts the bitmaps from the drawables and pass the bitmaps only, not the drawables. Finally, remember that onRetainNonConfigurationChange() should be used only to retain data that is expensive to load. Otherwise, keep it simple and let Android do everything.

Bluetooth Chat Application

This application allows two Android devices to carry out two-way text chat over Bluetooth. It demonstrates all the fundamental Bluetooth API capabilites, such as:

 

• Scanning for other Bluetooth devices
• Querying the local Bluetooth adapter for paired Bluetooth devices
• Establishing RFCOMM channels/sockets
• Connecting to a remote device
• Transfering data over Bluetooth

This is source code shown below is located in the corresponding directory in : <sdk>/samples/android-<version>/...

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.example.android.BluetoothChat"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk minSdkVersion="6" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
    <uses-permission android:name="android.permission.BLUETOOTH" />

    <application android:label="@string/app_name"
                 android:icon="@drawable/app_icon" >
        <activity android:name=".BluetoothChat"
                  android:label="@string/app_name"
                  android:configChanges="orientation|keyboardHidden">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".DeviceListActivity"
                  android:label="@string/select_device"
                  android:theme="@android:style/Theme.Holo.Dialog"
                  android:configChanges="orientation|keyboardHidden" />
    </application>
</manifest>

This article covers only the basic concepts .For core technical aspects & consultancy you can consult the following references or e-mail at : skphind@yahoo.co.uk

References & Web Links     

• Android Application Development: Programming with the Google SDK By Rick Rogers, John Lombardo, Zigurd Mednieks, G. Blake Meike ,O'Reilly Pub.

• The Busy Coder's Guide to Android Development By Mark L. Murphy , CommonsWare Pub.

• Android Programming Tutorials By Mark Lawrence Murphy , CommonsWare Pub.

• Practical Android Projects By Justin Bacon, Lucas Jordan, Pieter Greyling,Apress Pub.

• Professional Android Application Development By Author Reto Meier,John Wiley and Sons Pub.

• http://www.android.com/

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About the Authors

Sunil Kr.Pandey

Head- IT & Systems
Jaipuria Institute of Management
Jaipur, Rajasthan
E-mail:skphind@rediffmail.com

R.B.Mishra

Professor
Department of Computer Engineering
Institute of Technology(IT),
Banaras Hindu University(BHU),
Varanasi(UP)
India.

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