做了一个kotlin下的Recyclerview通用框架, 减少代码量, 聚焦业务

代码放在:

https://github.com/shaopx/LiteRecyclerViewAdapter

效果

image.png

实现逻辑 (一共3个kt文件)

Adapter.kt

/**
 * 通用 RecyclerView.Adapter类, 基本结构与普通RecyclerView.Adapter一致.
 * 内部使用一个arrayList列表变量dataItems来存储数据, 提供了addData和replace两个方法来更新数据
 * 在onCreateViewHolder中会根据viewType找到对应的viewHolder类,并创建iewHolder类实例, 如果找不到则返回一个空实现EmptyVH实例
 * 在onBindViewHolder中,交给VH实例自己进行数据绑定操作
 */
class Adapter(val context: Context) : RecyclerView.Adapter<VH<Data>>() {
    private val dataItems = ArrayList<Data>()

    override fun getItemViewType(position: Int): Int {
        return dataItems[position].itemViewType
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH<Data> {
        val view = LayoutInflater.from(parent.context).inflate(viewType, parent, false)
        VHList[viewType]?.let {
            return it(view) as VH<Data>
        }
        return EmptyVH(view)
    }

    override fun onBindViewHolder(holder: VH<Data>, position: Int) {
        holder.bind(dataItems[position], position)
    }

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

    fun addData(list: List<Data>) {
        dataItems.addAll(list)
        notifyDataSetChanged()
    }

    fun replace(list: List<Data>) {
        dataItems.run {
            clear()
            addAll(list)
        }
        notifyDataSetChanged()
    }
}

Data.kt

interface Data {
    val itemViewType: Int
}
open class CommonData(
        override var itemViewType: Int,
        vHConstructorFuc: (view: View)-> VH<out Data>)
    : Data {

    init {
        VHList.register(itemViewType, vHConstructorFuc)
    }
}

VH.kt

/**
 * 自定义的RecyclerView.ViewHolder子类.主要是为了增加bind(data: Data, position: Int)方法
 */
abstract class VH<T : Data>(itemView: View) : RecyclerView.ViewHolder(itemView) {
    abstract fun bind(data: T, position: Int)
}

/**
 * ViewHolder的注册表, 建立itemViewType与ViewHolder的对应关系
 * 存放在map中, 效率凑合
 */
object VHList {
    private var vhs = mutableMapOf<Int, (view: View) -> VH<out Data>>()

    fun register(viewType: Int, vHConstructorFuc: (view: View) -> VH<out Data>) {
        vhs[viewType] = vHConstructorFuc
    }

    operator fun get(viewType: Int): ((view: View) -> VH<out Data>)? = vhs[viewType]
}

/**
 * 这是一个空ViewHolder实现, 只会抛出异常
 */
class EmptyVH(itemView: View) : VH<Data>(itemView) {
    override fun bind(data: Data, position: Int) {
        TODO("not implemented")
    }
}

使用示例:

NotSimpleListActivity.kt:

class NotSimpleListActivity : AppCompatActivity() {
    private lateinit var adapter: Adapter
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_simple_list)

        recyclerview.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
        adapter = Adapter(this)
        recyclerview.adapter = adapter

        loadOnlineData()
    }

    private fun loadOnlineData() {
        ApiService.get()!!
                .getHotScreenList(mapOf("apikey" to API_KEY,  "count" to "30"))
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeBy(
                      onError ={ Log.e("NotSimpleListActivity", "error", it) },
                      onNext = {
                         adapter.addData(it!!.subjects?.map {
                            HotScreenData(it, R.layout.douban_hotscreen_item_layout,::HotScreenDataViewHolder)
                         }!!)
                      }
                )
    }
}

/**
 * define the wrapper data
 */
class HotScreenData(var backdata: HotScreenResult.SubjectsBean,
                    layoutId: Int,
                    funct: (view: View) -> VH<out Data>)
    : CommonData(layoutId, funct)

class HotScreenDataViewHolder : VH<HotScreenData> {
    var title: TextView? = null
    var dy: TextView? = null
    var actor: TextView? = null
    var watchNum: TextView? = null
    var rating: RatingBar? = null
    var image: ImageView? = null

    constructor(itemView: View) : super(itemView) {
        itemView.apply {
            title = findViewById(R.id.item_hot_screen_title)
            image = findViewById(R.id.item_hot_screen_image)
            rating = findViewById(R.id.item_hot_screen_rating)
            dy = findViewById(R.id.item_hot_screen_dy)
            actor = findViewById(R.id.item_hot_screen_actor)
            watchNum = findViewById(R.id.item_hot_screen_watch_num)
        }
    }

    override fun bind(data: HotScreenData, position: Int) {
        title?.text = data.backdata.title
        Glide.with(itemView.context).load(data.backdata.images?.small).into(image!!)
        rating?.rating = (data.backdata.rating?.average!! / 2).toFloat()
        dy?.text = "导演：" + data.backdata.directors!![0].name
        watchNum?.text = "${data.backdata.collect_count} 人看过"
        actor?.text = "主演：" + data.backdata.casts!!.map { it.name }
    }
}

这段代码就实现了本篇头部的效果截图.

总结

这个框架(实在想不出该用什么词表示了)最大的好处是数据与现实元素的聚合, 对于页面显示复杂的应用, 可以方便的添加recyclerview中的显示类型(viewType), 避免了大量if/when判断分支.
实现简单, 只有3个kt文件.
代码无侵入性, 非常接近原生的使用方式;

所有的viewHolder都与数据相对应, 高聚合, 且代码更清爽.