Q1 What is Broadcast Receiver?

Q1. What are the Lifecycle Events of an Android Activity?

Lifecycle is an Android Architecture Component released by Google to assist all Android developers. The Lifecycle is a class/interface that maintains information about an activity/fragment’s current state and allows other objects to see this state by keeping track of it. The events of an Android component’s lifecycle, such as those of an activity or fragment, are the focus of the lifecycle component....

Q2. How can Two Distinct Android Apps Interact?

On Android, there are essentially two ways for apps to communicate with one another:...

Q3. How would you communicate between Two Fragments?

All communication between fragments occurs either through a shared ViewModel or through the related Activity. Direct communication between two Fragments should not be allowed....

Q4. What is Android Data Binding?

A support library called the Data Binding Library allows you to take advantage of binding UI components to data sources in a layout using a declarative format....

Q5. What is a ViewHolder Pattern? Why should We use it?

When the adapter calls the getView() function, it also calls the findViewById() method. As a result of the mobile CPU having to perform such heavy lifting, the application’s performance suffers and battery life degrades. FindViewById shouldn’t be used repeatedly. Instead, utilize the ViewHolder design pattern....

Q6. What is the difference between Handler, AsyncTask, and Thread?

The Handler class offers a straightforward route for sending data to this thread and can be used to register to a thread. When using another background thread, a handler enables you to connect with the UI thread. The establishment of a background process and synchronization with the main thread are both handled by the AsyncTask class. Additionally, it allows for reporting on the status of ongoing tasks. A developer can employ a Thread, which is the fundamental building block of multithreading, with the following drawback: Handle synchronization with the main thread if you post back results to the user interface No default for canceling the thread No default thread pooling No default for handling configuration changes in Android...

Q7. Discuss Singletons vs Application Context for the app-global state.

Static singletons may usually perform the same purpose in a more scalable way. If your singleton requires a global context (for instance, to register broadcast receivers), you can provide a Context to the method that retrieves it, which internally uses Context. When creating the singleton for the first time, use getApplicationContext()....

Q8. How can We use AsyncTask in different Activities?

One approach is to build a callback interface using AsynTask in several Activities....

Q9. What is Android Jetpack Architecture Components?

You can create reliable, tested, and maintainable apps with the aid of the libraries that make up the Android Architecture Components. Android Jetpack includes Android Architecture Components....

Q10. What are some differences between Parcelable and Serializable?

We cannot just transfer objects to activities in Android. The objects must either implement the Serializable or Parcelable interface to accomplish this....

Q11. What is Broadcast Receiver?

Similar to the publish-subscribe design pattern, Android apps have the ability to transmit and receive broadcast messages from other Android apps and the Android system. The receiver component of an Android application is often referred to as the broadcast receiver. This component allows us to register receivers for any application- or system-level event. When that happens, the Android system will inform the registered receivers about the execution of the events in question....

Q12. What is MVVM in Android?

Model—View—ViewModel (MVVM) is the industry-recognized software Architecture Pattern that overcomes all drawbacks of MVP and MVC design patterns. MVVM suggests separating the data presentation logic(Views or UI) from the core business logic part of the application....

Q13. What is the difference between getContext(), getApplicationContext(), getBaseContext(), and this?

View.getContext(): Returns the context in which the view is executing at the moment. Typically, the active Activity. Activity.getApplicationContext(): Returns the context for the entire application (the process all the Activities are running inside of). If you require a context linked to the lifetime of the entire application, not just the current Activity, use this in place of the current Activity context. ContextWrapper.getBaseContext(): You use a ContextWrapper if you need access to a Context from within another context. GetBaseContext can be used to retrieve the Context that ContextWrapper is referring to....

Q14. What is Android Jetpack?

Android Jetpack is a set of software components, libraries, tools, and guidance to help in developing robust Android applications. Launched by Google in 2018, Jetpack comprises existing android support libraries and android architecture components with an addition of the Android KTX library as a single modular entity. Jetpack consists of a wide collection of libraries that are built in a way to work together and make robust mobile applications....

Q15. What is AndroidX?

The new open-source project known as Android Extension Library, also called AndroidX, is a considerable improvement over the original Android Support Library and can be used to create, test, package, and deliver libraries within Jetpack. The AndroidX namespace includes the Android Jetpack libraries. AndroidX is created independently of the Android OS and provides backward compatibility with earlier Android releases, much like the Support Library. The Support Library is entirely replaced by AndroidX packages, which provide feature parity and new libraries....

Q16. Explain Dependency Injection.

When a large number of objects have to be created that are dependent on a large number of other objects in a project, it becomes difficult as the project grows larger. With this increasing code base, good external support is required to keep track of everything. That is one of the scenarios in which we employ a Dependency Framework....

Q17. What is Singleton Class in Android?

The Singleton Pattern is a software design pattern that restricts the instantiation of a class to just “one” instance. It is used in Android Applications when an item needs to be created just once and used across the board. The main reason for this is that repeatedly creating these objects, uses up system resources. The identical object should therefore only be created once and used repeatedly. It is utilized in situations where we only require a single instance of the class, such as with network services, databases, etc. We, therefore, create a singleton class to implement the Singleton pattern in our project or product. In this article, we’ll look at how to create singleton classes in Java and Kotlin....

Q18. What is Jetpack Compose in Android?

Jetpack Compose is a modern UI toolkit that is designed to simplify UI development in Android. It consists of a reactive programming model with conciseness and ease of Kotlin programming language. It is fully declarative so that you can describe your UI by calling some series of functions that will transform your data into a UI hierarchy. When the data changes or is updated then the framework automatically recalls these functions and updates the view for you....

Q19. What is Coroutine on Android?

Coroutines are lightweight threads that allow us to do synchronous and asynchronous programming with ease. We can build the main safety and replace callbacks with coroutines without blocking the main thread. The concurrency design pattern of the coroutine allows for code simplification and asynchronous execution, which can offer very high levels of concurrency with a very small overhead....

Q20. What is Espresso in Android?

Google created the open-source Espresso testing framework for the Android user interface (UI). Espresso is an easy, efficient, and adaptable testing framework. Espresso tests avoid the distraction of boilerplate content, custom infrastructure, or complicated implementation details by stating expectations, interactions, and assertions in a straightforward and concise manner. Espresso tests execute really efficiently! It allows you to forego your waits, syncs, sleeps, and polls while manipulating and making assertions on the application UI while it is idle....

Q21. Types of Notifications in Android.

Notifications could be of various formats and designs depending upon the developer. In General, one must have witnessed these four types of notifications:...

Q22. What is Firebase Cloud Messaging?

Firebase Cloud Messaging or FCM, originally known as Google Cloud Messaging or GCM, is a free cloud service provided by Google that enables app developers to deliver notifications and messages to users across many platforms, including Android, iOS, and web applications. It is a free real-time method for instantly sending notifications to client applications. Notifications with a payload of up to 4Kb can be properly transmitted via Firebase Cloud Messaging....

Q23. What is the Google Android SDK?

The Google Android SDK is a set of tools that developers use to create apps that run on Android-enabled devices. It includes a graphical interface that simulates an Android-driven portable environment, allowing them to test and debug their applications....

Q24. What is the difference between Volly and Retrofit?

Retrofit Volley Retrofit can parse many other types of responses automatically like: Boolean: Web API response, to be a boolean. Integer: Web API response, to be an integer. Date: Web API response, to be a Long format date. String: Web API response, to be in String format. Object: Web API response, to be in a JSON object. Collections: Web API response, to be in a String Format. StringRequest: Request converts the response into a String. JsonObjectRequest: Request and response automatically converted into a JSONObject. JsonArrayRequest: Request and response automatically converted into a JSONArray. ImageRequest: Request converts the response into a decoded bitmap. Retrofit does not support caching. Volley has a flexible caching mechanism. When a request is made through volley first the cache is checked for an appropriate response. If it is found there then it is returned and parsed else a network hit is made. Retrofit does not support any retrying mechanism. But it can be achieved manually by doing some extra code. In Volley, we can set a retry policy using the setRetryPolicy method. It supports the customized request timeout, number of retries, and backoff multiplier. Retrofit has full support for Post Requests and Multipart uploads. Volley supports both post requests and multipart uploads but for post requests, we have to convert our java objects to JSONObject. Also for multipart uploads, we have to do some extra code and use some additional classes...

Q25. Types of Databases in Android.

Relational, key-value, and object-oriented databases are the three main types of databases used by Android devices....