MultiType的扩展使用(ViewBinding, Diff.Callba

该库是我目前使用过最好用的 adapter 库，严格的遵循数据驱动，针对使用方便性做了一些扩展。

Delegate 的封装

这一步封装，结合 viewbinding 省去 viewholder 的创建过程。

使用反射

abstract class ViewBindingDelegate<T, VB : ViewBinding> :
    ItemViewDelegate<T, ViewBindingViewHolder<VB>>() {

    override fun onCreateViewHolder(
        context: Context,
        parent: ViewGroup
    ): ViewBindingViewHolder<VB> {
        return ViewBindingViewHolder(inflateBindingWithGeneric(parent))
    }
}

ViewHolder 的创建需要传入 layout 对应的binding，这里使用反射生成。

相关反射代码如下：

@JvmName("inflateWithGeneric")
fun <VB : ViewBinding> Any.inflateBindingWithGeneric(layoutInflater: LayoutInflater): VB =
        withGenericBindingClass(this) { clazz ->
            clazz.getMethod("inflate", LayoutInflater::class.java).invoke(null, layoutInflater) as VB
        }

@JvmName("inflateWithGeneric")
fun <VB : ViewBinding> Any.inflateBindingWithGeneric(layoutInflater: LayoutInflater, parent: ViewGroup?, attachToParent: Boolean): VB =
        withGenericBindingClass(this) { clazz ->
            clazz.getMethod("inflate", LayoutInflater::class.java, ViewGroup::class.java, Boolean::class.java)
                    .invoke(null, layoutInflater, parent, attachToParent) as VB
        }

@JvmName("inflateWithGeneric")
fun <VB : ViewBinding> Any.inflateBindingWithGeneric(parent: ViewGroup): VB =
        inflateBindingWithGeneric(LayoutInflater.from(parent.context), parent, false)

fun <VB : ViewBinding> Any.bindViewWithGeneric(view: View): VB =
        withGenericBindingClass(this) { clazz ->
            clazz.getMethod("bind", LayoutInflater::class.java).invoke(null, view) as VB
        }

private fun <VB : ViewBinding> withGenericBindingClass(any: Any, block: (Class<VB>) -> VB): VB {
    any.allParameterizedType.forEach { parameterizedType ->
        parameterizedType.actualTypeArguments.forEach {
            try {
                return block.invoke(it as Class<VB>)
            } catch (e: Exception) {
            }
        }
    }
    throw IllegalArgumentException("There is no generic of ViewBinding.")
}

private val Any.allParameterizedType: List<ParameterizedType>
    get() {
        val genericParameterizedType = mutableListOf<ParameterizedType>()
        var genericSuperclass = javaClass.genericSuperclass
        var superclass = javaClass.superclass
        while (superclass != null) {
            if (genericSuperclass is ParameterizedType) {
                genericParameterizedType.add(genericSuperclass)
            }
            genericSuperclass = superclass.genericSuperclass
            superclass = superclass.superclass
        }
        return genericParameterizedType
    }

不使用反射

不使用发射，需要抽象一个方法，将 binding 的实例返回。

abstract class ViewBindingDelegate2<T, VB : ViewBinding> :
    ItemViewDelegate<T, ViewBindingViewHolder<VB>>() {

    override fun onCreateViewHolder(
        context: Context,
        parent: ViewGroup
    ): ViewBindingViewHolder<VB> {
        return ViewBindingViewHolder(binding(parent))
    }

    abstract fun binding(parent: ViewGroup): VB
}

class ViewBindingViewHolder<VB : ViewBinding>(val binding: VB) :
    RecyclerView.ViewHolder(binding.root)

结合 DiffUtil.Callback 做局部更新

这里考虑使用扩展函数，封装进行使用。

abstract class AnyCallback(val oldItems: List<Any>, val newItems: List<Any>) : DiffUtil.Callback() {
    override fun getOldListSize(): Int {
        return oldItems.size
    }

    override fun getNewListSize(): Int {
        return newItems.size
    }

    override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        val oldItem = oldItems[oldItemPosition]
        val newItem = newItems[newItemPosition]
        return areItemsTheSame(oldItem, newItem)

    }

    abstract fun areItemsTheSame(oldItem: Any, newItem: Any): Boolean


    override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
        val oldItem = oldItems[oldItemPosition]
        val newItem = newItems[newItemPosition]
        return areContentsTheSame(oldItem, newItem)
    }

    abstract fun areContentsTheSame(oldItem: Any, newItem: Any): Boolean
}

// 带动画的差分更新
fun MultiTypeAdapter.submitList(callback: AnyCallback) {
    val result = DiffUtil.calculateDiff(callback)
    items = callback.newItems
    result.dispatchUpdatesTo(this)
}

// 旧方法更新
fun MultiTypeAdapter.updateItems(items: List<Any>) {
    this.items = items
    notifyDataSetChanged()
}

参考资料

1. MultiType： github.com/drakeet/Mul…

2. DylanCaiCoding:ViewBindingKTX: github.com/DylanCaiCod…