Скачать или смотреть How to Properly Manage CircularProgressIndicator in Flutter During API Calls

Learn how to effectively manage the `CircularProgressIndicator` in your Flutter application while making API calls. This guide provides step-by-step solutions to handle loading states seamlessly.
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This video is based on the question https://stackoverflow.com/q/66808222/ asked by the user 'Matt' ( https://stackoverflow.com/u/2833027/ ) and on the answer https://stackoverflow.com/a/66809238/ provided by the user 'Loren.A' ( https://stackoverflow.com/u/15170515/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing CircularProgressIndicator in Flutter

When developing Flutter applications, handling API calls and displaying a loading indicator is crucial for enhancing user experience. A common problem arises when the CircularProgressIndicator continues to display even after the completion of an API call, leading to confusion for users. Today, we'll delve into a specific case where this issue occurs and explore how to resolve it effectively.

The Problem: Persistent Loading Indicator

In a Flutter app, particularly while navigating to an OrdersScreen, you may find that the CircularProgressIndicator remains visible indefinitely. This can occur due to improper handling of loading states during API calls or when exceptions arise.

Specifically, the error message encountered might look like this:

[[See Video to Reveal this Text or Code Snippet]]

This usually signifies that the app tried to process some data that wasn't properly fetched due to an issue with the API call, leading to the loading indicator not stopping.



Analyzing the Existing Code

Let's break down the existing code structure related to the API call and the handling of the loading indicator.

The API Call

Here’s a snippet of how the API call is made in your Orders class:

[[See Video to Reveal this Text or Code Snippet]]

The OrdersScreen Implementation

In the OrdersScreen, you set the loading state as follows:

[[See Video to Reveal this Text or Code Snippet]]

Here, _isLoading is toggled before and after the API call. However, it's clear this approach can lead to issues if the API call fails or if there are any exceptions.



The Solution: Using Consumer for State Management

To effectively manage the loading state, we can utilize the Consumer widget provided by the Provider package. This enables a cleaner and more efficient handling of states.

Step-by-Step Implementation

Modify the Orders class to include an isLoading boolean:

[[See Video to Reveal this Text or Code Snippet]]

Utilize the Consumer widget in the OrdersScreen build method:

Replace the current list-building logic with a Consumer widget to listen for changes in the Orders provider:

[[See Video to Reveal this Text or Code Snippet]]

Advantages of This Approach

Cleaner State Management: By using a Consumer, we avoid the need for local state variables like _isLoading. Instead, we can keep it centralized within the Orders provider.

Automatic UI Updates: With notifyListeners(), any change in loading state will automatically trigger a UI update, ensuring the loading indicator only displays when necessary.



Conclusion

Integrating CircularProgressIndicator in Flutter applications while making API calls can seem daunting, especially when dealing with loading states. By effectively managing the state through the Provider and Consumer widgets, you can ensure a seamless experience for your users, eliminating persistent loading indicators when not needed.

Now, implement these changes in your app, and you'll have a more robust and user-friendly interface. Happy coding!