I am thinking about turning `View` clicks into `Flow lt T gt

Question

I am thinking about turning `View` clicks into `Flow lt T gt ` has anyone done this What approach did you take If you think it s a bad idea why

louiscad · Answer

I made an `awaitOneClick ` suspending function and I prefer it that way looping on it if needed I actually put that into a library <https github com LouisCAD Splitties tree master modules views coroutines>

dewildte · Answer

< louiscad> Thanks for the reply I was looking at your code and I am not sure how you react to the click

dewildte · Answer

I think your have a way better understanding of the continuation mechanism then I do

louiscad · Answer

I resume the continuation which is essentially making the function return

louiscad · Answer

So I handle the click on the line after the line where I call `awaitOneClick ` simply

dewildte · Answer

Ok That s what I thought but was not sure

dewildte · Answer

That s very clever

dewildte · Answer

And you said you loop inside the wrapping suspend function

louiscad · Answer

It s like waiting for network I O but here it is UI I O where the output is enabling the view and the input is the click

dewildte · Answer

Could you give me a small example of the implementation side

louiscad · Answer

Yes I use a simple `while` loop where I wait for the click then react to that and once that s done I let the loop interate again if I m ready to accept further interactions All the examples I have are closed source for the company I work for unfortunately but I plan to use that in future sample code in open source projects Let me write a dummy example

dewildte · Answer

Thank you so much

dewildte · Answer

My use case is going to be turning the clicks into a `Flow lt T gt ` and then passing the flow to an EventBus for collection and redistribution

louiscad · Answer

Here s the simplest example I found on the top of my head ``` while true ui launchDemoBtn awaitOneClick speakHello Suspends until done ```

dewildte · Answer

Awesome

dewildte · Answer

you wrap the while loop into a `launch `

louiscad · Answer

Note that I tend to hide this behind an `interface` for the user interface where I expose suspending functions and regular functions with no dependencies on the platform though You can call it coroutines enabled MV

louiscad · Answer

I have one launch per independent UI process That makes it clear what can run concurrently and what runs sequentially

dewildte · Answer

Ok this is helpful thanks

louiscad · Answer

When you use coroutines and UI together it becomes increasingly important to have the root `CoroutineScope` cancelled when the view hierarchy is destroyed that s why I made this to not write the boilerplate each time <https github com LouisCAD Splitties tree master modules lifecycle coroutines> If you re in a `Fragment` be sure to use `viewLifecycleOwner`

Paul Woitaschek · Answer

Can t this be done through a channel ``` fun View clicks Flow lt Unit gt return flowViaChannel channel gt setOnClickListener channel offer Unit channel invokeOnClose setOnClickListener null ```

Dominaezzz · Answer

When do you close the channel

Paul Woitaschek · Answer

Shouldn t it be automatically get cancelled through the coroutine scope

Dominaezzz · Answer

What cancels the coroutine scope

Dominaezzz · Answer

Nvm I should just do some more reading on how Flow works I m not sure how it handles cancellation

Paul Woitaschek · Answer

Well I m not sure either would love to have some light here slightly smiling face

Paul Woitaschek · Answer

``` FlowPreview fun main val flow = flowViaChannel lt Unit gt channel gt coroutineScope launch repeat 10 channel offer Unit channel invokeOnClose println closed take 3 val result = runBlocking flow toList println flow emitted $result ```

Paul Woitaschek · Answer

This prints closed flow emitted kotlin Unit kotlin Unit kotlin Unit

Dominaezzz · Answer

And without the `take 3 `

Paul Woitaschek · Answer

Without it doesn t close why would it

Dominaezzz · Answer

That was the point I was initially trying to make

Paul Woitaschek · Answer

I don t get the point

Dominaezzz · Answer

Same

dewildte · Answer

IT is safe to use though

dewildte · Answer

And a nice implementation

dewildte · Answer

So I expanded on this idea and made ``` FlowPreview interface ChannelFlow lt T gt SendChannel lt T gt Flow lt T gt UseExperimental FlowPreview class fun lt A gt channelFlow bufferSize Int = 16 ChannelFlow lt A gt lateinit var c SendChannel lt A gt val f = flowViaChannel lt A gt bufferSize = bufferSize c = it return object ChannelFlow lt A gt SendChannel lt A gt by c Flow lt A gt by f ```

dewildte · Answer

Implementation looks something like ``` FlowPreview class ViewFacadeImpl ViewFacade private val channelFlow = channelFlow lt ViewEvent gt override val events Flow lt ViewEvent gt = channelFlow override suspend fun render viewState ViewState channelFlow send object ViewEvent ```

dewildte · Answer

hmm this seems to crash

dewildte · Answer

The instantiation order is not as expected

dewildte · Answer

I had to rewrite to ``` UseExperimental FlowPreview class fun lt A gt channelFlow bufferSize Int = 16 ChannelFlow lt A gt val eventChannel Channel lt A gt = Channel bufferSize val eventFlow Flow lt A gt = flow for event in eventChannel emit event return object ChannelFlow lt A gt SendChannel lt A gt by eventChannel Flow lt A gt by eventFlow ```