Flutter Interview Questions for Freshers/Flutter Interview Questions and Answers for Freshers & Experienced

What do you understand about tween animation?

The shortened version of in-between animation is tween animation. The start and endpoints of an animation must be specified in tween animation. Using this method, the animation can begin at the beginning and can progress through a series of values until it reaches the endpoint. Transition speed and duration are also determined by using the tween animation. Calculating the transition from the beginning to the end will be easier with the widget framework.

Explain pubspec.yaml file.

The pubspec.yaml file, also known as 'pubspec', is a file that is included when you create a Flutter project and is 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 you build the project, you will get the same package version. Additionally, you can set constraints for the app. During working with the Flutter 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.).

What do you mean by keys in flutter? When one should use it.

Keys are used in Flutter as identifiers for widgets, elements, and semantic nodes. GlobalKeys and LocalKeys are the subclasses of Key. Within the widget tree, keys are responsible for preserving the state of modified widgets. With keys, you can also reorganize and modify collections of widgets that have an equivalent type and defined state. The primary use of keys is to modify a widget tree that contains stateful widgets, not to modify a tree that is totally composed of stateless widgets.

how can you update a listview dynamically?

By using setState to update the listview item source and rebuild the UI

Name some best editors for flutter development.

With the Flutter development tools, developers can make Flutter development faster and thus boost their productivity. In order to develop mobile applications, Flutter IDE and tools require some plugins. With these plugins, we can compile Dart, analyze code, and develop Flutter. Here are some popular IDEs for Flutter development:

* Android Studio
* Visual Studio
* IntelliJ IDEA
* Xcode
* Eclipse
* Emacs
* Vim, etc.

What are packages and plugins in Flutter?

A package is a group of similar types of classes, interfaces, and sub-packages. The packages and plugins help us to build the app without having to develop everything from packages. In Flutter, it allows you to import new widgets or functionality into the app. The packages and plugins have a very small distinction. Generally, packages are the new components or the code written in dart languages, whereas plugins allow more functionality on the device by using the native code. In the DartPub, packages and plugins are both referred to as packages.

Write the difference between runApp() and main() in flutter.

main(): This function starts the program. Flutter does not allow us to write any program without the main() function.

runApp(): Using runApp(), you are able to return the widgets that are connected to the screen as a root of the widget tree that will be rendered on the screen. This function is called in the main function, which is the driver of the app.

How is Flutter native?

Flutter uses only the canvas of the native platform and draws the UI and all the components from scratch. All the UI elements look the same as native ones. This mainly reduces the burden of time for converting through some language to the native one and speeds up the UI rendering time. As a result, the UI performance is remarkably high

What is Flutter tree shaking (flutter web)?

When compiling a Flutter web application, the JavaScript bundle is generated by the dart2js compiler. A release build has the highest level of optimization, which includes tree shaking your code. Tree shaking is the process of eliminating dead code, by only including code that is guaranteed to be executed. This means that you do not need to worry about the size of your app’s included libraries because unused classes or functions are excluded from the compiled JavaScript bundle.

Is drag-and-drop easier than making a layout in code?

This is a challenging flutter interview question. To some extent this is true. Most flutter developers will settle for coding options. Similarly, that does not mean that drag-and-drop is impossible for flutter community to implement.

Above all, if your preference is drag-and-drop, the Flutter Studio is a resourceful tool that will help you generate layouts.

Why does the first Flutter app build take so long?

During the first time flutter app development, a device-specific APK or IPA file is created. Consequently, XCode and Gradle are used in building the files, thus, taking time. Thereafter, when the app is restarted, flutter patches the changes on the existing app, resulting in, a super-fast refresh.

Briefly, explain the steps of writing a flutter app?

Creating a flutter app is simple. As a result, the developer must be familiar with basic programming and object-oriented coding.

The following are the steps to follow while writing a flutter app;

Creating the starter flutter app– the developer should create a simple templated flutter app.
Apply an external package– in this category, the developer should start using an open-source package known as english_words. This package has some utility functions and thousands of English words.
Addition of a stateful widget– This step is important, because, it helps in maintaining state that might change during the lifetime of the widget.
Creation of an infinite scrolling ListView– This stage involves the expansion of RandomWordState which helps in generating and displaying a list of word pairings.
Lastly, profile runs– After finishing, it is important to analyze the performance of the created app.

From a business perspective, would say Flutter is a good solution?

Yes, it is a good solution business-wise. There are several factors that inflict drastic value for a business. For example, performance and stability of a platform, a wide talent pool, and room for further development.

As a result, any problems in the platform related to the above-mentioned aspects ignite the occurrence of risks which in turn results in an indirect or direct financial loss to the company.

It is from this perspective, that flutters come in handy, because of the following reasons;

* Ease of finding engineers who can professionally use Flutter.
* Because of Fuchsia OS created by Google, product development problems are reduced while using flutter.
* Ease of integration since there are several companies using Flutter.

What is use of Navigation.push and Navigation.pop function?

The push method is used to add a route to the stack of routes managed by the navigator. The pop method is used to remove the current route from the stack of routes managed by the navigator.

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.

What is 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.

What is 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.

What are staggered Animations?

Staggered animation utilizes few animation items to include consecutive or covering animations. An animation controller is used to control all the animations. You can use multiple animation objects to create staggered animations and each animation object specifies the animation during the interval. It is a straightforward approach to create visual changes in a series of operations rather than all at once.

What is Flex box 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.

What is the Container class in flutter?

The Container class provides the ability to create a widget with certain properties like padding, borders, height, width, border etc.

What is a Cookbook?

The Cookbook provides solutions or recipes for common occurring problems while developing flutter apps. Each recipe is an independent complete solution and can be referenced to help you build up an app.

What operating systems flutter support to build the apps?

Flutter app development can be done using Linux, MacOS, ChromeOS and Windows.

What do you understand from 'State'? What is the use of the setState() method?

State refers to the information that you can read synchronously when a widget is built and it might change during the lifetime of the widget. The widget implementor should ensure that the 'State' is promptly notified on change of state using State.setState method. The 'setState' method is used to notify the changed state of an internal object.

What is Flutter native?

Flutter is relatively a new framework used to build natively compiled applications for different platforms such as iOS, Android, web, 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.

what are DevTools in flutter?

DevTools in Flutter are a set of tools used for performance management and debugging. With these tools, you can inspect the UI layout, diagnose the UI performance issues, perform source-level debugging, view general log & diagnostics information, and more. This tool is still in preview release but you can test the alpha version of this tool by clicking the "beaker" icon in the upper-right corner of DevTools.

What is 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.

What is use of pubspec.yaml file?

The pubspec.yaml file is used to define the dependencies of your Flutter project. This metadata information is written in the YAML language. This file can have the following fields such as the name, version, description, homepage, repository, documentation, dependencies, environment, and more about the pubspec.yaml file.

What is a Spacer widget?

The Spacer class is used to create an adjustable, empty space. This empty space is used to manage the space between the widgets with the flex container. Spacer takes flex in the constructor to define the space.

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.

What is Hot Reload in Flutter?

A hot reload feature is used to quickly reload the changes code on your running app. With this feature, you can quickly and easily experiment, change UIs, add features, and more fix bugs on your application. This feature works by injecting the changed source code into the running Dart Virtual Machine. Then, Flutter automatically rebuilds the widget tree so you can quickly view the changed effects.

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.

Explain stateful widgets and stateless widgets in flutter?

A widget is either stateless or stateful in flutter. Let's understand each of them.

>> Stateful Widget - If a widget can change with the user interaction then it is a stateful widget. It is dynamic for example, it can change its appearance when it receives data or in response to events triggered by user interactions. Radio, Checkbox, slider are examples of stateful widgets.

>> Stateless Widget - It never changes with the user interaction. Stateless widgets examples include IconButton, Icon, Text etc.

What is the use of the pubspec.yaml file?

When you create a new Flutter project, It includes a pubspec.yaml file also known as 'pubspec' at the top of the project tree. IT contains metadata about the project that is required by Dart and Flutter tooling. It is written in YAML and human readable.
The pubspec file contains the dependency information that project requires like packages and their versions, fonts etc. It ensures that you get the same package version the next time when you build the project.

In What technology is Flutter built?

Flutter is built using C, C++, Skia - 2D rendering engine and Dart (a modern, concise, object-oriented language).

How does Flutter run the code on iOS?

The Flutter Engine's C, C++ code is compiled with LLVM (low level virtual machine - a compiling technology). The Dart code of both the SDK's and yours are compiled by AOT (ahead-of-time) into a native, ARM library. That ARM library is included in "runner" iOS project and the whole code base is built into an iOS App Store Package file .ipa. When the app launched, the app loads the flutter library. Any input or event handling, rendering and so on, are delegated to the compiled code of flutter and app. It is similar to working process of many game engines.
Debug mode works same as for Android app.

How does Flutter run the code on Android?

Android's NDK compiles the flutter engine's C,C++ code. The AOT (ahead-of-time) compiler compiles the Dart code of both (SDK's and your) into native, ARM, and x86 libraries. These libraries are added in a "runner" android project and the whole thing or artefact is built into an Android application package file .apk. The app loads the flutter library on launching of it. Any input or event handling, rendering and so on, are delegated to the compiled code of flutter and app. It is similar to working process of many game engines.
During debug mode, A VM (Virtual Machine) runs flutter code in order to enable hot stateful reload feature. When you run app in debug mode you will see a "debug" banner in top right corner of app. It reminds you that performance is not the characteristic of completed release app.

What do you understand from hot reload and hot restart?

Hot reload means injecting the updated source code files into running Dart VM (Virtual Machine). Hot reload process does not add only new classes but it also adds properties, fields and methods to existing classes, and changes existing functions.
Hot restart works by resetting the app's current state to the app's initial state.

Explain Flutter SDK.

Flutter SDK is an UI kit to build applications for mobile, web and desktop from a single codebase. This SDK comes with a flutter command line tool and dart command line tool to develop apps across platforms.

What makes Flutter unique?

Flutter uses only a single codebase to develop applications for web, mobile and desktop and the experience for mobile apps is native on both android and iOS. Flutter does not depend on web browser technology nor the set of widgets that each device contains. Instead it uses its own rendering engine to draw widgets. This rendering engine provides very high performance. This concept makes flutter unique.

Is Flutter Open source?

Yes, Flutter is a free and open-source UI toolkit by Google to develop desktop, web and mobile applications with one codebase only.

Explain the flutter widgets.

Flutter Widgets can be defined as an immutable description of a part of the UI. Each element on the flutter app's screen is considered as a widget. In flutter, the UI is built using widgets. There is no mutable state associated with a widget, you can use flutter stateful widget to associate a mutable state with a widget. For more about a widget class refer Widget class.

What type of applications can you develop using Flutter?

Flutter is an open-source UI toolkit by Google to develop android, iOS, Linux, Mac and Web applications from a single codebase. Flutter is a good choice for apps which needs to deliver high brand designs.

Who developed the flutter framework?

Flutter Framework is developed by Google.

What are the limitations of Flutter?

Flutter has certain limitations as:

1. Lack of third party libraries - Flutter has less number of third party libraries but it's increasing with the time.
2. Larger release size - Flutter frustrates developers when release size is not as per their expectations.
3. Dart is a good Object-oriented programming language but it lacks when compared with others like C# (C-Sharp), JavaScript etc.
4. iOS developers always think before choosing a flutter framework to develop the app for apple devices as it's developed by Google so android issues are fixed faster but issues for apple devices take much time.

List different types of widgets available in Flutter?

Two types of widgets present in the Flutter are stateless and stateful.

The stateless widgets don’t store any values which will change in the future. The stateless widgets don’t store any state. Icon, text widgets are some examples of stateless widgets.

The stateful widgets have a state object to keep track of all the changes and updates happening in the UI. These widgets are immutable but the state object is used to keep track of the changes. Checkbox and image are some of the examples of stateful widgets.

What is a widget in Flutter?

Widgets are high-level objects in the Flutter that is used to describe any part of a UI of the application. Widgets are used to build the UI of your application. They describe the view information such as their configuration, and state. The widgets are displayed in a hierarchical order to be displayed onto the screen. Text, Buttons, checkboxes, scroll, images, and every other UI component in the Flutter is a widget.

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.

List some advantages of Flutter?

Some advantages of using Flutter are,

1. With Flutter, you can use the same UI and Business logic on all platforms.
2. Flutter reduces the time of building application as it applies the changes instantly with the "hot reload" feature.
3. Flutter gives you similar to native app performance.
4. With Flutter, you can build applications not only for mobile platforms but also for desktop applications.
5. Flutter gives you the ability to fully customize the UI on all platforms.

Enlist some major features of Flutter?

Some of the major features of using Flutter is,

Fast Development - With the use of a rich set of fully customizable widgets, you can build native interfaces in minutes with Flutter.

Expressive and Flexible UI - The layered architecture present with the Flutter enables you to fully customize your UI. This results in fast rendering and expressive designs.

Native Performance - The widgets present in the Flutter incorporate all the critical platform differences such as scrolling, navigation, icons, and more. It gives a full native performance on all platforms

What is Flutter?

An open-source UI SDK, Flutter is developed by Google to develop UI for Android, iOS, Windows, Mac, and other major platforms. Initially released in May 2017, Flutter enables you to create natively compiled apps for mobile and web from a single codebase. Flutter simplifies the process of creating cross-platform mobile apps.

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