Popular Android Interview Questions and Answers

Android, which holds more than 70% of the market share, is the world’s most popular mobile operating system. Android was first launched by Google in 2008. Android is of great importance for companies and developers who want to target mobile devices.

Interest in Android developers is increasing day by day. We have listed frequently asked Android interview questions that will help you succeed in your Android developer interview and develop the skills you need to create successful mobile applications. You can review these questions to help you prepare for an Android-related role.

 

Most Popular Android Interview Questions and Answers

 

1. What is Android?

📱 Android is an open-source operating system used on mobile devices such as smartphones and tablets. It allows developers to create applications that can perform both basic and advanced functions.

Using Android is free. It allows everyone to access it for commercial use as well. This makes it different from Apple’s iOS, macOS, and Microsoft’s Windows.

 

2. What is Google Android SDK?

Google Android SDK is a set of tools that developers need to write applications for Android-equipped devices. It stands for “Android Software Development Kit.” With the help of the Android SDK, Android applications are easily created.

The Android SDK consists of several tools necessary for developing Android applications. These tools include features like testing code and debugging. The Android SDK is compatible with all operating systems, including Windows, Linux, macOS, etc.

 

3. What are the features of Android?

The important features of Android include:

✔️ It is free and open-source.

✔️ It is a customizable operating system.

✔️ Various applications can be developed.

✔️ Reduces overall complexity.

✔️ Supports messaging services, web browser, storage (SQLite), connectivity, media, and much more.

 

4. What is Android architecture?

Android architecture includes different components to support any Android device needs. Android software includes an open-source Linux kernel with a collection of numerous C/C++ libraries available through an application framework service.

Android architecture consists of 4 basic components:

• Linux Kernel
• Libraries
• Android Framework
• Android Applications

 

5. What is the Android Framework?

The Android Framework is an important aspect of Android architecture. It is a software platform used in the development of applications running on the Android operating system. This platform provides various components necessary for Android applications, as well as APIs and services.

The Android Framework provides solutions for many needs of applications, such as user interface, data storage, security, internet connectivity, device sensors, multimedia, and more. Additionally, other components necessary for the operation of Android applications, such as Activity, Fragment, Service, Broadcast Receiver components are also included within the Android Framework.

The Android Framework is written in the Java programming language and also uses the Java Class Library and C/C++ libraries.

 

6. Which languages are supported in Android application development?

Android supports the Java programming language for application development. Java is one of the most popular languages for application development. This allows even developers who are new to learning Android to quickly learn how to create and deploy applications in the Android environment. Additionally, the supported languages are:

 

• Kotlin: Kotlin is a modern, safe, object-oriented cross-platform programming language. When Android Studio 3.0 was released, Kotlin was announced as the official programming language for Android.
• C#: C# developers using the C# language can create native iOS and Android mobile applications.
• Python: Python has emerged as one of the most popular programming languages in recent times. Python, a dynamic and object-oriented programming language, is very popular in machine learning.

 

7. What is AAPT?

AAPT is an abbreviation for Android Asset Packaging Tool'. This tool is used to package the source codes and other components of Android applications.

AAPT is used during the compilation of Android applications and facilitates the creation of the APK (Android Package) file of the application. Additionally, it ensures that the application's source code, resource files, and other components are included in the APK file.

 

8. What are Android emulators?

Android emulators are software designed to mimic the hardware and software of an Android mobile device for development and testing purposes.

Android emulators run on Mac or PC to create Android applications. Playing or testing games is a popular reason to use Android emulators.

 

9. What does ActivityCreator do?

ActivityCreator is the first step in creating a new Android project. It is done by a shell script. It helps create a new file system structure necessary for writing code within the Android IDE.

 

10. What does "activity" mean in Android?

In Android, an "activity" is a component that represents the user interface of an application. Different states of the user interface (e.g., when the application is launched or when exiting the application) are represented by different activities. Activities are one of the core components of Android applications and play an important role in shaping the user experience of the application.

An activity is implemented as a subclass of the Activity class as follows 👇:

 

11. What are the four fundamental states of an activity?

Each activity has a specific lifecycle. This lifecycle starts from the creation of the activity (onCreate() method) and continues until the user leaves the activity (onDestroy() method).

 

• onCreate () : The activity is created.
• onStart () : This is a callback method.
• onResume () : The user can interact with the activity.
• onPause () : The activity is partially obscured by another activity.
• onStop () : The activity is no longer visible to the user.
• onDestroy () : The activity is destroyed. 

 

12. When is the onStop() method called?

In the case where another activity takes over, and the activity can no longer be seen by the user, the onStop method is used.

 

13. What elements are important in an Android project?

These are the basic elements that are present every time an Android project is created:

1. Manifest: Contains the XML file.
2. Build/: Contains the build output.
3. Res/: Contains non-code resources.
4. Src/: Contains code and resources.
5. Assets/: Contains files that can be converted into an .apk file.

 

14. What is a container?

Containers are structures that hold objects and window elements together. They include labels, fields, and buttons.

 

15. What is adb?

Adb (Android Debug Bridge) stands for Android Debug Bridge. It is a tool used to communicate between Android devices and computers.

ADB provides access to Android devices via a USB cable or Wi-Fi connection and allows developers to test their applications. Additionally, ADB is part of the Android SDK. It is also supported by integrated development environments like Android Studio.

 

16. What is ANR?

ANR (Application Not Responding) is an abbreviation for "application not responding." It is an error message that appears when a user interface of an Android application is not responding.

When the application does not respond for an extended period, it appears to the user as a dialog box. In this case, the GUI (Graphical User Interface) will lock, preventing the user from pressing any buttons.

ANR appears to the user in two situations: one is when the user does not receive a response within 5 seconds after inputting, and the other is when a broadcast receiver does not complete its execution within 10 seconds.

 

17. What role does Dalvik play in Android development?

📍 Dalvik is a virtual machine that runs applications and codes written in Java. The Java compiler converts the source code into Bytecode, and then it compiles into a .dex file that the Dalvik VM can read and use. Class files are converted into .dex files, and then they are read and executed by the Dalvik Virtual Machine. Through Dalvik, a device can efficiently run multiple virtual machines through better memory management.

 

18. What is AndroidManifest.xml?

AndroidManifest.xml contains the information that the Android system needs to know about the application in order to run the code. Its main features are:

✅ AndroidManifest.xml is the required XML file for an Android application.

✅ It includes the components of the application such as activities, services, broadcast receivers, content providers, etc.

✅ Responsible for allowing the application to access any protected areas.

✅ Specifies the Android API to be used in the application.

✅ Lists the instrumentation classes.

 

19. Do all phones support the latest Android operating system?

Some Android-supported phones allow upgrading to a higher version of the Android operating system. However, whether the latest Android version is supported largely depends on the phone’s capacity and features.

 

20. How does the build process work in Android?

1. Writing the source codes: Application developers write the source codes that determine the logic of the application’s operation and also create the necessary components and interface designs.
2. Compiling the codes: The source codes are converted to Java bytecode in a development environment like Android Studio or using a tool like the terminal.
3. Packaging the components and resource files: The compiled codes are combined with other components (e.g., images, sound files, font files, etc.) and the manifest file. This process is automatically carried out by a Gradle script.
4. Creating the APK file: All files are packaged and signed as an APK file. The APK file is loaded onto Android devices, making the application executable.

 

21. What is the Android Interface Definition Language (AIDL)?

AIDL is an interface definition language. Android Interface Definition Language or AIDL facilitates communication between the client and service. AIDL has a structure similar to the Java language and allows the definition of data types, methods, and interfaces. Additionally, AIDL files must also be defined in the application’s manifest file.

 

22. What is Android Runtime (ART)?

Android Runtime (ART) is an application used as the runtime environment by the Android operating system. It has replaced Dalvik VM (Virtual Machine). ART translates the application’s byte code into native instructions executed by the device’s runtime environment.

 

 

23. How to find memory leaks in Android applications?

Memory leaks in applications on the Android platform can be detected using the Android Device Monitor (ADM).

 

24. What is an Android intent?

An Android intent is a communication object used to request an action from another application component.

• ✔️ context.startActivity() – To start an activity
• ✔️ context.startService() – To start a service
• ✔️ context.sendBroadcast() – To send a broadcast

 

25. What are the types of Android intents?

In Android, intents are one of the basic mechanisms used to communicate between activities or components.

 

1️⃣ Implicit intent: An implicit intent is used when the target component is not defined in the intent, and the Android system needs to evaluate registered components based on the intent data. In other words, it is used to start target components whose functions are not specified.

For example, you can write the following code to display a webpage. 👇

 

2️⃣ Explicit intent: It is the direct definition of the target component in the intent. It helps you transition from one activity to another. It is also used to pass data using the putExtra method.

 

26. What is the difference between a file, class, and activity in Android?

• 🗃️ File is a block of information or resources used to store data. It can be of any file type.
• 📑 Class is a file compiled from a .Java file that Android uses to create an executable apk.
• 🖥️ Activity, is the basic component where the user interface exists and the user can interact with the application.

 

27. What is Android Toast?

✅ In Android, "Toast" is a temporary notification message that usually appears at the bottom.

✅ It is a commonly used notification mechanism to display important information or short messages to the user.

✅ It only occupies the space required for the message.

✅ Notifications open and close automatically.

✅ Toast provides simple feedback about an operation in a small popup window.

 

📍 Example syntax:

 

28. What is an Android Broadcast Receiver and how is it implemented?

A Broadcast Receiver is a mechanism that can listen for broadcasts sent by the system. It is used in actions like listening for incoming calls.

A Broadcast Receiver helps respond to broadcast messages from other applications or the system. It is used to manage communication between the Android operating system and other applications.

👇 To implement a Broadcast Receiver, you need to create your own class by inheriting the BroadcastReceiver class. This class should contain a method called onReceive(), which is automatically called when the broadcast is received and performs operations related to the broadcast.

 

 

29. How are data passed between activities in Android?

Bundles, also known as packages, are used to transfer data to sub-activities. 👇

 

30. How is WebView used in Android?

WebView is a component that displays web pages within an application. It uses the WebKit rendering engine to display web pages. This includes the necessary methods for navigating forward and backward, zooming in and out, searching text, and more.

To add WebView to the application, add the <WebView> element to the XML layout file. 

To add it in the XML file ⬇️:

 

31. What is an Android Service and how is it implemented?

In Android, a service is a background process used to perform long-running operations. Services can run even if the application is not active and can communicate with other components. For example, services can be used for operations like playing music, data synchronization, and file downloading.

 

32. What is Android DDMS (Dalvik Debug Monitor Server)?

DDMS is a debugging tool in the Android Software Development Kit (SDK). It reports details about every thread and the time spent in the Android operating system. DDMS comes with Android Studio or Eclipse IDE and is used to manage and monitor Android devices or virtual devices.

With DDMS, you can view applications running on the device, intervene in the device's file system, send mock locations, and take screenshots.

 

33. What is the Dalvik Virtual Machine (DVM)?

✅ Dalvik is the virtual machine used in the Android operating system. 

✅ Dalvik VM is a purely interpretive virtual machine that runs files in .dex format.

✅ The virtual machine can run class files compiled by the Java language compiler and converted to their native form using the 'dx' tool.

 

34. What is a .dex file?

Android programs are compiled into '.dex' (Dalvik Executable) files and packaged into a single .apk file. '.dex' files can be created by compiling Java-written applications into .dex, which is an optimized format for efficient storage and memory-mapped executions.

 

Next Step

If you are preparing for technical interviews for an Android developer role, first clarify all the basic concepts. Many questions asked in the interview test your technical skills.

We hope this article on Android interview questions will help you. If you want to learn Android and build a career in this field, don’t forget to check out our Android Bootcamps.