Flutter interview questions
There are most popular Flutter interview questions asked in many companies.
1. What is Flutter?
Flutter is a UI toolkit for creating fast, beautiful, natively compiled applications for mobile with one programing language and single codebase. It is an open-source development framework developed by Google. Generally, Flutter is not a language; it is an SDK. Flutter apps use Dart programming language for creating an app. The first alpha version of Flutter was released in May 2017.
Flutter is mainly optimized for 2D mobile apps that can run on both Android and iOS platforms. We can also use it to build full-featured apps, including camera, storage, geolocation, network, third-party SDKs, and more.
2. What is Dart?
Dart is a general-purpose, object-oriented programming language with C-style syntax. It is open-source and developed by Google in 2011. The purpose of Dart programming is to create a frontend user interfaces for the web and mobile apps. It is an important language for creating Flutter apps. The Dart language can be compiled both AOT (Ahead-of-Time) and JIT (Just-in-Time).
3. Should I learn Dart for Flutter?
Yes, it is very necessary to learn Dart language for building Flutter application.
4. Is Flutter Free?
Yes. Flutter is free and open-source.
5. What are Flutter widgets?
A Flutter app is always considered as a tree of widgets. Whenever you are going to code for building anything in Flutter, it will be inside a widget. Widgets describe how your app view should look like with their current configuration and state. When you made any alteration in the code, the widget rebuilds its description by calculating the difference of previous and current widget to determine the minimal changes for rendering in UI of the app.
Widgets are nested with each other to build the app. It means the root of your app is itself a widget, and all the way down is a widget also. For example, a widget can display something, can define design, can handle interaction, etc.
6. What do you understand by the Stateful and Stateless widgets?
A Stateful widget has state information. It is referred to as dynamic because it can change the inner data during the widget lifetime. A widget that allows us to refresh the screen is called a Stateful widget. This widget does not have a build() method. It has createState() method, which returns a class that extends the Flutters State Class. The examples of the Stateful widget are Checkbox, Radio, Slider, InkWell, Form, and TextField.
The Stateless widget does not have any state information. It remains static throughout its lifecycle. The examples of the Stateless widget are Text, Row, Column, Container, etc. If the screen or widget contains static content, it should be a Stateless widget, but if you want to change the content, it needs to be a Stateful widget.
7. What are the best editors for Flutter development?
The Flutter development tools allow to make Flutter development faster and thus boosting the developer's workflow. Flutter IDE and tools need some plugins to develop mobile applications. The plugins help us to dart compiling, code analysis, and Flutter development. The popular IDE for Flutter developments are as follows:
- Android Studio
- Visual Studio
- IntelliJ IDEA
8. What is pubspec.yaml file?
It is the project's configuration file that will use a lot during working with the Flutter project. It allows you how your application works. It also allows us to set the constraints for the app. This file contains:
- Project general settings such as name, description, and version of the project.
- Project dependencies.
- Project assets (e.g., images, audio, etc.).
9. What are packages and plugins in Flutter?
A package is a group of similar types of classes, interfaces, and sub-packages. The packages and plugins help us to build the app without having to develop everything from packages. In Flutter, it allows you to import new widgets or functionality into the app. The packages and plugins have a very small distinction. Generally, packages are the new components or the code written in dart languages, whereas plugins allow more functionality on the device by using the native code. In the DartPub, packages, and plugins, both are referred to as packages.
10. What are the advantages of Flutter?
The popular advantages of Flutter framework are as follows:
- Cross-platform Development: This feature allows Flutter to write the code once, maintain, and can run on different platforms. It saves the time, effort, and money of the developers.
- Faster Development: The performance of the Flutter application is fast. Flutter compiles the application by using the arm C/C++ library that makes it closer to machine code and gives the app a better native performance.
- Good Community: Flutter has good community support where the developers can ask the issues and get the result quickly.
- Live and Hot Reloading: It makes the app development process extremely fast. This feature allows us to change or update the code are reflected as soon as the alterations are made.
- Minimal code: Flutter app is developed by Dart programming language, which uses JIT and AOT compilation to improve the overall start-up time, functioning and accelerates the performance. JIT enhances the development system and refreshes the UI without putting extra effort into building a new one.
- UI Focused: It has an excellent user interface because it uses a design-centric widget, high-development tools, advanced APIs, and many more features.
- Documentation: Flutter has very good documentation support. It is organized and more informative. We can get everything that we want to be written in one place.
11. Which one is better between Flutter and React Native?
Flutter and React Native are both used to develop the native hybrid app from a single codebase. These apps can run on iOS and Android platforms.
React Native develop by Facebook, whereas Flutter framework first introduced by Google. So, both framework has a very good feature and community.
From the developer's point of view, it is very difficult to choose amongst them. Thus, it is very challenging to choose a winner between Flutter and React Native.
12. Why does the first Flutter app build take so long?
When you build the Flutter app the first time, it will take a longer time. It is because the Flutter built the device-specific APK or IPA file. Thus, the Gradle and Xcode are used to build the file, taking a long time.
13. Why is the Android and iOS folder in the Flutter project?
Android: This folder holds a complete Android project. It is used when you create the Flutter application for Android. When the Flutter code is compiled into the native code, it will get injected into this Android project, so that the result is a native Android application. For Example: When you are using the Android emulator, this Android project is used to build the Android app, which further deployed to the Android Virtual Device.
iOS: This folder holds a complete Mac project. It is used when you build the Flutter application for iOS. It is similar to the Android folder, which is used when developing an app for Android. When the Flutter code is compiled into the native code, it will get injected into this iOS project, so that the result is a native iOS application. Building a Flutter application for iOS is only possible when you are working on macOS and Xcode IDE.
14. What is Tween Animation?
It is the short form of in-betweening. In a tween animation, it is required to define the start and endpoint of animation. It means the animation begins with start value, then goes through a series of intermediate values and finally reached the end value. It also provides the timeline and curve, which defines the time and speed of the transition. The widget framework provides a calculation of how to transition from the start and endpoint.
15. Explain Hot Reload in Flutter?
The hot reload feature allows you to quickly and easily perform an experiment in the project. It helps to build UI, add new features, fix bugs, and make app development fast. To perform hot reloading of a Flutter app, do the following steps:
- Run the app in a supported Flutter editor or terminal window.
- Modify any of the Dart files in the project.
- If you use an IDE that supports Flutter, then select Save All or click the Hot Reload button on the toolbar. Immediately, you can see the result in your emulator or real device.
16. Name some popular apps that use Flutter?
Today, many organizations use Flutter for building the app. Some of the most popular app built on Flutter are as follows:
- Google Ads
- Birch Finance
- Coach Yourself
17. Name the popular database package used in the Flutter?
The most used and popular database packages used in the Flutter are as follows:
- sqflite database: It allows to access and manipulate SQLite database.
- Firebase database: It will enable you to access and manipulate the cloud database.
18. Which type of animation allows you to represent real-world behavior?
The Physics-based animation allows you to represent real-world behavior in Flutter.