BaseDiffAdapter.kt

/**
 * Created by Howard Chang on 2018/11/13.
 *
 * @param recyclerView 被綁定的RecyclerView
 * @param mIsLoadMore 是否要演出刷新動畫
 * @param mIsAnim 是否有LoadMore功能，有得話在刷新之後復位position
 */
abstract class BaseDiffAdapter<T, V : RecyclerView.ViewHolder>(
        protected val recyclerView: RecyclerView? = null
        , protected val mIsLoadMore: Boolean = false
        , protected val mIsAnim: Boolean = true) : RecyclerView.Adapter<V>() {

    init {
        if (recyclerView != null) {
            if (!mIsLoadMore && mIsAnim ||
                    !mIsAnim) {
                recyclerView.itemAnimator = null
            }
        }
    }

    protected abstract fun areItemsTheSame(oldItem: T, newItem: T): Boolean

    protected abstract fun areContentsTheSame(oldItem: T, newItem: T): Boolean

    protected abstract fun getChangePayload(oldItem: T, newItem: T): Any?

    fun notifyDiff(temp: MutableList<T>, new: List<T>) {

        if (!mIsAnim && recyclerView != null) {
            recyclerView.itemAnimator = null
        }

        val diffDisposable = Single.just(DiffUtil.calculateDiff(object : DiffUtil.Callback() {
            override fun getOldListSize(): Int {
                return temp.size
            }

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

            // return兩個對像是否是相同item
            override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
                return [email protected](temp[oldItemPosition]!!, new[newItemPosition]!!)
            }

            /**
             * return item是否同內容
             *
             * 當areItemsTheSame為true時才觸發
             * 當areItemsTheSame返回為false時，即不管areContentsTheSame是否為true皆進行刷新
             */
            override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
                return [email protected](temp[oldItemPosition]!!, new[newItemPosition]!!)
            }

            /**
             * areItemsTheSame() 返回 true 而 areContentsTheSame() 返回 false 時觸發
             *
             * 如果使用 RecyclerView 配合 DiffUtils 且調用此方法，RecyclerView 會用透過這些內容自動去執行正確的動畫
             * {@link android.support.v7.widget.RecyclerView.ItemAnimator ItemAnimator}
             *
             * 預設return null
             * @param oldItemPosition
             * @param newItemPosition
             * @return
             */
            override fun getChangePayload(oldItemPosition: Int, newItemPosition: Int): Any? {
                return [email protected](temp[oldItemPosition]!!, new[newItemPosition]!!)
            }
        }))

        // 如果是loadMore，記住當前滑動位置
        var mRecyclerViewState: Parcelable? = null
        if (isSaveInstanceState()) {
            mRecyclerViewState = recyclerView!!.layoutManager.onSaveInstanceState()
        }

        CompositeDisposable()
                .add(diffDisposable
                        .subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe { result ->

                            result.dispatchUpdatesTo(this)

                            // 非loadMore，先清空原有temp
                            if (!mIsLoadMore) {
                                temp.clear()
                            }

                            temp.addAll(new)

                            // 如果是loadMore，回復原來的滑動位置
                            if (isSaveInstanceState() && mRecyclerViewState != null) {
                                recyclerView!!.layoutManager.onRestoreInstanceState(mRecyclerViewState)
                            }
                        })
    }

    private fun isSaveInstanceState(): Boolean {
        return recyclerView != null && mIsLoadMore
    }
}