不囉唆，先上圖

今天我們想要透過畫面往下拉，去更新RecycleView顯示的項目的話。
我們需要在RecycleView外層，包上一層SwipeRefreshLayout，
並且實作。

上個Layout

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.SwipeRefreshLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".Activity_PullToRequest" android:id="@+id/srl_Layout">

    <android.support.v7.widget.RecyclerView
            android:layout_width="match_parent"
            android:layout_height="match_parent" android:id="@+id/rv_PulltoRequest"/>
</android.support.v4.widget.SwipeRefreshLayout>

宣告SwipeRefreshLayout在RecyclerView外面。

上個Activity

class Activity_PullToRequest : AppCompatActivity() {
    lateinit var gridLayoutManager: GridLayoutManager
    lateinit var itemsAdapter: RulltoRequest_RecycleViewAdapter
    var LoadCount = 1
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity__pull_to_request)
        gridLayoutManager = GridLayoutManager(this, 2)
        itemsAdapter = RulltoRequest_RecycleViewAdapter(PulltoRequestData.GetData(LoadCount), gridLayoutManager)

        rv_PulltoRequest.adapter = itemsAdapter
        rv_PulltoRequest.layoutManager = gridLayoutManager
        rv_PulltoRequest.itemAnimator = DefaultItemAnimator()

        // setup RefreshLayout
        srl_Layout.setProgressViewOffset(true, 50, 100)
        //顏色
        srl_Layout.setColorSchemeResources(
            android.R.color.holo_blue_light,
            android.R.color.holo_red_light,
            android.R.color.holo_orange_light
        )
        // size
        srl_Layout.setSize(SwipeRefreshLayout.LARGE)
        // 啟動下拉刷新
        srl_Layout.isEnabled = true
        // 監聽下拉刷新
        srl_Layout.setOnRefreshListener(productsRefreshListener)
    }

    var productsRefreshListener = SwipeRefreshLayout.OnRefreshListener {
        if (LoadCount >= 6) LoadCount = 0
        Thread.sleep(200)
        itemsAdapter.ChangeList(PulltoRequestData.GetData(LoadCount + 1))
        // 刷新畫面
        itemsAdapter.notifyDataSetChanged()
        // 停止下拉動畫
        srl_Layout.isRefreshing = false
        LoadCount++
    }
}

主要是透過設定

srl_Layout.isEnabled = true 
srl_Layout.setOnRefreshListener(productsRefreshListener)

開啟下拉監聽，並設置一個RefreshListener來完成下拉後要執行的動作。就可以達到我們要的實作效果。