Android Interview Questions

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1) What is Android?

It is a software package and open-source operating system that is used in mobile devices.

It is also a Linux kernel-based system operating system and application executes within its own instance and its own process.

2) What is the Android Architecture?

It is made up of 4 components:

  • Libraries
  • Linux Kernel
  • Android Framework
  • Android Applications

3) What is an Activity?

Activity is a windows, provides platform for graphical user interface.

4) What are the different Activity life cycle methods?

Followings are the android life cycle methods:

  • void onCreate(Bundle savedInstanceState)
  • void onStart()
  • void onRestart()
  • void onResume()
  • void onPause()
  • void onStop()
  • void onDestroy()

5) What is Fragment in android?

Fragment is a part of activity. Fragment provides facility to display multiple screens on single activity. It is also reusable.

6) Who is the founder of Android?

Andy Rubin is the founder of Android .

7) What are the four essential states of an activity?

Four essential states of an activity:

  • Active
  • Paused
  • Stopped
  • Destroyed

8) What is a service in android?

The Service is a component which performs background functionalities without UI interaction. For examples playing music player, calling alarm, doing transaction etc.

9) What is ADB?

ADB stands for Android Debug Bridge which is a command line tool. It is used to communicate with emulator instance. ADB is a client server program that includes three components:

  1. Client
  2. Server
  3. Daemon

10) What are Intents?

Intent is a class used to pass information to interact with android application

internal or external world. It is used to launch another activity, invoke web page etc. Intent is two types in android:

  1. Implicit Intent
  2. Explicit Intent

11) What is an Implicit Intent?

Implicit intent provides information of available components. It is used to invoke system components.

Example:

12) What is an Explicit Intent?

Explicit intent explicitly specifies and passes the target component name directly in the intent.

Example:

13) What is the AndroidManifest.xml file?

AndroidManifest.xml file contains information about Android application that the system musk known before code execution. It is declared inside the root directory of Android project.

14) When is the onStop() method invoked?

At the time, When no activity is longer visible to the user.

15) What are the different states where in a process is based?

There are four states :

  • empty process
  • visible activity
  • foreground activity
  • background activity

16) What data types are supported by AIDL?

Data types supported by AIDL are:

  • Map
  • List
  • string
  • charSequence

17) What are the different storage systems in Android?

Following are the storage systems in Android:

  • Shared Preferences
  • Internal Storage
  • External Storage
  • SQLite Databases
  • Network Connection

18) Is it possible to add a fragment without using a user interface?

Yes, It is possible.

By the use of add(Fragment, string) method to add a fragment.

19) What are the advantages of Android?

Advantages :

  • Open-source
  • Platform-independent
  • Supports various technologies
  • Highly optimized Virtual Machine

20) What are the core building blocks of android?

Core building blocks of android are:

  • View
  • Intent
  • Service
  • Fragment
  • Activity
  • Content Provider etc

21) Name some exceptions in android?

Exceptions in android are:

  • Inflate Exception
  • Surface.OutOfResourceException
  • WindowManager.BadTokenException
  • SurfaceHolder.BadSurfaceTypeException

22) How will you pass data to sub-activities?

Bundel class is used to pass data from sub-activity (one activity to another). The methods of Bundle class takes data as a form of key and value.

Example:

23) What is AAPT?

AAPT stands for Android Asset Packing Tool. It is used for packaging process which includes creating, executing as well as viewing its content.

24) What is the difference between setFlags() and addFlags() on an Intent object?

Difference between setFlags() and addFlags() are:

setFlags: we are replacing the oldFlags with a new set of Flags.

addFlags: we are appending more flags.

25) What are the different language uses for Android application development?

There are various language are used for Android application development like Java (Android SDK), C/ C++ (Android NDK). But Java is most preferred language for Android application development.

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