Flutter Interview Questions and Answers for 2025

AppWrite Flutter is based on the Dart programming language and uses the Skia graphics library. This allows developers to create apps that look and feel natural on both iOS and Android devices. It is used for beautiful cross-platform mobile apps. It is designed to help developers build high-quality apps that are both responsive as well as reliable. AppWrite Flutter is still in the early phase of development, but there are already many existing apps built with it.  

These include the popular to-do app Todo-MVC and the open-source note-taking app Evernote. If we want to build cross-platform mobile apps, then AppWrite Flutter is worth checking out. 

While the traditional frameworks available nowadays depend upon the OEM widgets of the device or they utilize the web view, Flutter on other hand uses its own high-performance rendering engine that renders every view component. This is the reason we can create Flutter-based applications that come with native-like performance characteristics.  

C/C++ code of the engine is compiled with LLVM ("Low-Level Virtual Machine) on iOS and NDK (Native-Development Kit) on Android. During the process of compilation, the Dart code is Ahead-Of-Time (AOT)-compiled into regular native code. The steps involved in the working of Google Flutter in a simplified way are as follows: 

• Step 1: When building an app on the Flatter framework, we can use it with either a Stateful widget or Stateless widget. 
• Step 2: These Widgets are then rendered onto Skia canvas and sent to the platform. 
• Step 3: The canvas is then shown to us by the platform. 
• Step 4: The events are sent back according to the need.

This is a frequently asked question in Flutter interview questions. 

• Debug Mode: The Debug mode in Flutter is used to debug the physical device, emulator, or Simulator. In this mode assertions and service extensions are enabled. The Compilation process is optimized for fast deployment. This process is enabled, and tools supporting source-level debugging can connect to the process. In the debug mode, Flutter optimizes the app to reflect changes faster. 
• Profile Mode: The Profile Mode in Flutter is used to analyze the performance of our app. Here, some extensions and tracing are enabled. The Profile mode is disabled on the emulator and simulator because their behavior is not representative of real performance. 
• Release Mode: The Release mode in Flutter is enabled to deploy our app. Here, assertions, service extensions, and debugging are disabled. The compilation process is optimized for fast startup, execution, and package sizes. This mode is used to deploy the app when we want maximum optimization and minimal footprint size. It is designed to get our app ready for the Play Store and App Store. 

The crossAxisAlignment property in Flutter determines how row and column can position their children on their cross axes. A row’s cross-axis is vertical, and a column’s cross-axis is horizontal. The crossAxisAlignment property has five values which are mentioned below: 

• CrossAxisAlignment.start- It positions the children near the start of the cross-axis. (Top for Row, Left for Column) 
• CrossAxisAlignment.end- It positions the children near the end of the cross-axis. (Bottom for Row, Right for Column) 
• CrossAxisAlignment.center- It positions the children at the middle of the cross-axis. (Middle for Row, Center for Column) 
• CrossAxisAlignment.stretch- It stretches the children across the cross axis. (Top-to-bottom for Row, left-to-right for Column) 
• CrossAxisAlignment.baseline- It aligns the children by their character baselines. (Text class only and requires that the textBaseline property is set to TextBaseline.alphabetic. 

Expect to come across this popular question in Flutter interview.  

Unit tests are used extensively for verifying the behavior of a single function, method, or class. The test package provides the core framework for writing unit tests, and the Flutter_test package provides additional utilities for testing the widgets. 

The core features provided by the test package are accessed by using the following steps: 

• Step 1- Adding the test or Flutter_test dependency. 
• Step 2- Creating a test file. 
• Step 3- Creating a class to test. 
• Step 4- Writing a test for our class. 
• Step 5- Combining multiple tests in a group. 
• Step 6- Running the tests. 

A must-know for anyone heading into a Flutter interview, this question is frequently asked in Flutter technical interview questions.  

As its name proposes, it is utilized for testing a single widget, and the objective of the widget testing is to check whether the widget works and looks true to form. The widget test tests the UI components, so it is also called Component Testing. It is used to test a single widget. The main goal of widget testing is to check whether the widget works as expected or not. A user has the freedom to write test cases for every widget present in the project. 

We can tell the steps for widget testing as follows: 

1. Adding the Flutter_test dependency. 
2. Creating a widget to test. 
3. Creating a testWidgets test. 
4. Building the widget using the WidgetTester. 
5. Searching for our widget using a Finder. 
6. Lastly, verify the widget using a Matcher. 

It's no surprise that this one pops up often in Flutter developer interview questions.  

Unit tests and widget tests are useful for testing individual classes, functions, or widgets. However, they are unable to test how individual pieces of code work together as a whole or capture the performance of an application running on a real device. These tasks are then performed with integration tests.  

The Integration tests in Flutter are written using the integration test package, provided by the software development kit (SDK). It is Flutter's version of Selenium WebDriver (generic web), Protractor (Angular), Espresso (Android), or Earl Gray (iOS). The package internally uses a Flutter driver to drive the test on any device. 

The steps for Integration testing as follow: 

• Step 1- Creating an application to test. 
• Step 2- Adding the integration_test dependency. 
• Step 3- Creating the test files. 
• Step 4- Writing the integration test. 
• Step 5- Finally, running the integration test. 

As far as Flutter is concerned, the following database packages are widely accepted and mostly used by the community. 

1- Firebase Database: It gives the users access and control over the cloud database. Firebase provides a NoSQL database for Flutter apps with the ability to manage data retrieval and storage through JSON protocol. Data sync and quick loading make it one of the most suitable options for Flutter Apps.  

Features in a Firebase database: 

• NoSQL DB  
• APIs (REST only)  
• Authentication 
• Analytics  
• Storage  

2- SQFlite Database: We can access and modify the SQLite database using this. With this database, we have full control over our database, queries, relationships, and anything you could desire.  

Features in SQFlite database are as folows: 

• Serverless  
• Zero configuration  
• Open-Source  
• Compact  
• Single DB file. 

In Flutter, a container is a widget that has the capacity to accommodate multiple child widgets and manage them efficiently through dimensions, padding, and background color. Whenever we want to style the background of a widget, either because of a shape, color, or size constraint, we may use a container widget.  

With the Container class, widgets can be stored and positioned on the screen at our discretion. In general, the container class resembles a box for storing contents. 

During development, a fast developer cycle is very important for iteration. The Dart VM offers a just-in-time compiler (JIT) that has features such as incremental recompilation (enabling hot reload), live metrics collections (powering DevTools), and rich debugging support. When apps are ready to be deployed to production—whether we are publishing to an app store or deploying to a production backend—the Dart ahead-of-time (AOT) compiler can compile to native ARM or x64 machine code.

The AOT-compiled app launches with a consistent, short startup time. The AOT-compiled code runs inside an efficient Dart runtime that enforces the sound Dart type system and manages memory using fast object allocation and a generational garbage collector.

Now, let us have a look at the Flutter interview question and answers for advanced developers who have a good command of Flutter development. These questions can also be termed Flutter advanced interview questions that are asked by the interviewer while hiring a Flutter developer. These questions are also called as Flutter senior interview questions as these are mostly asked for a senior position in an interview, but these questions can be asked to you as well, so never leave a void in your preparation.

Horizontal Scroll in Flutter can be built by the following steps as follows: 

Firstly, we need to create a ListView widget that supports horizontal lists. So that we can use the standard ListView constructor, passing in a horizontal scrollDirection, which overrides the default vertical direction as shown below. 

Code: - 

ListView( 
scrollDirection: Axis.horizontal, 
children: [ 
Container( 
width: 100, 
color: Colors.green, 
), 
Container( 
width: 100, 
color: Colors.yellow, 
), 
Container( 
width: 100, 
color: Colors.blue, 
), 
Container( 
width: 100, 
color: Colors.black, 
), 
Container( 
width: 100, 
color: Colors.orange, 
), 
], 
), 

The Equatable is used to simplify the process of comparing the instances of the same object without the need for boilerplate codes of overriding “==” and hashCodes. It is a Dart package that helps to implement value-based equality without needing to explicitly override the “==” and hashCode. We can understand it with the following example. 

This helps compare two objects. Two different objects for equaltity. 

 Code: - 

class Person {  
int age;  
String name;  
double height;   
// constructor  
Person({this.age, this.name, this.height});  
}  
//If we have three objects of this class like 
Person person1 = Person(17, "James", 6.2);  
Person person2 = Person(17, "Vince", 3.2);  
Person person3 = Person(17, "Peter", 6.2);  
Here person1 is not equal to person2, but it is the same as person3. 

Note: parameters should be final, or else they would be breaking hashing rules

The main() function in Flutter is responsible for starting the program. Without the main() function, we cannot write any program in Flutter. The runApp function is responsible for returning the widgets attached to the screen as a root of the widget tree and will be rendered on the screen. 

The main() function came from Java-like languages so it's where all the programs have started, without it, we can't write any program on Flutter even without the UI. The runApp() function should return a widget that would be attached to the screen as a root of the widget Tree that will be rendered on the screen. We know that Flutter is a Framework, whereas Dart is a language.  

The main() function starts the execution of Dart Language, which in turn provides methods to load Flutter Components which is the runApp() method, which works as the main function for the Flutter Framework. In short, we can say that the main is the starting point of execution for Dart Language, and runApp() is the same for Flutter Framework. 

This question is a regular feature in Flutter interview, be ready to tackle it.  

The pubspec.yaml file, also known as 'pubspec', is included when we create a Flutter project and located at the top of the project tree. This file contains information about the dependencies like packages and their versions, fonts, etc., that a project requires. It makes sure that the next time when we build the project, we will get the same package version. Additionally, we can set constraints for the application.  

During working with the Flutter project or collaborating on a project, this configuration file of the project will be required a lot. This specification is written in YAML, which can be read by humans.  

The following are included in this file:  

• General project settings, like name of the project, version, description, etc.  
• Dependencies within a project.  
• The assets of the project (e.g., images, audio, etc.). 

State management is one of the most important processes in the life cycle of an application. In Flutter, a state is whatever data we need to rebuild our UI at any moment in time. When this data changes, it will trigger a redraw of the user interface. The approaches for state management are as follows: 

• setState: The low-level approach to use for widget-specific, ephemeral state. You can simply use Statefulwidget and setState() method to get the state. 
• InheritedWidget & InheritedModel: It is another low-level approach used to communicate between ancestors and children in the widget tree. 
• Provider: It is a wrapper around InheritedWidgets to make them more reusable and easier to use in our app. 
• Riverpod: It is Reactive State-Management and Dependency Injection Framework with no dependency on Flutter. 
• BloC: It makes it easy to implement the Business Logic Component design pattern, which separates presentation from business logic. 
• GetIt: It is a service locator-based state management approach that doesn’t need a BuildContext. 
• Mobx: MobX is a state-management library based on observables and reactions. 

This is a frequently asked question in Flutter advanced interview questions.  

ScopedModel in Flutter can be defined as a set of utilities that allows us to easily pass a data Model from a parent Widget straight down to its descendants. In addition, it also rebuilds all the children that use the model when the model is updated. This library was originally extracted from the Fuchsia codebase. The ScopedModel library consists of various utilities that allow the children’s UI elements to receive data from their parent widget. 

This library consists of three major classes as follows: 

• ScopedModel – It can be used to wrap UI Components and access data from the Model. 
• ScopedModelDescendant – It can be used to identify the correct ScopedModel from the widget hierarchy. 
• The Model – We must extend the Model class to listen to the changes. 

For ScopedModel, we can give the example of Counter App and Todo app. 

Expect to come across this popular question in Flutter developer interview questions.  

The lifecycle of a stateful Widget explains the calling hierarchy of functions and it changes in the state of the widget. We know that everything in the Flutter is a widget. The Stateful and stateless are the types of widgets in Flutter. When Flutter builds a StatefulWidget, it creates a state object. This object is where all the mutable state for that widget is held. The concept of state is defined by two things.  

The data used by the widget might be changed. The data can't be read synchronously when the widget is built. (All state must be established by the time the build method is called). The Stateful widget lifecycle in Flutter has the following simplified steps in code. 

createState() 
mounted == true 
initState() 
didChangeDependencies() 
build() 
didUpdateWidget() 
setState() 
deactivate() 
dispose() 
mounted == false 

The Dart programming language has two types of optional parameters: named optional parameters and positional optional parameters. Dart's optional parameters are optional. In that, the caller isn't required to specify a value for the parameter while calling the function. Optional parameters can only be declared after any required parameters. The Optional parameters in Dart can have a default value, which is used when a caller does not specify a value. 

Positional optional parameters: - A parameter wrapped by [ ] is a positional optional parameter. Here is an example: 

Code: - 

getHttpUrl(String server, String path, [int port=80]) { 
  // ... 
} 

In the above code, the port is optional and has a default value of 80. We can call getHttpUrl with or without the third parameter. 

Code : - 

getHttpUrl('example.com', '/index.html', 8080); // here port = 8080 
getHttpUrl('example.com', '/index.html');       // here port = 80 

Named optional parameters : - A parameter wrapped by { } is a named optional parameter. Here is an example: 

Code : - 

getHttpUrl(String server, String path, {int port = 80}) { 
  // ... 
} 

We can call getHttpUrl with or without the third parameter. We must always use the parameter name while calling the function. Here is an example. 

Code : - 

getHttpUrl('example.com', '/index.html', port: 8080) ; // here port = 8080 
getHttpUrl('example.com', '/index.html') ;             // here port = 80 

We should always remember that you may use positional optional parameters or named optional parameters at a time, but not both in the same function or method. The phenomenon is not allowed. 

This constructor allows the Flutter developer to create a widget that displays on ImageStream obtained from the network. All the network images are cached regardless of the HTTP headers. An optional headers argument can be used to send custom HTTP headers with the image request. We make use of filterQuality to specify the rendering quality of image. The example is given below. 

Code: - 

Image.network(URL) // the URL is the URL of any image. 

The first step would be to import a simple library as given below: 

Code : - 

import ‘package:Flutter/foundation.dart’ as Foundation; 
Then, we can use kReleaseMode as shown below: - 

Code: - 

If(Foundation.kReleaseMode){ 
print(‘In release mode’); 
} else{ 
print(‘In debgugging mode’); 
} 

The asserts can be used to manually create an “is debug mode,” we should always avoid that. The issue with asserts is that the isInReleaseMode boolean value is not constant, so while shipping our application, both the dev as well as release mode codes are also shipped along with it. Over here the kReleaseMode is a constant, therefore the compiler can remove unused code correctly. 

Now we will see the Flutter interview question and answers for developers. These Flutter and dart interview questions can be asked to you if you are willing to join a company as a Flutter developer. 

I would make sure that I am making full use of all the features that are available in Flutter, by referring to the Flutter documentation and make use of different resources that are available online.

The Dart and Flutter provide us with tools, such as the http package, for this type of work. We can say the steps involved in making an HTTP request in Flutter are as follow:  

• Step 1- Adding the http package.  
• Step 2- Making a network request.  
• Step 3- Converting the response into a custom Dart object.  
• Step 4- Fetching the data.  
• Step 5- Displaying the data.

JSON serialization with code generation means that having an external library that generates the encoding boilerplate for us. After some initial setup, we run a file watcher that generates the code from your model classes. For example, json_serializable and built_value are these kinds of libraries.  

This approach always scales well for a larger project. No hand-written boilerplate is needed for this, and typos when accessing the JSON fields are caught at compile time. The downside with code generation is that it requires some initial setup. Also, the generated source files might produce visual clutter in our project navigator. 

Dart apps function exclusively on a single thread by default. This technique frequently makes writing the code simpler and is quick enough to prevent poor app performance or stuttering animations. However, there are times when we might need to carry out an expensive calculation, such parsing a huge JSON document. The users will feel jank if this process takes more than 16 milliseconds.  

We must run costly computations like this in the background to prevent this jank. This means scheduling work for a different thread on Android. We can employ a different Isolate in Flutter. The following are the procedures for parsing JSON in Flutter:  

• Step 1- Adding the http package.  
• Step 2- Using the http package to send a network request.  
• Step 3- Making the response into a gallery of images.  
• Step 4- Transferring this project to a different isolation. 

In a normal constructor, an instance gets created and the final variables get instantiated with the initializer list, this is why there is no return statement. The instance to return is already fixed, when executing the constructor. In a factory constructor, the instance to return is decided by the method. That is why it needs a return statement and why it will usually call a normal constructor in at least one path.  

So, a factory does nothing different than a static method could do (in other languages often called getInstance()), except you cannot overload the constructor with a static method but you can with a factory method. i.e., factory methods are a way to hide the fact that the user of your class is not calling a constructor but a static method.  

For example: 

Code: - 

// named generative 
  // delegates to the default generative constructor 
  Person.greek(String name) : this(name, "Romania");  
 
  // named factory  
  factory Person.greek(String name) { 
    return Greek(name); 
  } 
} 
 
class Greek extends Person { 
  Greek(String name) : super(name, "Romania"); 
} 

The alignment property describes a point in the child's coordinate system and a different point in the coordinate system of this widget. The Align widget positions the child such that both points are lined up on top of each other. Contrarily, this is true of a column. A column's children are arranged vertically, top to bottom (by default).  

Since it has a vertical primary axis, this means that using crossAxisAlignment in a Column determines how the children are aligned horizontally in that Column whereas using mainAxisAlignment in a Column aligns its children vertically (for example, top, bottom). 

Flutter uses Keys for a lot of things inside the framework. Since our widget extends StatelessWidget or StatefulWidget, this is the way our widget having a key so that the framework knows what to do with it.  

The Keys allows widgets to change parents anywhere in our application without losing state, or they can also be used to access the information about another widget in a completely different part of the widget tree. So, the keys are not needed in a stateless widget but they are needed in a Stateful widget. 

A must-know for anyone heading into a Flutter interview, this question is frequently asked in Flutter interview questions for experienced.  

Flutter's profile mode compiles and launches our application identically to that of release mode but with just enough additional functionality to allow debugging performance problems. For example, profile mode provides tracing information to the profiling tools. We should use profile mode when we want to analyze the performance of our application.

I will use release mode for deploying my application when I want maximum optimization and minimal footprint size. Mostly, I would use release mode when I am ready to release my application.