Android Basic Interview Questions

android basic interview questions

Android Developer Interview Questions

1.What is android?

 Android is open source Linux based operating system with middle ware and some key applications

2.What are the advantages of android?

Open-source:

It means no licence, distribution and development fee.

Platform-independent: 

Android is platform independent we can develop applications in mac, Linux and windows also by using android studio

Supports various technologies:

It supports camera, Bluetooth, WiFi, speech, EDGE etc. technologies.

DVM :

DVM is highly optimized virtual machine which will convert to .dex file

3.What is an Activity?

Activity is like a frame or window in java that represents GUI. It represents one screen of android.

4.What is Activity life cycle?

There are 7 life-cycle methods of activity. They are as follows:

  1. onCreate() — called when activity is first created.
  2. onStart() — onStatrt will invoked  when activity is becoming visible to the user.
  3. onResume() — onResume will invoked when activity will start interacting with the user.
  4. onPause() onPause will invoked when activity is not visible to the user.
  5. onStop() — onStop will invoked if activity is no longer visible to the user.
  6. onRestart() — onRestart will invoked if your activity is stopped and prior to start.
  7. onDestroy() — onDestroy will invoked before the activity is destroyed

5.What is the difference between margin and padding?

if you want to take your widget like TextView, EditText far away from other. You should use margin from top,right,left,bottom.

By giving padding the component size will be increased  

6.What is the difference between gravity and layout_gravity?

android:gravity Is to specify to place content with in the object.if gravity is left means object content is going to be left to the component.

android:layout_gravity is an attribution the child can supply to its parent, to specify the gravity the view within its parents

7.What is APK?

APK means Android Package Kit.android is going to make apk file with all resources and code to install on mobile phone

8.What DVM and difference between DVM and JVM?

DVM means Dalvik Virtual Machine

DVM is Register based and specially designed to run on low memory

uses its own byte code and runs .Dex file

JVM is Stack based and convert all java code to .class files

9.What is AndroidManifest.xml?

Every application must have an AndroidManifest.xml file (with precisely that name) in its root directory.We will register every activity ,services,broadcast receivers and content providers.We will declare all permissions in manifest file only.

10.What is a service in android?

Service is a background process that can run for a long time even after closing activity also.

11.What is Content Provider?

Content Providers are used to share data between the applications.

12.What is Broadcast Receiver?

A broadcast receiver (receiver) is an Android component it allows you to register for system events Like calls, notifications. Once we register a receiver, automatically receiver is going to call once that functionality is triggered.

 

Kotlin For Android Developers

Kotlin For Android Developers

Kotlin For Android Developers

Kotlin is a new programming language from JetBrains, the maker of the world’s best IDEs. Now Kotlin supported by Google For Android.
 
Kotlin comes from industry, not academia. It solves problems faced by working programmers today. As an example, the type system helps you avoid null pointer exceptions. Research languages tend to not have null at all.

1. Why Kotlin

 
1.1 Java Interoperability
 
Kotlin language is inter-operable with java. It means we can user previous java project with new kotlin classes also and all java frameworks are still available. We have a one click java to kotlin converters also.
 
1.2 Familiar syntax
 
Kotlin Language syntax is very familiar to any programing language who came from OOP domine. There are some differences compare to Java such as val, var
 
Class Example{
 
val a:String= “Kosmik” //val means unmodifiable
 
Var i:int=1 // var means modifiable
 
}
 
Fun hellworld(){
 
Val str=”hello”
 
print(“$str World”)
 
}
 
1.3 String Interpolation
 
It’s as if a smarter and more readable version of Java’s String.format() built into the Kotlin language
 
var x=4
 
var y=3
 
print(“sum of $x and $y is ${x+y}”) //sum of 4 and 7 is 11
 
1.4 Open Source
 
It is open source under apache 2.0
 
1.5 Compatibility
 
Kotlin is fully compatible with JDK6 and kotlin applications can run on older android devices also
 
1.6 Performance
 
Kotlin application will run fast as an equal to java
 
1.7 Support
 
Kotlin is fully supported from Android Studio 3.0
 
1.8 Some Syntaxes
  1. No more semicolons ;
  2. Variable declaration is different in kotlin like var is mutable and val is immutable
  3. Functions in kotlin (methods)

fun sum (x: Int ,y: Int): Int{

return x+y

}

  1. when function

Now switch changed into when a condition, which is very easy to understand  like below example

when (x) {

   1 -> print(“x is 1”)

   2 -> print(“x is 2”)

   3, 4 -> print(“x is 3 or 4”)

   in 5..10 -> print(“x is 5, 6, 7, 8, 9, or 10”)

   else -> print(“x is out of range”)

}

6.creating a class in kotlin

val rectangle = Rectangle(5.0, 2.0) //no ‘new’ keyword required

val triangle = Triangle(3.0, 4.0, 5.0)

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