Newsletter Issue #128

Published: 2022-08-16

Releases are getting more complicated, where we got 1.2.1, 1.3.0, and 1.3.0-alpha03 all at the same time!

Beyond that, we look at text in a Canvas() spend a lot of time on performance, including the use (or non-use) of @Stable. We examine consuming flows, implementing effects, and how Live Literals work. And we see how, with an annotation and a library, we can even get rid of having an Activity in our Compose UI apps.

Release Roundup and Alpha Analysis

Reviewing the release notes for the latest Jetpack Compose update!

Compose Compiler 1.3.0 is now stable, mostly for getting us up to Kotlin 1.7.10.

We also got 1.2.1 patch versions for the rest of the Compose artifacts. Those fix memory leaks and other bugs.

Plus, 1.3.0-alpha03 is out!

  • LayoutCoordinates got a bunch of changes, including findRootCoordinates() and transformFrom()

  • Font support was improved with FontVariation

Note that Paragraph is now a sealed interface, mostly to help with implementing it for both Compose for Android and Compose for Desktop.

One Off the Stack, One Off the Slack

You’ve got questions. That’s understandable!

How Do We Center Text in a Canvas()?

We now have drawText() in Canvas(). However, controlling the positioning is not as straightforward as it might be in a Box(). Learn how to use a TextMeasurer to center the text in this week’s highlighted Stack Overflow question!

Do We Really Need @Stable?

@Stable and @Immutable are recommended for Compose, to help guide where we can skip recompositions. But, how awful is it to have never used them? Learn more in this week’s highlighted Kotlinlang #compose Slack thread!

Composable Commentary

Posts, videos, and other new information related to Jetpack Compose!

Medium: Consuming flows safely in Jetpack Compose

Google’s Manuel Vivo walks us through the use of the new collectAsStateWithLifecycle() to convert a Flow into a State for use in a Compose app. As one might expect, collectAsStateWithLifecycle() is also lifecycle-aware, defaulting to only collecting while the associated lifecycle is at least STARTED.

Medium: Comparing Jetpack Compose performance with XML

Compose performance is a recurring concern for developers. Pratham Arora did some performance analysis of two screens implemented both in the classic View system and in Compose UI, using FrameMetricsAggregator for measuring results.

Medium: Quick Note on Jetpack Compose Recomposition

OK, so, what can we do about performance? One common area of poor performance is over-composition, where we recompose again and again and again unnecessarily. Radhika S’s post reminds us of how recomposition works and points out some common mistakes one can make when dealing with recomposition.

Medium: Optimizing Recomposition in Jetpack Compose: Stability System

Ji Sungbin then looks at a specific aspect of recomposition: stability. Proper use of stable/immutable data types can greatly enhance Compose’s ability to optimize recompositions, ignoring branches that should be unchanged because the inputs have not changed.

Medium: Exploring Jetpack Compose’s Hot-Reload Feature

Ji Sungbin also looked at how Live Literals work, indicating that the build process is converting literals (of some types) into State wrappers around those literals, so they can be updated on the fly by the IDE. Ji also points out the @NoLiveLiterals annotation to block this code generation for places where it is unnecessary and adds bloat.

Jetpack Compose Effect Handlers

Jorge Castillo has a new edition of his post reviewing the different types of effects (LaunchedEffect, DisposableEffect, SideEffect, etc.), reviewing their distinct roles and use cases.

Medium: AutoSize TextField in Android Jetpack Compose

Auto-sizing text is used to help ensure everything fits in a given space… but frequently it is only for static text. Ban Markovic wanted auto-sizing text in a field. Ban accomplished this using BoxWithConstraints() as a wrapper around a TextField().

Resource Roundup

100% pure code!

GitHub: Mori-Atsushi / compose-launcher

Mori Atsushi noticed that our Compose UI activities tend to be rather boilerplate, so Mori created a library that code-generates them for us. Simply add @Entry annotations to composables that represent the content for activities, and Mori’s KSP-based generator will set up the activity class and the manifest entry for you.

GitHub: jaikeerthick / Composable-Graphs

Jai Keerthick created a library offering composables for rendering line and bar graphs, with some flexibility in terms of colors, labels, etc.