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#compose
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Kevin Hester
03/04/2020, 7:01 PMHi ya'll any guess when the Compose support for better lifecycle awareness will drop? I'd eagerly use it (though currently onCommit and misc onStop glue is working fine.
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Leland Richardson [G]
03/04/2020, 7:11 PMis there something specific that you’re talking about here?
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Kevin Hester
03/04/2020, 7:23 PMsure. In my case, I'm doing stuff with hw so I have 'classic' android type services I need to start/stop based on which views are visible.
I used ya'lls good advice to use onActive, which got me part of the way there. Though even when other screens were visible (and this component was no longer visible) I would see the following line getting invoked repeatedly: https://github.com/meshtastic/Meshtastic-Android/blob/master/app/src/main/java/com/geeksville/mesh/ui/BTScanScreen.kt#L69
So I changed to
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onCommit(AppStatus.currentScreen)l
Leland Richardson [G]
03/04/2020, 7:40 PMwhen you say onShown/onHidden, are you specifically referring to actual visibility to the user? like “can the user see this pixel right now?”
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Kevin Hester
03/04/2020, 7:41 PMyeah (because when not visible to the user right now, I'd like to stop background services from burning CPU to generate data the user won't be looking at)
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Leland Richardson [G]
03/04/2020, 7:46 PMi see
yeah i think there has been some talk about working on some first-class APIs for this. it’s not trivial though (depending on what you want the guarantees of the API to be). It’s been brought up by some other folks as well
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if you weren’t aware of it already,
OnPositionedin particular, a lot of folks want this for logging infrastructure
it also makes a lot of sense to use to trigger certain data retrieval operations etc. as well
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Kevin Hester
03/04/2020, 7:49 PMyep. also pretty much a requirement for analytics that wants to say "user looked at screen X for 10 seconds then screen Y for 30 seconds after clicking on Z"
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Leland Richardson [G]
03/04/2020, 7:50 PMi believe in the use case, but i think there might still be some uncertainty around what the right primitive api to expose would be, and if some of this would be better built in user-land on top of those APIs
right now onCommit/onActive/etc are all compose-runtime-specific APIs. and the runtime itself has absolutely no notion of what “on screen” would mean. It only knows if its in the hierarchy or not
but there’s questions like if we should factor in clipping and layers drawing on top of other layers or not, which would make these types of calculations more accurate but also more expensive
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Kevin Hester
03/04/2020, 7:52 PMI think that just "is it in the current 'view' hierarchy at all (as opposed to hidden by layers or clipping" would handle my limited case. But I hear what you are saying.
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Leland Richardson [G]
03/04/2020, 8:02 PMwell “is it in the hierarchy” is what
onCommitbut that is different than “in the hierarchy, and bounds are inside the screen’s bounds”
which is also different from “in the hierarchy, in the screen’s bounds, and not being occluded by any other view”
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Kevin Hester
03/04/2020, 8:03 PMespecially when a very common use-case is to be underneath something like: https://github.com/meshtastic/Meshtastic-Android/blob/master/app/src/main/java/com/geeksville/mesh/ui/MeshApp.kt#L142
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Leland Richardson [G]
03/04/2020, 8:04 PMthe reason
onCommitCrossfade👍 1
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Kevin Hester
03/04/2020, 8:05 PMoh! this project all began as copypasta from some demo. So if I remove crossfade onCommit will work closer to what I want!
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Leland Richardson [G]
03/04/2020, 8:11 PMlooks like it
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Kevin Hester
03/04/2020, 8:12 PMand it does! thanks.
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Leland Richardson [G]
03/04/2020, 9:43 PMjust keep in mind the behavior of that component…. if i had
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if (x) { Foo() } else { Bar() } Copy code
@Composable fun Foo() { analyticsScreen("foo") ... }xk
Kevin Hester
03/04/2020, 9:44 PMthanks. gotcha!
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