jetc.dev Newsletter Issue #98
It was a quiet week in the world of Compose. Still, we try to remember when we need
rememberSaveable(), deal with composables per product flavor, and implement
an animated loading button. We also look at adding action menus and preference screens,
mimicking what we are used to in the pre-Compose world. And Kirill Grouchnikov
takes a deep dive into why some Compose-defined gradients turn out ugly.
One Off the Stack, One Off the Slack
You’ve got questions. That’s understandable!
Whenever your app’s UI moves to the background, your process is at risk of being
terminated to free up system RAM. We think of this a lot with system HOME navigation, and
occasionally for other things like launching a camera app. However, it could happen for
other launch-an-app scenarios as well. To handle those, we need to rely on
remember(), as we see in this week’s highlighted Stack Overflow question.
LaunchedEffect() runs your supplied lambda in a coroutine. The question is: is it
safe to then
launch() another coroutine from inside of that coroutine? In short, the answer
appears to be “yes”, as we see in this week’s highlighted Kotlinlang
#compose Slack thread.
Posts, videos, and other new information related to Jetpack Compose!
Sebastian Rieger works on a “white label” app, one that uses product flavors
to customize the app for different targets. In a
View-based system, you can easily
override resources for that. Porting that to Compose UI requires different approaches,
and Sebastian demonstrates how they handled per-flavor colors in this Medium post.
Francesc Vilarino Guell returns, this time looking at a button that changes
its content from a typical text label to an animated loading state and back again.
This is a bit tricky, particularly if you want the button to stay the same
size, rather than resizing as the content changes. Francesc demonstrates a
LoadingIndicator() composable for the animated loading state and a
composable that handles the full UI.
Ian Alexander wrote about how to minimize code duplication in a Kotlin/Multiplatform project by use of screen templates, to try to isolate only the differences in UI rendering and keep the rest of the presentation logic common between platforms.
Kirill Grouchnikov continues an exploration of Compose for Desktop. Gradient fills
are popular, but the way that the Skia-backed
actually interpolates between start and end colors sometimes gives poor results.
Kirill experiments with a few other gradient implementations to try to improve
on those results.
You have probably seen volume sliders and the like that have a floating bubble over
the slider thumb, showing the current value of the slider. That bubble moves along
with the thumb and updates to reflect changes in the value. Since the
composable in Compose Material does not currently support this, MK decided to create
one, and in this post shows how it is accomplished.
Piotr Prus needed to build an interactive bar chart, supporting both bar selections
and horizontal swipe gestures to show more of the chart. After an initial
implementation failed for performance reasons, Piotr created one using a raw
with some custom gesture management to handle the selections and scrolling.
Other Interesting Links
- Swipe to Dismiss — Jetpack Compose
- Medium: Using Jetpack Compose in XML/View and Vice Versa: Perfect Interoperability
- Medium: How to play youtube videos in Jetpack Compose
- Jetpack Compose Tidbits: The first dance with JC - Learning the steps
100% pure code!
TopAppBar() does not handle all of the functionality that we associate with an
action bar/toolbar/app bar. To help fill the gap, Jacob Ras released an implementation
of an action menu for
TopAppBar(), with support for toolbar icons, an overflow
menu, checkable items, and more!
PreferenceScreen and its related
Preference types handle both the UI for
displaying/collecting preference values and the logic to persist those. Jamal Mulla
took the same approach here, where you use
PrefsScreen() and related composables
to build up an equivalent UI with built-in
Other Interesting Links
…And One More Thing
This section took a vacation the week between Christmas and New Year’s, but it should return next week!
- 2023-01-24: Locales! Relay! Effects! Paging! Foldables! Permissions! Date pickers! Bi-directional scrolling! And what your MaterialTheme means... for your SwiftUI code?!?
- 2023-01-17: New Compose patches and alphas! Dealing with Navigation for Compose! Scaffolds! QR codes! Server-defined UI! And @firstname.lastname@example.org has joined the BOM squad! 😁 💥
- 2023-01-10: onNewIntent() and composables! ContactsContract and composables! Balloons! QR codes! Pencils! And a focus on focus!