一，自帶的條目動畫

我們先來看看系統自帶的動畫設置實現：

        rv_content.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false) as RecyclerView.LayoutManager?//設置顯示方式
        mAdapter = RecyclerViewSimpleAdapter(this, itemList)
        rv_content.adapter = mAdapter
        rv_content.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))//系統默認間隔線
        rv_content.itemAnimator = DefaultItemAnimator()//系統默認動畫

這樣我們就實現了動畫的添加，通過添加和刪除可以看出默認的動畫為：Alpha形式。

二，第三方條目動畫

2.1，第三方github地址：

github地址:recyclerview-animators

2.2，添加依賴

compile 'jp.wasabeef:recyclerview-animators:2.2.6'

2.3，動畫使用

2.3.1 子條目進入動畫

        rv_content.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false) as RecyclerView.LayoutManager?//設置顯示方式
        mAdapter = RecyclerViewSimpleAdapter(this, itemList)
        val adapter = SlideInLeftAnimationAdapter(mAdapter)//從左側進入
        rv_content.adapter = adapter
        rv_content.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))//系統默認間隔線
        rv_content.itemAnimator = DefaultItemAnimator()//系統默認動畫

通過SlideInLeftAnimationAdapter(mAdapter)我們就將子條目從左進入動畫設置成功了。當然還提供了從右的方法SlideInRightAnimationAdapter(mAdapter),從下的方法SlideInBottomAnimationAdapter(mAdapter)，縮放進入方法：ScaleInAnimationAdapter(mAdapter)，漸變進入方法：AlphaInAnimationAdapter(mAdapter)等等。
上面的方法都只能設置一種效果，可以將上面的方法組合起來，來設置子條目的進入動畫

        rv_content.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false) as RecyclerView.LayoutManager?//設置顯示方式
        mAdapter = RecyclerViewSimpleAdapter(this, itemList)
        val adapter = SlideInLeftAnimationAdapter(mAdapter)//從左側進入
        val adapterSec = ScaleInAnimationAdapter(adapter)//縮放進入
        rv_content.adapter = adapterSec
        rv_content.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))//系統默認間隔線
        rv_content.itemAnimator = DefaultItemAnimator()//系統默認動畫

2.3.2 子條目添加刪除動畫

        rv_content.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false) as RecyclerView.LayoutManager?//設置顯示方式
        mAdapter = RecyclerViewSimpleAdapter(this, itemList)
        val adapter = SlideInLeftAnimationAdapter(mAdapter)//從左側進入
        val adapterSec = ScaleInAnimationAdapter(adapter)//縮放進入
        rv_content.adapter = adapterSec
        rv_content.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))//系統默認間隔線
        rv_content.itemAnimator = SlideInLeftAnimator()//從左邊進入，從左邊退出

上面設置了添加子條目時從左邊進入，刪除時從左邊退出。這個設置子條目添加和刪除動畫有好多種類型，這里就不一一列舉了。
這里也可以更改插值器

        rv_content.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false) as RecyclerView.LayoutManager?//設置顯示方式
        mAdapter = RecyclerViewSimpleAdapter(this, itemList)
        val adapter = SlideInLeftAnimationAdapter(mAdapter)//從左側進入
        val adapterSec = ScaleInAnimationAdapter(adapter)//縮放進入
        rv_content.adapter = adapterSec
        rv_content.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))//系統默認間隔線
        val animator = SlideInUpAnimator(OvershootInterpolator(2f))//向前甩一定值后再回到原來位置
        rv_content.itemAnimator = animator

在這里更改的是向上動畫的插值器。更改插值器的方法也有很多種，自己可以試試。

2.3.3 動畫時間設置

        rv_content.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false) as RecyclerView.LayoutManager?//設置顯示方式
        mAdapter = RecyclerViewSimpleAdapter(this, itemList)
        val adapter = SlideInLeftAnimationAdapter(mAdapter)//從左側進入
        val adapterSec = ScaleInAnimationAdapter(adapter)//縮放進入
        rv_content.adapter = adapterSec
        rv_content.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))//系統默認間隔線
        val animator = SlideInUpAnimator(OvershootInterpolator(2f))//向前甩一定值后再回到原來位置
        rv_content.itemAnimator = animator
        rv_content.itemAnimator.addDuration = 3000//設置新增動畫時長
        rv_content.itemAnimator.removeDuration = 1000//設置移除動畫時長
        rv_content.itemAnimator.moveDuration = 1000//設置移動動畫時長
        rv_content.itemAnimator.changeDuration = 1000//設置所有變化動畫時長

2.3.4 動畫自定義

如果上面的沒有你想要的效果，例如‘添加從右側進，刪除從左側出’，那么我們就需要自己定制了

class CustomSlideInRightAnimtor : BaseItemAnimator{
    constructor()

    constructor(interpolator: Interpolator) {
        mInterpolator = interpolator
    }

    override fun animateRemoveImpl(holder: RecyclerView.ViewHolder?) {
       val viewCompat: ViewPropertyAnimatorCompat = ViewCompat.animate(holder!!.itemView)
        viewCompat.duration = removeDuration
        viewCompat.interpolator = mInterpolator
        viewCompat.startDelay = getRemoveDelay(holder)
        viewCompat.setListener(DefaultRemoveVpaListener(holder))
        viewCompat.translationX((-holder.itemView.rootView.width).toFloat())
        viewCompat.start()
    }

    override fun preAnimateAddImpl(holder: RecyclerView.ViewHolder?) {
        ViewCompat.setTranslationX(holder!!.itemView, (holder.itemView.rootView.width).toFloat())
    }

    override fun animateAddImpl(holder: RecyclerView.ViewHolder?) {
        val viewCompat: ViewPropertyAnimatorCompat = ViewCompat.animate(holder!!.itemView)
        viewCompat.duration = removeDuration
        viewCompat.interpolator = mInterpolator
        viewCompat.startDelay = getRemoveDelay(holder)
        viewCompat.setListener(DefaultRemoveVpaListener(holder))
        viewCompat.translationX(0F)
        viewCompat.start()
    }
}

定制動畫的使用

rv_content.itemAnimator = CustomSlideInRightAnimtor()//自定義動畫，從右邊進入，從左邊退出

這樣就實現了我們需要的效果。

三，子條目的拖拽動畫

系統提供了拖拽類ItemTouchHelper，具體的拖拽實現實在ItemTouchHelper.SimpleCallback中，我們只要實現了其中的onSwiped,onMove方法，也就完成了拖拽的操作

val itemTouchHelper = ItemTouchHelper(object : ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP or ItemTouchHelper.DOWN or ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT, ItemTouchHelper.START or ItemTouchHelper.END){

            override fun onMove(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder?, target: RecyclerView.ViewHolder?): Boolean {
                val fromPosition = viewHolder!!.adapterPosition
                val toPosition = target!!.adapterPosition
                if (fromPosition < toPosition){
                    for (i in fromPosition..toPosition-1){
                        Collections.swap(itemList, i, i+1)
                    }
                }else{
                    for (i in fromPosition downTo toPosition + 1){
                        Log.e("hjd", "fromPosition:$fromPosition,toPosition:$toPosition,i:$i")
                        Collections.swap(itemList, i, i-1)
                    }
                }

                mAdapter!!.notifyItemMoved(fromPosition, toPosition)
                return true
            }

            override fun onSwiped(viewHolder: RecyclerView.ViewHolder?, direction: Int) {
                val position = viewHolder!!.adapterPosition
                itemList.removeAt(position)
                mAdapter!!.notifyItemRemoved(position)
            }

        })

        itemTouchHelper.attachToRecyclerView(rv_content)

好了這個第三方的條目動畫的使用就簡單說到這里了，下一篇RecyclerView Header和Footer的添加

四，參考文章

github地址:[recyclerview-animators]: https://github.com/wasabeef/recyclerview-animators