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Jetpack Compose Efficiency — Half 1 | by Udit Verma | June 2023

Whereas discussing the levels of composability, we discovered that the compose runtime performs sure optimizations and skips recompiling sure elements of the UI tree based mostly on on state modifications. If it could actually detect that for a selected composable state, not one of the states change, it could actually skip the recombination course of for significantly better efficiency.

Though the compose runtime is wise sufficient to do that, it wants to satisfy sure situations earlier than it could actually appropriately resolve whether or not to skip the ingredient for a most editable work. resolve or not.

  1. Parameter

Once we cross parameters to a composable operate, they are often of any kind. Extra importantly, they are often immutable or mutable; steady or unstable. Let’s take a look at every of those phrases

1.1 Immutable parameters – Learn solely values. The one method a brand new state will be handed in these parameters is to create a brand new occasion of those varieties. This ensures the compose runtime can work out whether or not the worth of this parameter has modified. An information layer has solely val attributes are instance.

1.2 Parameters will be modified — Variables that permit studying and writing. Since we will edit the values ​​in these variable varieties with out having to create a brand new occasion, the compose runtime can by no means make sure if one thing has modified within the parameters This. Knowledge layer with a number of var is a first-rate instance of this kind.

3 Stability parameters — Variables can change however notifies the editor runtime of any state modifications so it could actually monitor. MutableState is an effective instance of this type of parameter.

2. Could be omitted Could be mixed

To have the ability to skip a compilation, the compose runtime ought to be capable to determine that out. Mainly, this summarizes all of the parameters to be composable as both Immutable or Secure.

📌 Compose treats all assortment lessons (Checklist, Map, and so on) as risky parameters. The identical applies to all information lessons declared in a module that wouldn’t have a compiler plugin as a dependency.

To seek out out if a composable is omitable, we will use compiler statements. For extra particulars on how one can use them, please learn This. For extra about Drafting Stability, you possibly can seek advice from this weblog posts.

Going again to our instance, in case you discover the ItemList operate, not one of the values ​​change as we scroll by means of the checklist.

personal enjoyable ItemList(
modifier: Modifier = Modifier,
objects: Checklist,
scrollState: ScrollState = rememberScrollState()

Nevertheless, filtering by means of the logs, we see Recomposing ItemList printed on each roll change

Let’s have a look at the output of the compiler report for this operate.

restartable scheme("[androidx.compose.ui.UiComposable]") enjoyable ItemList(
steady modifier: Modifier? = @static Companion
unstable objects: Checklist
steady scrollState: ScrollState? = @dynamic rememberScrollState(0, $composer, 0, 0b0001)

We see an unstable parameter, the checklist of things. Though the checklist is of immutable kind, the editor treats it as an unstable parameter. To resolve this downside, we’ll wrap it in an immutable information class

// information class with solely val varieties are immutable by default. 
// Had that not been the case, including the @immutable or @steady annotations are
// one other methods of letting the compose runtime know when it can not itself
// work out.
information class ItemHolder(
val objects: Checklist

Now the up to date composable turns into

personal enjoyable ItemList(
modifier: Modifier = Modifier,
itemHolder: ItemHolder,
scrollState: ScrollState = rememberScrollState()

and the compiler report for this operate says

restartable **skippable** scheme("[androidx.compose.ui.UiComposable]") enjoyable ItemList(
steady modifier: Modifier? = @static Companion
**steady** itemHolder: ItemHolder
steady scrollState: ScrollState? = @dynamic rememberScrollState(0, $composer, 0, 0b0001)

Now all parameters are marked as steady. This in flip marks the operate as skippable, which suggests it could actually now be ignored if no state change is detected. Strive operating the code and overview the log.

And we eliminated that additional refactoring!

📌 As an alternative of a knowledge layer, You need to use Kotlinx’s Immutable Collections additionally

The supply code for this step will be accessed This.

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Updated: June 26, 2023 — 6:17 pm

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