Flutter is a popular cross-platform and open-source framework that was developed by Google. According to Statista around 42% of the app developers in 2021 use this framework to build apps. With its powerful programming language, Dart, and a single code base, you can create natively compiled high-performance mobile applications with its UI toolkit.
This framework allows you to create mobile applications both for iOS and Android platforms. Thanks to its amazing performance, beautiful UI, and simplicity in development, Flutter will continue to have a big impact on creating high-quality mobile applications.
Therefore, if you love programming and want to have a lucrative career in mobile app development, then you must learn this amazing framework. If you have already mastered Flutter, and are now looking for a job in a good company that has an expert team of flutter developers, then you may face these questions listed here in the interview.
To make your job easier, we have segregated these questions into three sections; questions for the beginners, for the experienced, and the most asked questions.
Interview questions for the beginners
These questions are related to Flutter and are generally asked by the interviewer to gauge your skills and knowledge regarding the basics of Flutter.
1). What is Flutter?
It is an open-source UI software development kit created by Google for developing desktop, web, and mobile applications with a single code base. It uses a highly dynamic programming language called the Dart to write codes for the app. The main elements of Flutter include the following:
- Dart platform.
- Flutter engine.
- Foundation library.
- Design specific widgets.
2). Explain about Dart?
It is an object-oriented and general-purpose programming language that comes with C-language syntax. This open-source freeware was built by Google and allows you to build a highly attractive front-end user interface for web and mobile apps.
3). What are the benefits of using Flutter?
There are multiple benefits of using Flutter, some of these include the following:
- It has a highly flexible and expressive UI with a personalized layered architecture. It helps in easy design, expressive UI, and rapid rendering.
- It comes with a ‘Hot Reload’ feature that ensures faster deployment of the app.
- The compilers of Dart allow the code to be compiled into the natural AR and machine code by using the native compilers of Dart.
4). What are some of the restrictions you will face in Flutter?
When you are using Flutter, then you have to face certain restrictions which involve the following:
- The release size is large.
- The availability of third-party libraries is limited. Additionally, few of the widgets in Flutter can be accessed only on one platform.
- It offers limited complexity which hinders game engines, 3D modeling, and unity integration.
- Flutter doesn’t offer continuous support as it is not extensively used yet.
5). What are Flutter widgets?
To describe a Flutter application, you can compare it is a web of widgets. Anytime, you try to code for creating anything in a Flutter, it would automatically be in the widget. The advantage of a widget is that it would explain how the application will look in its current state and configuration. Anytime you make any change in the code, the widget rearranges its description by computing the difference of previous widgets to the current one. Based on its computation, the widget will then evaluate the least change to render the UI of the app.
6). If you create a Flutter application by using the firebase service, in which the user has to log in to this application through his/her Firebase user accounts. In which Firebase products, the accounts of the app user will be stored?
7). If you want to add child widgets to the container widget, how many you can do?
Only one child widget.
8). Which properties must be utilized for in-line, adding the label, and icon suggestion text to the text field widget?
9). What is the definition of Padding?
It is a widget that is used to wrap the container, column, row, or other widgets. This widget helps you to insert the filing size around the child widget.
10). Which widget allows us to have a specific height or width between the widgets?
Interview questions for the experienced
These questions would help you to get a good idea about what kind of questions you will face for those job interviews where the interviewers are looking for an advanced programmer of Flutter.
11). Which command checks the environment to prepare the report about the status of Android Studio and Flutter in addition to IDE software installation.
12). Mention the similarities between future and stream?
- Both of these can work asynchronously.
- They have the same potential.
- A stream could be a mixture of futures.
- A future has only a single response, whereas the stream can have multiple responses.
13). How can you access screen size in the future?
To access the screen size and other related properties like the pixel density, aspect ratio et cetera, you have to use MediaQuery. For example; MeadiaQuery.of(Context).size,width.
14). Why do we require mixins?
Multiple inheritances are not endorsed by Dart. Therefore, if you want to implement multiple inheritances in Flutter, then you will require mixins. Mixins offer you a way to write reusable class codes in several class hierarchies.
15). Is Flutter a language?
No, Flutter is an SDK.
Most asked Flutter developer interview questions
The questions we have listed here are the most asked Flutter developer interview questions. Learn them carefully to crack the interview.
16). What is meant by tree shaking in Flutter?
This term is used as the optimization technique to remove any unutilized module that is left in the bundle in the build process. It is also used as a code elimination technique to optimize the application.
17). What is the difference between setState and Provider?
It is used to manage the local state which is in a similar stateful widget as its child. The disadvantage of setState is that everything is in the same class like business logic, UI code, and mixin UI which violates clean code principles.
In the Provider pattern, we outlined everything in distinct classes, which indicates that the UI presentation is defined in multiple logics that specify differently. This makes the code looks clean and of high quality. Moreover, you don’t need to transmit the state from one screen to another through a constructor.
18). Distinguish between Hot Restart and Hot Reload?
Works primarily with States value.
It helps the developer to easily retrieve the compiled applications because it destroys the preserved state value and puts them to default. Therefore, after every Hot Restart, the application widget tree gets completely rebuilt according to the new type code.
It takes a longer time compared to the Hot Reload for updating and compiling the app.
It works with a small r key at the terminal or the command prompt.
The hot reload feature allows you to swiftly compile any recently inserted code inside a file and then pass it to the Dart Virtual Machine. After the Dart Virtual Machine completes the update, it immediately updates the app’s UI.
It helps you to create UI, fix any bugs, insert new features and accelerate the app development process.
19). Which is better, React Native or Flutter?
Both the react native and Flutter are used to create a native hybrid app using a single code base. The application so created can be easily installed and run on both the Android and the iOS platforms.
The Flutter framework was created by Google and React Native was developed by Facebook. Both of these frameworks have some amazing features and huge online communities.
Both of these have their advantages and disadvantages and it is difficult to choose them from the perspective of a developer. Therefore, there is no clear winner when we compare these two robust and feature-rich frameworks.
20). Explain pubspec.yaml file?
This is also known as the configuration file of a project that is user-locked when you are working with the Flutter project. This file allows you to track how the application is working. It also helps you to configure the constraints for the application. This file may include the following:
- Project dependencies.
- Project assets.
- Project common settings like name, the project version, and description.
21). What are the packages and plug-ins in Flutter?
The package can be defined as a set of the same types of interfaces, classes, and sub- packages. The packages and plug-ins help you to create the app without developing everything from scratch. When you are using Flutter, it enables you to import the latest functionalities and widgets into the application.
There is a very small difference between packages and plug-ins. In layman’s terms, the packages could be described as the latest elements or code built-in Dart programming language, whereas the plug-in offers greater functionality on the device by using the native code.
22). What are stateless and stateful widgets?
A widget with no state information is called a stateless widget and it remains static throughout its life-cycle. Some examples of stateless widgets include container, text, column et cetera. If you find a widget or a screen that includes some static content, then it must be a stateless widget.
A widget that provides state information is called a stateful widget. Such a widget is defined as dynamic as it can change the inner data during its lifetime. A widget that allows you to refresh the screen is an example of a stateful widget. Such a widget does not have the build() method, but it has the createState() method.
23). Why did the Flutter app take so long to make?
Whenever you try to build the Flutter application for the first time, it will take some extra time. The reason behind taking more time is due to the device-specific IPA or ATK file. Therefore, whenever Gradle and Xcode are utilized to build the file, it takes more time.
24). What is Tween animation?
It is a short form of in-betweening. In this, you have to define both the starting point and the endpoint of the automation. It means that when the animation starts, it begins with a starting value. After the animation progresses through a series of intermediary values, it arrives at last at the end value. It also offers you the timeline and curve, which helps you to define the time of variation and speed.
25). Give some examples of famous Flutter applications.
Flutter is widely used by businesses all over the world and there are many popular apps built with flutter, some of these includes the following:
- Google ads.
- Birch Finance.
- Coach Yourself.
26). What is the name of the database packages utilized in Flutter?
There are multiple database packages in a Flutter, amongst these two are used more often. They are as follows:
- SQLite database: It helps you to manipulate and access the SQLite database.
- Firebase Database: it helps you to access and manipulate cloud databases.
27). Distinguish between “runApp()” and “main()” functions in Flutter?
The main() function is utilized to start the program. Without the main () function, no program on the Flutter could be started.
The runApp() is utilized to bring back widgets that are attached to the screen as the root of the widget tree and put on the screen.
28). Write about the different build modes in the Flutter?
The Flutter SDK can work in three modes while it is compiling the application. You can select these modes by looking at where you are in the development life-cycle. These modes are named as follows.
29). Where do we use Keys in Flutter?
Flutter developers use the Keys in multiple ways. When you are using Flutter, keys are used as identifiers for the semantic nodes, elements, and widgets. It is utilized whenever a new widget updates any available element. The key needs not to be specific when it is in the elements of the same parent. The key has subclasses which are called LocalKey and GlobalKey. The keys are useful to change a group of widgets (like adding, reordering, or removing) of a similar type that is in a similar state.
30). What is profile mode?
This mode is used to measure the performance of the applications. In the profile mode, some debugging ability is kept for profiling the performance of your app. This mode is deactivated on the emulator and simulator as they do not delegate the performance. To profile this mode, you can use this command:
Flutter run –profile
31). Explain BuildContext.
BuildContext is part of the widgets in a Flutter in the element tree in which every widget has its BuildContext. It is used to get a reference to another widget or theme.
These are some of the interview questions that would give you an idea about what type of questions are generally asked for a Flutter job interview. You can go through these questions carefully to prepare yourself for your upcoming interview and easily crack it to get the job that you want.