Question: Handling clicks in RecyclerView Adapter

Hello,

I was wondering How can I handle clicks from a view inside a RecyclerView Adapter and later collect them outside this adapter for instance in a Fragment/Activity? I’m probably looking for something like PublishSubject in RxJava

For instance

  override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DiscoverHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.section_title, parent, false)
        view.clicks().collect() //How can I somehow propagate those clicks to a property?
        ..............
    }

I used to do this with callbacks but I want to achieve a similar thing using this library.

[ychescale9]

Oh now I remember Subject is both a Subscriber and an ObservableSource😃

You can implement a similar API with Flow with an extension function:

fun <T> Flow<T>.transferToChannel(channel: Channel<T>): Flow<T> = onEach {
    channel.offer(it)
}

itemView.clicks().map { myItem }
            .transferToChannel(itemClicksChannel)
            .launchIn(coroutineScope)

Only saved a few characters though:)

[ychescale9]

The equivalence of RxJava Subject in Coroutines is Channel.

You could use a Channel in your adapter to collect the view.clicks() Flows emitted by each item, and expose it as a single itemClicks: Flow<MyItem> for Fragment / Activity to consume:

class MyListAdapter(
    private val coroutineScope: CoroutineScope // pass in the `lifecycleScope` from Activity / Fragment
) : ListAdapter<MyItem, MyViewHolder>(diffCallback) {

    private val itemClicksChannel: Channel<MyItem> = Channel(Channel.UNLIMITED)
    val itemClicks: Flow<MyItem> = itemClicksChannel.consumeAsFlow()

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        ...
        return MyViewHolder(view, itemClicksChannel, coroutineScope)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.bind(getItem(position))
    }
}

class MyViewHolder(
    private val view: View,
    private val itemClicksChannel: Channel<MyItem>,
    private val coroutineScope: CoroutineScope
) : RecyclerView.ViewHolder(view) {

    fun bind(myItem: MyItem) {
        ....
        view.clicks().onEach {
            clickChannel.offer(myItem)
        }.launchIn(coroutineScope)
    }
}

In Activity / Fragment:

...
myAdapter = MyListAdapter(lifecycleScope)
myAdapter.itemClicks.onEach { myItem ->
    // handle clicked item
}.launchIn(lifecycleScope)