Flutter Catalog is an open-source Android app developed by Maxing that displays different Flutter components. It is a great resource for developers to learn more about Flutter and its capabilities. The app showcases various Flutter widgets and provides side-by-side source code views for each component.

The app's homepage contains a list of items that, when clicked, display demos of the different Flutter components. The source code for each demo is conveniently located beside the preview, making it easy for developers to learn and implement these components in their own projects. Flutter Catalog is free to use and is a great tool for both beginner and experienced developers looking to expand their knowledge of Flutter.