Prosto: remove boilerplate when working with RecyclerView

To display a list of data we use RecyclerView(- Thank you, cap!). He knows a lot of things from the box and other well-known blablabs. But there is plenty of pain with him. No one likes to write the same boilerplate code. And I'm not really ...

A brief history of the plot "Reduce the code a bit":

For example, a simple data class Person () was created: with first name, last name, email. mail and dog availability.

To display a list of people, you must create RecyclerView.Adapterand RecyclerView.ViewHolder, most of whose + code is the same.

Adapter ViewHolder-, . , , ViewHolder, .

Adapter ViewHolder, .

RecyclerView.Adapter<RecyclerView.ViewHolder>

class ClassicAdapter : RecyclerView.Adapter<ClassicHolder>() {

    private val viewModel = PersonItemViewModel()

    private val data: List<Person>
        get() = viewModel.data

    fun setData(persons: List<Person>) {
        viewModel.data = persons
        notifyDataSetChanged()
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ClassicHolder =
        ClassicHolder.create(parent)

    override fun getItemCount(): Int = data.size

    override fun onBindViewHolder(holder: ClassicHolder, position: Int) {
        holder.bind(viewModel, position)
    }
}

class ClassicHolder(private val binding: ItemPersonBinding) : RecyclerView.ViewHolder(binding.root) {
    fun bind(viewModel: PersonItemViewModel, position: Int) {
        binding.setVariable(BR.viewModel, viewModel)
        binding.setVariable(BR.position, position)
        binding.executePendingBindings()
    }

    companion object {
        fun create(parent: ViewGroup): ClassicHolder {
            val inflater = LayoutInflater.from(parent.context)
            val binding: ItemPersonBinding =
                DataBindingUtil.inflate(inflater, R.layout.item_person, parent, false)
            return ClassicHolder(binding)
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<layout>
    <data>
        <variable
            name="position"
            type="Integer" />

        <variable
            name="viewModel"
            type="plus.yeti.prostoadapter.ui.main.PersonItemViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout>

        <TextView
            android:text="@{viewModel.getName(position)}"
            ... />

        <TextView
            android:text="@{viewModel.getEmail(position)}"
            .../>

        <ImageView
            app:visible="@{viewModel.hasDog(position)}" 
            .../>

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

class PersonItemViewModel : ProstoViewModel<Person>() {
    override var data: List<Person> = emptyList()

    fun getName(position: Int) = data[position].lastName + ", " + data[position].firstName
    fun getEmail(position: Int) = data[position].email
    fun hasDog(position: Int): Boolean = data[position].hasDog
}

ProstoAdapter ProstoHolder

, Adapter ViewHolder , .

ProstoViewModel. , ProstoViewModel, , , . ViewModel -:

abstract class ProstoViewModel<T>: ViewModel() {
    abstract var data: List<T>
}

ProstoHolder

open class ProstoHolder<TBinding : ViewDataBinding>(val binding: TBinding) : RecyclerView.ViewHolder(binding.root) {
    open fun <TData, TViewModel : ProstoViewModel<TData>> bind(viewModel: TViewModel, position: Int) {
        binding.setVariable(BR.viewModel, viewModel)
        binding.setVariable(BR.position, position)
        binding.executePendingBindings()
    }

    companion object {
        fun <TBinding : ViewDataBinding> create(parent: ViewGroup, layoutId: Int): ProstoHolder<TBinding> {
            val inflater = LayoutInflater.from(parent.context)
            val binding: TBinding = DataBindingUtil.inflate(inflater, layoutId, parent, false)
            return ProstoHolder(binding)
        }
    }
}

, , ProstoAdapter:

abstract class ProstoAdapter<TBinding : ViewDataBinding, TData> : RecyclerView.Adapter<ProstoHolder<TBinding>>() {

    abstract val viewModel: ProstoViewModel<TData>
    abstract val layoutId: Int

    private var dataSize: Int = 0

    open fun setData(data: List<TData>) {
        this.dataSize = data.size
        viewModel.data = data
        notifyDataSetChanged()
    }

    open var onBind: ((ProstoHolder<TBinding>) -> Unit)? = null

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ProstoHolder<TBinding> =
        ProstoHolder.create(parent, layoutId)

    override fun getItemCount(): Int = dataSize

    override fun onBindViewHolder(holder: ProstoHolder<TBinding>, position: Int) {
        holder.bind(viewModel, position)
        onBind?.invoke(holder)
    }
}

Adapter-a ViewModel c , item's layout id Binding-, layout-, item-.

, :)

class MainFragment : Fragment() {
    private val adapter =
        object : ProstoAdapter<ItemPersonBinding, Person>() {
            override val viewModel = PersonItemViewModel()
            override val layoutId = R.layout.item_person
        }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        mainRecyclerView.adapter = adapter
    }

    fun setNewPersonList(persons: List<Person>){
        adapter.setData(personList)
    }
}

4 .

github.com/klukwist/Prosto

ViewHolder-.

:)