Posted by: phillipnb | February 10, 2013

Beginning Android


From this month, I am going to take a break from PHP. It is not that PHP has lost its charm or I have started disliking PHP. PHP will always remain in the programming world for what it is destined for and I will continue to program in PHP whenever required. But recently I received a project to build an Android application and I thought why not give it a try. So, from this month you will see a few posts (every month) on Android Programming. As I said before, I will continue to post articles on PHP whenever I feel that I should talk about a particular topic in PHP.

To start working on Android or to create Android Apps, as a pre-requisite, one should know the following:
a).Good understanding of Object Oriented Programming Concepts
b).Minimum knowledge in Java Programming. The more knowledge you have in Java, the better.
c).Good understanding of DML and DDL queries from SQL.

Once you have the above, start reading about Android from the android developer website or use a book that talks about Android Programming. If you like to learn Android Programming using a class room, then join an institution that provides training in Android Programming. What ever method that you choose to learn Android Programming, as an Android Developer, you should know the following:

a).What is Android?
Android is a Linux-based Open Source Operating System developed Google for mobile devices(smartphones and tablets with touch screen). Android’s core libraries are written using C and C++.

b).How to set up the Android Development Environment?
Follow the instructions in the developer guide.

c).What is Dalvik Virtual Machine?
Dalvik Virtual Machine is a process virtual machine and is a part of the Android stack. DVM was originally developed by Dan Borstein. In brief, this is what happens when you execute your android code. The java code written as part of the android app is first converted to bytecode(.class file) by the java compiler. This byte code gets converted to .dex (dalvik executable) format using the dx tool of Android. The dex file is then executed by the Dalvik VM.

d).What is an apk file?
apk(application package file) is a file format that is used to distribute and install applications on devices powered by the Android Operating System.

e).What is an Activity?
Activity uses Views and Fragments to create a user interface, a visual representation of the Android application. So, Activity can be called as a Visual Representation.

j).What is a View?
Widgets, like buttons, text fields etc, that create a user interface are known as View in Android.

j).What is a Fragment?
Components that run in the context of an activity are called Fragments.

f).What is a Service?
Services are kind of opposite to Views in Android. They perform certain designated task in the background without user intervention.

g).What is a BroadCast and Receivers?
These are Android components that are used to get notifications about system wide events.

i).What are Content Providers?
The job of a content provider in Android is to provide an interface to the application data.

k).What are Notifications?
The idea of Notifications is to inform the recipient about an event. In Android, ‘Notification’ is a class whose job is to present a notification to the user.

l).What is an Intent?
Intents usually are used to start a Activity or carry data to an Activity. It provides a binding between components or activities.

m).What are the different Android API levels?
Android API level is a number (integer) that denotes the Android API revision for that particular Android version. e.g.Android version 2.3.2, 2.3.1 and 2.3 have a API level of 9.

n).What is an Activity Life Cycle?
In Android, there are usually 5 major states that an application will go through and they are start state, running state, paused state, stopped state and destroyed state. At any given time an android application will be in one of these state and together all these states constitute the activity life cycle.

o).What are Layouts?
Layout are used to create how the widgets should be laid out on the user interface, it creates a visual structure for the UI.

p).Android Manifest File
The manifest file of an Android app describes the characteristics of the application. All the components of the application are listed in this file.

q).Values or the string.xml file
A single string in Android can be referenced from the application or from the string.xml resource file. This xml file is stored in the res/values/something.xml

r).R.java
R.java is a class that represents all the resources that can be instantiated your android code. It does not contain any data and is auto generated file, a file that is created when you build your application. It contains unique identifiers for every type (drawable, string, layout, color, etc.) of resource that is available in your android application so that these can be accessed quickly in the application.

Please remember that the above given definitions are not complete. To get a detailed explanation of the above terms, please refer the android developer guide. If you are comfortable with the terms described above and if you have the required pre-requisites mentioned above, then you are all set for developing applications using Android.

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