一、需求及规范

1、需求

RecyclerView 是我们常用的列表控件，直接使用时通常大量代码编写于 Adapter 中，当 item 包含视图类型过多时，Adapter 会臃肿不堪，故需要将各个类型视图单独定义编写。

2、规范

主要定义五个模块：adapter、viewHolder、viewHolderFactory、itemView、model

adapter：及 RecyclerView.Adapter 适配器，用来整合填充数据
viewHolder：及 RecyclerView.ViewHolder 视图固定器，用来实现视图重用
viewHolderFactory：创建 viewHolder，并实现多类型视图设置
itemView：item视图代码编写
model：定义公共model，便于使用

二、代码编写

RecyclerViewAdapter

abstract class RecyclerViewAdapter<M: RecyclerViewModel>(private var context: Context) :
    RecyclerView.Adapter<RecyclerViewHolder<M, out ViewDataBinding, out ItemRecyclerView<M, out ViewDataBinding>>>() {

    private val dataList: MutableList<M> by lazy {
        ArrayList<M>()
    }

    fun addAllDataList(dataList: List<M>) {
        this.dataList.addAll(dataList)
        notifyDataSetChanged()
    }

    override fun getItemCount(): Int {
        return dataList.size
    }

    override fun onCreateViewHolder(
        parent: ViewGroup,
        viewType: Int
    ): RecyclerViewHolder<M, out ViewDataBinding, out ItemRecyclerView<M, out ViewDataBinding>> {
        return createViewHolderFactory().createViewHolder(context, parent, viewType)
    }

    protected abstract fun createViewHolderFactory(): ViewHolderFactory<M>


    override fun onBindViewHolder(
        holder: RecyclerViewHolder<M, out ViewDataBinding, out ItemRecyclerView<M, out ViewDataBinding>>,
        position: Int
    ) {
        holder.itemRecyclerView.dataBinding(dataList[position], position)
    }

}    

RecyclerViewHolder

class RecyclerViewHolder<M: RecyclerViewModel, VDB: ViewDataBinding, V: ItemRecyclerView<M, VDB>>(var itemRecyclerView: V)
    : RecyclerView.ViewHolder(itemRecyclerView.rootView)

ViewHolderFactory

abstract class ViewHolderFactory<M: RecyclerViewModel> {
    abstract fun createViewHolder(context: Context, parent: ViewGroup, viewType: Int):
            RecyclerViewHolder<M, out ViewDataBinding, out ItemRecyclerView<M, out ViewDataBinding>>
}

ItemRecyclerView

abstract class ItemRecyclerView<M: RecyclerViewModel, VDB: ViewDataBinding>(context: Context, parent: ViewGroup) {

    val binding: VDB by lazy {
        DataBindingUtil.inflate(LayoutInflater.from(context), getItemLayoutId(), parent, false) as VDB
    }

    val viewHolder: RecyclerViewHolder<M, VDB, out ItemRecyclerView<M, VDB>> by lazy {
        RecyclerViewHolder(this)
    }

    val rootView: View by lazy {
        binding.root
    }

    abstract fun dataBinding(m: M, position: Int)

    abstract fun getItemLayoutId(): Int
}

RecyclerViewModel

abstract class RecyclerViewModel

三、使用

DemoViewHolderFactory

class DemoViewHolderFactory: ViewHolderFactory<DemoModel>() {
    override fun createViewHolder(
        context: Context,
        parent: ViewGroup,
        viewType: Int
    ): RecyclerViewHolder<DemoModel, *, *> {
        return DemoItemView(context, parent).viewHolder
    }
}

DemoItemView

class DemoItemView(context: Context, parent: ViewGroup):     ItemRecyclerView<DemoModel, ItemDemoBinding>(context, parent) {
    override fun dataBinding(m: DemoModel, position: Int) {
        binding.demo = m
    }

    override fun getItemLayoutId(): Int {
        return R.layout.item_demo
    }
}

DemoModel

class DemoModel: RecyclerViewModel() {
    var title: String? = null
    var content: String? = null
}

DemoAdapter

class DemoAdapter(context: Context): RecyclerViewAdapter<DemoModel>(context) {
    override fun createViewHolderFactory(): ViewHolderFactory<DemoModel> {
        return DemoViewHolderFactory()
    }
}

MainActivity

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        binding.demoListView.layoutManager = LinearLayoutManager(this)
        val adapter = DemoAdapter(this)
        binding.demoListView.adapter = adapter

        val dataList = ArrayList<DemoModel>()
        for (i in 0..20) {
            val data = DemoModel()
            data.title = "title $i"
            data.content = "content $i"
            dataList.add(data)
        }

        adapter.addAllDataList(dataList)
    }
}

activity_main

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">

    <data>

    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/demo_list_View"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

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

item_demo

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
        <variable
            name="demo"
            type="com.ww7h.bigobj.DemoModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:id="@+id/title"
            android:text="@{demo.title}"
            app:layout_constraintTop_toTopOf="parent"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

        <TextView
            android:text="@{demo.content}"
            app:layout_constraintTop_toBottomOf="@+id/title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

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