Flutter Interview Questions
1) What is the meaning of Flutter?
Flutter is a Google open-source UI toolkit for creating beautiful, natively built desktop, web, and mobile applications from a single codebase. The Dart programming language is used to create Flutter apps.
2) In Flutter, how many different sorts of widgets are there?
Widgets are divided into two categories:
- StatelessWidget: A widget that doesn’t need mutable state to function.
- StatefulWidget: A widget with state that may be changed.
3) What are the multiple Flutter construction modes?
- When generating your app, the Flutter toolset provides three options, as well as a headless mode for testing.
- Depending on where you are in the development cycle, you select a compilation mode.
- Debug, Profile, and Release are the modes available.
4) What is Dart and why is it used by Flutter?
Flutter apps are written in Dart, an object-oriented, garbage-collected programming language. It was also developed by Google, but it is open-source and has a community both within and outside of the company. The language Dart was selected for Flutter for the following reasons:
- Dart is AOT (Ahead Of Time) compiled to native code, making it possible to write practically all of Flutter in Dart. This not only speeds up Flutter, but it also allows almost everything (including widgets) to be changed.
- Dart may also be JIT-compiled for lightning-fast development cycles and game-changing workflows (such as Flutter’s popular sub-second stateful hot reload).
- Because Dart’s declarative, programmatic layout is easy to comprehend and visualise, Flutter can avoid using a separate declarative layout language like JSX or XML, or separate visual interface builders. And because all of the layout is done in one language and in one location, Flutter can easily provide additional tooling that makes layout a breeze.
5) What exactly is a widget? Mention how crucial it is in Flutter.
- Widgets are Flutter’s user interface components.
- It’s a way of describing an Element’s configuration.
- They’re modelled after React components.
Everything in a Flutter application is a Widget, from a simple “Text” to “Buttons” to “Screen Layouts,” so Widgets are crucial.
6) What does an App state entail?
- Application state is a state that isn’t ephemeral, that you want to share across multiple portions of your app, and that you want to maintain between user sessions (sometimes also called shared state).
- Application state examples include: – Individual preferences – Notifications in a social networking app – Login information – An e-commerce app’s shopping cart – The read/unread status of a document
7) What’s the difference between Flutter’s main() and runApp() functions?
- The main () function was inspired by Java-like languages, and it’s where all programmes begin; without it, you won’t be able to develop any programme on Flutter, even without UI.
- The Widget that will be attached to the screen as the root of the Widget Tree that will be rendered should be returned by the runApp() function.
8) Describe the Flutter Provider.
Widgets are used to construct the provider. With the new widget subclasses it produces, you may utilize all of the objects in the provider as if they were just part of Flutter. This also implies that the supplier isn’t cross-platform compatible. The provider is the most straightforward approach to manage state. It is based on the PUB-SUB idea, which means that there is one provider and multiple subscribers.
9) What can you expect in Flutter? Make a note of how you’ll be using it.
Await stops the process flow until the async procedure completes. Wait here till this method is finished so you can retrieve its return value, which is what await means in general. Only async can be used with await. This puts all presently executing functions on pause until the PF nature is finished.
10) Explain the distinction between SizedBox and Container.
- Container: This parent widget allows you to effortlessly control and manage several child widgets by modifying their size, padding, and colour. If a widget requires any styling, such as a colour, a shape, or a size constraint, we can wrap it in a container widget.
- SizedBox: This is a box of a given size. Unlike Container, it does not allow us to customise the widget’s colour or adornment. We simply need to resize the widget that was supplied as a child in this situation. In other words, it imposes a size constraint on its child widget.
11) How well do you grasp the concept of tween animation?
Tween animation is a condensed version of in-between animation. In tween animation, the start and endpoints of an animation must be specified. The animation can start at the beginning and move through a sequence of values until it reaches the destination using this method. The tween animation is also used to determine the transition speed and duration. The widget framework will make it easier to calculate the transition from beginning to end.
12) What are the many kinds of Streams?
The capability of streams is part of Dart and is passed down to Flutter. There are two types of streams in Flutter:
- Single Subscription Streams: These streams offer events in a predetermined order. They’re thought of as individual sequences within a greater totality. When the sequence in which events are received matters, such as when reading a file, these streams are used. Throughout the sequence, there can only be one listener, and the event will not be triggered if there isn’t one.
- Broadcast Streams: These streams provide subscribers with information about upcoming events. Subscribers can immediately begin listening to events after subscribing to them. These are flexible streams that allow multiple listeners to listen at the same time. Furthermore, even after cancelling a previous subscription, one can listen again.
13) What exactly is the flutter SDK?
Flutter SDK (Software Development Kit) allows developers to create mobile, web, and desktop apps from a single codebase. The following functionalities are included in the Flutter SDK:
- Dart SDK
- It includes a rendering engine, widgets, testing and integration APIs, and more.
- Native Machine Code Compilation Tools (code for iOS and Android).
- Modern framework in the React style
- To communicate with system and 3rd-party SDKs, provide Interop and plugin APIs.
14) Explain the distinction between a hot reload and a hot restart.
The initial execution of any dart programme takes a significant amount of time. To address this issue, flutter provides two features: Hot Reload and Hot Restart, which shorten the time it takes for our programme to execute after it has been launched.
- Hot Reload: This is a fantastic feature of flutter that takes around a second to complete. You may easily and rapidly make modifications, repair issues, develop UIs, and add functionality with this method. We can quickly build fresh code in a file and transmit it to Dart Virtual Machine by using the hot reload functionality (DVM). DVM changes the app’s UI as soon as the update is finished.
- Hot Restart: It differs slightly from a hot reload in terms of functionality. The preserved states of our app are deleted, and the code is recompiled from the ground up. It takes longer than a hot reload, but it’s quicker than the full restart option.
15) Describe the construct BuildContext.
Widgets in widget trees are identified or located using BuildContexts. Each widget has its own BuildContext, hence each widget has its own BuildContext. We primarily use it to locate references to other widgets and themes. You can also use it to communicate with widget parents and access widget data.
16) What exactly do you mean when you say “widget testing”?
Flutter may run three different sorts of tests:
- Unit tests: You can use unit tests to test a class or method. The rendering to screen, communicating with external services, and user interactions are not covered by unit tests.
- Widget tests: You may test a single widget with widget testing. This verifies that the widget’s UI is as intended and that it responds to events in a timely manner. To put it another way, it guarantees that the widget’s design, rendering, and interaction with other widgets are all up to par.
- Integration tests: You can use integration testing to test the app’s important flows. It’s crucial to double-check that all widgets and services function together properly. You can also use it to benchmark and measure.
17) What is the definition of state management?
State management is critical whether you’re developing a mobile app or a web website. It is used to consolidate the states of numerous UI components in order to manage data flow across an application. A text field, radio button, checkbox, dropdown, toggle, form, and so on are all examples. State management in Flutter can be divided into two categories:
- Ephemeral State: An ephemeral state, also known as a UI state or a local state, refers to a specific widget. To put it another way, it’s a state that’s contained within a widget. Flutter provides support for this state via StatefulWidget.
- App State: This differs from the ephemeral state in that it is a state that we want to keep across sessions and that we want to communicate across different areas of the app. As a result, these types of states can be employed globally. Flutter provides support for this state via scoped model.
18) What are the benefits of using Mixins?
Dart does not support multiple inheritances. To implement multiple inheritances in Flutter/Dart, we require mixins. Mixins make it simple to build reusable class code at several levels of the class hierarchy. Mixins can also be utilised to do various useful tasks (such as RenderSliverHelpers in Flutter).
19) What is Ticker’s purpose in Flutter?
In Flutter, we utilise a ticker to show how often our animation is refreshed. This type of signal-sending class sends signals at a set frequency, such as 60 times per second. Our watch, which is continually ticking, helps us grasp it better. A callback method is supplied for each tick, with the time since the first tick at each second since it began. Even if the tickers start at separate times, they are instantly synchronised.
20) Describe the Flutter Inspector.
The XML file allows us to inspect our app’s blueprint and properties in the same way as Native Android does. For Flutter applications, there is a sophisticated tool called Flutter Inspector that allows you to visualise the blueprint of your widgets and their properties. You can use it to identify numerous layout difficulties and gain a better understanding of the current layout.
The following are some of the advantages of using Flutter Inspector:
- Select widget mode
- Toggle platform
- Show paint baselines
- Show debug paint
- Refresh widget
- Enable slow animations
- Show/hide performance overlay
21) What are some of the benefits of using Flutter?
Flutter has a number of advantages, including:
- Faster Development – Flutter’s rapid reload makes development go faster. On sub-second reload times, state can be retained.
- Flutter’s customizable layered architecture aids in flexible design, expressive UI, and rapid rendering.
- Dart compilers play a critical part in compiling your flutter code because it is compiled into native ARM machine code using Dart’s native compilers. On both Android and iOS, Flutter widgets act like native apps.
- Flutter offers internationalisation and accessibility to a wide spectrum of users all over the world.
22) What are Flutter’s limitations?
Flutter has some limitations, such as:
- Lack of third-party libraries – Flutter has less third-party libraries than other programming languages, but this is changing.
- Larger release size – Flutter irritates developers when the size of the release does not meet their expectations.
- Because the flutter framework is built by Google, iOS developers should think twice before using it to develop apps for Apple devices. Because it is developed by Google, issues for Android devices are resolved faster, but issues for Apple devices take a long time to resolve.
23) How did the flutter framework come to be?
Google created the Flutter Framework.
24) What kinds of applications can you make with Flutter?
Flutter is a Google open-source UI toolkit that allows developers to create apps for Android, iOS, Linux, Mac, and the Web using a single codebase. Flutter is a wonderful solution for apps that require high-end branding.
25) Describe how to use the flutter widgets.
Flutter Widgets are an immutable description of a component of the user interface. Every element on the screen of the flutter app is referred to as a widget. Widgets are used to create the UI in flutter. There is no mutable state linked with a widget; however, you can associate a mutable state with a widget using the flutter stateful widget. Widget class is a good place to start if you want to learn more about widget classes.
26) Describe the Flutter SDK.
Flutter SDK is a user interface kit that allows you to create apps for mobile, web, and desktop from a single codebase. To develop apps across platforms, this SDK includes a flutter command line tool and a dart
27) What do you mean when you say “hot reload” and “hot restart”?
The term “hot reload” refers to injecting updated source code files into a Dart VM that is already running (Virtual Machine). The hot reload procedure not only adds new classes, but also alters existing functions and adds properties, fields, and methods to existing classes.
The app’s current state is reset to the app’s starting state during a hot restart. Visit Hot reload for additional information.
28) How does Flutter execute Android code?
The NDK for Android compiles the C and C++ code of the flutter engine. Both the SDK’s and your Dart code are compiled into native, ARM, and x86 libraries using the AOT (ahead-of-time) compiler. These libraries are included in an Android “runner” project, and the entire item (or artefact) is packaged as an.apk file. The flutter library is loaded when the app is launched. Any input or event handling, rendering, and so on are assigned to flutter and app’s generated code. It’s comparable to how many gaming engines operate.
command line tool. Flutter SDK can be used to learn more.
29) What is Flutter’s method for executing code on iOS?
LLVM is used to compile the C and C++ code in the Flutter Engine (low level virtual machine – a compiling technology). AOT (ahead-of-time) compiles both the SDK’s and your Dart code into a native, ARM library. The ARM library is included in the iOS project “runner,” and the entire code base is packaged as an iOS App Store Package file. ipa. The flutter library is loaded when the app is launched. Any input or event handling, rendering, and so on are assigned to flutter and app’s generated code. It’s comparable to how many gaming engines operate.
30) What technology has been used to create Flutter?
Flutter is written in C, C++, Skia (a 2D rendering engine), and Dart (a programming language) (a modern, concise, object-oriented language). Visit Flutter System Architecture and Flutter Architectural Overview for further information.
31) Which operating systems does flutter support for app development?
Linux, MacOS, ChromeOS, and Windows may all be used to create Flutter apps.
32) What is the difference between a cookbook and a recipe book?
The Cookbook contains solutions or recipes for common issues that arise while developing flutter apps. Each recipe is a stand-alone, full solution that may be used to aid in the development of an app. Cookbook is a good resource for more information.
33) In flutter, what is the Container class?
The Container class allows you to make a widget with certain parameters like as padding, borders, height, width, and border.
34) What does the word ‘State’ mean to you? What does the setState() method do?
The information that you may access synchronously when a widget is formed is referred to as state, and it may change over time. When the ‘State’ is alerted of a change in state, the widget implementor should use the State.setState function to ensure that the ‘State’ is notified as soon as possible. The’setState’ method is used to notify an internal object of a change in state.
35) What is a StatefulWidget’s lifecycle?
The lifecycle methods for State objects are as follows.
36) Which editors are the best for Flutter development?
The Flutter development tools make Flutter development faster, allowing developers to work more efficiently. To design mobile applications, the Flutter IDE and tools require specific plugins. Dart compiling, code analysis, and Flutter development are all made easier with the plugins.
The following are some of the most popular IDEs for Flutter development:
- Android Studio
- Visual Studio
- IntelliJ IDEA
37) What are the differences between packages and plugins in Flutter?
A package is a collection of classes, interfaces, and sub-packages that are all of the same kind. Packages and plugins allow us to build the app without having to write all of the code ourselves. It is possible to import new widgets or functionality into a Flutter app. There isn’t much of a difference between packages and plugins. Plugins offer greater functionality on the device by using native code, whereas packages are new components or code written in different languages. Packages and plugins are both referred to as packages in the DartPub.
38) Why does it take so long to construct the first Flutter app?
It will take longer to construct the Flutter app for the first time. The reason for this is that Flutter created a device-specific APK or IPA file. As a result, the file is built using Gradle and Xcode, which takes a lengthy time.
39) Why are there folders for Android and iOS in the Flutter project?
- Android: This folder contains an Android project in its entirety. It is required when creating an Android Flutter application. The Flutter code will be injected into this Android project once it has been compiled into native code, resulting in a native Android application. For instance, while utilising the Android emulator, this Android project is used to create an Android app that is then published to the Android Virtual Device.
- iOS: It is required when creating an iOS Flutter application. It’s comparable to the Android folder, which is utilised when creating an Android app. The Flutter code will be injected into this iOS project once it has been compiled into native code, resulting in a native iOS application. Only macOS and the Xcode IDE may be used to create a Flutter app for iOS.
40) What is Tween Animation, and how does it work?
It’s the abbreviated version of in-betweening. In a tween animation, the start and endpoints of the animation must be defined. It signifies that the animation starts with the start value and progresses through a succession of intermediate values before arriving at the finish value. It also includes a timeline and curve that specify the transition’s duration and speed. The widget framework calculates the best way to transition between the start and endpoints.
41) What are some well-known apps that employ Flutter?
Many firms now use Flutter to create their apps. The following are some of the most popular Flutter apps:
- Google Ads
- Birch Finance
- Coach Yourself
42) What is the name of the popular database package that is used in Flutter?
The following are the most commonly used and popular database packages in Flutter:
- SQLite database can be accessed and modified using sqflite database.
- It will allow you to access and manipulate the cloud database using the Firebase database.
43) Which animation technique allows you to depict real-world behaviour?
Flutter’s physics-based animation lets you represent real-world behaviour.
44) What is the definition of BuildContext?
In Flutter, the BuildContext is a component of the widgets in the Element tree, with each widget having its own BuildContext. It’s primarily used to gain a link to another widget or theme. If we wish to employ a material design element, we must reference it to the scaffold, for example. The Scaffold.of(context) method can be used to obtain it.
45) What is profile mode and when should it be used?
Our applications’ performance is measured using profile mode. In this mode, you can still debug and profile the performance of your programme. Because the emulator and simulator are not reflective of real-world performance, this mode is disabled.
To compile the profile mode, run the following command:
flutter run –profile
46) How can you explain the various Flutter build modes?
When generating an app, Flutter typically supports three modes, as well as a headless option for testing. The compilation mode you choose is determined by where you are in the development cycle.
The different build modes in Flutter are as follows:
47) What are FlutterActivity’s responsibilities?
FlutterActivity is an Android app that presents a Flutter experience. The various tasks of a FlutterActivity are as follows:
- The Flutter flash screen and the Android launch screen are displayed.
- It alters the appearance of the status bar.
- It chooses Flutter’s first path.
- It chooses an entry point and the execution path for the Dart app package.
- Transparency can be added to the Activity if desired.
48) What is the name of the animation that allows you to show real-life behaviour?
The physics-based animation in Flutter allows you to show real-world behaviour.
49) What is the function of a Flutter inspector?
Flutter Inspector is a tool for visualising and examining widget trees in Flutter. It aids in the comprehension of the current layout and the diagnosis of various layout faults.
The following are some of Flutter Inspector’s benefits:
- Select widget mode
- Toggle platform
- show paint baselines
- Show debug paint
- Refresh widget
- Enable slow animations
- Show/hide performance overlay
50) What are the main distinctions between Flutter and React Native?
Both Flutter and React Native are used to create hybrid apps from a single codebase. These frameworks can be used to create apps that operate on both iOS and Android platforms.