[英]How to implement ViewHolder using sealed class in Kotlin
I saw an interesting viewholder implementation in this tweet https://twitter.com/AndroidDev/status/972502799496790018 我在此推文中看到了一个有趣的Viewholder实现https://twitter.com/AndroidDev/status/972502799496790018
override fun onBindViewHolder(holder: SealedAdapterViewHolder, position: Int) {
return when (holder) {
is HeaderHolder -> holder.displayHeader(items[position])
is DetailsHolder -> holder.displayDetails(items[position])
}
}
Unfortunately i can't figure out how to implement thouse holders. 不幸的是,我不知道如何实施thouse持有人。 And I didn't find any examples of this trick. 而且我没有找到这个技巧的任何例子。
In my viewholders I have to extend RecyclerView.ViewHolder and I have to extend sealed class so i can use it in "when clauses". 在我的观察者中,我必须扩展RecyclerView.ViewHolder,并且必须扩展密封类,以便可以在“ when子句”中使用它。 Multiple inharitance is not allowed. 不允许多次骚扰。
So is it possible and if it is then how? 这样有可能吗?
PS PS
original authors write this: 原始作者这样写:
You can also use sealed classes in a RecyclerView adapter. 您还可以在RecyclerView适配器中使用密封类。 They're a perfect fit for ViewHolders - with a clean set of types to dispatch explicitly to each holder. 它们非常适合ViewHolders-具有一组清晰的类型可以显式分配给每个所有者。 Used as an expression, the compiler will error if all types aren't matched. 用作表达式时,如果所有类型都不匹配,则编译器将出错。
Something like this: 像这样:
sealed class SealedAdapterViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
class HeaderHolder(view: View) : SealedAdapterViewHolder(view)
class DetailsHolder(view: View) : SealedAdapterViewHolder(view)
}
it's in the first post of the thread. 它在线程的第一篇文章中。
fun foo(holder : SealedAdapterViewHolder){
when (holder) {
is HeaderHolder -> holder.displayHeader(items[position])
is DetailsHolder -> holder.displayDetails(items[position])
}
}
sealed class SealedAdapterViewHolder(view: View) : RecyclerView.ViewHolder(view)
data class HeaderHolder(val view: View): SealedAdapterViewHolder(view){
fun displayHeader(...){}
}
data class DetailsHolder(val view: View): SealedAdapterViewHolder(view){
fun displayDetails(...){}
}
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