Application Developer Interview Questions

Step into the world of Application Developer Interview Questions, where we explore the key aspects of a role that involves creating and enhancing software. As an Application Developer, you’ll need a solid grasp of the entire process, from coming up with ideas to making sure the software works well in real-world situations. Candidates for this role should be comfortable with coding, solving problems, and keeping up with the latest in technology. It’s also important to work well with different teams, ensuring that the software can handle growth and ultimately provide users with reliable and effective applications.

Application Developer Interview Question

Attaining the desired role of an Application Developer involves possessing exceptional technical proficiency and understanding the intricacies of the specific interview process. This article delves extensively into the landscape of technical interviews for Application Developers, providing valuable insider information and insights into the types of questions you may encounter.

Q1. What is an activity?
An activity is the entry point for interacting with the user. Every activity contains a layout with a user interface to interact with the user. As we know every activity contains a layout associated with it, so it can be said that the activity class is the gateway, through which a user can interact programmatically with the UI. Layout for a particular activity is set with the help of setContentView(). setContentView() is a function that takes View as a parameter.

Q2. What are the features of Android architecture?
The Android software stack generally consists of a Linux kernel and a collection of C/C++ libraries that are exposed through an application framework that provides services, and management of the applications and run time.

• Linux Kernel
• Libraries
• Android Runtime
• Application Framework
• Applications

Q3. What is the life cycle of Android activity?
The Lifecycle is a class/interface that holds the information about the state of an activity/fragment and also it allows other objects to observe this state by keeping track of it. The LifeCycle component is concerned with the Android LifeCycle events of a component such as an Activity or a Fragment, it has three main classes:

• Lifecycle
• Lifecycle Owner
• Lifecycle Observer

Q4. What’s Android Interface Definition Language (AIDL) in Android?
The Android Interface Definition Language (AIDL) is analogous to other IDLs you would possibly have worked with. It allows you to define the programming interface that both the client and repair agree upon to speak with one another using interprocess communication (IPC). Traditionally the Android way a process cannot access the memory of some other process. So to be able to communicate they decompose their objects into primitives that the Operating System can understand well, and marshall the objects across that boundary for you.

Q5. What is Dalvik Debug Monitor Service(DDMS)?
The Dalvik Debug Monitor Service (DDMS) is a debugging tool for the Android platform. The Dalvik Debug Monitor Service is available as part of the Android SDK. The DDMS provides a variety of services, including port forwarding, on-device screen capture, thread and heap monitoring, and radio state information. The Dalvik Debug Monitor Service enables developers to identify flaws in programs that run on either an emulator or an actual Android device.

Q6. What is a framework?
A framework is like a structure that provides a base for the application development process. With the help of a framework, you can avoid writing everything from scratch. Frameworks provide a set of tools and elements that help in the speedy development process. It acts like a template that can be used and even modified to meet the project requirements. Frameworks are based on programming languages.

Q7. What is Intent in Android?
Intents, in general, are used for navigating among various activities within the same application, but note, is not limited to one single application, i.e., they can be utilized from moving from one application to another as well. Intents could be Implicit, for instance, calling intended actions, and explicit as well, such as opening another activity after some operations like onClick or anything else.

Q8. What is context?
React Context is a method to pass props from parent to child component(s), by storing the props in a store(similar in Redux) and using these props from the store by child component(s) without actually passing them manually at each level of the component tree.Whenever you want a store to keep your states or variables in and use them elsewhere in your program, use Context.

Q9. Explain Sensors in Android.
Most Android-powered devices have built-in sensors that measure motion, orientation, and various environmental conditions. Android Sensors can be used to monitor the three-dimensional device movement or change in the environment of the device such as light, proximity, rotation, movements, magnetic fields, and much more.

Q10. What is a Toast?
A Toast is a feedback message. It takes a very little space for displaying while the overall activity is interactive and visible to the user. It disappears after a few seconds. It disappears automatically. If the user wants a permanently visible message, a Notification can be used. Another type of Toast is custom Toast, in which images can be used instead of a simple message.

Q11. What’s the difference between Implicit Intent and Explicit Intent?

Explicit Intent	Implicit Intent
Explicit intents are those in which the user has a clear vision and knows exactly which activity can handle the requests.	Implicit intents do not name a specific component like explicit intent, instead declare general action to perform, which allows a component from another app to handle.
Explicit intent can do the specific application action which is set by the code like changing activity, downloading the file in the background, etc.	It specifies the only action to be performed and does not directly specify Android Components.
In explicit intent, you can pass data to other activities by using the putExtra method and retrieve by using getIntent().	Here we just mention the action in the intent and OS decides which applications are suitable to handle the task, action across two different applications.
Explicit intents are used for communication inside the application. Like changing activities inside the application.	They are used for communication across two different applications.

Q12. What is the use of Bundle in Android?
Android Bundles are generally used for passing data from one activity to another. Basically here concept of key-value pair is used where the data that one wants to pass is the value of the map, which can be later retrieved by using the key. Bundles are used with intent and values are sent and retrieved in the same fashion, as it is done in the case of Intent.

Q13. What’s the Difference Between Foreground Service and Activity in Android?

Foreground service	Activity
foreground service executes an action that is visible to the user. A foreground service, for example, would be used by an audio app to play an audio track.	A single, concentrated item that the user may accomplish is referred to as an activity.
A Notification must be displayed by foreground services. Even when the user is not interacting with the app, foreground services continue to execute.	All the activities enlisted in the android manifest are meant to be used by the user and hence they are in front while being executed.
You must give notice when utilizing a foreground service so that users are aware that the service is functioning. This is done through notifications that are not dismissible	When using an activity for your android app, there is no need to provide notification as it resides as full glanceable content.
This message will not go away unless the service is either terminated or removed from the foreground.	The activities in android can also be used in mini modes and can be resizable.

Q14. What is SimpleAdapter in Android?
Adapter acts as a bridge between the UI component and data sources. Here Simple Adapter is one type of Adapter. It is basically an easy adapter to map static data to views defined in our XML file(UI component) and is used for customization of List or Grid items.

Q15. What is Batch Scheduling?
Batch scheduling is a manufacturing approach wherein products are assembled in groups, referred to as “batches”. In this technique, each step in the production process is simultaneously applied to a group of items, and the batch progresses to the next stage only after the entire batch is completed.

Q16. What’s the difference between Serializable and Parcelable?

Serializable	Parcelable
Serializable is the standard Java interface for persistence.	Parcelable is the Android-specific interface for persistence.
Serializable objects are stored in memory and can be retrieved quickly.	Parcelable objects are stored in an Android application bundle and require more time to access.
Serializable objects are implemented by implementing the Serializable interface.	Parcelable objects are implemented by extending the Parcelable class.
Objects are serialized using the Java Serialization API.	Objects are serialized using the Android Parcelable API.

Q17. What are broadcast receivers?

Broadcast in android is the system-wide events that can occur when the device starts, when a message is received on the device or when incoming calls are received, or when a device goes to airplane mode, etc. Broadcast Receivers are used to respond to these system-wide events. Broadcast Receivers allow us to register for the system and application events, and when that event happens, then the register receivers get notified. There are mainly two types of Broadcast Receivers:

• Static Broadcast Receivers: These types of Receivers are declared in the manifest file and works even if the app is closed.
• Dynamic Broadcast Receivers: These types of receivers work only if the app is active or minimized.

Q18. What is ANR in Android?
ANR stands for Application Not Responding. An ANR will occur if you’re running a process on the UI thread which takes an extended time, usually around 5 seconds. During this point, the GUI (Graphical User Interface) will lock up which can end in anything the user presses won’t be actioned. After the 5 seconds approx. has occurred, if the thread still hasn’t recovered then an ANR dialogue box is shown informing the user that the appliance isn’t responding and can give the user the choice to either wait, in the hope that the app will eventually recover, or to force close the app.

Q19. What is Android Activity “launchMode”?

Launch mode is an Android OS command that determines how the activity should be started. It specifies how every new action should be linked to the existing task.Types of Launch Modes for Activities:

Standard
This is the default launch mode of activity (If not specified). It launches a new instance of an activity in the task from which it was launched.
Syntax: 

<activity android:launchMode=”standard” />

Single Top
If an instance of the activity already exists at the top of the current task in this launch mode, no new instance will be generated, and the Android system will send the intent data through onNewIntent ().
Syntax:

<activity android:launchMode=”singleTop” />

Single Task
In this method of operation, a new task is always generated, and a new instance is added to the task as the root one.
Syntax: 

<activity android:launchMode=”singleTask” />

Single Instance
This is a highly unique start option that is only used in programs with a single activity. It works similarly to Single Task, except that no additional activities are generated in the same task.
Syntax:

<activity android:launchMode=”singleInstance” />

Q20. What is Builder Pattern?
The builder pattern is defined as a creational design pattern that separates the construction of a complex object from its representation, allowing us to create different representations of an object using the same construction process. It’s beneficial when an object has many optional properties or configurations.

Q21. What is refactoring?
Refactoring or Code Refactoring is defined as systematic process of improving existing computer code, without adding new functionality or changing external behaviour of the code. It is intended to change the implementation, definition, structure of code without changing functionality of software.

Q22. What is virtual DOM?

The Virtual DOM is an in-memory representation of the DOM. DOM refers to the Document Object Model that represents the content of XML or HTML documents as a tree structure so that the programs can be read, accessed and changed in the document structure, style, and content.

Q23. What is Booting Process?

In computing, booting is starting up a computer or computer appliance until it can be used. It can be initiated by hardware such as a button press, or by software command. After the power is switched on the computer is relatively dumb, and can read only part of its storage called Read-only memory. There a small program is stored called firmware. It does power-on self-tests, and most importantly, allows accessing other types of memory, like hard disk and main memory.

Q24. What is Volley Library in Android ?

Volley manages the processing and caching of network requests and it saves developers valuable time from writing the same network call/cache code again and again. Volley is not suitable for large download or streaming operations since Volley holds all responses in memory during parsing.

Q25. What is Typecasting?
Typecasting in Java is the process of converting one data type to another data type using the casting operator. When you assign a value from one primitive data type to another type, this is known as type casting. To enable the use of a variable in a specific manner, this method requires explicitly instructing the Java compiler to treat a variable of one data type as a variable of another data type.

Syntax

<datatype> variableName = (<datatype>) value;

Q26. What’s the Difference between Upcasting and Downcasting in Java?

Upcasting	Downcasting
Upcasting is the typecasting of a child object to a parent object	Downcasting means the typecasting of a parent object to a child object.
Upcasting can be done implicitly.	Downcasting cannot be implicit.
Syntax: Parent p = new Child();	Syntax: Child c = (Child)p;
Upcasting will be done internally and due to upcasting the object is allowed to access only parent class members and child class specified members (overridden methods, etc.) but not all members.	Downcasting has to be done externally and due to downcasting a child object can acquire the properties of the parent object.

Q27. What is hybrid app development?
Hybrid app development means building a single app compatible with all mobile platforms like Android, iOS, and Windows. Unlike native app development, where developers have to use a platform-specific programming language to build apps for different operating systems, a hybrid app uses a single code base for all OS.

Q28. What is Singleton Method Design Pattern?
Singleton Pattern is probably the most widely used design pattern. It is a simple pattern, easy to understand and to use. Sometimes it is used in excess and in scenarios where it is not required. In such cases, the disadvantages of using it outweigh the advantages it brings. For this reason, the singleton pattern is sometimes considered an antipattern or pattern singleton.

Q29. What is Xamarin ?
Xamarin has entirely converted the Android and iOS SDK to C# to make it more familiar to the developers. One can easily use the same codebase for both the platforms without the hassle of remembering the syntax of different languages all the time. Besides, the User Interface(UI) remains almost same. It has to be separately built for both the platforms and then has to be bound by the common codebase.

Q30. What’s the difference between Ionic and React Native?

Ionic	React Native<
Ionic uses HTML, CSS, JavaScript, AngularJS and TypeScript to build apps.	React Native uses React and JavaScript to build apps.
It is slower than React Native due to its web apps.	It is faster than Ionic.
Documentation of Ionic is very simple, clear and consistent	Documentation of React Native is not much good.
It is difficult to develop graphics in Ionic.	It is easy to develop graphics in React Native.

Q31. What is meant by progressive web apps?
Progressive Web Apps (PWA) are built and enhanced with modern APIs(like Service Workers) to deliver native capabilities, reliability, and installability while reaching anyone, anywhere, on any device with a single codebase.Unlike traditional applications, progressive web apps are a hybrid of regular web pages (or websites) and a mobile application. This new application model attempts to combine features offered by most modern browsers with the benefits of mobile experience.

Q32. What is data binding in Android?
Data Binding as a single term refers to the technique that connects data from end consumers and users and then keeps them in sync. Android’s Data Binding Library lets the developer keep the UI within the layout XML files and generates code from them. The library also does the work of synchronizing the View with data that comes from the ViewModel. 

Q33. What is Component Driven Development ?
Component Driven Development (CDD) is a fundamental feature in ReactJS, playing a significant role in our preference for building applications with the React library. The essence of CDD lies in the segmentation of large file content into smaller, reusable parts that find application across multiple areas.

Q34. What is Cross Origin Resource Sharing (CORS)?
CORS (Cross-Origin Resource Sharing) is a mechanism by which data or any other resource of a site could be shared intentionally to a third party website when there is a need. Generally, access to resources that are residing in a third party site is restricted by the browser clients for security purposes.

Q35. What is Desugaring?
Desugaring is basically forward/upward compatibility (which can be also referred as backport) for new types and APIs. It enables us to use this newer Java libraries in older versions of android paying a small price on app size.

Q36. What is Spinner in Kotlin?
Android Spinner is a view similar to a dropdown list which is used to select one option from the list of options. It provides an easy way to select one item from the list of items and it shows a dropdown list of all values when we click on it. The default value of the android spinner will be the currently selected value and by using the Adapter we can easily bind the items to the spinner objects.

Q37. What is Firebase?
Firebase is a product of Google which helps developers to build, manage, and grow their apps easily. It helps developers to build their apps faster and in a more secure way. No programming is required on the firebase side which makes it easy to use its features more efficiently. It provides services to android, ios, web, and unity. It provides cloud storage.

Q38. What is Fragments in Android?
Fragment is a piece of an activity that enables a more modular activity design. A fragment encapsulates functionality so that it is easier to reuse within activities and layouts. Android devices exist in a variety of screen sizes and densities. Fragments simplify the reuse of components in different layouts and their logic. You can build single-pane layouts for handsets (phones) and multi-pane layouts for tablets.

Q39. What are the types of Android Fragments?

Single Fragment: Display only one single view on the device screen. This type of fragment is mostly used for mobile phones.

List Fragment: This Fragment is used to display a list-view from which the user can select the desired sub-activity. The menu drawer of apps like Gmail is the best example of this kind of fragment.

Fragment Transaction: This kind of fragments supports the transition from one fragment to another at run time. Users can switch between multiple fragments like switching tabs.

Q40. Explain Webpack.
Webpack is a static module bundler used for JavaScript applications. Since webpack understands only JavaScript and JSON files, It transforms front-end assets such as HTML, CSS, and images into valid modules if the corresponding loaders are included. While Processing your application webpack internally builds a dependency graph that maps every module your project needs and produces one or more output bundles.