README.md

Core Adapter

This module represents work with DynamicAdapter. DynamicAdapter is adapter for ListItems based on Hannes Dorfmann AdapterDelegates but without necessity to create all AdapterDelegates with adapter creation. Delegates creates by necessity via factory depends on set of ListItem added to adapter. Also DynamicAdapter encapsulates logic of working with DiffUtil.

Example

First need to init DynamicAdapter:

val delegatesFactory = SomeAdapterDelegatesFactory()
val adapter = DynamicAdapter(delegatesFactory)

AdapterDelegatesFactory could be like this:

class SomeDelegatesFactory : AdapterDelegatesFactory {

    override fun createDelegate(clazz: Class<ListItem>): AdapterDelegate =
            when (clazz) {
                SomeItem1::class.java -> SomeDelegate1()
                else -> throw IllegalArgumentException("No delegate defined for ${clazz.simpleName}")
            }
}

For ListItem subclasses we recommend to use Kotlin data classes. You need to override ListItem.getUniqueProperty if your list could contains more that one element of same ListItem.

If you need to updated some view that represents one of item property using DiffUtils - override ListItem.getChangePayload.

Example of ListItem with payloads:

data class SomeItemWithPayloads(val id: String, val title: String, val subTitle: String, @ColorInt val color: Int) : ListItem {

    override fun getUniqueProperty(): Any = id
    
    override fun getChangePayload(other: ListItem): Any {
        if (this::class == other::class) {
            other as ExampleItemWithPayloads
            return mutableSetOf<Payload>().apply {
                if (title != other.title) add(Payload.TITLE_CHANGED)
                if (subTitle != other.subTitle) add(Payload.SUB_TITLE_CHANGED)
                if (color != other.color) add(Payload.COLOR_CHANGED)
            }
        }
        return super.getChangePayload(other)
    }

    enum class Payload {
        TITLE_CHANGED, SUB_TITLE_CHANGED, COLOR_CHANGED
    }
}

AdapterDelegate for SomeItemWithPayloads could be like this:

class SomeDelegateWithPayloads : AdapterDelegate() {

    override val layoutResource: Int = R.layout.item_some_with_payloads
    override val itemType: Any = SomeItemWithPayloads::class
    
    override fun onBindViewHolder(items: List<ListItem>, position: Int, holder: RecyclerView.ViewHolder) {
        val item = items[position] as SomeItemWithPayloads

        with(holder.itemView) {
            titleView.text = item.title
            subTitleView.text = item.subTitle
            colorView.setBackgroundColor(item.color)
        }
    }
    
    override fun onBindViewHolder(items: List<ListItem>, position: Int, holder: RecyclerView.ViewHolder, payload: Any) {
        val item = items[position] as SomeItemWithPayloads
        when (payload) {
            SomeItemWithPayloads.Payload.TITLE_CHANGED -> {
                holder.itemView.titleView.text = item.title
            }
            SomeItemWithPayloads.Payload.SUB_TITLE_CHANGED -> {
                holder.itemView.subTitleView.text = item.subTitle
            }
            SomeItemWithPayloads.Payload.COLOR_CHANGED -> {
                holder.itemView.colorView.setBackgroundColor(item.color)
            }
        }
    }
}

For click handling you should override AdapterDelegate.onCreateViewHolder

override fun onCreateViewHolder(parent: ViewGroup): RecyclerView.ViewHolder {
        return super.onCreateViewHolder(parent).apply {
            val onClickListener = View.OnClickListener { view ->
                this.withAdapterPosition<SomeItem> { item, position ->
                    when (view.id) {
                        // handle click action depends on view id
                    }
                }
            }
            this.itemView.setOnClickListener(onClickListener)
        }
    }

In this example we used extensions for ViewHolder to get access to items from adapter but you can handle click in regular way without it.

Pay attention in simple AdapterDelegate.onBindViewHolder or with payloads, items: List<ListItem> passed as argument valid only for particular method call, this means that you can't use AdapterDelegate.onBindViewHolder for setting listeners if you are going to update items with payloads. In this case listener will hold reference to old list of items and you will receive not valid result.

Wrong way:

override fun onBindViewHolder(items: List<ListItem>, position: Int, holder: RecyclerView.ViewHolder) {
        val item = items[position] as ExampleItemWithPayloads

        with(holder.itemView) {
            titleView.text = item.title
            subTitleView.text = item.subTitle
            colorView.setBackgroundColor(item.color)
            setOnClickListener { 
                val clickedItem = items[position]
                // some other actions with item
            }
        }
    }

For full implementation guide, view sample project.