Flutter and Dart Interview Questions and Answers

by Nithyanandham, on Dec 22, 2022 4:24:54 PM

Interview Questions (30)

Q1. What is Flutter?


  • Open-source UI toolkit.
  • Natively compiled applications for desktop, web, and mobile from one codebase.
  • That is build using dart programing language .
  • Flutter 1.0 is officially announced on Dec 04, 2018.

Q2. what's Dart?

Ans:Dart may be a general-purpose, object-oriented programing language originally developed by Google.Dart is an Open Source programing language developed by Google in 2011. The Dart programing language is majorly deployed for creating the frontend UI for mobile and web apps. It plays a serious role within the development of Flutter apps.

Dart supports all the common concepts of programming languages like interfaces, classes, functions, and it doesn't support array directly. It supports the gathering , which is employed to represent various data structures like generics, arrays, and optional typing.

Q3. Name a number of the favored apps that use flutter?

Ans: Many organizations across the planet are building apps using flutter. this is often thanks to , its ability to create native apps in varied categories. Therefore, the foremost popular apps built with flutter are;

  • Firstly, Google Ads for utility bills.
  • Secondly, Reflectly on lifestyle.
  • Alibaba for commerce
  • Birch Finance
  • Coach Yourself
  • Tencent
  • Watermaniac
  • Cryptograph
  • SG Bus tracker

Q4. What is Dart and why does Flutter use it?

Ans: Dart is an object-oriented, garbage-collected programing language .

Dart was chosen because the language of Flutter for the subsequent reason:

  • Dart is AOT (Ahead Of Time) compiled to fast, predictable, native code, which allows most of Flutter to be written in Dart. 
  • This not only makes Flutter fast, virtually everything (including all the widgets) are often customized.
  • Dart also can 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 necessity for a separate declarative layout language like JSX or XML, or separate visual interface builders, because Dart’s declarative, 
  • programmatic layout is straightforward to read and visualize. And with all the layout in one language and in one place, it's easy for Flutter to supply advanced tooling that creates layout a snap.

Q5. Name the simplest editors for flutter development?

Ans: Flutter IDE and tools make flutter development faster, therefore, boosting the developer’s workflow. Above all, 

flutter IDE and tools are good for developing mobile apps. As a result, you'll need some plugins. Usually, the plugins help with Dart compiling, 

code analysis, and flutter development.

Therefore, the simplest editors for flutter development are; Android studio and VS code.

Flutter Training

Q6. What are the benefits of Flutter?


  • Learn Once write Everywhere
  • Cross-platform Development
  • Faster Development
  • Good Community
  • Live and Hot Reloading
  • Native Performance
  • Provids Native Look and Feel
  • Expressive and versatile UI
  • Q7. Who is that the Developer Of Dart?

Ans: Google is that the developer of Dart.

Q8. How to Install Flutter?

Ans: you'll install it any OS like Windows, Linus, MacOS etc

Q9. What Is Rune In Dart?

Ans : In Dart, rune is an integer representing Unicode code point.

Q10. How to Install Flutter?

Ans : you'll install it any OS like Windows, Linus, MacOS etc

Q11. What is Streams in Flutter/Dart? 

Ans : 

  • Asynchronous programming in Dart is characterized by the longer term and Stream classes.
  • A stream may be a sequence of asynchronous events. it's like an asynchronous Iterable—where, rather than getting subsequent event once you invite it, the stream tells you that there's an occasion when it's ready.
  • Streams are often created in some ways but all of them are utilized in an equivalent way; the asynchronous for loop ( await for).

Example :

 Future sumStream(Stream stream) async {

 var sum = 0;

 await for (var value in stream) {

 sum += value;


 return sum;


  • Streams provide an asynchronous sequence of knowledge .
  • 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 how to reply to errors.
  • There are two sorts of streams: single subscription or broadcast.

Q12. Between flutter and react native which one is better?

Ans : This an easy but quite tricky flutter interview question. 

First of all, Flutter and React Native is employed in developing hybrid native apps for iOS and Android from one codebase.

React Native is older within the market since it had been released on March 26, 2015. 

While flutter was introduced in May 2017.

Consequently, it's difficult to settle on the simplest between the 2 , because, all of them have great features.

Therefore, the developer has the duty to make a decision on which one to use while running a project.

Q13. Differentiate StatelessWidget and StatefulWidget?

Ans : 

  • Stateless: Widget state creates just one occasion , then it can update values but not state explicitly. 
  • That’s why it's just one class which extends with StatelessWidget. they will never re-run build() method again.
  • Stateful: Widgets can update their STATE (locally) & values multiple times upon event triggered. That’s the rationale , 
  • the implementation is additionally different. In this, we've 2 classes, one is StatefulWidget& the opposite is it’s State implementation handler i.e. State. So if I say, they will re-run build() method again & again supported 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.

Q14. What are best editors for Flutter Development?


  • Android Studio

  • VS Code

Q15. What Is the utilization Of This Keyword In Dart?

Ans: In Dart, this keyword refers to the present instance of the category .

void main() { 

 Car c1 = new Car(‘E1001’); 

class Car { 

 String engine; 

 Car(String engine) { 

 this.engine = engine; 

 print(“The engine is : “); 


Q16. Why does the primary Flutter app build take so long?

Ans: During the primary time flutter app development, a device-specific APK or IPA file is made . 

Consequently, XCode and Gradle are utilized in building the files, thus, taking time. Thereafter, when the app is restarted, 

flutter patches the changes on the prevailing app, leading to , a super-fast refresh.

Q17. What are keys in Flutter and when to use it?


  • A key's an identifier for Widgets, Elements and SemanticsNodes.
  • A new widget will only be wont to update an existing element if its key's an equivalent because the key of the present    widget related to the element.
  • Keys must be unique amongst the weather with an equivalent parent.
  • Subclasses of Key should either subclass LocalKey or GlobalKey.
  • Keys are useful when manipulating collections of widgets of an equivalent type.
  • If you discover yourself adding, removing, or reordering a set of widgets of an equivalent type that hold some state, then, you ought to use a key.

Q18. How does one handle indentation and structure in Flutter code?

Ans: First of all, it's important to notice that Android Studio has tools that make structuring flutter code simple.

Hence, the 2 main aspects are;

Alt + Enter/ Command + Enter

This enables developers to wrap, swap, and take away widgets during a complex hierarchy. to seek out this, direct your cursor to the widget declaration and click on on the keys to access more options.


DartFMT is great since it formats your code to make sure a clean identification and hierarchy.

Additionally, it makes your codes easier to figure with by just twiddling with a couple of brackets.

Q19. Which Command is employed To Compile Dart Into Javascript

Ans :The following command is employed to compile Dart into dart2js – – out=.js .dart 

Q20. How to declare async function as a variable in Dart? 

Ans: Async functions are normal functions with some sugar on top. The function variable type just must specify that it returns a Future:

class Example {

 Future Function() asyncFuncVar;

 Future asyncFunc() async => print('Do async stuff...');

 Example() {

 asyncFuncVar = asyncFunc;

 asyncFuncVar().then((_) => print('Hello'));



void main() => Example();

Q21. What are the similarities and differences of Future and Stream?

Ans : 


Future and Stream both work asynchronously.

Both have some potential value.


A Stream may be a combination of Futures.

Future has just one response but Stream could have any number of Response.

Q22. Why are functions passed to widgets?

Ans : Normally, functions are passes to the widget if they provide the response,

 “invoke this function when something happens”. In Dart, functions are first-class objects and may be passed to parameters of other functions.

Finally, interfaces that use Callbacks have much boilerplate code for a traditional callback.

Java callback

utton.setOnClickListener(new View.OnClickListener() {


 public void onClick(View view) {

 // Do something here




Dart Equivalent


 onPressed: () {

 // Do something here



Q23. How is whenCompleted() different from then() in Future? 

Ans: whenComplete will fire a function either when the longer term completes with a mistake or not, while .then returns a replacement Future which is completed with the results of the decision to onValue (if this future completes with a value) or to onError (if this future completes with an error)

.whenCompleted is that the asynchronous equivalent of a "finally" block.

Q24. What Are the varied Methods to control Strings?

Ans : There are various methods to control string that are given in table:

String Methods Description

toLowerCase():It converts all the string character into small letter .

toUpperCase():It converts all the string character into capital .

trim():It returns the string with none leading and trailing whitespace.

compareTo():It compare objects to a different objects.

Q25. What are the benefits of flutter?

Ans :

There are several benefits related to using flutter. For that reason, i counsel you to use it in your next project and see the benefits .

Particularly, below are a number of the advantages of using flutter;

  • It provides an equivalent UI and business logic altogether work platforms. Currently, no application framework that supports the sharing of both UI code and UI itself except Flutter.
  • Shorter code development time.
  • It features a flexible and expressive UI.
  • The capability to customize an animated UI of any complexity.
  • Additionally, flutter has its own rendering engine.
  • Furthermore, flutter also supports cross-platform development.
  • Lastly, its potential ability to travel beyond mobile, makes it useful in other capacities.
Topics:Interview Questions with Answers