How to Update Multiple UI Components with One UI State in Android using ViewModel

Описание: Learn how to efficiently update individual UI components in Android using a single UI state and ViewModel, with practical examples in Kotlin and Jetpack Compose.
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This video is based on the question https://stackoverflow.com/q/76689295/ asked by the user 'Egor' ( https://stackoverflow.com/u/17849531/ ) and on the answer https://stackoverflow.com/a/76689663/ provided by the user 'ObscureCookie' ( https://stackoverflow.com/u/21163959/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Update Multiple UI Components with One UI State in Android using ViewModel

Building dynamic user interfaces in Android can be tricky, especially when you want different components to react independently to data updates. Let's explore a way to handle this using Kotlin and Jetpack Compose in an organized manner.

The Problem

Imagine you have a screen that contains multiple components, such as a row displaying stories and a column showing cards. Your challenge is to ensure that, while loading data on the screen, all components update simultaneously without having to reload the entire UI state every time. Moreover, when you want to refresh just one of those components—like stories—how can you do that without affecting the others?

Defining the UIState

You initially use a sealed class UiState defined as follows:

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

In this setup, if a user clicks a button to refresh just the stories, the entire UI gets reloaded, which isn't ideal.

The Solution

A more efficient way would be to separate the data streams for your components but still keep a unified approach in managing your UI state. Here’s how you can achieve that:

1. Modify the ViewModel

Instead of keeping a single state, create separate StateFlow objects for stories and cards. You can then use the combine function to merge the results into a single UI state.

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

2. Amend the UI

Now, in your Jetpack Compose UI, observe the individual flows for stories and cards, allowing updates to work independently.

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

3. Update Component Independently

When the button to update stories is clicked, you can simply call a function in the ViewModel to refresh just the stories.

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

This approach allows you to keep your UI components responsive and independent without the need to reload everything unnecessarily.

Conclusion

By separating the flows for each UI component while maintaining a unified UI state using combine, you can efficiently manage data and ensure that updates are seamless and localized. This method not only improves the user experience but also optimizes performance, which is crucial in mobile applications.

Now you can confidently handle independent updates to components in your Android applications using ViewModel and Jetpack Compose!