Solving the Flutter Plugin Compilation Issue with dart:html for Web Only Deployments

Learn how to address compilation failures in a Flutter plugin that uses `dart:html` and ensure smooth builds for web applications.
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This video is based on the question https://stackoverflow.com/q/73824273/ asked by the user 'Globe' ( https://stackoverflow.com/u/17424122/ ) and on the answer https://stackoverflow.com/a/73824426/ provided by the user 'Vitali' ( https://stackoverflow.com/u/7979621/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the Flutter Plugin Compilation Issue with dart:html for Web Only Deployments

If you’ve ever faced issues while compiling a Flutter plugin intended solely for web applications, you're not alone. This could be particularly frustrating when the plugin you're creating relies on the dart:html library — a library that is only compatible with web platforms. The scenario can thicken if you receive compilation errors while trying to build your mobile application, despite intending for the plugin to operate exclusively on the web. In this guide, we will dissect this common problem and explore a structured solution to ensure your Flutter plugins compile seamlessly for their intended platforms.

Understanding the Problem

In the code provided, a local plugin was created to implement AdSense in Flutter, which made use of an IFrameElement. The issue arises when, despite the plugin being structured to support only web applications, the mobile version attempts to compile the code that requires dart:html. This results in build failures, leading to significant roadblocks for developers aiming to deliver a cross-platform experience.

Key Elements of the Plugin

IFrameElement - Used to embed HTML content, crucial for displaying AdSense.

dart:html - Required for web implementations but incompatible with mobile platforms.

Intended Platform - The plugin should only function on the web.

A Step-by-Step Solution

To tackle the compilation issue efficiently, we can create a set of classes that clearly differentiate between web and mobile implementations. Here’s how to do it:

Step 1: Create a Web-Specific Class

Your first requirement is to maintain your existing AdsenseWeb class that imports dart:html. This is essential for the web-specific functionality of the plugin. You can name the file adsense_web.dart.

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Step 2: Create a Mobile Stub Class

Next, you will create a corresponding stub class for mobile builds. This class can also be named AdsenseWeb but reside in a different file, which can be named adsense_web_stub.dart. Importantly, this version should not have any references to dart:html.

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Step 3: Implement a Wrapper for Selection

Finally, you will create a wrapper that intelligently selects the correct class based on the platform. This wrapper will allow Flutter to determine whether to load the web or mobile implementation at compile time.

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How It Works

Conditional Imports: The if statements ensure that Flutter picks the correct implementation based on the target platform.

Streamlined Compilation: As a result, the mobile application will no longer attempt to import dart:html, and you can build without compilation errors.

Conclusion

By following these steps, you should be able to solve the compilation issues associated with using dart:html in a Flutter plugin. This approach of class separation not only resolves immediate build concerns but also sets a clean architecture for future expansions or modifications in your plugin. Whether you're developing for mobile or web, this structure encourages scalability and maintainability in your Flutter projects.

Always remember: proper organization and clear separation of platform-specific code is key to avoiding cross-platform headaches when working with Flutter. Happy coding!

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