kotlinlang #compose

Was handling Rx errors by re-throwing them from the composition point considered? I think it’s more dangerous to drop exceptions automatically then thrown them – I’ve been bitten quite often by forgetting to wire up the Rx error handling behavior and dropping exceptions because of that. It would seem intuitive to me for

subscribeAsState

to behave like `Flow`’s

collect

. If you wrapped the exception outside the

remember

block before rethrowing, the stack traces would probably be really helpful for debugging as well. Errors still “should” be handled by

onErrorReturn

and friends, but at least that would reduce the likelihood that actual exceptions get dropped on the floor by accident.

codeslubber

04/15/2020, 9:57 PM

Updated to 09. I cannot BELIEVE the TextField stuff is broken again, and there’s no mention of it in the release notes. Just feels like utterly pointless thrashing….

🙃 1

Siyamed

04/15/2020, 11:30 PM

Hi all! I wondered if any of you had any issues or suggestions related to multi-style text (AnnotatedString and its builder)?

molikto

04/16/2020, 3:55 AM

I've been using the dev build http://androidx.dev/ Compose and it was working fine. But seems after the Kotlin rebase PR using dev build doesn't work anymore, because

composeOptions.kotlinCompilerVersion

needs the new compiler dependency. Does anyone know how to get the correct compiler dependencies? If there are no straightforward way then it is fine, I will just wait for dev10 published.

Vinay Gaba

04/16/2020, 5:26 AM

I was wondering when AndroidImageAsset is going to be exposed(it’s an internal class right now) so that I don’t have copy paste it. Moreover, is there an alternate way to do what I’m trying to do?

Zach Klippenstein (he/him) [MOD]

04/16/2020, 10:05 PM

I'm not sure if this is something the compose team has any influence over, and I think it's been mentioned in the channel before, but googling for Compose documentation is surprisingly difficult. I know the priority at this time is actually building the thing, not optimizing SEO, but it seems weird to me that the official docs are ranked so low that it's almost always easier to just go to the main site and search manually.

👍🏻 4

Siyamed

04/17/2020, 3:25 AM

I renamed them as ui-text, ui-text-core and ui-text-android

👍 4

flosch

04/18/2020, 10:05 AM

Hey guys, I am trying to provide a

ColorPalette

appwide like that:

object AppColors {
    private val primaryColor: Color = Color(0x464763)

    val lightPalette: ColorPalette = lightColorPalette(
        primary = primaryColor
    )

    val darkPalette: ColorPalette = darkColorPalette(
        primary = primaryColor
    )

    @Composable
    val currentPalette: ColorPalette
        get() = if (isSystemInDarkTheme()) darkPalette else lightPalette
}

When I use it for my

MaterialTheme(colors = AppColors.currentPalette) { … }

, the primary color is just invisible or set to transparent, what am I doing wrong? If I dont overwrite the primary, then everything works as expected (images in thread).

Timo Drick

04/18/2020, 1:35 PM

Cool to see the Material FilledTextField in the new dev-09. But i am missing following attributes: "keyboardType", "imeAction" and also a callback for "onImeActionPerformed".

MBegemot

04/18/2020, 3:10 PM

Apparently when I change the material theme all subcomponents get correctly updated, except those placed inside a dialog .... those seem to keep the initial value of the theme, but the same component called outside the dialog changes accordingly .... I might be utterly wrong but ..

jitinsharma

04/18/2020, 4:11 PM

I got an compiler error when I tried to use Flow with compose, which is already reported here https://github.com/Kotlin/kotlinx.coroutines/issues/1637 Is coroutines/flow support available with compose(dev-08)?

SrSouza

04/19/2020, 5:31 PM

There is any RichText composable?

louis993546

04/20/2020, 8:21 AM

Any suggestion on how to implement stagger grid (i.e. pinterest) with compose?

molikto

04/21/2020, 3:14 AM

Question: textstyle, content color, emphasis, how they interact? and what's the intended use of them collaboratively? for example currently the default light Material Theme use a 0x000000 content color, I would expect

Text

pick up a Emphasis.high, so the actual content color for Text is not pure black.

bhatnagarm

04/21/2020, 9:09 AM

Hey Everyone, Did anyone try to start a progressBar on a button click. For me it gives an compile time error

Functions which invoke @Composable functions must be marked with the @Composable annotation

which is fine. I'm wondering what's the alternative to this.

Laura Oran

04/21/2020, 4:28 PM

Hello, anyone knows how to align center a Text with more than 1 line? With 1 line it is align center horizontally correctly, but with more no

semoro

04/21/2020, 7:15 PM

Why image corners not being clipped if using

ContentScale.FillWidth

? When image width is bigger then clip area

Image(
    asset = image,
    modifier = Modifier.clip(RoundedCornerShape(20.dp)),
    contentScale = ContentScale.FillWidth
)

Fudge

04/21/2020, 7:50 PM

https://android-review.googlesource.com/c/platform/frameworks/support/+/1290729 Are there plans to make Compose apps work on desktop platforms?

👀 14

Gabriel Feo

04/21/2020, 8:25 PM

How can one disable selection on

Text

or filter all touch events?

Mark Murphy

04/21/2020, 9:16 PM

If at compile time all modifiers are valid for all composables (https://kotlinlang.slack.com/archives/CJLTWPH7S/p1587486859370700?thread_ts=1587486512.370000&cid=CJLTWPH7S)... will there be any sort of compile-time checking for validity here? Lint rules, perhaps?

Vinay Gaba

04/22/2020, 5:29 AM

I know that coroutine support is coming soon (hopefully dev10). Would that version also allows us to use kapt in the same module as compose?

romainguy

04/22/2020, 4:49 PM

Elevation matches Material Design specs and has the immense benefit of guaranteeing consistency

flosch

04/22/2020, 5:33 PM

Any plans for some kind of blur api? 🤔

👍🏻 5

sunnat629

04/22/2020, 5:48 PM

Hello everyone, where I can get the list of all compose dependencies like

androidx.ui:ui-framework:$compose_version

? Thanks in advance...

Gabriel Feo

04/23/2020, 12:36 AM

For a shape which has three clickable like this one, how would one identify click coordinates?

PointerInput

doesn't seem to be a fit, as

PointerInputHandler

can't be

@Composable

molikto

04/23/2020, 4:47 AM

I think this is a bug but want to confirm: I have a

savedInstanceState

inside a "view pager" page, and when I go to another page then come back I got an

Key -751342538 was already registered. Please call unregister before registering again

at androidx.ui.savedinstancestate.UiSavedStateRegistryImpl.registerProvider

Luoqiaoyou

04/23/2020, 8:18 AM

Who knows where can get the source code of Compose IDE Plugin? I follow this guideline:https://android.googlesource.com/platform/frameworks/support/+/androidx-master-dev/README.md , And I can see the Compose Kotlin Compile Plugin in the path “./frameworks/support/compose/compose-compiler-hosted”, but not IDE Plugin

molikto

04/23/2020, 1:40 PM

Is there a way to mark a parameter of type

List<String>

as stable?

ShreemanArjun

04/23/2020, 7:39 PM

How to place a Text in center in latest update dev 09 version? There is no composable function Center(deprecated). Please help if anyone can...

🎉 1

Colton Idle

04/24/2020, 1:11 AM

@Brian Gardner your droidcon online session today was really good and it has me excited!

Title

Colton Idle

04/24/2020, 1:11 AM

@Brian Gardner your droidcon online session today was really good and it has me excited!

Leland Richardson [G]

04/24/2020, 5:55 AM

Was it recorded? I have seen a ton of positive feedback about it and would love to check it out

Colton Idle

04/24/2020, 6:52 AM

@Leland Richardson [G] yep. Should be recorded and going onto droidcon videos soon. I'll ping ya if I see it. 😄

Brian Gardner

04/24/2020, 2:18 PM

Thanks! I’m glad you liked it! I had a ton of fun with the session and I’m looking forward to making more video content soon

👍 1

The recording is now live https://www.droidcon.com/media-detail?video=412304809

👍 2

Leland Richardson [G]

04/27/2020, 9:01 PM

@Brian Gardner this was great. really nice intro for people. I’m a bit curious about the state issue you mentioned with AdapterList. Is this a known issue reported somewhere? cc @Ryan Mentley Also, i’m curious if you intentionally were saying to use

mutableStateOf(...)

where you used it instead of

state { ... }

. The latter seems more correct based on the usage.

Ryan Mentley

04/27/2020, 9:02 PM

Which state issue? Timecode?

Brian Gardner

04/27/2020, 9:03 PM

I reported the issue here https://issuetracker.google.com/u/2/issues/151860426

Leland Richardson [G]

04/27/2020, 9:04 PM

in the video above, he is creating a toggleable button in each item of an adapterlist but said that it wasn’t updating when the state would get changed. My hunch is that the problem was actually just that mutableStateOf was being used instead of

state

though.

Brian Gardner

04/27/2020, 9:04 PM

I likely wasn’t intentional about the state part. Why would the

mutableStateOf()

work differently than

state

Leland Richardson [G]

04/27/2020, 9:06 PM

mutableStateOf

is like a constructor, and will create a new instance each time (with the value you pass in). The

state

function is a composable function which will only execute the

init

lambda the first time, and it will remember the instance each time. when creating state ina composable function, this is usually what you want. it is basically shorthand for

remember { mutableStateOf(init()) }

Ryan Mentley

04/27/2020, 9:07 PM

The

mutableStateOf

in the preview, I think, is the one that probably should lost be

state

Brian Gardner

04/27/2020, 9:08 PM

Ok, so creating the mutable state won’t trigger a recompose unless it’s wrapped in a

remember{}

block inside the composable function?

Ryan Mentley

04/27/2020, 9:09 PM

The code looks...otherwise mostly correct, but there's one suspicious bit. @Leland Richardson [G] is it valid to pass a

MutableState

directly like this? https://github.com/BrianGardnerAtl/JetpackComposePlayground/blob/adapter-list-state-spike/app/src/main/java/tech/briangardner/composeplayground/MainActivity.kt#L58

Leland Richardson [G]

04/27/2020, 9:09 PM

@Brian Gardner it does actually trigger an update… but when it recomposes the function, you just create a different mutable state instance (initialized to the same original value as before), so it doesn’t look like it’s doing anything

Ryan Mentley

04/27/2020, 9:09 PM

or should the value be passed directly?

Leland Richardson [G]

04/27/2020, 9:10 PM

it’s valid to do either

Brian Gardner

04/27/2020, 9:10 PM

ah ok, I didn’t realize it was calling the composable function again to recreate the view. I wasn’t sure how the recompose step worked but that makes sense

Ryan Mentley

04/27/2020, 9:11 PM

alright, in that case that does look like it's probably an AdapterList bug, because the rest of the mutable state code outside of the preview looks correct

I'd have to debug it to be sure, though.

Leland Richardson [G]

04/27/2020, 9:11 PM

yeah it calls the function again. similar to react, flutter, etc, you want to write your composable functions as if they can be called “again” at any time, so if the function itself is introducing the state, you want to make sure and hold onto it properly (hence, use remember or state)

Brian Gardner

04/27/2020, 9:13 PM

Another question I have is where it’s appropriate to create the state, since the functions can be called again. It seems like the state should be declared at the top-level, ‘screen’ component and passed down to the children. At least if the view state needs to change based on user interaction

Leland Richardson [G]

04/27/2020, 9:17 PM

there’s a whole can of worms that can be opened by that question… more or less, i try to think of it as create it in the place where the state is “owned”. That can be hard to define, but in general a good “rule of thumb” first candidate is going to be the closest ancestor composable where the value is used entirely “below” it, and nowhere else. If that scope changes, just move the state “up” until it is satisfied again

but there’s a lot more that goes into it and i might give a different answer depending on the context.

for instance, if there’s some state variable like “current logged in user”, that is going to be used at a much higher level than something more locally scoped or even just something less business-logic-specific and more ui-logic specific

Brian Gardner

04/27/2020, 9:20 PM

That makes sense. The main scenario I think of is loading data from a database (or web server). I can setup the state when the data loads but when I need to modify the data based on the user interaction, how do I update the screen with the new data?

Assuming the ViewModel (or presenter) handles the data loading and updates, would I just create a new composable with the updated data or is there a better way to swap it out

Leland Richardson [G]

04/27/2020, 9:22 PM

in those cases i think the better thing is to use something other than state (like LiveData or Flow etc.) and then join that data into the composable hierarchy using state, but keep state as an implementation detail

you can see how this is done with some of our interop libraries with Rx and LiveData

Brian Gardner

04/27/2020, 9:23 PM

Yeah, I saw that compose has the flow/rxjava to state stuff now which is cool. I’ll have to look into that more.

Leland Richardson [G]

04/27/2020, 9:23 PM

but in this case it is important to leverage tools such as

onCommit

to do it properly

also we will be releasing some new APIs around coroutines and such that will make a lot of this really really nice if your data layer uses suspend functions

Brian Gardner

04/27/2020, 9:24 PM

Sweet! We’re definitely moving towards suspend functions for our data layers so that will be nice

Leland Richardson [G]

04/27/2020, 9:25 PM

nice

Brian Gardner

04/27/2020, 9:25 PM

I haven’t messed with

onCommit

onActive

too much so I’ll look into those next

Thanks for talking through this stuff with me!

Leland Richardson [G]

04/27/2020, 9:26 PM

no problem!

thanks for creating such good content. it was a very well done live coding example

also, if you can, can you try updating your example to use

state

and see if that fixes the adapterlist bug you filed?

Brian Gardner

04/27/2020, 9:27 PM

I’m glad you liked it! I can take some time tomorrow morning to rework my sample to see if using

state

works

Leland Richardson [G]

04/27/2020, 9:28 PM

awesome, thanks!

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