Top 35 Android Interview Questions and Answers

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

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

Android Interview Questions Quiz: Prove Your Mobile Programming Expertise

An ultimate quiz on Android Interview Questions to help you land your dream mobile development job. This is suitable for any mobile developer, software engineer, or anyone preparing for Android interviews to master mobile development concepts.

Questions for Android Engineer Interview

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

Given below is the list of the most commonly asked Android Interview Questions

Q #1) What is Android?

Answer: Android is an open-source operating system and is mainly popular for smartphones and tablets.

This operating system is Linux Kernel-based. Using the Android operating system, the developer develops the functions or programs that can perform basic as well as advanced types of operations on the Smartphone.

Q #2) What is the Android SDK?

Answer: To develop a mobile application, Android developers require some tools, and this requirement is satisfied by “Android SDK”, which is a set of tools that are used for developing or writing apps.

It has a Graphical User Interface that emulates the Android environment. This emulator acts like an actual mobile device on which the developers write their code and then debug/test the same code to check if anything is wrong.

Q #3) What are the different versions of Android OS that you remember?

Answer: The various versions of Android are given below.

Version	Name
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

Q #4) What is the difference between Mobile Application Testing and Mobile Testing?

Answer: Mobile app testing is the testing of applications on a device, which mainly focuses on the functions and features of the application.

And Mobile Testing is the testing of the actual mobile device and focuses on mobile features like Calls, SMS, Contacts, Media Players, inbuilt browsers, etc.

Q #5) Name the languages supported for Android development.

Answer: Java is the widely used language for Android development. It also supports C/C++, and when used with the Android SDK, it improves the performance speed too.

Q #6) What are the advantages of the Android Operating System?

Answer: It is open-source and platform-independent. It supports various technologies like Bluetooth, Wi-Fi, etc

Q #7) Explain Android Architecture briefly.

Answer: Android architecture is a software stack of components.

The diagram below 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 the Linux kernel, Android provides a connection between the other software layers. 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 the API framework. It comprises library modules that are specific to the hardware component.
• Android Runtime: Linux kernel provides a multi-tasking execution environment so that multiple processes can execute; each process runs on its instance of Android Runtime (ART). Android has core runtime libraries like Dalvik VM-specific libraries, Java Interoperability Libraries, Android Libraries, and C/C++ libraries.

[Via Deevelopers]

• Application Framework (Java API Framework): The entire Android functionality is 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, contacts, etc, are included in this top layer. It also includes third-party applications that are installed by the user, such as Games, etc.

Q #8) Define and explain the Android Framework.

Answer: Android framework is a set of APIs that Android developers write code for mobile apps. It contains the methods and classes to write the programming code.

Android framework includes a different set of tools to create image panes, text fields, 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.

Q #9) Which components are necessary for a New Android project?

Answer: Whenever a new Android project is created, the below components are required:

• manifest: It contains an 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 that should be compiled into a .apk file.

The below image shows the Project View once an Android project is created:

Q #10) Provide the important core components of Android.

Answer: The core components of Android operating systems are:

• Activity
• Intents
• Services
• Content Provider
• Fragment

Android Interview Questions for Freshers

Q #11) Explain briefly – what is meant by Activities?

Answer: Activities are the part of the mobile app that the user can see and interact with.

For example, if you open an SMS app that has multiple activities like creating a new SMS, adding a contact from the address book, writing the content in the SMS body, sending an SMS to the selected contact, etc.

Activity keeps track of the following:

• Keeps track of what a user is currently looking for in an app.
• Keeps 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 the Activity class as shown below:

Public class MyActivity extends Activity
{
}

Q # 12) What is meant by Services?

Answer: Service is an Android component that runs in the background and acts independently. It does not provide any user interface.

Though the services are running behind the scenes, user can continue their work on different apps. Most of the time, the users are not aware of the services that 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 the Service class:

Public class MainService extends Service
{
}

Q #13) Explain the Activity Lifecycle briefly.

Answer: When a user interacts with the app and moves here and there, out of the app, returns to the app, etc. During this process, “Activity” instances also move through 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 diagram below describes the Activity Lifecycle:

When a user is working on an app, 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.

Q #14) What is an Intent?

Answer: 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

Q #15) Explain Implicit and Explicit Intents.

Answer: Implicit Intent calls the system components while Explicit Intents invoke the Activity class.

Q #16) What is the importance of setting up permissions in app development?

Answer: 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 the code, which results in defect leakage.

Q #17) What is the .apk extension in Android?

Answer: It is a default file format that is used by the Android Operating System. Application Package Kit (APK) is used for the installation of mobile apps. The .apk contains a resource file, certificate, manifest file, and other code.

APK files are archive files in the zip format with .apk extension.

Q #18) What is the database used for the Android platform?

Answer: SQLite is the database that is used for the Android platform. It is an open-source, serverless database.

Q #19) What is ANR in Android?

Answer: 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.

Q #20) Which are the dialog boxes supported by the Android platform?

Answer: Android supports four types of dialog boxes:

• AlertDialog: It has a maximum of 3 buttons, and sometimes AlertDialog includes checkboxes 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.

Android Developer Interview Questions for Experienced

Q #21) What is ADB?

Answer: Android Debug Bridge (ADB) is a command-line tool that performs shell commands.

ADB is used for direct communication between the emulator ports. It gives direct control of the communication between the emulator instances to the developer.

Q #22) What is ActivityCreator?

Answer: ActivityCreator is a batch file and shell script that was used to create a new Android project. It is now replaced by the “Create New Project” in Android SDK.

Q #23) What is Orientation?

Answer: Orientation is the key feature in Smartphones nowadays. It can rotate the screen between Horizontal or Vertical modes.

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 that you can set screen alignments. HORIZONTAL and VERTICAL are two values that 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 the onCreate() method of the Activity gets fired.

When the orientation of the Android mobile device changes, 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.

Q #24) What is AIDL?

Answer: In the Android platform, there are remote methods that facilitate the use of methods from one program to another. To create and implement the remote methods, the first step is to define the communication interface in AIDL.

AIDL stands for Android Interface Definition Language. It facilitates communication between the client and the 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.

Q #25) What are the data types supported by AIDL?

Answer: Data Types supported by AIDL are as follows:

• String
• List
• Map
• charSequence
• Java data types such as INT, Long, Char, Boolean, etc

Q #26) Explain the AndroidManifest.xml file and why you need this?

Answer: Every application must have an AndroidManifest.xml file in the root directory. It contains information about your app and provides the same to the Android system.

The information includes the package name and 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 that implement these components.
• It is responsible for protecting the application, and it declares the permission for accessing the protected part of the app.
• It also declares the Android API that is going to be used by the application.
• It contains the library file details, which are used and linked to the application.

Scenario-Based Android Interview Questions

Q #27) What devices have you worked on?

Answer: There are many mobile devices available in the market with different operating systems.

Specifically, I have worked on Android, Windows, Symbian, iPhone, etc

Q #28) Which tools are used for debugging on the Android platform?

Answer: 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 the iOS platform, the 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.

Q #29) Which scenario can be tested only on real devices but not on an emulator?

Answer: Emulators are used for performing similar kinds of testing that is performed on real devices. Emulators are used as a replacement for real devices, as sometimes real devices are not available for testing. The use of real mobile devices for testing purposes is costlier at times.

But a few scenarios cannot be tested using an 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.

Q #30) Name the mobile automation tools that are available in the market.

Answer: 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, and Ranorex are paid mobile automation tools, while Appium, KIF, Robotium,and Calabash are a few free tools.

Q #31) How do you troubleshoot the Android application that is crashing frequently?

Answer: Given below are the few steps that we need to follow while troubleshooting the crashing issue:

• Free up memory space: There is only limited space available on mobile devices for mobile apps. To avoid crashing issues or memory-related issues, 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 are 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 not always possible to test mobile apps on all mobile devices, browsers, operating systems, etc. So you need to test your mobile app on as many mobile devices as you can to avoid any compatibility issues.

Q #32) How do you find memory leaks in the mobile app on the Android platform?

Answer: Android Studio uses Android Device Manager (ADM), this ADM is used to detect memory leaks in the Android platform.

When you open ADM in 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.

Q #33) What is DDMS?

Answer: 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 Android Studio. To launch the DDMS, you need to open the Android Device Monitor (ADM) first and then click on the DDMS menu button. Once DDMS is launched, on the left-hand side, the list of connected devices is displayed along with the processes that are running on each device.

With the help of DDMS, you can debug both on real devices and emulators.

Q #34) What are the different data storage options available on the Android platform?

Answer: The Android platform provides a wide range of data storage options. These options must be used based on the need, such as whether the data is secure and used with 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 a key-value pair.
• SQLite: It stores structured data in a 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

Q #35) Explain Sensors in Android.

Answer: Android-enabled devices have built-in sensors that measure orientation, motion, and other conditions.

These sensors provide data with high accuracy, which will help to monitor the positioning and movement of the device. Some of the sensors are hardware-based, and a few are software-based.

There are three categories of sensors as mentioned below:

• Motion Sensors: These sensors measure the rotational & acceleration forces, and they include gravity sensors, rotational vector sensors, accelerometers, etc.
• Environmental Sensors: They measure air temperature, pressure, humidity, etc.
• Position Sensors: They measure the physical position of the device and include orientation sensors and magnetometers.

There are four types of Java Classes as shown below:

• Sensor Manager
• Sensor
• SensorEvent
• SensorEventListener

Conclusion

Almost all the important Android interview questions and answers have been covered here in this article. I hope that this has been very useful to you.

I’m sure that you can crack any Android interview successfully with a thorough knowledge of all these questions.