Top 80+ Android Interview Questions and Answers

Top 80+ Android Interview Questions Answers

Basic Android interview questions for experienced and freshers developers and testers:

In this technological era, there is a huge demand for Android Application developers and it is one of the highly paid jobs too.

Hence many tech-savvy people are trying to make their way into this career. There are several tricky interview questions that are asked in many MNC’s and some small scale companies. And this article includes a set of such Android interview questions and answers that will be helpful to millions of job seekers.

Let’s Explore!!

Android Interview Questions

This article includes a set of most commonly asked android interview questions and answers covering almost all the important concepts in simple terms in order to enable any job seeker to clear the interview successfully.

Most Popular Android Interview Questions & Answers
Given below is the list of most commonly asked Android Interview questions



01. What is android?
Android is a mobile operating system developed by Google and later the OHA (Open Handset Alliance). It is an open-sourced operating system that is used primarily on mobile devices, such as cell phones and tablets. It is based on a modified version of the Linux kernel and other open source software, and is designed primarily for touchscreen mobile devices such as tablets,computers and smartphones.

02. What Is the Google Android SDK?
The Google Android Software Development kit (SDK) is a toolset that developers need in order to write apps on Android enabled devices. It contains a vartual graphical interface that emulates an Android driven handheld environment, allowing them to test and debug their developed codes in vartual divice.

03. What is Android Programming
An Android app is a software application running on the Android platform. Because the Android platform is built for mobile devices, a typical Android app is designed for a smartphone or a tablet Computers running on the Android OS.

04. Which of the following is a commonly used programming language in Android application?
The official language for Android development is Java. Large parts of Android are written in Java and its APIs are designed to be called primarily from Java. It is possible to develop C and C++ app using the Android Native Development Kit (NDK), however it isn't something that Google promotes
05. What are the different versions of Android OS that you remember?
Given below are the various versions of Android.

Version	Name
Android 11.0
Android 10.0
Android 9.0	pie
Android 8.0	Oreo
Android 7.0 – 7.1.2	Nougat
Android 6 – 6.0.1	Marshmallow
Android 5 – 5.1.1	Lollipop
Android 4.4 – 4.4.4	KitKat
Android 4.1 – 4.3	Jelly Bean
Android 4.0-4.0.4	Ice Cream Sandwich

06. What is the difference between Mobile Application Testing and Mobile Testing?
Mobile app testing is the testing of applications on a Mobile device which mainly focuses on functions and features of the application. And Mobile Testing is the testing of the actual mobile device and focuses on the mobile features like Call, Sound, Display, SMS, Contacts, Media Player, inbuilt browsers etc.

07. Why is Android used?
The first reason why Android is so widely used is that it is compatible with all the major browsers within your mobile ecosystem which endears it to the mobile users. Android is an open source platform and which is one of its biggest strengths as compared to any other operating system of the past or the present.

08. What is the Android Architecture?
Android Architecture is made up of 4 key components:
Linux Kernel
Libraries
Android Framework
Android Applications

09. Can You Describe the Android Framework.
The Android Framework is an important aspect of the Android Architecture. Here you can find all the classes and methods that developers would need in order to write applications on the any Android environment.

10. What is AAPT?
AAPT means Android Asset Packaging Tool. This tool provides developers with the ability to deal with zip-compatible archives, which includes creating, extracting as well as viewing its contents.

11. What is the importance of having an emulator within the Android environment?
The emulator lets developers "play" around an interface that acts as if it were an actual mobile device. They can write and test codes, even debug and get better performance. Emulators are a safe place for testing codes especially if it is in the early design phase of development.

12. What is the use of an activityCreator?
An activityCreator is the first step towards the creation of a new project in Android. It is made up of a shell script that will be used to create new file system structure necessary for writing codes within the Android IDE.

13. Can You Describe Activities?
Activities are what you refer to as the window to a user interface. Just as you create windows in order to display output or to ask for an input in the form of dialog boxes, activities play the same role, though it may not always be in the form of a user interface.

14. What are Intents?
Intents displays notification messages to the user from within the Android enabled device. It can be used to alert the user of a particular state that occurred. Users can be made to respond to intents.

15. Differentiate Activities from Services?
Activities can be closed, or terminated anytime the user wishes. On the other hand, services are designed to run behind the scenes, and can act independently. Most services run continuously, regardless of whether there are certain or no activities being executed.

16. Explain Android Architecture briefly?
Android architecture is in the form of software stack components.The below diagram describes the different layers in the Android architecture.
Linux Kernel: Linux Kernel is placed at the bottom of the software stack and is the foundation of the Android architecture. Using Linux kernel, Android provides a connection between the other layers of the software. It helps to develop drivers like the keypad, display, audio for device manufacture etc.
Hardware Abstraction Layer (HAL): HAL provides an interface between device drivers and API framework. It consists of library modules which are specific to the hardware component.
Android Runtime: Linux kernel provides multi-tasking execution environment so that multiple processes can execute each process runs on its own instance of Android Runtime (ART). Android has core runtime libraries like Dalvik VM specific libraries, Java Interoperability Libraries, Android Libraries and C/C++ libraries.
Application Framework (Java API Framework): The entire android functionalities are available through the API. It consists of multiple services like Activity Manager, Resource Manager, Notification Manager, etc., which form the environment in which the android application runs.
Applications: The Android application is a top layer and all types of in-built applications such as SMS, Browsers, Contact, etc are included in this top layer. It also includes third party applications which are installed by the user such as Games, etc.

17. Define and explain Android Framework?
Android framework is a set of API’s using which the Android developers write code for the mobile apps. It contains the methods and classes to write the programming code.
Android framework includes a different set of tools to create image pane, text field, buttons, etc. It also includes “Activities” with which the user interacts and “Services”, which are the programs that run in the background. It is a package of different components like Intents, Broadcast Receivers, Content Providers, etc.

18. Which components are necessary for a New Android project?
Whenever a new Android project is created, the below components are required:
manifest: It contains xml file.
build/: It contains build output.
src/: It contains the code and resource files.
res/: It contains bitmap images, UI Strings and XML Layout i.e. all non-code resources.
assets/: It contains a file which should be compiled into a .apk file.
The below image shows the Project View once an Android project is created:

19. Provide the important core components of Android?
The core components of Android operating systems are:
Activity
Intents
Services
Content Provider
Fragment

20. Explain briefly – what is meant by Activities?
Activities are the part of the mobile app which the user can see and interact with.For Example, if you open an SMS app which has multiple activities like create new SMS, add a contact from the address book, write the content in the SMS body, send SMS to the selected contact, etc.
Activity keeps a track of the following:
Keeps track of what a user is currently looking for in an app. Keeps a track of previously used processes, so that the user can switch between ongoing process and previous process. It helps to kill the processes so that the user can return to their previous state An activity is implemented as a subclass of Activity class as shown below:

 Public class MyActivity extends Activity
 {
 }

21. What is meant by Services?
Service is an Android component which runs in the background and acts independently. It does not provide any user interface.
Though the services are running behind the scene, a user can continue their work on different apps. Most of the time, the users are not aware of the services which are running in the background. These services allow the system to kill the process without interrupting the user’s ongoing work.
A service is implemented as a subclass of Service class:

 Public class MainService extends Service
 {
 }

22. Explain Activity Lifecycle briefly?
When a user interacts with the app and moves here and there, out of the app, returns to the app, etc. During all this process “Activity” instances also move in the different stages in their lifecycle.
There are seven different states like – onCreate(), onStart(), onRestart(), onResume(), onPause(), onStop(), and onDestroy(). These are termed as a ‘callback’. Android system invokes these callbacks to know that the state has been changed.
The below-given diagram describes the Activity Lifecycle:
When a user is working on an app, then there are many activities involved in it like Open, Close, Save, Delete, Send, etc.
Based on the user action these activities are partially disconnected from the UI but these activities always reside in the memory so that when the user calls back the same activity, the user will be in the same state where he has left off.

23. What is an Intent?
Android has an Intent class when the user has to navigate from one Activity to another. Intent displays notifications from the device to the user and then the user can respond to the notification if required.
Given below are the two types:
Implicit Intents
Explicit Intents

24. Explain Implicit and Explicit Intents?
Implicit Intent calls the system components while explicit Intents invoke the Activity class.

25. What is the importance of setting up permission in app development?
Once the permissions are set for the app development, then the data and code are restricted to the authorized users only.
If the code is kept without any restriction or if it is accessible to anyone then there are chances of compromise of code which results in defect leakage.

26. What is .apk extension in Android?
It is a default file format that is used by Android Operating System. Application Package Kit (APK) is used for installation of mobile apps. The .apk contains resource file, certificate, manifest file and other code.
APK files are archive files in the zip format with .apk extension.

27. What is the database used for Android platform?
SQLite is the database that is used for Android platform. It is an open-source, serverless database.

28. What is ANR in Android?
ANR stands for Application Not Responding. It is a notification or pop-up displayed by the Android platform whenever the application is performing too many functions at a time and if it is suddenly not responding for a long time to the user action.

29. Which are the dialog boxes supported by Android platform?
Android supports four types of dialog boxes:
AlertDialog: It has a maximum of 3 buttons and sometimes AlertDialog includes check boxes and Radio buttons to select the element.
ProgressDialog: It displays the progress bar or wheels.
TimePickerDialog: Using this dialog box, a user selects the Time.
DatePickerDialog: Using this dialog box, a user selects the Date
30. What is ADB?
Android Debug Bridge (ADB) is a command line tool which performs shell commands.
ADB is used for direct communication between the emulator ports. It gives the direct control of the communication between the emulator instances to the developer.

31. What items are important in every Android project?
These are the essential items that are present each time an Android project is created:
AndroidManifest.xml
build.xml
bin/
src/
res/
assets/

32. What is the importance of XML-based layouts?
The use of XML-based layouts provides a consistent and somewhat standard means of setting GUI definition format. In common practice, layout details are placed in XML files while other items are placed in source files.

33. What are containers?
Containers, as the name itself implies, holds 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.

34. What is Orientation?
Orientation, which can be set using setOrientation(), dictates if the LinearLayout is represented as a row or as a column. Values are set as either HORIZONTAL or VERTICAL.

35. What is the importance of Android in the mobile market?
Developers can write and register apps that will specifically run under the Android environment. This means that every mobile device that is Android enabled will be able to support and run these apps. With the growing popularity of Android mobile devices, developers can take advantage of this trend by creating and uploading their apps on the Android Market for distribution to anyone who wants to download it.

36. What is adb?
Adb is short for Android Debug Bridge. It allows developers the power to execute remote shell commands. Its basic function is to allow and control communication towards and from the emulator port.
37. What are the four essential states of an activity?
Active – if the activity is at the foreground
Paused – if the activity is at the background and still visible
Stopped – if the activity is not visible and therefore is hidden or obscured by another activity
Destroyed – when the activity process is killed or completed terminated

38. What is ANR?
ANR is short for Application Not Responding. This is actually a dialog that appears to the user whenever an application have been unresponsive for a long period of time.

39. Which elements can occur only once and must be present?
Among the different elements, the and elements must be present and can occur only once. The rest are optional, and can occur as many times as needed.

40. How are escape characters used as attribute?
Escape characters are preceded by double backslashes. For example, a newline character is created using '\\n'

41. What is the importance of settings permissions in app development?
Permissions allow certain restrictions to be imposed primarily to protect data and code. Without these, codes could be compromised, resulting to defects in functionality.

42. What is the function of an intent filter?
Because every component needs to indicate which intents they can respond to, intent filters are used to filter out intents that these components are willing to receive. One or more intent filters are possible, depending on the services and activities that is going to make use of it.

43. Enumerate the three key loops when monitoring an activity?
Entire lifetime – activity happens between onCreate and onDestroy
Visible lifetime – activity happens between onStart and onStop
Foreground lifetime – activity happens between onResume and onPause

44. When is the onStop() method invoked?
A call to onStop method happens when an activity is no longer visible to the user, either because another activity has taken over or if in front of that activity.

45. Is there a case wherein other qualifiers in multiple resources take precedence over locale?
Yes, there are actually instances wherein some qualifiers can take precedence over locale. There are two known exceptions, which are the MCC (mobile country code) and MNC (mobile network code) qualifiers.

46. What are the different states wherein a process is based?
There are 4 possible states:
foreground activity
visible activity
background activity
empty process

47. How can the ANR be prevented?
One technique that prevents the Android system from concluding a code that has been responsive for a long period of time is to create a child thread. Within the child thread, most of the actual workings of the codes can be placed, so that the main thread runs with minimal periods of unresponsive times.

48. What role does Dalvik play in Android development?
Dalvik serves as a virtual machine, and it is where every Android application runs. Through Dalvik, a device is able to execute multiple virtual machines efficiently through better memory management.

49. What is the AndroidManifest.xml?
This file is essential in every application. It is declared in the root directory and contains information about the application that the Android system must know before the codes can be executed.

50. What is the proper way of setting up an Android-powered device for app development?
The following are steps to be followed prior to actual application development in an Android-powered device:
-Declare your application as "debuggable" in your Android Manifest.
-Turn on "USB Debugging" on your device.
-Set up your system to detect your device.

51. Enumerate the steps in creating a bounded service through AIDL.

1. create the .aidl file, which defines the programming interface
2. implement the interface, which involves extending the inner abstract Stub class as well as implanting its methods.
3. expose the interface, which involves implementing the service to the clients.

52. What is the importance of Default Resources?
When default resources, which contain default strings and files, are not present, an error will occur and the app will not run. Resources are placed in specially named subdirectories under the project res/ directory.

53. When dealing with multiple resources, which one takes precedence?
Assuming that all of these multiple resources are able to match the configuration of a device, the 'locale' qualifier almost always takes the highest precedence over the others.

54. When does ANR occur?
The ANR dialog is displayed to the user based on two possible conditions. One is when there is no response to an input event within 5 seconds, and the other is when a broadcast receiver is not done executing within 10 seconds.

55. What is AIDL?
AIDL, or Android Interface Definition Language, handles the interface requirements between a client and a service so both can communicate at the same level through interprocess communication or IPC. This process involves breaking down objects into primitives that Android can understand. This part is required simply because a process cannot access the memory of the other process.

56. What data types are supported by AIDL?
AIDL has support for the following data types:
-string
-charSequence
-List
-Map
-all native Java data types like int,long, char and Boolean

57. What is a Fragment?
A fragment is a part or portion of an activity. It is modular in a sense that you can move around or combine with other fragments in a single activity. Fragments are also reusable.

58. What is a visible activity?
A visible activity is one that sits behind a foreground dialog. It is actually visible to the user, but not necessarily being in the foreground itself.

59. When is the best time to kill a foreground activity?
The foreground activity, being the most important among the other states, is only killed or terminated as a last resort, especially if it is already consuming too much memory. When a memory paging state has been reach by a foreground activity, then it is killed so that the user interface can retain its responsiveness to the user.

60. Is it possible to use or add a fragment without using a user interface?
Yes, it is possible to do that, such as when you want to create a background behavior for a particular activity. You can do this by using add(Fragment,string) method to add a fragment from the activity.

61. How do you remove icons and widgets from the main screen of the Android device?
To remove an icon or shortcut, press and hold that icon. You then drag it downwards to the lower part of the screen where a remove button appears.

62. What are the core components under the Android application architecture?
There are 5 key components under the Android application architecture:
- services
- intent
- resource externalization
- notifications
- content providers

63. What composes a typical Android application project?
A project under Android development, upon compilation, becomes an .apk file. This apk file format is actually made up of the AndroidManifest.xml file, application code, resource files, and other related files.

64. What is a Sticky Intent?
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.

65. Do all mobile phones support the latest Android operating system?
Some Android-powered phone allows you to upgrade to the higher Android operating system version. However, not all upgrades would allow you to get the latest version. It depends largely on the capability and specs of the phone, whether it can support the newer features available under the latest Android version.

66. What is portable wi-fi hotspot?
Portable Wi-Fi Hotspot allows you to share your mobile internet connection to other wireless device. For example, using your Android-powered phone as a Wi-Fi Hotspot, you can use your laptop to connect to the Internet using that access point.

67. What is an action?
In Android development, an action is what the intent sender wants to do or expected to get as a 

response. Most application functionality is based on the intended action.

69. What is the difference between a regular bitmap and a nine-patch image?
In general, a Nine-patch image allows resizing that can be used as background or other image size requirements for the target device. The Nine-patch refers to the way you can resize the image: 4 corners that are unscaled, 4 edges that are scaled in 1 axis, and the middle one that can be scaled into both axes.

70. What language is supported by Android for application development?
The main language supported is Java programming language. Java is the most popular language for app development, which makes it ideal even for new Android developers to quickly learn to create and deploy applications in the Android environment.

71. What is ActivityCreator?
ActivityCreator is a batch file and shell script which was used to create a new Android project. It is now replaced by “Create New Project” in Android SDK.

72. What is Orientation?
Orientation is the key feature in Smartphones nowadays. It has the ability to rotate the screen between Horizontal or Vertical mode.
Android supports two types of screen Orientations as mentioned below:
Portrait: When your device is vertically aligned.
Landscape: When your device is horizontally aligned.
setOrientation() is a method using which you can set a screen alignments. HORIZONTAL and VERTICAL are two values which can be set in the setOrientation() method. Whenever there is a change in the display orientation i.e. from Horizontal to Vertical or vice versa then onCreate() method of the Activity gets fired.
Basically, when the orientation of the Android mobile device gets changed then the current activity gets destroyed and then the same activity is recreated in the new display orientation. Android developers define the orientation in the AndroidManifest.xml file.

73. What is AIDL?
In the Android platform, there are remote methods which facilitate the use of methods from one program to another. To create and implement the remote methods the first step is to define communication interface in AIDL.
AIDL stands for Android Interface Definition Language. It facilitates the communication between the client and service. It also communicates the information through inter-process communication.
For communication between processes, the data is broken down into chunks which are easily understandable by the Android platform.

74. What are the data types supported by AIDL?
Data Types supported by AIDL are as follows:
String
List
Map
charSequence
Java data types such as INT, Long, Char, Boolean etc

75. Explain AndroidManifest.xml file and why do you need this?
Every application must have AndroidManifest.xml file in the root directory. It contains the information about your app and provides the same to the Android system.
The information includes the package name, Android components such as Activity, Services, Broadcast Receivers, Content Providers, etc. Every Android system must have this information before running any app code.
AndroidManifest.xml file performs the following tasks:
It provides a name to the Java package and this name is a unique identifier for the application.
It describes the various components of the application which include Activity, Services, Content Providers, etc. Also, it defines the classes which implement these components.
It is responsible to protect the application and it declares the permission for accessing the protected part of the app.
It also declares the Android API which is going to be used by the application.
It contains the library file details which are used and linked to the application.

76. What all devices have you worked on?
There are many mobile devices available in the market with different operating systems.
Specifically, I have worked on Android, Windows, Symbian, iPhone, etc

77. Which tools are used for debugging on the Android platform?
To understand the cause of the failure or cause of any issue, debugging is important. On the Android platform Android Monitor.bat utility is used while on iOS platform, iPhone Configuration utility is used for debugging purposes.
There are different tools for debugging which include – Android DDMS, Android Debug Bridge, iOS simulator, Debugging from Eclipse with ADT, Remote debugging on Android with Chrome etc.

78. Which scenario can test only on real devices but not on emulator?
Emulators are used for performing similar kind of testing which is performed on the real devices. Basically, emulators are used as a replacement for real devices as sometimes real devices are not available for testing, use of real mobile devices for testing purpose is costlier at times.
But there are few scenarios which cannot be tested using emulator, these can be tested only using real devices. These scenarios are interrupted scenarios i.e. message, phone call interruption while using the app, low battery, Bluetooth, memory card mount and unmount etc.

79. Name the mobile automation tools that are available in the market?
There are quite a few mobile automation testing tools that are available in the market but these are used only if the project requires it and if the application supports the automation.
These tools are paid as well as free tools, hence analysis needs to be done within the project team and then the appropriate mobile automation tool needs to be selected. Silk Mobile, SeeTest, Ranorex are the paid mobile automation tool while Appium, KIF, Robotium, Calabash are few free tools.

80. How do you troubleshoot android application which is crashing frequently?
Given below are the few steps that we need to follow while troubleshooting the crashing issue:
Free up memory space: There is only a limited space available on the mobile devices for mobile apps. To avoid crashing issue or memory related issue, you need to first check the memory space.
Clear app data usage: You can clear the app data using the Application Manager under “Settings”. This will clear the cache memory and allow some free space to install another app or it will boost up your current app.
Memory Management: Some apps run perfectly on one type of mobile device but the same app may not work on another type of device as for such devices the processing power, memory management, and CPU speed is different. For any app to run properly on any type of mobile device, you should manage the memory on the device.
Compatibility issue: It is always not possible to test mobile app on all mobile devices, browsers, operating systems etc. So you need test your mobile app on as many mobile devices as you can in order to avoid any compatibility issue.

81. How do you find memory leaks in the mobile app on Android platform?
Android Studio is using Android Device Manager (ADM), this ADM is used to detect the memory leaks in the Android platform.
When you open ADM in the Android Studio then on the left-hand side of the ADM, you will find your device or emulator in which a heap sign will be displayed. When you are running any mobile app then you will see the heap size, memory analysis and other statistics displayed on it.

82. What is DDMS?
Android Studio has debugging tools known as DDMS i.e. Dalvik Debug Monitor Server.
It has wide debugging features which include:
Port forwarding services.
Screen capture on the device.
Thread and Heap information.
Incoming call and SMS spoofing.
Logcat
Radio state information.
Location data spoofing.
DDMS is integrated with the Android studio. To launch the DDMS, you need to open Android Device Monitor (ADM) first and then click on the DDMS menu button. Once DDMS is launched, then on the left-hand side the list of connected devices are displayed along with the processes which are running on each device.
With the help of DDMS, you can debug both on real devices and emulators.

83. What are the different data storage options available on the Android platform?
Android platform provides a wide range of data storage options. These options must be used based on the need such as data is secure and used with the permission only or can be accessed publicly.
Below is the list of data storage options on the Android platform:
SharedPreference: It stores data in XML files. It is the simplest way to store private data in the key-value pair.
SQLite: It stores structure data in the private database.
Internal Storage: It stores data in the device file system and any other app cannot read this data.
External Storage: Data is stored in the file system but it is accessible to all apps in the device

84. Explain Sensors in Android?
Android-enabled devices have built-in Sensors which measures Orientation, Motion and other conditions.
These sensors provide data with high accuracy, which will help to monitor positioning and movement of the device. Some of the sensors are hardware based and few are software based.
There are three categories of sensors as mentioned below:
Motion Sensors: These sensors measure the rotational & acceleration forces and it includes gravity sensors, rotational vector sensor, accelerometers, etc.
Environmental Sensors: It measures air temperature, pressure, humidity, etc.
Position Sensors: It measures the physical position of the device and includes orientation sensors and magnetometers.
There are four types of Java Classes as shown below:
Sensor Manager
Sensor
SensorEvent
SensorEventListener

85. What do you think are some disadvantages of Android?
Given that Android is an open-source platform, and the fact that different Android operating systems have been released on different mobile devices, there's no clear cut policy to how applications can adapt with various OS versions and upgrades. One app that runs on this particular version of Android OS may or may not run on another version. Another disadvantage is that since mobile devices such as phones and tabs come in different sizes and forms, it poses a challenge for developers to create apps that can adjust correctly to the right screen size and other varying features and specs.