Adds interactive widget previews to the project using the previews.dart system. Use when creating new UI components or updating existing screens to ensure consistent design and interactive testing.

Previewing Flutter Widgets Contents [Preview Guidelines]( preview guidelines) [Handling Limitations]( handling limitations) [Workflows]( workflows) [Examples]( examples) Preview Guidelines Use the Flutter Widget Previewer to render widgets in real time, isolated from the full application context. Target Elements: Apply the @Preview annotation to top level functions, static methods within a class, or public widget constructors/factories that have no required arguments and return a Widget or WidgetBuilder . Imports: Always import package:flutter/widget previews.dart to access the preview annotations. Custom Annotations: Extend the Preview class to create custom annotations that inject common properties (e.g., themes, wrappers) across multiple widgets. Multiple Configurations: Apply multiple @Preview annotations to a single target to generate multiple preview instances. Alternatively, extend MultiPreview to encapsulate common multi preview configurations. Runtime Transformations: Override the transform() method in custom Preview or MultiPreview classes to modify preview configurations dynamically at runtime (e.g., generating names based on dynamic values, which is impossible in a const context). Handling Limitations Adhere to the following constraints when authoring previewable widgets, as the Widget Previewer runs in a web environment: No Native APIs: Do not use native plugins or APIs from dart:io or dart:ffi . Widgets with transitive dependencies on dart:io or dart:ffi will throw exceptions upon invocation. Use conditional imports to mock or bypass these in preview mode. Asset Paths: Use package based paths for assets loaded via dart:ui fromAsset APIs (e.g., packages/my package name/assets/my image.png instead of assets/my image.png ). Public Callbacks: Ensure all callback arguments provided to preview annotations are public and constant to satisfy code generation requirements. Constraints: Apply explicit constraints using the size parameter in the @Preview annotation if your widget is unconstrained, as the previewer defaults to constraining them to approximately half the viewport. Workflows Creating a Widget Preview Copy and track this checklist when implementing a new widget preview: [ ] Import package:flutter/widget previews.dart . [ ] Identify a valid target (top level function, static method, or parameter less public constructor). [ ] Apply the @Preview annotation to the target. [ ] Configure preview parameters ( name , group , size , theme , brightness , etc.) as needed. [ ] If applying the same configuration to multiple widgets, extract the configuration into a custom class extending Preview . Interacting with Previews Follow the appropriate conditional workflow to launch and interact with the Widget Previewer: If using a supported IDE (Android Studio, IntelliJ, VS Code with Flutter 3.38+): 1. Launch the IDE. The Widget Previewer starts automatically. 2. Open the "Flutter Widget Preview" tab in the sidebar. 3. Toggle "Filter previews by selected file" at the bottom left if you want to view previews outside the currently active file. If using the Command Line: 1. Navigate to the Flutter project's root directory. 2. Run flutter widget preview start . 3. View the automatically opened Chrome environment. Feedback Loop: Preview Iteration 1. Modify the widget code or preview configuration. 2. Observe the automatic update in the Widget Previewer. 3. If global state (e.g., static initializers) was modified: Click the global hot restart button at the bottom right. 4. If only the local widget state needs resetting: Click the individual hot restart button on the specific preview card. 5. Review errors in the IDE/CLI console fix repeat. Examples Basic Preview Custom Preview with Runtime Transformation MultiPreview Implementation

flutter-add-widget-preview