package com.codepath.customadapter;import android.widget.AbsListView;/** * Created by Administrator on 2016/7/11. */public abstract class EndlessScrollListener implements AbsListView.OnScrollListener { //在你滑動項下最少為多少時開始加載數據 private int visibleThreshold = 5; //已經加載數據的當前頁碼 private int currentPage = 0; //上一次加載數據后數據庫的數據量 private int previousTotalItemCount = 0; //我們是否在等待最后一組數據的加載 private boolean loading = true; //設置開始頁的下標 private int startingPageIndex = 0; public EndlessScrollListener() { } public EndlessScrollListener(int visibleThreshold) {  this.visibleThreshold = visibleThreshold; } public EndlessScrollListener(int visibleThreshold, int startingPageIndex) {  this.visibleThreshold = visibleThreshold;  this.startingPageIndex = startingPageIndex; } //這個方法可能會在滑動調用很多次，所以在設計時要保持謹慎 //我們需要一些有用的參數來幫助我們，當我們需要加載更多數據的時候 //但是我們首先要檢查是否我們在等待先前的加載結束//onScroll()當列表或網格視圖被滾動后將會調用，參數一：報告狀態的視圖參數二：第一個可以看見的項的下標，參數三：可見項的數量參數四：listAdapter中所有的項數 @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {  //如果總項數為0，而且先前沒有項，那么這個列表是無效的應該被設定為初始狀態  if (totalItemCount < previousTotalItemCount) {   this.currentPage = this.startingPageIndex;   this.previousTotalItemCount = totalItemCount;   if (totalItemCount == 0) {this.loading = true;}  }  //如果仍在加載中我們可以檢查一下數據集合是否改變了，如果改變的話那就是已經完成了loading需要更新當前  //頁數和數據總量  if (loading && (totalItemCount > previousTotalItemCount)) {   loading = false;   previousTotalItemCount = totalItemCount;   currentPage++;  }  //如果當前沒有加載，我們需要檢查當前是否達到了閾值，如果是的話我們需要  //加載更多的數據，執行onLoadMore  if (!loading && (firstVisibleItem + visibleItemCount + visibleThreshold) >= totalItemCount) {   loading = onLoadMore(currentPage + 1, totalItemCount);  } } //定義實際加載數據的過程，如果數據加載完成返回false，如果正在加載返回true； public abstract boolean onLoadMore(int page, int totalItemCount); @Override public void onScrollStateChanged(AbsListView view, int scrollState) {  //不采取動作 }}

public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstance) {  //向平常一樣   ListView lvItems = (ListView) findViewById(R.id.lvItens);   //將監聽器綁定到上面    lvItems.setOnScrollListener(new EndlessScrollListener() {   @Override   public boolean onLoadMore(int page, int totalItemsCount) {    // 當新數據需要綁定到列表上的時候觸發    // 加載數據需要的代碼Add whatever code is needed to append new items to your AdapterView    customLoadMoreDataFromApi(page);     // or customLoadMoreDataFromApi(totalItemsCount);     return true; //數據加載中為true，不然為false； ONLY if more data is actually being loaded; false otherwise.   }  }); } //加載更多的數據 public void customLoadMoreDataFromApi(int offset) {  //這個方法通常會發起一些網絡請求，然后向適配器添加更多的數據  //將偏移量數據作為參數附在請求里來獲得一個數據的分頁  //解析API返回的值并且獲得新的對象構建適配器 }}

 protected void onCreate(Bundle savedInstanceState) {  // Configure the RecyclerView獲得RecylerView的實例  RecyclerView rvItems = (RecyclerView) findViewById(R.id.rvContacts);  LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);  recyclerView.setLayoutManager(linearLayoutManager);  // Add the scroll listener  rvItems.addOnScrollListener(new EndlessRecyclerViewScrollListener(linearLayoutManager) {   @Override   public void onLoadMore(int page, int totalItemsCount) {    // Triggered only when new data needs to be appended to the list    // Add whatever code is needed to append new items to the bottom of the list    customLoadMoreDataFromApi(page);    }  }); } // Append more data into the adapter // This method probably sends out a network request and appends new data items to your adapter.  public void customLoadMoreDataFromApi(int page) {  // Send an API request to retrieve appropriate data using the offset value as a parameter.  // --> Deserialize API response and then construct new objects to append to the adapter  // --> Notify the adapter of the changes }}

public abstract class EndlessRecyclerViewScrollListener extends RecyclerView.OnScrollListener { // The minimum amount of items to have below your current scroll position // before loading more. private int visibleThreshold = 5; // The current offset index of data you have loaded private int currentPage = 0; // The total number of items in the dataset after the last load private int previousTotalItemCount = 0; // True if we are still waiting for the last set of data to load. private boolean loading = true; // Sets the starting page index private int startingPageIndex = 0; RecyclerView.LayoutManager mLayoutManager; public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager) {  this.mLayoutManager = layoutManager; } public EndlessRecyclerViewScrollListener(GridLayoutManager layoutManager) {  this.mLayoutManager = layoutManager;  visibleThreshold = visibleThreshold * layoutManager.getSpanCount(); } public EndlessRecyclerViewScrollListener(StaggeredGridLayoutManager layoutManager) {  this.mLayoutManager = layoutManager;  visibleThreshold = visibleThreshold * layoutManager.getSpanCount(); } public int getLastVisibleItem(int[] lastVisibleItemPositions) {  int maxSize = 0;  for (int i = 0; i < lastVisibleItemPositions.length; i++) {   if (i == 0) {    maxSize = lastVisibleItemPositions[i];   }   else if (lastVisibleItemPositions[i] > maxSize) {    maxSize = lastVisibleItemPositions[i];   }  }  return maxSize; } // This happens many times a second during a scroll, so be wary of the code you place here. // We are given a few useful parameters to help us work out if we need to load some more data, // but first we check if we are waiting for the previous load to finish. @Override public void onScrolled(RecyclerView view, int dx, int dy) {  int lastVisibleItemPosition = 0;  int totalItemCount = mLayoutManager.getItemCount();  if (mLayoutManager instanceof StaggeredGridLayoutManager) {   int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastVisibleItemPositions(null);   // get maximum element within the list   lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions);  } else if (mLayoutManager instanceof LinearLayoutManager) {   lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();  } else if (mLayoutManager instanceof GridLayoutManager) {   lastVisibleItemPosition = ((GridLayoutManager) mLayoutManager).findLastVisibleItemPosition();  }  // If the total item count is zero and the previous isn't, assume the  // list is invalidated and should be reset back to initial state  if (totalItemCount < previousTotalItemCount) {   this.currentPage = this.startingPageIndex;   this.previousTotalItemCount = totalItemCount;   if (totalItemCount == 0) {    this.loading = true;   }  }  // If it's still loading, we check to see if the dataset count has  // changed, if so we conclude it has finished loading and update the current page  // number and total item count.  if (loading && (totalItemCount > previousTotalItemCount)) {   loading = false;   previousTotalItemCount = totalItemCount;  }  // If it isn't currently loading, we check to see if we have breached  // the visibleThreshold and need to reload more data.  // If we do need to reload some more data, we execute onLoadMore to fetch the data.  // threshold should reflect how many total columns there are too  if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) {   currentPage++;   onLoadMore(currentPage, totalItemCount);   loading = true;  } } // Defines the process for actually loading more data based on page public abstract void onLoadMore(int page, int totalItemsCount);}