Flutter Interview Questions: A Comprehensive Guide

Basic Flutter interview questions and answers

Why is Flutter preferred over other mobile app developing tools?

Flutter is a free and open-source mobile UI framework, introduced by Google in May 2017. Flutter enables you to develop a native mobile app using only one codebase. This means you can use the same programming language and codebase to make two different apps (for iOS and Android).

There are many reasons why Flutter is better than other mobile app development tools like Java and React Native. A few of them are:

• Flutter supports cross-platform development
• Programming in Flutter is extremely easy and flexible
• Flutter’s building process is much faster than those of all of its competitors.

What are packages and plugins in Flutter?

Users can make modular code that is easy to share by putting together a package, which is made up of classes, interfaces, and sub-packages. Instead of starting from scratch, using packages can help construct applications fast. In Flutter, you may use a package to add new widgets or functionality to an app.

On the other hand, a plugin is a piece of software that enhances your apps functionality. Plugins play a crucial role in the Flutter ecosystem.

What are the limitations of Flutter?

Since Flutter is still a relatively new tool, it has some limitations. They are as follows:

• The number of third-party libraries is very small
• The release size of Flutter is larger than expected
• Flutter requires to be used along with another OOP language, Dart which cannot compete with other OOP languages such as Java, C#.
• Mobile ad platforms don’t support Flutter because it’s not very complicated.
• Flutter is still not used by a wide audience

Why does it generally take a long time to develop a Flutter app?

Building a Flutter app takes a lot longer the first time because Flutter makes an IPA or APK file that is specific to each device. This method, which normally takes a long time, uses Xcode and Gradle to build a file.

What are keys and how do you use them?

A set of IDs for Widgets, Elements and SemanticsNodes make up the key class. Keys are responsible for preserving the state of widgets when they are updated inside the widget tree. You can also use keys to change and rearrange groups of widgets of the same type and set states.

Otherwise, keys may be superfluous to the code, even if they arent harmful in any manner. When editing a widget tree with stateful widgets, keys come in handy. But when the tree is made up of only stateless widgets, keys don’t help.

What are the different types of streams in Dart?

Streams provide an asynchronous sequence of data. Asynchronous programming uses the idea of streams. They refer to a programs asynchronous succession of data occurrences. We put a value on one end and a listener on the other, similar to a pipe. Several listeners can be put together to make one stream. When this stream is put in the pipeline, all of the listeners will get the same data. It is possible to utilize the SteamController to establish new streams or manage existing ones. There are two types of streams:

• Single Subscription Streams These streams convey events in chronological order. Theyre thought of as individual sequences inside a greater totality. These streams are used when the order in which events happen is important, like when reading a file. There can only be one listener at a time during the sequence, and the event won’t happen if there isn’t one.
• Broadcast Streams: These broadcasts tell subscribers about events that are coming up. After subscribing to an event, subscribers can start listening to it right away. These are flexible streams that let more than one person listen at the same time. Also, people can listen again even after canceling a previous membership.

What is pubspec.yaml file?

When you make a Flutter project, there is always a certain type of file at the top of the project. This file is known as the pubspec. yaml file, also called ‘pubspec’. This file contains information about a projects dependencies, such as packages and their versions, typefaces, and so on. It ensures that the package version is the same the next time you create the project. You can also place restrictions on the app. This projects configuration file will be used a lot while working with the Flutter project. This specification is written in YAML, a human-readable markup language.

Flutter is an open source software development kit (SDK) UI used for cross-platform applications from a single codebase. Flutter is primarily used for creating natively compiled, multi-platform applications across iOS and Android seamlessly.

Flutter is developed by which company?

What was the first version of Flutter which ran on an Android operating system?

Sky is the first version of Flutter which ran on Android OS. At the 2015 Dart developer summit, it was announced that the goal was to be able to render at 120 frames per second all the time.

Can you tell us the four main elements of Flutter?

The four main elements of Flutter are:

• Flutter engine
• Widgets
• Design-specific widgets
• Foundation Library

When was the first version of Flutter released?

The first version of Flutter was released in May 2017, but it was first announced in 2015. In December 2018, Google released Flutter 1. 0. In December 2019, Flutter 1. 12 was released.

Flutter is written in which language?

Flutter was written in the Dart language. Flutter runs in the Dart virtual machine, which has a just-in-time execution engine, while an app is being written and debugged.

What does the acronym SDK stand for?

Software Development Kits are groups of software tools and programs that hardware and software companies sell to developers so that they can make apps that work on certain platforms. An SDK helps developers easily integrate their apps with a vendors services. SDKs can have APIs (Application Programming Interfaces), sample code, documentation, and other tools that help programmers make software apps.

Can you name some best editors for Flutter development?

Some popular IDEs (Integrated Development Environment) for Flutter include the following:

• Android Studio
• IntelliJ Idea
• Emac
• Visual Studio
• Codemagic

Which operator is used to evaluate and return values between two expressions?

This “??” operator is used to evaluate and return values between two expressions. This operator first checks expression 1 and returns its value if it is not null. If it is not null, it evaluates expression 2 and returns its value.

Can you tell us how many kinds of widgets there are in Flutter?

There are two main types of widgets in Flutter. These include:

StatelessWidget- It does not have any state information. It is static throughout its lifecycle. Examples are Row, Text, Column, and Container.

StatefulWidget- It has state information. It contains two classes: the state object and the Widget. It is dynamic because it can change the inner data during the Widgets lifetime. Examples are Radio, Form, Checkbox, and TextField.

Can you name the command used to compile the release mode?

This command “Flutter run — release” is used to compile the release mode. When a web app is in release mode, it is compiled with the dart2js compiler to make it run as quickly as possible.

Name the different types of build modes in Flutter.

There are three types of build modes in Flutter. These include:

Debug- It is used to test the apps. On Android Studio, you can find a green play button on the top panel. “Flutter run”.

Profile: Some debugging features are still available in this mode, which is enough to make a profile of your app’s performance. It also has the same performance as the release mode. “Flutter run — profile”.

Release– It is used for deploying the app on marketplaces. “Flutter run – – release”

Which widget in Flutter is a box that comes with a different size?

SizedBox is a widget in Flutter that allows us to specify an arbitrary size for a widget. It is basically used to add empty space between widgets. SizedBox also supports specifying a specific aspect ratio for its child.

Suppose you have to represent real world behavior in Flutter, which animation would you use?

The choice of animation in Flutter would depend on the specific behavior that needs to be represented. Flutter provides several animation options that can be used to represent real-world behavior. These include Physics-based animation, Tween animation, Curved animation, and Hero animation.

Name some popular apps that use Flutter.

Some of the most popular apps that employ Flutter include:

Which folder is used to write Android apps in Flutter?

Android Folder is used to write Android apps in Flutter. The Android Folder has the files and folders that the app needs to run. These files are automatically made when a Flutter project is created.

What is the use of the Await function?

The Await function is an asynchronous function. Its job is to wait until it gets the final value. Await is used with async functions that run asynchronously. This lets users decide whether to wait for the interruption to end before moving on.

Can you tell us which function compiles and updates the app?

In Flutter, there are several functions and commands that can be used to compile and update the app. However, the most commonly used function for this purpose is hot reload.

With Flutter’s “hot reload” feature, you can make changes to your app’s code without having to restart the whole thing.

Can you tell which function is accountable for starting the program?

main () function is used to start a program. This function is highly critical as, without it, one cannot write any function.

What is the purpose of animation controller class in Flutter?

The Animation Controller class in Flutter is used to control and manage animations. You can start, stop, or pause an animation with this tool. You can also set the animation’s length, speed, and direction.

The Animation Controller class’s main job is to set up an animation that can be used in the user interface of your app. The class has methods for setting up and changing animations, like changing the length and curve that controls the animation’s progress.

How can you test a single Widget?

With Widget tests, you can make sure that different parts of the user interface work the way they should without using a real device or simulator. This is the best way to separate small parts of your app and check to see if your code is working as it should.

Can you use WidgetsApp for basic navigation?

Yes, a material app widget creates a navigator. The navigator manages a stack of widgets that are identified by strings, which are also called routes objects. The navigator gives you two ways to manage the stack.

Which widget allows us to refresh the screen?

RefreshIndicator Widget enables us to refresh the screen. The onRefresh callback is called when the user pulls down on the widget. This usually means getting new data from a server or making some other changes to the UI.

Can you state a few examples of stateless widget?

Some examples of a stateless widget include the following:

Text – This displays a string of text with a single style.

Container: This widget can contain other widgets and provide padding, margins, and other layout properties.

Icon: This is where you can see a list of the material icons that can be used with this class.

Explain the term “Tree shaking” in Flutter.

Tree shaking is a method of removing the unused module in the bundle during the development process. Tree shaking serves as a sort of optimization technique that optimizes the code by removing the dead code.

While importing or exporting codes, there might be dead codes hanging around. Removing these dead codes reduces the code size which in turn improves the performance of the application.

What is used to import packages for your project?

pubspec. yaml file is used to import packages in the Dart code. It allows us to set the constraints for the application. This file contains project dependencies, general project settings, and project assets.

What’s the use of Navigation.push in Flutter?

The role of Navigation. In Flutter, push means to add a route to a group of routes that are managed by the navigator.

Why HTTP package is used in Flutter?

HTTP package is used in Flutter for making HTTP requests to web servers. It allows Flutter developers to send HTTP requests and receive HTTP responses from APIs or web servers. To get data or send data to a server, Flutter apps need to talk to APIs or web servers. The HTTP package provides a convenient and easy-to-use way to make HTTP requests in Flutter.

Explain profile mode in Flutter?

The profile mode in Flutter is used to test the functionality of an app while launching it. It compiles and runs your app almost exactly the same way release mode does, but it has extra features that let you fix performance issues.

Whats the role of BuildContext in Flutter?

The BuildContext is an object in Flutter that lets you know where a widget is in the widget tree hierarchy and give you access to services like Theme, MediaQuery, and Navigator. Icons use the BuildContext to get to the parent widget’s properties, like its size, position, and theme. It is is also used to navigate between screens using the Navigator widget.

Could you tell us which class in Flutter is in charge of giving an app the basic material design visual layout structure?

In Flutter, the scaffold class is a widget that is used to set up the basic visual layout structure for material design. The scaffold class makes it faster to create a general-purpose mobile application. Moreover, it contains almost everything we need to create a functional and responsive Flutter application.

Could you tell us what the default return type is for a function if you don’t tell it what type to use?

In Flutter, Dart is the programming language used to develop the framework. What kind of return type does Dart use by default? If you don’t tell it, dynamic will be used. Dart thinks that a function can return any type of value if you don’t tell it what type to return when you declare it in Flutter. The dynamic type is then assigned to the return value by default.

What’s the name of a constructor for a class in Flutter?

The name of a constructor for a class is the same as that of the class itself. Constructor is a special strategy that is used to create objects with predetermined values for the properties. There are three types of constructors in Flutter: named constructor, standard constructor, and factory constructor.

What’s the core of the Flutter layout mechanism?

The main core of the Flutter layout mechanism is the Widgets. The widgets are what make up the user interface. They are organized in a way that looks like a tree, which is called the widget tree. The , text, icon, and even the layout of your application are all widgets.

Which widget can be used to display one after another in scroll format?

The ListView Widget is used to display a large number of items as a scrollable list. ListView is a more advanced version of the Column widget that lets you scroll through the list of items when they don’t fit on the screen.

What is a layout in Flutter?

A layout in Flutter refers to how widgets are arranged on the screen. The parent widget sets the requirements for the layout, which tells the child widget where to go and how big it should be.

Can you tell us how we can test a single widget in Flutter?

Widget tests allow building and interacting with widgets in a test environment. It is used to check whether the Widget works as expected or not. Hence, using this testing UI component, you can test a single widget.

What’s the latest version of Flutter?

3. 7 is the latest version of Flutter. Along with a better framework, this new version has lots of cool new features, such as better support for Material 3, cascading menus and menu bars, an impeller preview, custom context menus, and updates to DevTools, to name a few.

Is Flutter a front-end framework or back-end?

Flutter is primarily a front-end framework. It has widgets and tools to help you make user interfaces that look great and keep people interested. It works on iOS, Android, and the web, among other platforms. However, the framework does provide some back-end functionalities. Flutter applications can communicate with web APIs or connect to backend services through third-party packages or plugins.

What’s the function of the future in Dart?

A future function is used to predict a potential error or value that may occur in the future. It can be completed with a value or an error. Here, developers can plug call backs for each case. Some programming languages use “promise” for the same function.

What’s the role of .network() constructor in Flutter?

The .network() constructor is a widget in Flutter that allows you to display s from the network in your application. It is used to load and display s from a URL. Example: .network(https://piccol.photos/259?=8’,)

Can you tell us what you know about Rune In Dart?

In dart programming language strings are a sequence of UTF-16 which is a 16 bit unicode Transformation Format. Rune refers to an integer that is used to describe any Unicode code point.

Yes. It is a free and open source mobile UI framework created by Google. Here, with only one codebase, you can create native mobile applications.

Why do we use const keyword in Flutter?

We use the keyword to declare constants. Basically, when we know the value of a variable at compile time. This means the compiler knows in advance what value to store .

What are some operators commonly used in Dart?

Here are some of the operators that are commonly used to build apps in Dart:

= (assignment operator): Used to assign a value to a variable. ?? (null-aware operator): This is used to see if a variable is empty and give it a value if it is. ! (bang operator): Used to assert that an expression is not null. (dot operator): Used to access properties and methods of an object.

Why do we use a ticker in Flutter?

In Flutter, tickers are used because they make it safe to update the UI at 60 frames per second. It’s a class that listens to the frameCallback and calls a tick function that tells the ticker listener how much time has passed between the current frame and the last frame.

How can you reduce execution time for running code?

It will depend on the size and adaptability of the app packages. According to which we can integrate just-in-time compilers to run code which will enhance the apps performance. Dart code execution is faster than many other languages where Ahead-of-time compilers also shorten execution times. Adding these compilers helps cut down on run time and add more features to many different kinds of programs that need to merge sequential streams.

Dart is a general-purpose, object-oriented programming language that was initially developed by Google in 2011. It is made to be quick, effective, and scalable, which makes it perfect for making a lot of different kinds of apps, like web and mobile apps, server-side apps, and command-line tools.

What process will you use to reduce widget rebuild?

On rebuilding, the state of the widget changes. This, however, helps the user to see the UI reflect state changes. At this point recreating sections of the user interface that do not need to be changed is unnecessary.

If you don’t want to rebuild the widgets over and over, you can split the widget tree into smaller widgets, each with its own build process. Here const constructor can be used to inform Flutter that the dont need to be rebuilt.

The Spacer widget in Flutter is a flexible widget that fills empty space in a Row, Column, or Flex layout. It’s often used to make space between widgets, either vertically or horizontally, or to share available space between several widgets.

Advanced Flutter interview questions and answers

Flutter Vs React: Which is better?

It’s hard to choose between the two frameworks because they are both so good and are loved by developers and businesses. However, you can pick one based on your particular needs.

Why do we need separate directories for iOS and Android in Flutter?

Here’s why you would need two different directories for Android and iOS files in Flutter:

Android Folder: You need an Android folder to keep files of an Android project. When the code is written by any Flutter framework, the compiler turns it into native code that can be imported into Android projects to make a native Android app.

iOS: This stores all the files for Mac projects. If you’re creating a project for the iOS platform, the iOS folder will be used. You’d need the iOS folder because you can only make iOS apps with the Xcode IDE and macOS in Flutter.

Can you explain how to use Flutters built-in navigation system to create a multi-level navigation hierarchy?

Using the Navigator widget to manage a stack of pages, Flutter’s navigation system lets you set up a multi-level navigation hierarchy. You can push new pages onto the stack using the Navigator. push method and remove them using the Navigator. pop method.

Can you describe how to use Flutters gesture recognition system to detect user input?

Flutter’s gesture recognition system gives you a list of pre-defined gestures, like tap, drag, and scale, that you can use to understand what the user is doing and respond to it. You can use the GestureDetector widget to listen for gestures and the GestureDetector. onTap method to handle taps. You can also create custom gestures by subclassing the GestureRecognizer class.

How would you create a custom widget in Flutter, and what are the benefits of doing so?

You need to make a new class that extends either StatefulWidget or StatelessWidget in Flutter to make your own widget. This depends on whether your widget needs to be stateful or not. The benefits of creating custom widgets include reusability, encapsulation of complex logic, and improved code organization.

Example code:

What is the difference between hot reload and hot restart?

Hot Reload is the fastest and easiest way to make changes in Flutter, make UIs, fix bugs, and add features to an app. All of these changes can be made quickly with a Hot Reload, and the UI changes won’t affect the whole app.

Here’s how to perform Hot Reload:

• Run the Flutter editor using command prompt or editor.
• You can use debug mode and hot reload after making the project.
• To do a hot reload in Windows, press “Ctrl” or the button. You can do a hot reload on a Mac by pressing “cmd s.” If you’re using the command prompt enter ‘r’ to run.

A Hot Restart is not the same as a Hot Reload because it deletes the app’s saved states and starts over with the code. Hot Restart takes more time as compared to Hot Reload but takes less time than restart function. Here’s how to perform Hot Restart:

• Run the editor using command prompt
• Make some changes and run the hot restart
• Press the ctrl shift key or press the hot reload button to start hot restart.

Can you describe how to use the Flutter animations API to create custom animations?

You can make your own animations with the Flutter animations API. It gives you a set of classes and widgets that you can use to make tween animations and physics-based animations. You can change the state of an animation with the AnimationController class and set its values over time with the Tween class.

Can you describe in detail the Flutter IDEs?

Some of the most popular Flutter IDEs include the following:

• IntelliJ IDEA has a lot of features, supports a lot of languages, and helps you write code in a smart way. The free Community Edition should be enough for most new developers, but you need to pay for the Ultimate Edition to get access to more features.
• Android Studio works like IntelliJ IDEA but for Android only. Unlike the latter, though, Android studio is free and open-source. It seems like the best choice for programming for Android devices since it has smart coding help and a built-in debugger.
• VS Code, which stands for Visual Studio Code, is a free tool made by Microsoft. It speeds up development and lowers development time. It works with Windows, macOS, and Linux.

You can also ask what their favorite IDE is and why they chose it as this is one of the most important Flutter interview questions to see how much they know.

How do you implement a custom transition between screens in Flutter?

You can make your own transition between screens by using the PageRouteBuilder class and giving it a custom transitionBuilder function.

For example, to create a fade transition:

Then, to use the custom transition, you can simply push the new route:

Navigator.of(context).push(FadeRoute(page: MyNewPage()));

How do you implement a draggable widget in Flutter?

To implement a draggable widget in Flutter, you can use the Draggable and DragTarget widgets. For example, to create a draggable widget that can be dropped onto a specific target:

How do you implement a custom animation curve in Flutter?

You can make a class that extends the Curve class and provide a custom implementation of the transform method in Flutter to make your own animation curve. Here is an example of how to create a bounce-in curve:

In the transform method, you can use any mathematical formula to create a custom curve. In this example, were using a mathematical formula that simulates a bounce-in effect.

Then, to use the custom curve in an animation, all you have to do is pass it to the Tween class’s curve property:

We are using the BounceInCurve property as the curve property of the CurvedAnimation widget in this case. This property is then passed to the parent property of the Tween widget. This will create an animation with the bounce-in effect.

Flutter Interview Questions & Answers | Flutter Developer Interview Questions | Edureka

FAQ

Can you tell us the four main elements of Flutter?

Why does a Flutter app usually take a long developing time?

What is Dart and Flutter?

How many flutter interview questions are there?

In this article, we have compiled a curated list of 100 Flutter interview questions that cover various topics related to Flutter, Dart, and mobile app development. Whether you are a beginner or an experienced developer, these questions will help you test your knowledge and ace your next interview. Let’s dive in! 1. What is Flutter?

How flutter interview questions can be mastered?

By mastering these concepts and practicing with real-world projects, you can confidently tackle Flutter interview questions and excel in Flutter development. Flutter developer sharing knowledge through informative blog posts .

Should you ask all candidates the same flutter developer interview questions?

Ask all candidates the same Flutter developer interview questions Structured interviews, in which you ask the same questions and in the same order, help you be more objective and minimize bias.

How do I conduct a technical interview for flutter developers?

Conducting a technical interview for Flutter developers is a nuanced process that demands meticulous planning and execution. To ensure you get the most out of the interview and truly gauge the candidate’s capabilities, here are some pivotal tips to consider: Depth Over Breadth: Focus on the depth of understanding.