Скачать или смотреть Should I Use a Value Directly or Pass a Lambda in Jetpack's Compose?

Explore the difference between using a value and passing a lambda in Jetpack's Compose. Learn best practices to optimize your app's performance and avoid unnecessary recompositions.
---
This video is based on the question https://stackoverflow.com/q/75894567/ asked by the user 'fshdn19' ( https://stackoverflow.com/u/2979045/ ) and on the answer https://stackoverflow.com/a/75914044/ provided by the user 'Милош Којадиновић' ( https://stackoverflow.com/u/6844930/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Whether I should use value directly or delay composation by passing a lambda in Jetpack's Compose

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Jetpack Compose: Value vs. Lambda

Jetpack Compose has revolutionized how we build user interfaces in Android. One of the choices you'll encounter when creating composables is whether to pass a value directly or delay composition by passing a lambda. This decision can have implications for your app's performance, particularly in terms of recomposition. In this post, we'll dive deep into this question and help clarify your options.

The Dilemma: Value vs. Lambda

Consider the following situation: you have a state that changes over time, and you want to display this value in your composable. Your options are either to pass the value directly to the composable function like this:

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

Or to pass a lambda that returns the value like this:

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

Your question is: Which approach should you use, and why?

Key Observations

1. Both Approaches Work

In the example you provided, both approaches will indeed work correctly. This means that no matter which method you select, your code will run without errors and produce a functioning UI. However, there’s more than meets the eye, especially when performance is considered.

2. The Impact of Recomposition

The real difference appears when you analyze how Compose manages recompositions. If you modify your code and use the ComposableTextDirect like below, you'll notice an increase in recompositions:

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

In contrast, if you opt for ComposableTextLambda, the recompositions will be significantly reduced:

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

Why Does This Matter?

Mutable State Observation: When you utilize ComposableTextDirect, you’re directly observing a mutable state, causing the composable to recompose each time the value changes.

Performance Optimization: Using the lambda approach allows Compose to defer the evaluation of the value until the composable is recomposed. This can help improve performance, especially in complex UIs where unnecessary recompositions can introduce lag and degrade the user experience.

Best Practices for Using Composables

To summarize, here are some best practices to ensure optimal performance when using mutable states in Jetpack Compose:

Use mutable state at a low level: Whenever possible, utilize mutable state in composables that require it to minimize the area of recompositions. This will prevent unnecessary updates to the UI.

Favor lambdas for dynamic data: Consider passing a lambda when dealing with data that frequently changes. It can help optimize performance by reducing the number of recompositions.

Profile your app: Use layout inspector tools to observe how changes affect performance, ensuring that your UI remains smooth and responsive.

Final Thoughts

Choosing between passing a value directly vs. a lambda in Jetpack’s Compose can seem trivial at first, but it has important implications for performance. While both methods work, understanding the difference can help you create more efficient, performant Android applications. Aim to optimize your use of state to foster high-quality user experiences.

Now that you’re armed with this knowledge, go ahead and make the best choice for your Jetpack Compose projects!