Core Building Blocks of Android –

Component in Android –

In the android  component is an already  pre written code which has  a  life cycle.  

The  Core building blocks  include these components. In  which  the Android Applications  can be built. In android  Core building  blocks are fundamental  components. Android  Developers  should understand  these  components.

Fundamental components of Android are –

Activity, Intent, Service, Content Provider, Broadcast Receiver.

Activity –

Activity   is  a screen . Activity  is the main Screen which  contains  UserInterface(UI) and Logic .Contains XML and java code.

Activity  file contains  two files  Activity.xml which  is used  for UserInterface(UI).and second file  contains java file (Activity.java) used for writing Logic .

Intent –

Intent     is a message  passing  object. If you want  to  communicate  from  one activity  to  another then we can go  for intent. Intent  also helps to communicate between other components like service or broadcast receiver.

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Use of intent is –

• Start Activity.
• Start Service.
• Delivering broadcasts.
• Opening  a  webpage.

 

There   are  two  types  of  intent  –

• Implicit  Intent
• Explicit Intent

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Overview of Services In Android-

Services   is an android   component that can perform long-running tasks   in the background. Service  doesn’t have any user Interfaces . Because service runs in the background. Service runs only on another application . Service  cannot start  by itself .Android   service   is  not a thread   or separate  process –

Examples of  services are –

1. Music player  which plays music in the background.
2. Network  transactions  Applications.
3. Content provider which does database  related tasks in the background.
4. Performing    file input  and output 

Above  are  very  common  examples   of  services.

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Life cycle of service –

When  service gets  started  with startService()   method  then  its  life cycle starts . service will  run in background until  it is stopped  by stopService()  or stopSelf()  method. Service  Always  runs on the main thread.

1)Background service: A  service  that  performs  an  operation that  is not  directly noticed by the user.

2)Foreground service:   A  service  that  performs a certain  operation    that  is  noticeable   to the end user  is  called  foreground service.

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Example is : Playing   audio track. we  need  to close  the  services  to  stop service. Foreground service  must  display  notification.

Differences  between  Service  and  Thread –

Service: Service runs on the main UI Thread.  Service is a component of android. Service performs a long running operation in the background. Generally  service does not have any UI. 

Thread : Thread is an operating System level  feature that performs  some operation  at Background.

Difference  between  Thread    and  Service

Thread :  Thread is  not an android  component.   If the thread  gets  destroyed, Android    will not restart the  thread.  For this reason Users may lose their data.

Service:   Service  is an android  component. Android  handles it. Because service has its built-in component. The Service  has priority  levels  in  android . For doing some background tasks better   to   select a  service. Above  are some differences between  thread  and service.

Let us see the Steps for creating  a service in Android –  

• To  create  a  service. Service needs  to  be declared in AndroidMenifest.xml .
• Extend a class with  Service. When  we extend  with a Service class we get two  methods. 

@Override

public   int  onStartCommand(Intent  intent,int flags,int startId)

{

//   code

return    Service.START_NOT_STICKY; 

 

}

The  above  method  returns   int value   which  defines  the  restart  behavior   when  service  gets terminated by  android platform.

    onstartCommand()     is  used  to   start a  service . 

To  stop  a service we  have to use the stopService()   method . This   will  kill  the  service.   

Sometimes we want to stop service by  itself, in that case we can go for the stopSelf()   method . This method stops service when service finishes its task.

 stopSelf()   is  also  used  if service finishes  its  task.

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Lets   us  discuss  the   different  call back methods  of service

While   creating  a  service   we  can override  certain  methods  like below.  We  have already discussed OnstartCommand()  , stopService()  and stopService()  methods .

onCreate() 

System  invokes  this  method  to perform ontime setup. When service is  created . if service already runs this  method  will  not get invoked.

onDestroy()

when  service is no longer  in use.  Then this  method  will  destroy   the service.

@Override

Public   IBinder    OnBind(Intent  intent)

{

 return   null;  

}

This  method binds  to  the services, sends requests ,receives responses and performs inter process communication(IPC). Abound service typically lives only while it  serves another application component  and does not  run in  the background indefinitely.

After  discussing  the  Core  building  block of  Android . we  will  discuss  choosing Language  in android studio.

Choosing   Programming  Language in Android Studio –

While  creating App   using Android studio(Android  studio is   Integrated Development  Environment   for creating   mobile App. Which is specially designed  for  creating only mobile App.)   we  need  to  choose a language  in  Android studio.android  developers    can  choose  kotlin  or java. As  for  writing   the  logic  for the App. 

Android   Developer’s   can   have   an option  to  choose   the  language for writing  app  logic. 

Android developer’s   can  choose   java language  or   kotlin language. 

Let  us  discuss  What  is  Kotlin?

Kotlin   is  programming Language for JavaVirtual Machine(JVM). Android Developer’s   can use the kotlin language  for  development. Apart  from mobile App Development  .We can  use  kotlin for   client/server  programming  also. Kotlin Language  is  developed   by  JetBrains. Currently  kotlin  is  predominantly used  for Android  App  Development. 

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Kotlin   is more  concise  than java. Kotlin has inbuilt null safety. Kotlin can solve Null pointer exception .  Null Pointer exception  is a commonly occurring  exception  that  developers  must handle. In android  null means  nothing  or  to represent  absent value. Mostly  it  is used to   represent  null value. When  exception   occurs  in  application. It   is the role of  a  developer that must handle exceptions . Using Related exception handling techniques.

In Kotlin language    inbuilt features  for  null safety. Since  Kotlin language  has  a built-in feature for handling null pointer exceptions, development  becomes  faster,  because  the  language  itself   takes  care  of  exception handling so android  development  becomes   faster.

Kotlin  code development  speed  is   fast   as compared  to  java. Kotlin supports  lambda  expressions . In  which  anonymous methods  (functions) can be treated as values. You  can pass  parameters  to  methods,   any  logic that you can implement. For  community support  java  has a very  large  community. Kotlin  has  very  small community. Kotlin is  interoperable with java.

Android   studio  has excellent  support  for kotlin. Once  we install  kotlin plugin . Kotlin  supports  Lambda expressions .   Java  8  onwards  only Java supports  lambda expressions. Adapting kotlin  concepts is very easy. From a performance  point  of  view  kotlin   is  slower  than java. 

Android  development   is  always  done  with  java..  Because  of    simplicity , performance and maintainability robustness.kotlin  code  is  lightweight.

Language  than java.kotlin add  some modern features like 

1. Compiling  code to javascript  or Native Script.
2. Kotlin can build code  that  runs  on ios   also.
3. Kotlin  is  Statically typed  and open source language.

Lets  us  see  Top  Companies   using Kotlin  for  Development

Uber,Gradle,and Pivotal   are  some companies  using Kotlin. 

Here is a discussion  about kotlin and java – 

Kotlin Language  is developed  by Google as a First-Class  Language  supported on android. While  doing  Mobile App  Development Kotlin  is Preferable than java. Kotlin   is code safer Language . In kotlin documentation is very well implemented. So  Conclusion  is  that  While  android  Development  we can choose Kotlin. 

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To  know  interview Questions   on  Android  you  can refer  a link.

https://www.sevenmentor.com/android-interview-questions-and-answers-for-freshers/   

 

Author:-

Bhagyashri Sangam

SevenMentor Pvt Ltd

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