Updated July 7, 2023
Android Interview Questions – Introduction
Android interview questions and answers can test the competence of an Android developer.
With the world becoming closer and smaller and all things coming on mobile, the need for mobile application developers is on the rise. Interestingly, Android has captured the mobile space, with a 71.8% market share among all mobile operating systems. As a result, the demand for Android developers is high, with the average salary being $125344 per year.
This article lists the top Android interview questions, and answers asked in interviews in 2023. One can test their skills and knowledge by conducting practice interviews using the listed Android interview questions and answers.
Key Highlights
- Android interview questions and answers gauge the knowledge of an Android developer in terms of Android application development.
- Android interview questions revolve around Android architecture, components, app lifecycle, data storage and management in Android, and more.
- Other topics questioned include Android UI, layout and design principles, Android networking and APIs, and Android debugging and performance optimization.
- Having knowledge of Android development tools and frameworks is essential to become a good Android developer.
Part 1 – Android Interview Questions (Basic)
Q1. What is Android? Explain the main components of Android.
Answer:
Android is an open-source operating system that enables the user to develop applications on mobile devices and tablets. It is a Linux based operating system that allows the user to create and run applications on mobile with the rich high-end components it has. A user can perform all basic and advanced operations and create apps. The main components of Android are:
- Linux kernel
- Android framework
- Runtime
- Libraries
- Android OS
These components enable the developer to create high-end applications that provide all the facilities in a single application with an amazing look and feel.
Q2. What is an activity in Android?
Answer: An activity is a single screen in an Android app that users can interact with. It represents a single focused task that the user can perform, such as composing an email or viewing a map.
Q3. What is intent in Android?
Answer: Intent is a messaging object that is used to request an action from another component of the Android system, such as starting an activity or launching a service.
Q4. What is a content provider in Android?
Answer: A content provider is a component of the Android system that manages access to a central repository of data, such as a database. It provides a standard interface for querying and updating data from multiple applications.
Q5. What is an APK in Android?
Answer: An APK (Android Package Kit) is the file format used to distribute and install applications on Android devices. It contains all of the necessary files for an application to run, including the code, resources, and manifest file.
Q6. How do you handle screen rotations in Android?
Answer: You can handle screen rotations in Android by saving the state of your application’s data and restoring it when the screen is rotated. You can use the onSaveInstanceState() and onRestoreInstanceState() methods to save and restore data, respectively.
Q7. What is the Android Manifest file?
Answer: The Android Manifest file is an XML file that contains information about your application, such as its name, version, permissions, and activities. It is required by the Android system to properly install and run your application.
Q8. What is the difference between Serializable and Parcelable in Android?
Answer: Serializable and Parcelable are both interfaces in Java that are used to serialize and deserialize objects. However, Parcelable is optimized for Android and is faster and more efficient than Serializable, especially when dealing with large amounts of data.
Q9. What is the Activity lifecycle in Android?
Answer: The Activity lifecycle in Android is the set of states that an activity goes through as it is created, started, paused, resumed, stopped, and destroyed. The key methods in the Activity lifecycle include onCreate(), onStart(), onResume(), onPause(), onStop(), and onDestroy().
Q10. How do you optimize the performance of an Android app?
Answer: To optimize the performance of an Android app-
- Minimize object creation
- Reduce memory usage
- Optimize layouts
- Using asynchronous operations
- Use tools such as the Android Profiler to monitor the app’s performance and identify bottlenecks.
Part 2 – Android Interview Questions (Advanced)
Q11. What are the important items in an Android project?
Answer: Most important items in an Android project include-
- xml
- xml
- bin/
- src/
- res/
- assets/
Q12. Explain in brief the files and folders which are created when an Android project is created.
Answer:
A new Android project has the following files-
- src- This file contains Java source files for the newly created project. The code for the application is to be written in this file. It should be made available under the name of a project.
- Assets- This is a folder that will contain all information regarding HTML files, text files, and databases.
- gen- This folder must have the R.java file. It is a file generated by the compiler, and it references the resources that are found in the project. This file should not be modified as it is generated by the compiler.
- Android library- This folder contains an android.jar file that has all the libraries needed for creating an Android application.
- bin- It contains the .apk file that is created by ADT during the code build process. This file is the application binary file. When a developer runs his code, this file has everything required to run the code.
- res- This is a folder that contains all resource files used by the application. It has subfolders like drawable, menu, layout, values, etc.
Q13. What is ANR? What are the precautions to be taken to avoid ANR in an application?
Answer: ANR stands for “Application Not Responding,” which refers to a situation where an Android app has become unresponsive to user input. ANR usually occurs when an application performs a long-running operation on the main UI thread, such as network operations or database queries.
To avoid ANR in an application:
- Perform long-running operations in the background thread instead of the main UI thread.
- Use AsyncTask or HandlerThread to perform background tasks.
- Use IntentService or JobScheduler for long-running tasks.
- Optimize your code to reduce processing time and improve performance.
- Use a progress dialog or notification to keep the user informed of the app’s progress.
- Use tracing tools like Systrace and Traceview to identify performance bottlenecks.
- Test your application thoroughly to ensure it is responsive and stable.
- Handle exceptions and errors properly to prevent ANR from occurring.
Q14. Write code for a Toast that will display the message “Hello, this is a Toast”.
Answer:
Toast.makeText(getApplicationContext(), “Hello, this is a Toast”,
Toast.LENGTH_LONG).show();
Q15. What is Google Android SDK?
Google SDK is a development toolkit that is used by developers to write programs for mobile devices. It provides a graphical user interface simulating an Android-driven environment and enabling the developer to test and debug their codes.
Q16. Explain the importance of XML-based layouts in Android projects.
- XML-based layouts in Android projects are important because they allow developers to separate the visual presentation of an app from its functionality.
- This means that the layout can be designed and edited independently, making it easier for designers and developers to work together on an app.
- XML-based layouts are also easy to read and modify, and they can be reused across different screen sizes and devices, which saves time and effort in the development process.
- XML-based layouts make it possible to create dynamic and responsive user interfaces that adapt to changes in the app’s content or the device’s orientation.
Q17. Write code to generate a button dynamically.
Answer:
protected void onCreate(Bundle newInstanceState) {
super.onCreate(newInstanceState);
Button button = new Button(this);
button.setText(“Button”);
setContentView(button);
});
Q18. What is AIDL? What are the different data types supported by AIDL?
Answer:
AIDL (Android Interface Definition Language) is a language used to define the interface between a client and a service in Android. AIDL allows the client to access the methods and data of the service across different processes. It provides an RPC (Remote Procedure Call) mechanism for inter-process communication in Android.
Different data types supported by AIDL include:
- Primitive data types (int, long, boolean, etc.)
- Java objects that implement the Parcelable interface
- Lists and arrays of primitive data types and objects
- Map collections of primitive data types and objects
- Other AIDL interfaces.
Q19. How to handle multiple-resolution screens in Android?
Answer:
Five ways of handling multiple screen resolutions in Android are-
- Use density-independent pixels (dp) instead of pixels (px) for defining the sizes and positions of UI elements. This will ensure that the UI elements are displayed proportionally on different screen resolutions.
- Provide multiple versions of images in different densities (ldpi, mdpi, hdpi, xhdpi, xxhdpi, xxxhdpi) to ensure that images look sharp and clear on different screen resolutions.
- Use layout managers such as LinearLayout, RelativeLayout, and ConstraintLayout to design the UI. These layout managers automatically adjust the UI elements based on the screen size and orientation.
- Test the app on different screen resolutions and orientations to ensure that the UI looks good and functions properly on all devices.
Q20. Explain the process to launch an activity on an application.
Answer:
To launch an activity developer needs to explicitly define intent. It specifies the activity that we wish to start. The following code will help you understand that activity that is sent in the second parameter in the new activity class.startActivity(). The first parameter is the Intent constructor in the current activity context.
Intent intent1= new Intent(this, SecondActivity.class);
startActivity(intent1);
If the user wishes to start an activity from a particular fragment then-
Intent intent1= new Intent(getActivity(), SecondActivity.class);
getActivity(),startActivity(intent1);
Q21. What are the states of an activity?
Answer:
There are four states of activity-
- Active- When the activity is active in the foreground
- Paused- When an activity is in the background and still visible.
- Stopped- When an activity is not visible.
- Destroyed- When an activity is killed or terminated.
Q22. What is the difference between a Service and an IntentService in Android?
Answer:
Service:
- A Service is a component in Android that runs in the background, performing long-running operations or handling network requests.
- Service needs to be stopped explicitly using the stopService() method.
- Service can be used for longer-running tasks.
IntentService:
- IntentService is a subclass of Service that is specifically designed to handle asynchronous requests in the background, one at a time, using a worker thread.
- IntentService automatically stops itself once it has completed its task.
- IntentService is typically used for short-lived operations.
Final Thoughts
Preparing for an Android interview requires a strong understanding of Java or Kotlin programming languages, as well as experience with the Android SDK and IDE. Additionally, knowledge of RESTful APIs, database management, and version control systems such as Git can be beneficial. By studying Android interview questions in this article, one can gain insights into what employers are looking for in Android developers and prepare for the interview process. Staying up-to-date with the latest industry trends and continually honing one’s skills can set one apart from other candidates and help one excel in the Android development career.
FAQs
Q1. What does an Android developer do?
Answer: An Android developer is responsible for designing and developing applications for the Android platform. They work with a team of developers, designers, and product managers to create mobile applications that meet client needs and adhere to best practices. They may also be responsible for testing, debugging, and updating existing applications.
Q2. What are the skills of an Android Developer?
Answer: An Android developer should have a strong understanding of Java and Kotlin programming languages, as well as experience with the Android SDK and Android Studio IDE. Other essential skills include knowledge of RESTful APIs, database management, and version control systems such as Git. Good communication and problem-solving skills are also important.
Q3. How do I become a full Android Developer?
Answer: To become a full Android developer, you should start by learning the basics of Java or Kotlin programming languages and familiarize yourself with the Android SDK and IDE. Online tutorials, courses, and certifications can be helpful in gaining knowledge and build a portfolio of projects. Additionally, gaining practical experience by working on real-world projects can be beneficial.
Q4. What should I study for an Android interview?
Answer: For an Android interview, it’s essential to have a strong understanding of Java or Kotlin programming languages, as well as experience with the Android SDK and IDE. You should also be familiar with the basics of RESTful APIs, database management, and version control systems such as Git. Additionally, knowledge of design patterns, architecture components, and popular libraries such as Retrofit and Glide can be helpful.
Q5. Is Android a good career?
Answer: Yes, Android development is a promising career with high demand and growth potential. As mobile technology continues to advance, the need for skilled Android developers will continue to increase. Android developers can work in various industries, from startups to large corporations, and have opportunities for career advancement and salary growth.
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