How to inject adapter with hilt

Question

I have a complete recyclerView example, now I want to use hilt inject the ItemListAdapter of this example to my ItemListFragment. But it seems something that can not be done if I still want the way of hilt.

class ItemListFragment : Fragment() {

    private val viewModel: ItemListViewModel by viewModels()
    private var adapter: ItemListAdapter? = null

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val binding = FragmentItemListBinding.inflate(inflater)
        binding.lifecycleOwner = this
        binding.viewModel = viewModel

        adapter =
            ItemListAdapter(
                ItemListOnClickListener { itemId ->
                    viewModel.onItemClicked(itemId)
                })
        binding.itemList.adapter = adapter

        return binding.root
    }
}

class ItemListAdapter(private val onClickListener: ItemListOnClickListener):
    ListAdapter<Item, ItemListAdapter.ViewHolder>(
        ItemListDiffCallback()
    ) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(
            ListItemBinding.inflate(LayoutInflater.from(parent.context))
        )
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val item = getItem(position)
        holder.bind(item)
    }

    class ViewHolder constructor(private val binding: ListItemBinding) :
        RecyclerView.ViewHolder(binding.root) {
        fun bind(item: Item) {
            binding.item = item
            binding.executePendingBindings()
        }
    }
}

class ItemListDiffCallback : DiffUtil.ItemCallback<Item>() {
    override fun areItemsTheSame(oldItem: Item, newItem: Item): Boolean {
        return oldItem == newItem
    }

    override fun areContentsTheSame(oldItem: Item, newItem: Item): Boolean {
        return oldItem.id == newItem.id
    }
}

class ItemListOnClickListener(val clickListener: (itemID: String) -> Unit) {
    fun onClick(itemID: String) = clickListener(itemID)
}

Answer 1

Is this what you want? Can you check if this works and satisfies your need.

NOTE : I expect that you did setup annotations well so hilt was setup and works correctly in your project (ex: annotating ItemListFragment fragment with @AndroidEntryPoint , etc...)

I had such case, and I thought rather than feeding the callback in the constructor, I should provide it through a setter method of the adapter.

For ItemListAdapter , we can make a property of type ItemListOnClickListener , and provide setOnClickListener setter method. That's it, now you can make use of onClickListener in ViewHolder (Now ItemListAdapter constructor is a no-arg one, and Hilt is able to provide a binding for it for your case):

@Singleton
class ItemListAdapter @Inject constructor():
    ListAdapter<Item, ItemListAdapter.ViewHolder>(ItemListDiffCallback()) {
    
    private var onClickListener: ItemListOnClickListener? = null

    ...

    fun setOnClickListener(onClickListener: ItemListOnClickListener) {
        this.onClickListener = onClickListener;
    }

    inner class ViewHolder constructor(private val binding: ListItemBinding) :
            RecyclerView.ViewHolder(binding.root) {
        fun bind(item: Item) {
            binding.item = item
            binding.executePendingBindings()

            // Use `onClickListener` when binding `OnClickListener` callback
            binding.view.setOnClickListener(v -> onClickListener?.onClick(...))
        }
    }
}

For ItemListFragment , you don't need to construct an adapter, because Hilt will be able to provide you with one. All you have to do is provide a listener through setOnClickListener method of this adapter:

@AndroidEntryPoint
class ItemListFragment: Fragment() {

    @Inject
    var adapter: ItemListAdapter? = null

    private val viewModel: ItemListViewModel by viewModels()

    override fun onCreateView(
            inflater: LayoutInflater, container: ViewGroup?,
            savedInstanceState: Bundle?
    ): View? {
        val binding = FragmentItemListBinding.inflate(inflater)

        ...

        adapter?.setOnClickListener(
                ItemListOnClickListener { 
                        itemId -> viewModel.onItemClicked(itemId) 
                }
        )

        binding.itemList.adapter = adapter

        return binding.root
    }
}

Answer 2

Answer Feb 2021

This is the easiest answer.

In Module class

@Module
@InstallIn(SingletonComponent::class)
class AppModule {

    @Provides
    @Singleton
    fun provideAdapter(): MyAdapter = MyAdapter()
}

In Adapter class

private var onItemClickListener: ((RestaurantX) -> Unit)? = null
fun setOnItemClickListener(listener: (RestaurantX) -> Unit) {
        onItemClickListener = listener
}

Then put this line inside view.setOnClckListener

onItemClickListener?.let {
   it(restaurantX)
}

In Activity/Fragment

 @Inject
 lateinit var myAdapter: MyAdapter

And then inside a method

myAdapter.setOnItemClickListener {it->
            //do whatever you like
}

If you still have confussion here is full source code