Flutter Interview Questions and Answers

Flutter is free and Open source UI development framework created by Google. It is not a language; it’s an SDK. It was released in 2017. It is mainly used building high performance applications for Android, iOS, windows, Linux, Mac, Google Fuchsia and web.

official Flutter website: “Flutter is Google’s UI toolkit for building beautiful, natively compiled applications for mobile, web, and desktop from a single codebase.” – Google

 Software Development Kit -A collection of tools that are going to help you develop your applications. This includes tools to compile your code into native machine code (code for iOS and Android).

• It is free and opensource
• Be highly productive and high performance
• Develop for iOS and Android from a single codebase (only One programming used for both android & iOS apps)
• Create beautiful, highly-customized user experiences
• Similar to native app experience
• Less testing
• Everything’s a Widget

Dart is an open source and general-purpose programming language originally developed by Google and later approved as a standard by Ecma (ECMA-408). It is used to build mobile, desktop, backend and web applications.

• Android Studio
• IntelliJ IDEA
• Gitter
• Pub and libraries
• Test code
• Visual studio Code
• Test Magi c
• Panache
• Codemagic
• appetize
• Supernova
• Adobe

• the app UI and logic don’t change depending on the platform
• faster code development
• increased time-to-market speed
• close to native app performance
• enormous UI customization potential
• separate rendering engine
• no reliance on platform-specific UI components
• suitable for any target platform
• minimizes the risks and losses for your business

Media query is depending device height and width.

var deviceSize = MediaQuery.of(context). size;

deviceSize.height

 deviceSize.width

A BuildContext is reference to the location of widgets within the tree structure of all widgets which are built.It only belongs to one widget.As a State object is associated with a BuildContext, State object is not directly accessible through another BuildContext.

Flutter hot reload features works with combination of Small r key on command prompt or Terminal. Hot reload feature quickly compile the newly added code in our file and sent the code to Dart Virtual Machine.

Hot restart is much different than hot reload. In Hot restart it destroys the preserves State value and set them to their default.

• Activity which displays a fullscreen Flutter UI.
• FlutterActivity is the simplest and most direct way to integrate Flutter within an Android app.
• The Dart entrypoint executed within this Activity is “main ()” by default. The entrypoint may be specified explicitly by passing the name of the entrypoint method as a String in EXTRA_DART_ENTRYPOINT, e.g., “myEntrypoint”.
• The Flutter route that is initially loaded within this Activity is “/”.

It is used to save, reset and validate every FormField that is descendant of the associated. Form.GlobalKey to save and get from values at any time and for validating.

Arrow Operator is a short hand in Dart. only one line of code.

Key is unique identifier of the widget. It is used to Two or more Container

Example: Container(key:key(”))

await only use inside the async.It is suspends currently running function until the result is completed. Result is completion pf future.

FocusScope.of(context).requestFocus(FocusNode());

The Pubspec.yaml allows you to define the packages your app relies on, declare your assets like images, audio, video, etc. It also allows you to set constraints for your app. For Android developers, this is roughly similar to a build.gradle file, but the differences between the two are also evident.

NetworkImage class creates an object the provides an image from the src URL passed to it. It is not a widget and does not output an image to the screen.

Image.network creates a widget that displays an image on the screen. It is just a named constructor on the Image class (a stateful widget). It sets the image property using the NetworkImage . This image property is used finally to display the image.

If you just want to display the image as a widget on screen use Image.network and use NetworkImage wherever an ImageProvider is expected.

• GridView.count()
• GridView.builder()
• GridView.custom()
• GridView.extend()

ScopedModel and BLoC(Business Logic Components) are common Flutter app architecture patterns to help separate business logic from UI code and using fewer Stateful Widgets.

The inspector is powerful tool for visualizing and exploring Flutter these widget trees. It is very useful Understanding existing layouts and Diagnosing layout issues.

• ListView
• ListView.builder
• ListView.separated
• ListView.custom
• ListView(scrollDirection: Axis.horizontal,children: List.generate(filterItemList.length, (index) {});