与 Kotlin 通用适配器的类型不匹配

Question

我正在尝试创建一个基础适配器 class，它可以由所有其他 RecyclerView 适配器扩展，因为它们彼此之间没有太大区别。

这是我的 BaseAdapter class:

private const val IS_EMPTY = 0
private const val IS_NOT_EMPTY = 1

abstract class BaseAdapter<T>(
    @LayoutRes open val layoutId: Int,
    private val dataList: ArrayList<T>?
) : RecyclerView.Adapter<BaseViewHolder<Any>>() {

    abstract fun setViewHolder(parent: ViewGroup): BaseViewHolder<Any>
    abstract fun bind(containerView: View, item: T)

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BaseViewHolder<Any> {
        return setViewHolder(parent)
    }

    override fun onBindViewHolder(holder: BaseViewHolder<Any>, position: Int) {
        bind(holder.containerView, dataList!![position])
    }

    override fun getItemCount(): Int = dataList!!.size

    override fun getItemViewType(position: Int): Int = if (dataList!!.size == 0) IS_EMPTY else IS_NOT_EMPTY
}

这是我的 BaseViewHolder class:

abstract class BaseViewHolder<in T: Any>(override val containerView: View) : RecyclerView.ViewHolder(containerView),
    LayoutContainer

来自 class (LessonsRecyclerViewAdapter) 的片段，我正在尝试实现它：

override fun setViewHolder(parent: ViewGroup): BaseViewHolder<Any> {
        val view = LayoutInflater.from(parent.context).inflate(layoutId, parent, false)
        return LessonsViewHolder(view)
        //Type mismatch: Required: BaseViewHolder<Any> Found: LessonsRecyclerViewAdapter.LessonsViewHolder
    }

LessonsViewHolder 只是一个空的 class，扩展 BaseViewHolder:

class LessonsViewHolder(override val containerView: View): BaseViewHolder<Lesson>(containerView)

当 LessonsViewHolder 扩展 BaseViewHolder 时，为什么我会收到类型不匹配错误？

Answer 1

那是因为您混合使用 T 和 Any 类型，试试这个：
BaseViewHolder

abstract class BaseViewHolder<T>(override val containerView: View) :
    RecyclerView.ViewHolder(containerView),
    LayoutContainer

BaseViewAdapter

abstract class BaseAdapter<T>(
    @LayoutRes open val layoutId: Int,
    private val dataList: ArrayList<T>?
) : RecyclerView.Adapter<BaseViewHolder<T>>() {

    abstract fun setViewHolder(parent: ViewGroup): BaseViewHolder<T>
    abstract fun bind(containerView: View, item: T)

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BaseViewHolder<T> {
        return setViewHolder(parent)
    }

    override fun onBindViewHolder(holder: BaseViewHolder<T>, position: Int) {
        bind(holder.containerView, dataList!![position])
    }

    override fun getItemCount(): Int = dataList!!.size

    override fun getItemViewType(position: Int): Int =
        if (dataList!!.size == 0) IS_EMPTY else IS_NOT_EMPTY
}

与 Kotlin 通用适配器的类型不匹配

Type Mismatch with Kotlin Generic Adapter

generics

android

adapter

kotlin

android-recyclerview