Top Android Interview Questions & Answers

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android interview questions

 

Android is a mobile operating system (OS) by Google. Released under open-source license, the OS is based on the Linux kernel and is designed primarily for smartphones and tablets. It was first developed by the Android Inc., which was bought by Google in 2005. With the introduction in 2007, it became one of the most popular mobile operating systems in the world, with a huge percentage of smartphones using the OS.

As the growth of smartphone users continued and hardware technology getting updated every year, Android is also becoming more developed. The industry has a great demand for expert Android developers and is expected to increase in the coming years.

If you are looking to move into the industry, you can enroll in an Android certification course to get certified and be job-ready. Here is a comprehensive list of Android interview questions, along with their answers.

 

Q1. What are activities?

 

Ans. Activities are what you refer to as the window to a user interface.

 

Q2. What are the four essential states of an activity?

 

Ans. Active, Paused, Stopped and Destroyed

 

Q3. What are Intents?

 

Ans. Intents displays notification messages to the user from within the Android enabled device.

 

Q4. What are the components of an Android application architecture?

 

Ans. Linux kernel, libraries, Android framework, and Android applications

 

Q5. What are the three common cases of an Intent?

 

Ans. 

  • to start an activity
  • to start a service
  • to deliver a broadcast

 

 

Q6. Differentiate between explicit Intent and implicit Intent

 

Ans. Explicit intent specifies the component to be invoked from activity.

Implicit Intent doesn’t specify the component.

 

Q7. What is the Google Android SDK?

 

Ans. Google software development kit (SDK) is a toolset to help developers to write apps on Android-enabled devices

 

Q8. What are the tools are placed in An Android SDK?

 

Ans. Android Emulator, DDMS (Dalvik Debug Monitoring Services), AAPT (Android Asset Packaging tool) and ADB (Android Debug Bridge)

 

Q9. Define AAPT

 

Ans. Android Asset Packaging Tool (AAPT) tool provides developers with the ability to deal with zip-compatible archives, which includes creating, extracting as well as viewing its contents.

 

Q10. What is DDMS?

 

Ans. Dalvik Debug Monitor Server (DDMS) provides a wide array of debugging features.

 

Q11. What is the APK format?

 

Ans. Android Package Kit (APK) is the package file format used by the Android operating system for distribution and installation of mobile apps and middleware.

 

Q12. What is the use of an activityCreator?

 

Ans. An activityCreator is the first step towards the creation of a new Android project.

 

Q13. Differentiate between fragment and activity

 

Ans. An activity is typically a single, focused operation that a user can perform whereas a fragment is essentially a modular section of an activity, with its own lifecycle and input events, and which can be added or removed at will.

 

Q14. What are containers?

 

Ans. Containers holds objects and widgets together, depending on which specific items are needed and in what particular arrangement that is wanted.

 

Q15. What is Android Debug Bridge (adb)?

 

Ans. It allows developers the power to execute remote shell commands.

 

Q16. What is the importance of settings permissions in app development?

 

Ans. Permissions allow certain restrictions to be imposed primarily to protect data and code.

 

Q17. What is the AndroidManifest.xml?

 

Ans. This file is essential and contains information about the application that the Android system must know before the codes can be executed.

 

Q18. What is the difference between Service and IntentService?

 

Ans. Service is the base class for Android services that can be extended to create any service.

IntentService is a subclass of Service that handles asynchronous requests (expressed as “Intents”) on demand.

 

Q19. What is the importance of Default Resources?

 

Ans. When default resources, which contain default strings and files, are not present, an error will occur and the app will not run.

 

Q20. Define AIDL

 

Ans. Android Interface Definition Language (AIDL) handles the interface requirements between a client and a service so that both can communicate at the same level through inter-process communication (IPC).

 

Q21. What is a Sticky Intent?

 

Ans. A Sticky Intent is a broadcast from sendStickyBroadcast() method such that the intent floats around even after the broadcast, allowing others to collect data from it.

 

Q22. What language is supported by Android for application development?

 

Ans. The main language supported is Java.

 

Q23. Where and how are layouts placed in android?

 

Ans. Layouts are placed in the Layout folder as XML files

 

Q24. What are application Widgets in android?

 

Ans. Widgets are miniature application views that can embedded in other applications (such as the Home screen) and receive periodic updates.

 

Q25. What is drawable folder in android?

 

Ans. It is a compiled visual resource that can used as a backgrounds, banners, icons, splash screen etc.

 

26. What is a ContentProvider and what is its use?

 

Ans. A ContentProvider typically manages access to a structured set of data. It is responsible to encapsulate the data and ensure data security by defining security mechanisms. It is a standard interface, connecting data to codes running in another process.

Ans. The interview may get trickier with these technical Android interview questions. All you need to do is prepare for the related questions. Take a look.

 

27. Which are the important components of every Android project?

 

Ans. Here are the essential items required in every Android project:

AndroidManifest.xml
build.xml
bin/
src/
res/
assets/
 

28. What is ANR?

 

Ans. ANR is the abbreviation for Application Not Responding. If any application is unresponsive for a long period, this dialog appears to the user.

 

29. What is Armv7?

 

Ans. ARMv7 is the most common CPU architecture in Android. Its popularity is because of the fact that it is evolved and optimized for more powerful computing.

 

30. Why can’t we run standard Java bytecode on Android?

 

Ans. This happens because Java and Android use separate environment to run the code. Android uses DVM (Dalvik Virtual Machine) instead of JVM (Java Virtual Machine).

 

31. How does Activity respond when a user rotates the screen?

 

Ans. So, this is among the most commonly asked Android interview questions. You can reply –
When a user rotates the screen, the current Activity is ended and a new instance of Activity is created, in the new orientation and onRestart() method is invoked. Similarly, other lifecycle methods also get invoked when Activity was first created.

 

32. What is the difference between Activity & Service?

 

Ans. Activity is an application component providing a screen to the user interface (UI), such as dialing the phone, clicking a photo, sending an email, or even when viewing a map. Services is used to perform background operations and it does not have an UI.

 

33. What is a visible activity?

 

Ans. A visible activity is one where the user is not interacting with the activity, but the activity is still visible, though partially.

 

34. Where will you declare your activity such that it can be accessed by the system?

 

Ans. Activity needs to be declared in the manifest file.

 

35. What all devices have you worked on?

 

Ans. This is among the popular Android interview questions, as an answer to this, you may name many mobile devices available in the market having different operating systems. You can name Android, Windows, Symbian, iPhone, etc.

 

36. What is a broadcast receiver?

 

Ans. The broadcast receiver is a component that responds to system-wide broadcast announcements or messages, such as “check if an internet connection is available”, ”download complete”, ”boot completed”, etc.

 

37. Why should you use only the default constructor to create a Fragment?

 

Ans. It is always suggested to use only the default constructor to create a Fragment because device has to restore the state of a fragment correctly to the same state as it was in the initial state, in instances like configuration change.

 

38. What are the three key loops when monitoring an activity?

 

Ans. 

  • Entire lifetime – Activity occurs between onDestroy and onCreate
  • Visible lifetime – Activity occurs between onStop and onStart
  • Foreground lifetime – Activity occurs between onPause and onResume

 

39. Which dialog boxes can you use in your Android application?

 

Ans. 

  • AlertDialog: Supports 0 – 3 buttons and a list of selectable elements
  • ProgressDialog: An extension to AlertDialog, where buttons may be added to it
  • DatePickerDialog: Used for selecting a date by the user
  • TimePickerDialog: Used for selecting time by the user

 

40. What is the difference between margin and padding?

 

Ans. Margin is the outer space of an element, while padding is the inner space.

 

41. What is the difference between RelativeLayout and LinearLayout?

 

Ans. In the LinearLayout, the elements are arranged either vertically or horizontally (in a row or column), while in RelativeLayout, elements are arranged corresponding to the parent or other elements.

 

42. What are Adapters?

 

Ans. An Adapter is a bridging element between an AdapterView and the underlying data for that view. It offers an access to the data items and makes a View for each item in the data set.

 

43. What is Orientation?

 

Ans. It is a key feature of all the smart phones. It is the feature of rotating the screen between horizontal (Landscape) or vertical (Portrait) mode.

 

44. What is the difference between AsyncTasks & Threads?

 

Ans. The main difference is about the way they are triggered. A Thread can be triggered from any thread, main(UI) or background; but AsyncTask is only triggered from the main thread.

 

45. What is the difference between a regular bitmap and a nine-patch image?

 

Ans. A Nine-patch image allows choosing the area of an image and resizing it in the device. Images in regular bitmap are scaled along the height and the width in the same way.

 

46. Which method is called only once in a fragment lifecycle?

 

Ans. onCreate() method is fired only once during the life cycle.

 

47. Can you create an activity in Android without a user interface?

 

Ans. Yes, it can be created without any user interface and these activities are treated as abstract activities.

 

48. Is it possible to change the name of an application after it is deployed?

 

Ans. It is possible, but not suggested. This action may break some functionality.

 

49. How will you remove icons and widgets from Android device main screen?

 

Ans. For removing an icon or shortcut, we will press and hold that icon and then drag it downwards to the part of the screen where the remove button appears.

These are some of the popular questions asked in Android interviews. Always be prepared to answer all types of questions — technical skills, interpersonal, leadership or methodology. If you are someone who has recently started your career in Android development, you can always get certified in one of the technical courses to get the requisite app development skills and methodologies.

About the Author

Hasibuddin Ahmed

Hasibuddin Ahmed

Hasib is a professional writer associated with learning.naukri.com. He has written a number of articles related to technology, marketing, and career on various blogs and websites. As an amateur career guru, he often imparts nuggets of knowledge related to leadership and motivation. He is also an avid reader and passionate about the beautiful game of football.