Office Hours Transcript: 2021-05-06
Jan joined
Hi, Mark
Is there a difference in context or dispatcher when run code directly inside a launch body versus launch body calling a suspend fun?
Example:
Inside a view model:
Version 1:
suspend fun retryConnects(ntries: Int) {
connectJob = async { bluetoothInteractor.connectToDevice(device) }
withTimeout(WAIT_TIME) {
val connected = connectJob?.await() ?: false
}
}
fun onContinueClicked() {
launch {
retryConnects(4)
}
}
versus:
Version 2:
fun onContinueClicked() {
launch {
-->??? same dispatcher/context/scope as when these lines run from retryConnects ???
connectJob = async { bluetoothInteractor.connectToDevice(device) }
withTimeout(WAIT_TIME) {
val connected = connectJob?.await() ?: false
}
}
}
I ask because app is running better today when yesterday it kept getting the
Gatt 133 bluetooth connection error.
The above was the change I made but probably just a coincidence. Android bluetooth stack seems unstable.
Is there a difference in context or dispatcher when run code directly inside a launch body versus launch body calling a suspend fun?
No. Your coroutine could suspend at the point of any suspend function call (whether it is a function that you wrote or one from a library). But the scope and dispatcher remain the same.
Because I’m running it in viewmodel, would it be using main dispatcher?
The default dispatcher is based on the CoroutineScope and how it is set up. viewModelScope uses Dispatchers.Main.immediate as the default dispatcher.
And, you can pass whatever dispatcher you want to launch(), such as launch(Dispatchers.IO)
Ok. Thanks for clearing that up.
Jan left
trocchietto_ivano joined
hallo w0rl1
hello, Ivano! how can I help you today?
hi mark this hack chat is fantastic
and I have an out of box question today
go right ahead!
basically there is a sw called zoom notes int he app store that allow to zoom infinitely a canvas to add notes nested into notes, images etc. https://apps.apple.com/us/app/zoomnotes/id462234530
the funny thing is that I was using it while I was having a mini ipad 2 with really low hardware/ram specifications
and I could zoom indefinetely
in the Android world there is the great app to draw called infinitive design
that is fantastic and also allow to zoom a lot
how is possible to zoom with such extent without having an out of memory Ex?
Well, the details may vary, but in the end, your question is pretty much the same as "how can we have a scrolling list with tens of thousands of items in it without running out of memory?"
The answer is: you cheat. 😁
you mean i recycle
right
this is an hack reply for an hack chat !
take https://github.com/tibbi/subsampling-scale-image-view for example
it’s a popular Android library for zooming into large images, including ones far too big to hold in memory
it basically loads a downscaled version of the image, then loads portions as needed as the user zooms
Google Maps does the same sort of thing with map tiles
this is so fascinating
https://github.com/peterLaurence/MapCompose offers a Jetpack Compose version of the same sort of map tile management
and do you know if these software use services, or store the images in other activities, canvas
in general, it needs to be loaded "on the fly" for the very memory issues that you cited
so, with Google Maps and MapCompose, as the user pans and zooms, it loads new tiles
and is not recreated a math fourier transformation
well, some things might be able to algorithmically handle that sort of approach
I have not dealt with anything like that personally
I need to study the math beyond that, I have been always fascinated by our matrix work to scale images
well perfect thanks
you untangled the mystery #root access!
I go to sleep thank you very much I am going to have a deeper look tomorrow
you’re welcome, and pleasant dreams!
thanks
trocchietto_ivano left