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A Flutter sample app that shows a state management approach using the Provider package. This is the app discussed in the Simple app state management section of

An animated gif of the app in action

Goals for this sample

  • Show simple use of Provider for providing an immutable value to a subtree
  • Illustrate a simple state management approach using the ChangeNotifier class
  • Show use of ProxyProvider for provided objects that depend on other provided objects

The important bits


Here the app sets up objects it needs to track state: a catalog and a shopping cart. It builds a MultiProvider to provide both objects at once to widgets further down the tree.

The CartModel instance is provided using a ChangeNotifierProxyProvider, which combines two types of functionality:

  1. It will automatically subscribe to changes in CartModel (if you only want this functionality simply use ChangeNotifierProvider).
  2. It takes the value of a previously provided object (in this case, CatalogModel, provided just above), and uses it to build the value of CartModel (if you only want this functionality, simply use ProxyProvider).


This directory contains the model classes that are provided in main.dart. These classes represent the app state.


This directory contains widgets used to construct the two screens of the app: the catalog and the cart. These widgets have access to the current state of both the catalog and the cart via Provider.of.


If you have a general question about Provider, the best places to go are:

If you run into an issue with the sample itself, please file an issue in the main Flutter repo.

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