Android Interview Questions And Answers | Android Tutorial | Android Online Training | Edureka

Android Market and Salary Trends

Android Market
Android is most used mobile technology with around 82% of all mobile phones based on Android.
Operating System 1Q17 Units 1Q17 Market
Share (%)
1Q16 Units 1Q16 Market
Share (%)
Android 327,163.6 86.1 292,746.9 84.1
IOS 51,992.5 13.7 51,629.5 14.8
Other OS 821.2 0.2 3,847.8 1.1
Total 379,977.3 100.0 348,224.2 100.0
Source: Gartner (May 2017)

Android Salary Trends
Source: Indeed.com

Android Interview Questions

Que1 : What is Android?

➢ Android is a mobile operating system (OS) developed by Google.
➢ Designed for touchscreen mobile devices such as smartphones and
tablet computers.
➢ Open source
➢ Written in Java
➢ Android's kernel is based on one of the Linux kernel's long-term
support (LTS) branches.
Que1 : What is Android?

Que2 : What are the features of Android?

Que2 : What are the features of Android?
✓ User Interface
✓ Messaging
✓ Web Browser
✓ Connectivity
✓ Wi-Fi Direct
✓ Multi-touch
✓ Multi-tasking
✓ Multi-Language
✓ Storage
✓ Android Beam

Que3 : Explain Android Architecture?

Que4 : What are the different versions of Android?

Que5 : What is an activity?

Que5 : What is an activity?
➢ An Activity is the window representation of any application in Android.
➢ It serves as an entry point for user’s interaction.
➢ Each activity has a layout file where you can place your UI.
➢ An application can have different activities.

Que6 : Explain Activity Life Cycle?

Que7 : What are intents?

Que7 : What are intents?
➢ An intent is a messaging object you can use to
request an action from another app component.
➢ Methods are used to deliver intents to different
components:
• context.startActivity()
• context.startService()
• context.sendBroadcast()

Que8 : What is implicit intent?

Que8 : What is implicit intent?
Implicit intent is when the target component is not defined in the intent and the android
system has to evaluate the registered components based on the intent data.
Intent i = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.edureka.co"));
startActivity(i);
Action Specification

Que9 : What is explicit intent?

Que9 : What is explicit intent?
Explicit intent is when an application defines the target component directly in the
intent.
Intent i = new Intent(this, ActivityTwo.class);
i.putExtra("Value1", "This is ActivityTwo ");
i.putExtra("Value2", "This value two for ActivityTwo");
startActivity(i);
Target component

Que10 : What are the tools placed in android SDK?

Que10 : What are the tools placed in android SDK?
➢ Android Emulator
➢ DDMS - Dalvik Debug Monitoring Services
➢ AAPT - Android Asset Packaging tool
➢ ADB - Android debug bridge

Que11 : What is an android runtime?

Que11 : What is an android runtime?
➢ Android Runtime consists of Dalvik Virtual machine and
Core Java libraries.
➢ DVM is optimized for low processing power and low
memory environments.
➢ Unlike JVM, the Dalvik Virtual Machine doesn’t run .class
files, instead it runs .dex files.
➢ Android 2.2 "Froyo“ brought trace-based just-in-time (JIT)
compilation into Dalvik, optimizing the execution of
applications and dynamically compiling frequently executed
short segments of their bytecode into native machine code.

Que12 : What is DDMS?

Que12 : What is DDMS?
It stands for Dalvik Debug Monitor Server. It gives the wide array of debugging features:
1. Port forwarding services
2. Screen capture on the device
3. Thread and heap information
4. Logcat
5. Incoming call and SMS spoofing
6. Location data spoofing

Que13 : Explain in brief about the important file and folder when you create new app?

Que13 : Explain in brief about the important file and folder when you create new app?
App - It describes the fundamental characteristics of the app and defines
each of its components.
java - This contains the .java source files for your project. By default, it
includes an MainActivity.java source file.
res - It is a directory for files that define your app’s user interface.
Gradle Scripts - This is an auto generated file which contains
compileSdkVersion, buildToolsVersion, applicationId, minSdkVersion,
targetSdkVersion, versionCode and versionName.

Que14 : What is an android manifest file?

Que14 : What is an android manifest file?
The manifest file provides essential
information about your app to the Android
system, which the system must have before
it can run any of the app's code.

Que15 : Name some exceptions in android?

Que15 : Name some exceptions in android?
➢ Inflate Exception
➢ Surface.OutOfResourceException
➢ SurfaceHolder.BadSurfaceTypeException
➢ WindowManager.BadTokenException

Que16 : Name the dialog box which are supported by android?

Que16 : Name the dialog box which are supported by android?
➢ Alert Dialog
➢ Progress Dialog
➢ Date Picker Dialog
➢ Time picker Dialog

Que17 : What are the core building blocks of android?

Que17 : What are the core building blocks of android?
✓ Activity : An Activity is the screen representation of any application in
Android. Each activity has a layout file where you can place your UI.
✓ Content Provider: Content providers share data between applications.
✓ Service: It is a component that runs in the background to perform long-
running operations without interacting with the user and it even works if
application is destroyed.
✓ Broadcast Receivers: It respond to broadcast messages from other
applications or from the system itself. These messages are sometime called
events or intents.

Que18 : What is a service in Android?

Que18 : What is a service in Android?
A service in android is a background process which is used to perform long running operations. Let’s say, a
service of location is active in the background while the user is in different application. So it does not
disturb the user interaction with an activity. Types -
Local : This service is accessed from within the application.
Remote : This service is accessed remotely from other applications running on the same device.
public class MyService extends Service {
}
It is implemented as a subclass of Service class as follows :

Que19 : What are the different types of services?

Que19 : What are the different types of services?
Handler service
Intent Service
Service (AIDL)
1
2
3

Que20 : What is the difference between Service and Thread?

Que20 : What is the difference between Service and Thread?
❖ Service is like an Activity but has no interface.
❖ A Service is not a separate process. It works in
background until the service or someone else
explicitly stop it.
❖ Service is not killed when an application is killed.
❖ It expose some of its functionality to other
applications by calling Context.bindService().
❖ A Thread is a concurrent unit of execution.
❖ By default, all components of the same
application run in the same process and
thread (called the "main" thread).
❖ Thread is killed when an Application is killed.
❖ GOOGLE has brought in Handlers and
loopers into android threads.
Service Thread

Que21 : What is a fragment?

Que21 : What is a fragment?
➢ Fragment is a part of Activity
➢ You can combine multiple fragments in a single activity
which helps to display multiple screens and reuse a
fragment in multiple activities.

Que22 : What is the difference between a fragment and an activity?

Que22 : What is the difference between a fragment and an activity?
➢ Activity is typically a single, focused operation that a user can perform such as dial a number, take a
picture, send an email, view a map etc.
➢ Fragment is a modular section of an activity, with its own lifecycle and input events, and which can be
added or removed at will. Also, a fragment’s lifecycle is directly affected by its host activity’s lifecycle i.e.
when the activity is paused, so are all fragments in it, and when the activity is destroyed, so are all of its
fragments.

Que23 : What does APK stands for?

Que23 : What does APK stands for?
➢ APK stands for Android Packaging Kit.
➢ The Android packaging key is compressed with classes, UI's, supportive assets and manifest.
All these files are compressed to a single file which is called as APK.

Que24 : Does android support any other language than java?

Que24 : Does android support any other language than java?
➢ Yes, android app can be developed in C/C++.
➢ It should be used with android NDK (Native Development Kit) and android SDK( Software
Development Kit).

Que25 : What is a content provider?

Que25 : What is a content provider?
➢ Content providers manage access to a structured set of data. It is the standard interface that connects
data in one process with code running in another process.
➢ They encapsulate the data and provide mechanisms for defining data security.
➢ Content providers are used to share the data between different applications.
It is implemented as a subclass of ContentProviderclass and must implement a standard set of APIs that
enable other applications to perform transactions.
public class MyContentprovider extends ContentProvider {
public void onCreate(){}
}

Que26 : What is a singleton class in Android?

Que26 : What is a singleton class in Android?
➢ A singleton class is a class which can
create only an object that can be shared
all other classes.
New Instance 1
Single InstanceNew Instance 2
Instance n

Que27 : What’s the difference between a file, a class and an activity in android?

Que27 : What’s the difference between a file, a class and an activity in android?
It is a chunk of arbitrary
information, or resource for
storing information.
It’s a compiled form of Java
file. Android uses the .class
files to produce an executable
apk
An activity is the comparable
to a Frame/Window in GUI
toolkits. It is not a file or a
file type, it’s just a class that
can be extended in Android
for loading UI elements on
view.
ActivityFile Class

Que28 : What is Dalvik Virtual Machine?

Que28 : What is Dalvik Virtual Machine?
➢ Dalvik is the name of Android’s virtual machine.
➢ The Dalvik VM is an interpreter-only virtual machine that executes files in the Dalvik
Executable (.dex) format.
➢ The virtual machine is register-based and can run classes compiled by Java language
compiler that have been altered into its native format using the included ‘dx’ tool.
➢ The Dalvik core class library is envisioned to provide a familiar development base for
those used to programming with Java Standard Edition, but is geared explicitly for the
needs of a small mobile device.

Que29 : What is the significance of the .dex files?

Que29 : What is the significance of the .dex files?
➢ Android programs are compiled into ‘.dex’ (Dalvik Executable) files, which are zipped into
a single .apk file on the device.
➢ ‘.dex’ files can be created by translating compiled applications written in Java.
➢ (.dex) is a format that is optimized for effective storage and memory-mappable
executions.

Que30 : What is a toast?

Que30 : What is a toast?
➢ Toast notification is a message that pops up on the window.
➢ It only covers the expanse of space required for the message and the user’s recent activity
remains visible and interactive.
➢ The notification automatically fades in and out and does not accept interaction events.
Toast.makeText(ProjectActivity.this, “Your message here”,Toast.LENGTH_LONG).show();
Syntax :

Que31 : What are the exemptions in Android?

Que31 : What are the exemptions in Android?
 InflateException : When an error conditions occur this exception is thrown.
 Surface.OutOfResourceException: When a Surface is not created or resized, this exception is
thrown.
 SurfaceHolder.BadSurfaceTypeException: When invoked on a Surface
‘SURFACE_TYPE_PUSH_BUFFERS’, this exception is thrown from lockCanvas() method.
 WindowManager.BadTokenException: This exception is thrown at the time of trying to view an
invalid WindowManager.LayoutParamstoken.

Que32 : What is the use of WebView in Android?

Que32 : What is the use of WebView in Android?
 WebView is a view that display web pages inside your application.
 According to Android, “this class is the basis upon which you can roll your own web browser or
simply display some online content within your Activity. It uses the WebKit rendering engine to
display web pages and includes methods to navigate forward and backward through a history,
zoom in and out, perform text searches and more.”
 In order to add WebView to your application, you have to add <WebView>element to your xml
layout file.

Que33 : What are the different kinds of context in Android?

Que33 : What are the different kinds of context in Android?
 this / getActivity()
 getContext()
 getBaseContext()
 getApplicationContext()
Which Context should I use in Android?
Memory leak

Que34 : What are the different storage methods in Android?

Que34 : What are the different storage methods in Android?
Android offers several options to save persistent application data. They
are:
1. Shared Preferences – Store private primitive data in key-value pairs.
2. Internal Storage – Store private data on the device memory
3. External Storage – Store public data on the shared external storage
4. SQLite Databases – Store structured data in a private database.

Que35 : Can you deploy executable JARs on android? Which package is supported by it?

Que35 : Can you deploy executable JARs on android? Which package is supported by it?
➢ No, Android does not support JAR deployments.
➢ Applications are packed into Android Package(.apk) using Android
Asset Packaging Tool(APT)and then deployed on to Android
platform.

Que36 : What are containers?

Que36 : What are containers?
✓ It hold objects and widgets together, depending on which specific items are needed and in
what particular arrangement that is wanted.
✓ Containers may hold labels, fields, buttons, or even child containers, as examples.

Que37 : Can you change the name of an application after its deployment?

Que37 : Can you change the name of an application after its deployment?
➢ It is not recommended to change the application after its deployment.
➢ This may break some functionality .

Que38 : Define Android application resource files?

Que38 : Define Android application resource files?
✓ animator
✓ anime
✓ color
✓ drawable
✓ Mipmap
✓ xml
✓ layout
✓ values
✓ menu
✓ raw
✓ asset
It is a directory for files that define your app’s user interface. As an android developer, you can inject
files such as:

Que39 : What is the importance of an emulator in Android?

Que39 : What is the importance of an emulator in Android?
✓ The emulator lets you play around an interface that acts
as if it were an actual device.
✓ It let you write and test codes, and even debug.
✓ It acts as a safe place for testing codes especially if its in
the early design phase.

Que40 : How are escape characters used as attribute?

Que40 : How are escape characters used as attribute?
✓ Escape characters are preeceded by double backslashes.
✓ For example - a newline character is created using 'n'.

Que41 : What is NDK ?

Que41 : What is NDK ?
✓ NDK stands for Native Development Kit.
✓ By using NDK, you can develop a part of app using native language such as
C,C++ etc.

Que42 : What are broadcast receivers?

Que42 : What are broadcast receivers?
➢ Broadcast Receiver is a mechanism using which host application can listen for System level events.
➢ Broadcast receiver is used by the application whenever they need to perform the execution based on
system events. Like listening for Incoming call, sms etc.
➢ Broadcast receivers helps in responding to broadcast messages from other application or from the
system.
➢ It is used to handle communication between Android operating system and applications.
public class MyReceiver extends BroadcastReceiver {
Public void onReceive( context, intent) {}
}
It is implemented as a subclass of BroadcastReceiver class and each message is broadcaster as an Intent object.

Que43 : What are the security measures that are taken to make Android secure?

Que43 : What are the security measures that are taken to make Android secure?
✓ Android application uses sandbox that is very popular and allow limited
access to the information that is very private and sensitive for the user.
✓ It allows the permissions to be set for the use of the information. The
security measures that are provided by android is the use of the
encryption of the messages that allow user to remain without worry about
there phone security.
✓ They also consists of user terms and agreements that also taken care of.
✓ Device policy - App restriction Scheme – cypher.
✓ As android is open source it is not fully secure but lots of security issues
are being solved for make it more popular and bug free.

Que44 : What does ADB stands for?

Que44 : What does ADB stands for?
✓ ADB stands for Android Debug Bridge.
✓ It is a command line tool that is used to communicate with the emulator instance.
✓ ADB can control your device over USB from a computer, copy files back and forth, install and
uninstall apps, run shell commands, and more.
✓ It is a client-server program that includes three components:
• Client - which runs on your development machine. You can invoke a client from a shell by
issuing an ADB command. Other Android tools such as DDMS also create ADB clients.
• Server, which runs as a background process on your development machine. The server
manages communication between the client and the ADB daemon running on an emulator or
device.
• Daemon, which runs as a background process on each emulator or device instance.

Que45 : How will you pass data to sub-activities?

Que45 : How will you pass data to sub-activities?
✓ We can use Bundles to pass data to sub-activities.
✓ There are like HashMaps that and take trivial data types. These Bundles transport
information from one Activity to another.
Bundle b=new Bundle();
b.putString(“Email”, “abc@xyz.com”);
i.putExtras(b); //where I is intent
Syntax:

Que46 : What is Orientation in android?

Que46 : What is Orientation in android?
✓ Orientation helps to represent the layout in a row or column.
✓ Values are set as either HORIZONTAL or VERTICAL.
✓ It can be set using setOrientation().
How it is done?

What is Android Studio?
Que47 : What database is used in Android? How does it differ
from client-server database management systems?

Que47 : What database is used in Android? How does it differ
from client-server database management systems?
✓ SQLite is the open-source relational database.
✓ The SQLite engine is serverless, transactional, and self-contained.
✓ Instead of the typical client-server relationship of most database management systems, the SQLite
engine is integrally linked with the application.
✓ The library can also be called dynamically, and makes use of simple function calls that reduce
latency in database access.

Que48 : Can you list and explain the four Java classes related to
using sensors on the Android platform?

Que48 : Can you list and explain the four Java classes related to
using sensors on the Android platform?
➢ Sensor Manager: This class provides methods regarding the registration of sensor event listeners,
the management of data acquisition, and calibration. It also provides methods for accessing and
listing sensors.
➢ Sensor: This class creates an instance of a specific sensor, providing methods that allow you to
determine its capabilities.
➢ SensorEvent: This class provides information on a sensor event by creating a sensor event object.
➢ SensorEventListener: This interface provides two callback methods that can receive notifications of
sensor events.

Que49 : What are some measures you can take to avoid ANR?

Que49 : What are some measures you can take to avoid ANR?
➢ ANR is typically caused when the app performs too much on the main thread.
➢ To avoid ANR, an app should perform lengthy database or networking operations in separate
threads.
➢ For background task-intensive apps, you can alleviate pressure from the UI thread by using the
IntentService.
➢ In general, it helps to always define time-outs for all your web service calls and to remain ever
vigilant for infinite loops in complex calculations.

Que50 : What is AIDL? What are the datatypes supported by AIDL ?

Que50 : What is AIDL? What are the datatypes supported by AIDL ?
➢ AIDL stands for Android Interface Definition Language.
- It handles the interface requirements between a client and a service to communicate at the same
level through interprocess communication.
- The process involves breaking down objects into primitives that are Android understandable.
✓ String
✓ List
✓ Map
✓ CharSequence
✓ Native Java data types (int,long, char and Boolean)
Data types
:

Android Interview Questions And Answers | Android Tutorial | Android Online Training | Edureka

Android Interview Questions And Answers | Android Tutorial | Android Online Training | Edureka

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