Flutter Interview Questions – Most Asked Interview Question

Flutter Interview Questions
Flutter Interview Questions

Flutter Interview Questions – Most Asked Interview Question

Flutter Interview Questions – Set 1

#1 What is Flutter?

Flutter is an open-source UI toolkit from Google for crafting beautiful, natively compiled applications for desktop, web, and mobile from a single codebase. Flutter apps are built using the Dart programming language.

#2 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
  • Xcode

#3 What is Dart and why does Flutter use it? 

Dart is an object-oriented, garbage-collected programming language that you use to develop Flutter apps. It was also created by Google, but is open-source, and has community inside and outside Google. Dart was chosen as the language of Flutter for the following reason:

  • Dart is AOT (Ahead Of Time) compiled to fast, predictable, native code, which allows almost all of Flutter to be written in Dart. This not only makes Flutter fast, virtually everything (including all the widgets) can be customized.
  • Dart can also be JIT (Just In Time) compiled for exceptionally fast development cycles and game-changing workflow (including Flutter’s popular sub-second stateful hot reload).
  • Dart allows Flutter to avoid the need for a separate declarative layout language like JSX or XML, or separate visual interface builders because Dart’s declarative, programmatic layout is easy to read and visualize. And with all the layout in one language and in one place, it is easy for Flutter to provide advanced tooling that makes layout a snap.

#4 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.

 #5 What is a “widget” and mention its importance in Flutter?

  • Widgets are basically the UI components in Flutter.
  • It is a way to describe the configuration of an Element.
  • They are inspired by components in React.

Widgets are important in Flutter because everything within a Flutter application is a Widget, from a simple “Text” to “Buttons” to “Screen Layouts”.

#6 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. This one is most important Flutter Interview Questions

#7 What is the latest release of Flutter SDK?

The latest release of the Flutter framework is Flutter-v1.12.13 on 27 Jan 2020.

#8 How many types of widgets are there in Flutter? 

There are two types of widgets:

  1. StatelessWidget : A widget that does not require a mutable state.
  2. StatefulWidget: A widget that has a mutable state.

#9 Differentiate StatelessWidget and StatefulWidget? 

Stateless: Widget state creates ONLY ONCE, then it can update values but not state explicitly. That’s why it has only one class which extends with StatelessWidget. They can never re-run the build() method again.

Stateful: Widgets can update their STATE (locally) & values multiple times upon event triggered. That’s the reason, the implementation is also different. In this, we have 2 classes, one is StatefulWidget & the other is its State implementation handler i.e. State<YourWidget>. So if I say, they can re-run build() method again & again based on events triggered.

  • A StatelessWidget will never rebuild by itself (but can from external events). A StatefulWidget can.
  • A StatelessWidget is static wheres a StatefulWidget is dynamic.

#10 What are the different build modes in Flutter? 

The Flutter tooling supports three modes when compiling your app, and a headless mode for testing.

  • You choose a compilation mode depending on where you are in the development cycle.
  • The modes are:
    • Debug
    • Profile
    • Release

#11 List minimum system requirements to install Flutter on Linux?

 Minimum requirements to install Flutter on Linux are the 64-bit version of Linux, 600 MB free disk space, shared libraries, and other tools.

Flutter uses tools such as bash, curl, git, mkdir, rm, unzip, which, zip, xz-utils.

#12 Talk about different build modes in Flutter?

 The three different types of build modes in Flutter are Debug, Release, and Profile.

Debug mode is used to debug the application on the physical device, emulator, or simulator. Here, assertions, service extensions are enabled. Then compilation is optimized for fast deployment.

Release mode is enabled to deploy your app. Here, assertions, service extension, and debugging are disabled. Finally, the compilation is optimized for fast startup, execution, and package sizes.

Profile mode is used to analyze the performance of your app. Here, some extensions and tracing are enabled.

#13 What is Streams in Flutter/Dart? 

Asynchronous programming in Dart is characterized by the Future and Stream classes.

  • stream is a sequence of asynchronous events. It is like an asynchronous Iterable—where, instead of getting the next event when you ask for it, the stream tells you that there is an event when it is ready.
  • Streams can be created in many ways but they all are used in the same way; the asynchronous for loop( await for). E.g
  •   Future<int> sumStream(Stream<int> stream) async {
  •     var sum = 0;
  •     await for (var value in stream) {
  •       sum += value;
  •     }
  •     return sum;


  • Streams provide an asynchronous sequence of data.
  • Data sequences include user-generated events and data read from files.
  • You can process a stream using either await for or listen() from the Stream API.
  • Streams provide a way to respond to errors.
  • There are two kinds of streams: single subscription or broadcast.

# 14 List the companies who using Flutter?

 Some companies that use Flutter are

  • realtor.com,
  • Tencent,
  • the new york times,
  • square,
  • google,
  • eBay,
  • Sonos,
  • BMW,
  • Emaar,
  • Groupon, and capital one.

#15 What is Flutter native?

 Flutter is relatively a new framework used to build natively compiled applications for different platforms such as iOSAndroidweb, and desktop. It can be used in place of React Native as React is too reliant on third-party libraries. So flutter can be used if you need more native modules. This one is most important Flutter Interview Questions

# 16 What is Flexbox in Flutter?

The Flex class in Flutter is used to display its children in a one-dimensional array. With this widget, you can control the axis where the children are placed. This axis is called as the main axis.

#17 What is the use of HTTP package in Flutter?

 The HTTP package is used in the Flutter project to provide a simple way to fetch data from the Internet. You can use the HTTP package by just adding it to the pubspec.yaml package.

#18 What are Packages in Flutter?

 Packages are used to quickly build an application without developing everything from scratch.

Some example packages are HTTP (for network request), fluro (custom navigation/ route handling), and more.

You can install the package by specifying it in the pubspec.yaml file. You can also create your own package and share it with others.

#19 Name the popular database package used in the Flutter?

The most used and popular database packages used in the Flutter are as follows:

  • SQLite database: It allows to access and manipulate SQLite database.
  • Firebase database: It will enable you to access and manipulate the cloud database.

#20 What is tree shaking in Flutter?

 Tree shaking is an optimization technique to remove the unused module in the bundle during the build process. It is a dead code elimination technique used to optimize the code. This one is most important Flutter Interview Questions

#21 What is the context in flutter?

Context is a handle to the location of the widget in the widget tree. It is a BuildContext instance that gets passed to the builder of a widget in order to know where it is inside the widget tree. It is nothing but a reference to the location of a Widget within the tree structure of all the built widgets.

#22 What is profile mode and when do you use it? 

  • In profile mode, some debugging ability is maintained—enough to profile your app’s performance.
  • Profile mode is used when you want to analyze performance.
  • Profile mode is disabled on the emulator and simulator because their behavior is not representative of real performance.
  • On mobile, profile mode is similar to release mode, with the following differences:
    • Some service extensions, such as the one that enables the performance overlay, are enabled.
    • Tracing is enabled, and tools supporting source-level debugging (such as DevTools) can connect to the process.
  • Profile mode for a web app means that:
    • The build is not minified but tree shaking has been performed.
    • The app is compiled with the dart2js compiler.
  • The command flutter run –profile compiles to profile mode.

These were the Flutter interview questions Stay tuned to learn more.

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