How to Ignore State Updates in Flutter with Cubit

Learn how to selectively update widgets in Flutter using Cubit by managing states effectively while ignoring certain state changes.
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How to Ignore State Updates in Flutter with Cubit

Managing state in Flutter applications can be a challenge, especially when dealing with multiple widgets that depend on different pieces of state. In this guide, we’ll explore a common problem that many developers face when using Cubit for state management: how to ensure that specific widgets only update when relevant state changes occur. Specifically, we’ll focus on the issue of unintentionally reverting a widget to its initial state when unrelated state changes are emitted.

The Problem

Imagine you're developing a media player where users can both play media and adjust the zoom scale of the app interface. You use Cubit to manage the state, emitting states whenever relevant actions occur:

TestValueUpdated: emitted when the media is played.

TestScaleUpdated: emitted when the user adjusts the zoom level.

However, you might encounter a situation where:

Widget A, which displays the media playback status, resets every time the zoom scale changes because it doesn't differentiate which state changes should trigger a rebuild.

Widget B, responsible for displaying the zoom status, suffers the same fate when the media is played.

To keep your widgets consistent and responsive without reverting them to their initial state, you'll need a solution.

Solution: Selective Widget Updates

The ideal way to deal with this situation is by using the buildWhen method provided by BlocBuilder. This method allows you to specify conditions under which the widget should rebuild. This way, you can control the rebuild process based on the type of state emitted.

Step-by-Step Implementation

Define Your States: You already have the basic states defined (TestInitial, TestValueUpdated, and TestScaleUpdated).

Modify Your BlocBuilder: Update your BlocBuilder implementation to specify when the widget should rebuild based on the type of state. Here’s how to implement it in both widget A and widget B:

For Widget A (Media Playback)

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

For Widget B (Zoom Scale)

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

Benefits of This Approach

Performance: Minimizes unnecessary rebuilds, leading to enhanced application performance.

User Experience: Prevents flickering or resetting of state that can frustrate the user, providing a smoother experience.

Maintainability: By keeping your widget updates localized, your code becomes clearer and easier to maintain.

Alternative: Merging States

As an alternative, if you find yourself often needing multiple pieces of information for your widgets, you could merge these states into a single state that contains all pertinent data. However, this approach might lead to complexity and is not necessary for every situation.

Conclusion

Managing state in Flutter with Cubit can be streamlined by using the buildWhen parameter in BlocBuilder. This allows you to selectively update widgets based on the state that is emitted, ensuring that your UI behaves as expected. Testing this technique can significantly enhance both the performance and usability of your application.

By implementing this strategy, you can effectively manage different widgets' states without worrying about them interfering with each other. Happy coding and may your Flutter journey be smooth!