Is there some sample code out there for a recyclerview adapt

Question

Is there some sample code out there for a recyclerview adapter using `produce ` coroutines

gildor · Answer

RecyclerView How do you want to use it in RecyclerView

gildor · Answer

You cannot use it as source of items for example because RecyclerView API is synchronous you must return item immediately

Mark · Answer

Yes but that can be worked around

gildor · Answer

How

Mark · Answer

by adding received items to a list on the main thread

gildor · Answer

Only returning some placeholder

gildor · Answer

Not sure what you mean

gildor · Answer

Because of course you can do that

gildor · Answer

but it means nothing for recycler view

gildor · Answer

because you have to update adapter and notify it about changes

gildor · Answer

so you can of course use produce as source of items but you should group them to list create adapter and set it to recycler view or notify it about changes

Mark · Answer

Imagine some complex logic that calculates lots of items I just want to show those via an adapter Is there another way

Mark · Answer

because I don t want to perform the calculations for items not yet in view

Mark · Answer

channels seem perfect for this

Mark · Answer

In Java I would use wait notify

gildor · Answer

Wait notify But this will API of monitors it will block you main thread

Mark · Answer

Yes to stop the complex logic pressing on and calculating items that might not be shown too far down the list In other words a mechanism to pause

gildor · Answer

Not sure that I get it

gildor · Answer

yes you can of course do something like that but you cannot use directly with RecyclerView

Mark · Answer

Exactly so I m looking for whether someone has already hooked up the adapter with a Channel

gildor · Answer

if you know amount of items you can display item placeholders and when of items is ready notify adapter to replace with actual data

Mark · Answer

Nope it s much more complex than that

gildor · Answer

Okay my main point you cannot use any asynchronous API directly in adapter because you have to tell RV about amount of items and ready to create view and bind it to data synchronously so you already need data to do that

Mark · Answer

Right

gildor · Answer

Way to connect it to any async API not only produce it s when there is new data update adapter and notify recycler view

Mark · Answer

Yes sure

Mark · Answer

This is what I had to do when using the wait notify approach

gildor · Answer

not sure how it should work tho

gildor · Answer

just one note that you need some code that collects data from channel and notifies adapter about new items

Mark · Answer

It sounds like a perfectly useful thing to have a ChannelAdapter like we had a CursorAdapter just a little more complex

gildor · Answer

Cursor adapter is pretty different

gildor · Answer

but in general yes

gildor · Answer

Of course you can write some adapter for channel but it highly depends on what is data emitted by this channel

gildor · Answer

there is no universal solution

Mark · Answer

Same could be said for Cursor no

gildor · Answer

because some channel can emit only new items another new and updated

gildor · Answer

no cursor just monitors changes in database + provides some sort pretty bad paging for this data

Mark · Answer

what do you mean updated

gildor · Answer

cursor can get notifications when table data updated and cursor adapter does this when data updated adapter also will be updated

gildor · Answer

but it s pretty different from how channels work

Mark · Answer

I mean when you said some channels new and updated

gildor · Answer

imagine if a channel emits something like ```ItemStatus lt T gt ``` where ```data class ItemStatus val status ItemStatus val item T ``` ```enum class ItemStatus New Updated Deleted ```

gildor · Answer

Because if channel emits only `T` it means that it always new item

gildor · Answer

but it s not how you usually want to organise you adapter

Mark · Answer

ok

gildor · Answer

you want to fetch at least 1 page to display to user and than get new items or updated ones

maddy · Answer

That makes sense So a combination of Paging Library and a producer which outputs the requested number of items

gildor · Answer

Yes it makes sense

gildor · Answer

`produce` in this case is just a source of data any data for example it can emits pages of data for Paginng Library

maddy · Answer

A producer wrapping a producer