Ash Final Seminar Report

8/7/2019 Ash Final Seminar Report

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CONTENTS

Abstract (i)Acknowledgement (ii)

1. Introduction

2. Platform

3. Application Development

4. Overall evaluation

5. Future work

6. Snapshots

7. Conclusions

8. References


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DEVELOPMENT, MAINTENANCE & VISUAL OF ANDROID

1. WHAT IS DIFFERENT ABOUT ANDROID?

The good news is for both the consumers and developers. While consumers could enjoy a

low-cost Smart phones running Android, developers were given an unrestricted

customization rights. From a developer's point of view, Android has several unique features,

as listed below:

The entire Application framework can be reused and replaced by selective

components

Dalvik virtual machine enhances the power management systems (Learn about

Dalvik VM in the following subtitle)

Support for 2D and 3D graphics (OpenGL ES 1.0), So lot of business for animation

developers.

Reliable and enhanced data storage ( using SQLite framework)

Developers can create media common applications since it supports common media

file formats(MPEG, MPEG3, MPEG4, H.286, AAC, AMR, JPG, PNG, GIF and

more) GSM, EDGE, 3G, HSCSD, Wi-Fi network applications support (Depends on

hardware).

2. PLATFORM

2.1 HARDWARE

First and foremost, Android is a software stack for mobile devices. This means that

high on the list of priorities is the preservation of battery power and the efficient management

of limited memory resources. There are five distinct layers to the Android system stack:

The Acorn RISC Machine (ARM) Linux core forms the solid base upon which all the

other layers stand. Linux is a proven technology that is highly reliable, and the ARM

processor family is known for high performance on very low power requirements.

The libraries provide the reusable and sharable low-level code for basic functions suchas codecs software for coding and decoding digital sound and video functions

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for the presentation of rich graphics on a small displays, secure shell support for

encrypted TCP/IP traffic into the cloud, as well as component support for Web

browsing (WebKit), SQL database functionality (SQLite), and standard C library

functionality you would expect in a Linux system. The Dalvik run-time byte-code interpreter, which strongly resembles the Java

language byte-code interpreter, adds a few distinct features that uniquely define the security

and power-preserving model of Android. Every application currently running, for example,

has its own user ID and its own copy of the interpreter running to strictly separate processes

for security and reliability.

The Android application framework enables you to use and replace components as

you see fit. These high-level Java classes are tightly integrated components that define

the Android API.

The Android core applications include the WebKit browser, Google calendar, Gmail,

Maps Application, SMS messenger, and a standard e-mail client, among others.

Android applications are written in the Java programming language, and you can

download many more from the Android market on the fly.

Android is not a single piece of hardware; it's a complete, end-to-end software

platform that can be adapted to work on any number of hardware configurations. Everything

is there, from the boot loader all the way up to the applications. And with an Android device

already on the market, it has proven that it has what it takes to truly compete in the mobile

arena.

2.2 Operating System(s)

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Fig (ii) Operating system

Android uses Linux for its device drivers, memory management, process

management, and networking. However you will never be programming to this layer directly.

The next level up contains the Android native libraries. They are all written in C/C++

internally, but youll be calling them through Java interfaces. In this layer you can find the

Surface Manager (for compositing windows), 2D and 3D graphics, Media codecs (MPEG-4,

H.264, MP3, etc.), the SQL database (SQLite), and a native web browser engine (WebKit).

Next is the Android runtime, including the Dalvik Virtual Machine. Dalvik runs dex

files, which are converted at compile time from standard class and jar files. Dex files are

more compact and efficient than class files, an important consideration for the limited

memory and battery powered devices that Android targets.

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The core Java libraries are also part of the Android runtime. They are written in Java,

as is everything above this layer. Here, Android provides a substantial subset of the Java 5

Standard Edition packages, including Collections, I/O, and so forth.

The next level up is the Application Framework layer. Parts of this toolkit are

provided by Google, and parts are extensions or services that you write. The most important

component of the framework is the Activity Manager, which manages the life cycle of

applications and a

common back-stack for user navigation.

Finally, the top layer is the Applications layer. Most of your code will live here, along

side built-in applications such as the Phone and Web Browser.

2.3 Network Connectivity

It supports wireless communications using:

GSM mobile-phone technology

3G

Edge

802.11 Wi-Fi networks

2.4 Security

Android is a multi-process system, in which each application (and parts of the system)

runs in its own process. Most security between applications and the system is enforced at the

process level through standard Linux facilities, such as user and group IDs that are assigned

to applications. Additional finer-grained security features are provided through a

"permission" mechanism that enforces restrictions on the specific operations that a particular

process can perform, and per- URI permissions for granting ad-hoc access to specific pieces

of data.

Security Architecture

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A central design point of the Android security architecture is that no application, by

default, has permission to perform any operations that would adversely impact other

applications, the operating system, or the user. This includes reading or writing the user's

private data (such as contacts or e-mails), reading or writing another application's files,

performing network access, keeping the device awake, etc.

An application's process is a secure sandbox. It can't disrupt other applications, except

by explicitly declaring the permissions it needs for additional capabilities not provided by the

basic sandbox. These permissions it requests can be handled by the operating in various

ways, typically by automatically allowing or disallowing based on certificates or by

prompting the user. The permissions required by an application are declared statically in that

application, so they can be known up-front at install time and will not change after that.

2.5 Performance

Devices hosting Android applications have limited capabilities. That's why code

should be efficient, avoid all unnecessary memory allocations, method calls (it takes a lot of

time) and so on.

In order to make our applications working fast on a mobile device we need to leave

back some habits, good from OOP point of view. In a mobile device we are not able to make

a full model of reality what we want to operate on.

Few things to remember:

- avoid object instantiation - create objects only if it is really necessary, because it

costs time and memory. More instances means more-frequent garbage collection what

lowers user-experience (freezes).

- use native built-in methods - they're written in C/C++ what makes them faster about

10-100 times than implemented JAVA code (loops etc.). However note that calling native

method is more expensive then calling implemented one.

- virtual over interface - in conventional programming it is usual to declare variables as

interfaces, i.e.:Map myMap1 = new HashMap();

It is not good for embedded applications. Calling a method from interfaces

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takes 2 times more time than in normal way: HashMap myMap2 = new HashMap();

- static over virtual - declare methods static if they do not need access to the object's

fields. It can be called faster, because it doesn't require a virtual method tableindirection. It's also good practice, because you can tell from the method signature that

calling the method can't alter the object's state.

- cache field lookups,because accessing object fields is lower than local variables. The

same situation is with methods - i.e. by for-statements, you should cache size() method

if it is possible.

3. Application Development

3.1 Programming language(s)

The officially supported programming language on the Android platform is Java. It is

also recommended to have some knowledge of XML as the descriptor file as well as the user

interface of an application is based on that.

As the Linux kernel of the Android platform is based upon an ARM processor

architecture it would also be possible to write code in C or other languages and compile it to

ARM native code.

3.2 Application Building Blocks

There are four building blocks to an Android application:

Activity

Intent Receiver

Service

Content Provider

Not every application needs to have all four, but your application will be written with some

combination of these.

Once you have decided what components you need for your application, you should

list them in a file called AndroidManifest.xml. This is an XML file where you declare the

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components of your application and what their capabilities and equirements are. We will

discuss soon, what the AndroidManifest.xml is responsible for.

ActivityActivities are the most common of the four Android building blocks. An activity is usually a

single screen in your application. Each activity is implemented as a single class that extends

the Activity base class. Your class will display a user interface composed of Views and

respond to events. Most applications consist of multiple screens. For example, a text

messaging application might have one screen that shows a list of contacts to send messages

to, a second screen to write the message to the chosen contact, and other screens to review

old messages or change settings.Each of these screens would be implemented as an activity. Moving to another screen is

accomplished by a starting a new activity. In some cases an Activity may return a value to the

previous activity for example an activity that lets the user pick a photo would return the

chosen photo to the caller. When a new screen opens, the previous screen is paused and put

onto a history stack. The user can navigate backward through previously opened screens in

the history.

Screens can also choose to be removed from the history stack when it would be

inappropriate for them to remain. Android retains history stacks for each application launched

from the home screen.

Intent and Intent Filters

Android uses a special class called Intent to move from screen to screen. Intent

describe what an application wants done. The two most important parts of the intent data

structure are the action and the data to act upon. Typical values for action are MAIN (thefront door of the application), VIEW, PICK, EDIT, etc. The data is expressed as a Uniform

Resource Indicator (URI).

For example, to view a website in the browser, you would create an Intent with the

VIEW action and the data set to a Website-URI.

new Intent(android.content.Intent.VIEW_ACTION, ContentURI.create("http://anddev.org"));

There is a related class called an IntentFilter. While an intent is effectively a request to do

something, an intent filter is a description of what intents an activity (or intent receiver, see

below) is capable of handling. An activity that is able to display contact information for a

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person would publish an IntentFilter that said that it knows how to handle the action VIEW

when applied to data representing a person. Activities publish their IntentFilters in the

AndroidManifest.xml file.

Navigating from screen to screen is accomplished by resolving intents. To navigate

forward, an activity calls startActivity(myIntent). The system then looks at the intent filters

for all installed applications and picks the activity whose intent filters best matches myIntent.

The new activity is informed of the intent, which causes it to be launched. The process of

resolving intents happens at run time when startActivity is called, which offers two key

benefits:

Activities can reuse functionality from other components simply by making a request

in the form of an Intent

Activities can be replaced at any time by a new Activity with an equivalent

IntentFilter

Intent Receiver

You can use an IntentReceiver when you want code in your application to execute in

reaction to an external event, for example, when the phone rings, or when the data network is

available, or when it's midnight. Intent receivers do not display a UI, although they may

display Notifications to alert the user if something interesting has happened. Intent receivers

are also registered in AndroidManifest.xml, but you can also register them from code using

Context.registerReceiver(). Your application does not have to be running for its intent

receivers to be called; the system will start your application, if necessary, when an intent

receiver is triggered. Applications can also send their own intent broadcasts to others with

Context.broadcastIntent().

Service

A Service is code that is long-lived and runs without a UI. A good example of this is a

media player playing songs from a play list. In a media player application, there would

probably be one or more activities that allow the user to choose songs and start playing them.

However, the music playback itself should not be handled by an activity because the user will

expect the music to keep playing even after navigating to a new screen. In this case, themedia player activity could start a service using Context.startService() to run in the

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background to keep the music going. The system will then keep the music playback service

running until it has finished. (You can learn more about the priority given to services in the

Content Provider Applications can store their data in files, a SQLite database, preferences

or any other mechanism that makes sense. A content provider, however, is useful if you wantyour application's data to be shared with other applications. A content provider is a class that

implements a standard set of methods to let other applications store and retrieve the type of

data that is handled by that content provider.system by reading Life Cycle of an Android

Application.) Note that you can connect to a service (and start it if it's not already running)

with the Context.bindService() method. When connected to a service, you can communicate

with it through an interface exposed by the service. For the music service, this might allow

you to pause, rewind, etc.

3.4 Creating a new Android Project

1. The first thing that needs to be for every Android Application is to create a

new Android Project. To do that, simply open the Package Explorer in Eclipse

right-click on New option.

New > Project

2. Select

Android > Android Project

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3. Fill out the form with values fitting your applications purpose...

This are all the files for your first Android-Application (don't panic, mostly all of them are

resource-files)

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4. Running your first application

Now we need to create a Run-Configuration. Open the -DropDown in the Eclipses upper

menu and Click "Open Run Dialog..."

Creating Run

Having done that youll see this:

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4 Overall Evaluation

4.1 Advantages

There are a host of advantages that Googles Android will derive from being an open

source software. Some of the advantages include:

The ability for anyone to customize the Google Android platform will open up the

applications playing field to small and new players who lack the financial muscle to

negotiate with wireless carriers like AT&T and Orange.

The consumer will benefit from having a wide range of mobile applications to choose

from since the monopoly will be broken by Google Android.

Although this will depend on the carrier, one will be able to customize a mobile

phones using Google Android platform like never before, right down to the screen.

Features like weather details, opening screen, live RSS feeds and even the icons on

the opening screen will be able to be customized.

In addition, as a result of many mobile phones carrying Google Android, companies

will come up with such innovative products like the location aware services that will

provide users with any information they might be in need of.

This information could include knowing the location of a nearby convenience store or

filling station. In addition the entertainment functionalities will be taken a notch

higher by Google Android being able to offer online real time multiplayer games.

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4.2 Limitations

Bluetooth limitations:

Google Talk functions and only the simplest implementation of Bluetooth. It'll work

with Bluetooth headsets but that's about it; no Bluetooth stereo, no contacts exchange, no

modem pairing and no using wireless keyboards.

Android uses a non-standard jvm: there is no guarantee that the same software will run on

multiple devices

Firefox Mobile isn't coming to Android because of Android Limitations :

Fennec won't play nice with Android Market because apps in Android Market need to be

programmed with a custom form of Java to run on Android. Mozilla and the Fennec peeps

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won't have that and won't be releasing any form of Firefox until Google amends the limitation

of Android Apps.

5. Future Work

The good news is for both the consumers and developers. While consumers could

enjoy a low-cost Smart phones running Android, developers were given an unrestricted

customization rights. From a developer's point of view, Android has several advantages, as

listed below:

The entire Application framework can be reused and replaced by selective

components

Dalvik virtual machine enhances the power management systems (Learn about

Dalvik VM in the following subtitle)

Support for 2D and 3D graphics (OpenGL ES 1.0), So lot of business for

Animation developers.

Reliable and enhanced data storage ( using SQLite framework)

Developers can create media common applications since it supports common

media file formats(MPEG, MPEG3, MPEG4, H.286, AAC, AMR, JPG, PNG,

GIF and more)

GSM, EDGE, 3G, HSCSD, Wi-Fi network applications support (Depends on

hardware)

6. Snapshots

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6. Conclusion

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In this presentation we have studied about

Android marketing strategy

Android applications and its development aspects

Android future views Maintenance

Advantages and limitations of android

We can only hope that the next versions of Android have overcome

the actual limitations and that the future possibilities became a

Reality.

7. References

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Websites:

http://code.google.com/android/

http://android-developers.blogspot.com

http://code.google.com/p/apps-for-android/

http://source.android.com

http://www.anddev.org

E-Books:

Beginning Android - Mark L Murphy

Hello Android (2nd Edition) - Ed Burnette

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http://code.google.com/android/http://android-developers.blogspot.com/http://code.google.com/p/apps-for-android/http://source.android.com/http://www.anddev.org/http://code.google.com/android/http://android-developers.blogspot.com/http://code.google.com/p/apps-for-android/http://source.android.com/http://www.anddev.org/

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Ash Final Seminar Report

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