Android is a open source Linux Kernel based operating system designed for mobile devices such as smart phones or tablet computers. This was initially developed by Google in the year 2007 and the first commercial version was released in the year 2008 . Its user Interface mainly based on direct manipulation using touch gestures which loosely correspond to the real world interactions. It offers a unified approach to application development of mobile devices which allows the application to run on different services by android.
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The architecture of Android is categorized into five parts. Let us discuss them briefly.
It is the essential component of Android. It provides the level of abstraction between device hardware and essential drivers like Keypad, Camera, display etc. It also handles the things such as networking and a vast array of device drivers. It is responsible for Memory Management, Power Management, and Device management.
In android runtime there are core libraries and DVM(Dalvik Virtual Machine) which is responsible to run android application . The Android DVM is line JVM which is optimized for mobile devices . It consumes less memory and fast performance . It enables the list of core Libraries which enable android application developers to write android applications using JAVA programming language.
Application Frame work offers many higher level services in the form of JAVA Classes .It allows application developers to make user of their services in their applications.
It provides the following services:
Activity Manager: All aspects of application life cycle was controlled by the Activity Manager.
Content Providers – It allows applications to publish and share data with other applications.
Resource Manager – access to non-code embedded resources such as strings , color settings and user interface layout was provided by the Resource Manger.
Notification Manager – User can get the display alerts and notifications by the notification manager .
View System – An extensible set of views used to create application user interfaces.
This can be find at the top layer. All applications such as home , contact , settings, games and browsers were used by the android framework which in turn uses Android runtime and libraries .
The life cycle of Android is controlled by the seven methods of android.app.activity class. This is the subclass of Context Theme Wrapper class. An activity represents a single screen with a user interface like window or Java. Programs written in C, C++ (or) Java Starts with a main function. Similarly Android system initiates its program with a call onCreate() call back method. The life cycle of Android is shown below.
OnCreate (): It is called when the activity is first created.
OnStart () : It is called when the activity becomes visible to the user.
OnResume (): It is called when the user starts interacting application.
OnPause ():This is called only when the current activity is being
paused and previous activity is being resumed.
On Stop (): This is called when the activity is no longer visible.
On Destroy ():This is called when the system is about to be destroyed.
On Restart ():This is called when the activity restarts after stopping it.
Beautiful UI: It basic screen provides a beautiful and intuitive user interface.
Connectivity: GSM/EDGE, Wi-Fi, WiMAX, CDMA, Bluetooth, LTE, NFC
Storage: SQLite is a lightweight relational database and is used for data storage purposes.
Messaging: SMS, MMS
Multi –tasking: User can jump from one task to another at the same time simultaneously.
Prerequisites: It’s good to have a basic knowledge on object oriented programming languages like JAVA. But it is not mandatory. Trainers will train you if you do not have knowledge on it.
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