The Ultimate Guide to Flutter Frameworks in 2021

Flutter is one of the most exciting and promising new technologies in modern application development. The platform is rapidly evolving to include new targets, add revolutionary new features, and attract high-quality developers every week. With the release of Flutter 2.0, the platform is now reaching entirely new heights.

Understanding what Flutter is, how it works, and how it can shape your organisation is critical to having intelligent conversations about how best to deploy it in your future applications.

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What is Flutter

The features of Flutter and the cross-platform capabilities it unlocks lend it to easy comparison with mobile application frameworks such as React Native and Xamarin. Technically speaking, however, this isn’t entirely accurate. Flutter is so much more than “just” a framework.

Flutter is a Software Development Kit (SDK) that includes the complete suite of tools and resources necessary to build cross-platform applications. An all-in-one solution. While developers target Flutter applications in the same way they would any other framework, it’s the underlying technologies that make Flutter stand out amongst the crowd.

With a working knowledge of Flutter, a copy of the platform, and a suitably outfitted IDE—you have everything to begin building apps for Android, iOS, Windows, macOS, and the web. Better yet, you can target all six platforms from one single codebase without pulling in any extra tooling or support.

Flutter is an exciting tech to watch precisely because its methods depart from those of the most highly popular frameworks in use today. The cost of these exciting new changes is in adapting to the language and architectural differences which create the foundation of the platform.

While developers are still getting up to speed with Flutter and its community is still growing, there will be something of a leap to make to adapt to the Flutter way of building as it gains popularity, support, and momentum.

The cost of that leap, however, is a small one to pay for the advantages that come with Flutter application development. Understanding the architecture of Flutter and the components which go into making it one of mobile app development's most powerful tools is a stepping stone to building powerful new applications.

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What Is Google Dart

One of the largest technical and mental stumbling blocks of Flutter development is in adopting the Dart programming language.

Built by Google, Dart is the company's internally developed language. Created in 2011, Dart has seen a comparatively slow uptake until more recent innovations. Its use in both Flutter and the company's own mobile operating system, Fuchsia, has seen more and more developers come on board.

The initial investment in learning Dart turns out to be less than many imagine. The language is practically tailor-made for multi-platform development. It’s one that will be instantly familiar to developers with a background in web or JavaScript development.

Abundantly available resources, provided by Google, and a surprisingly rich community help make the transition into the language relatively smooth.

The trade-off, in exchange for learning Dart, is a rich array of modern tools that enable rapid construction and testing to be brought to the forefront of application development. Amongst these tools, Dart’s flexible typing and rich static analysis features make it a valuable ally to have in future development projects.

Flutter Architecture

It’s Flutter’s architecture and design that make it such a powerful app development platform.

Flutter is designed to be a series of interchangeable layers sitting on top of the underlying target system. These layers abstract application design from the platform the app runs on, such as Android or iOS, to allow developers to target one common codebase instead. This feature set and the way that Flutter achieves it enables developers to come ever closer to a true “build once run everywhere” philosophy.

At the foundational layer of Flutter is the platform embedder—the lowest-level component and the only one that’s designed independently for each target platform. The role of the embedder is to provide the essential classes which directly interact with the targeted system. The embedder provides an entry-point for Flutter’s platform-agnostic code to communicate with the device and operating system underneath. Put simply, the embedder provides Flutter-specific abstractions for system-specific features.

At the next level of the Flutter, hierarchy is the engine responsible for many of the platform’s stand-out features. At the heart of this is the rendering engine powering Flutter’s UI and widgets—something that deserves a second look.

Related components that go into Flutter’s engine include networking, plug-in support, and the runtime files and compiler for the Dart language. The essential systems and libraries that allow Flutter code to be executed before interfacing with the underlying system—via the embedder—are included here.

Interacting with the engine, the topmost layer in Flutter’s architecture is the framework itself. The layer Flutter developers spend almost their entire time writing input into, this layer also provides a convenient shorthand between developers to refer to the Flutter SDK as a whole.

Within this framework layer, we have the UI widgets, application components, and interfaces that go into constructing a multi-platform application. By necessity, the Flutter framework includes diverging UI components for both Google’s Material Design standard and Apple’s Cupertino design libraries.

Flutter’s layered component style architecture allows applications to stay relatively focused and streamlined in their performance. It allows for the inclusion of only the application components necessary to run the underlying app, excluding the parts they don’t need and won’t use.

Additional features developers may want to lean on, such as a device’s camera or sensors, the web-view, in-app payments, and authentication can be added in code modules as required by the Project.

Flutter’s Unique Advantage: Rendering

Flutter’s stand-out features and the unique selling points of the platform come primarily from its rendering engine. Relatively unique amongst multi-platform application frameworks, Flutter renders its own UI components for the screen as one of the architecture’s core design philosophies.

By drawing every pixel on the screen, Flutter provides a level of detail and control that few frameworks can match.

The conventional way of doing things is for a mobile application framework to create an abstraction layer to make calls to the system’s native UI libraries. This simplifies framework design and allows the target system to do the ‘heavy lifting’ instead of the framework. The disadvantage is in the additional overhead created by interpreting another language, typically JavaScript, before interacting with system-specific libraries.

Flutter, in contrast, minimises this overhead by implementing its own set of widgets for use across every platform. Flutter apps bypass the system’s UI libraries entirely, rendering their own visuals into native code and providing up to 120 frames per second rendering performance.

From a user’s perspective, the drawback of Flutter’s approach comes from minor changes to buttons and UI features between Flutter apps and non-flutter applications. The components rendered by Flutter are native-like but come from a library other than the system itself.

The benefit is an interface that is reliable, consistent, and that performs across multiple platforms and wildly varying screen sizes.

Combining Flutter and Native

Because Flutter departs from a more conventional way of using frameworks and creating cross-platform applications; there are some natural concerns about merging Flutter code into native applications and vice-versa.

Combining the two worlds is more than a technical demonstration of Flutter’s abilities. Such applications are essential when there’s a significant investment in pre-existing work or unique requirements that can’t be met by any framework. In many cases, a gradual change of an extensive codebase is a better solution than abrupt interruption or re-design from the ground up.

Flutter solves this issue and creates ways of both including platform-specific views into Flutter apps and importing Flutter components into native apps.

Platform view widgets enable you to import native views into Flutter apps. Solving a tricky multi-platform problem and allowing the widget to act as an intermediary between the view and the application.

The converse scenario is achieved with a Flutter module that allows a Flutter application to be embedded inside a parent native app. Included within the module is the engine, shared libraries, and tools that a Flutter app needs to run.

Including everything a Flutter app needs inside the app has a natural trade-off, sacrificing outright performance for compatibility. Far from a perfect solution, it’s one that serves as a reasonable intermediate step to accessing Flutter functionality when only a native app will do.

Flutter in Practice

New technologies are inherently exciting and attractive. Brand new solutions make teams want to jump on board at the first chance and take advantage of new trends and cutting-edge tools. Few things should be done so lightly, however.

To invest in new technology or platform, you must prove that this change in direction will provide real, quantifiable value and solutions into the future. There’s no shortage of businesses who have skipped this step to be met only with the drawbacks and disadvantages of technology.

With Flutter, the value and advantages of the platform are readily demonstrated in its architecture and design.

Claims of native-like performance, rapid cross-platform application development, and expressive UIs are justified by the vast departure from more conventional architectures. Favouring an approach that makes fuller use of the technology and the platform, the additional features of Flutter make it worth serious consideration.

There are, of course, drawbacks too. The most significant of which comes with the changes that Flutter makes to implementing layouts and deploying widgets.

Changes in how Flutter works will take some time to get developers up to speed. Developers not yet familiar with Dart will require time to learn the deepest features and depths of Google’s language too—a process which turns out to be surprisingly short and simple.

The platform’s all-in-one approach, the decision to include everything the app needs to run internally, also increases the size of resulting apps. More lightweight native solutions may still be a better approach for applications that require a smaller footprint.

The payoff for investment in the comparatively new platform is new levels of UI customisation, a reduction in time-to-market, and abundant codeshare between competing platforms.

Understanding Flutter

Getting to know the ins and outs of Flutter can take a lot of the anxiety and nerves out of investing in the platform. Luckily, learning it in-depth is a lot easier to do than you might imagine.

With an understanding of Flutter’s architecture and an understanding of its strengths and weaknesses, it’s all the easier to start considering and weighing up its advantages and drawbacks within your teams.