结合 MultiType 实现加载更多

• 摘要：MultiType是一个分发管理类,帮助我们轻松实现复杂布局.建议大家阅读源码,作者的思路并不复杂但很巧妙.下面附上主要源码:publicclassLoadMoreDelegate{privateItemsmItems;privateMultiTypeAdaptermMultiTypeAdapter;privateOnLoadMoreListenermOnLoadMoreListener;privateScrollListenermScrollListener;publicL
• 
  

  MultiType 是一个分发管理类,帮助我们轻松实现复杂布局.建议大家阅读源码,作者的思路并不复杂但很巧妙.

  
  

  下面附上主要源码:

  
  public class LoadMoreDelegate { 
  private Items mItems; 
  private MultiTypeAdapter mMultiTypeAdapter; 
  private OnLoadMoreListener mOnLoadMoreListener; 
  private ScrollListener mScrollListener; 
  
  public LoadMoreDelegate(MultiTypeAdapter multiTypeAdapter, Items items, OnLoadMoreListener onLoadMoreListener) { 
  mMultiTypeAdapter = multiTypeAdapter; 
  mItems = items; 
  this.mOnLoadMoreListener = onLoadMoreListener; 
  } 
  public void attach(RecyclerView recyclerView) { 
  LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager(); 
  mScrollListener = new ScrollListener(mMultiTypeAdapter, mItems, linearLayoutManager, mOnLoadMoreListener); 
  recyclerView.addOnScrollListener(mScrollListener); 
  } 
  public void loadMoreComplete() { 
  mScrollListener.setLoading(false); 
  } 
  public void addData(Items items) { 
  int originSize = mItems.size() - 1; 
  mItems.remove(originSize);//删除"加载更多" 
  mItems.addAll(items);//添加新数据 
  //从最后的位置插入新数据 
  mMultiTypeAdapter.notifyItemRangeInserted(originSize, items.size() - 1); 
  } 
  public interface OnLoadMoreListener { 
  void onLoadMore(); 
  } 
  private static class ScrollListener extends RecyclerView.OnScrollListener { 
  private final int size = 2; 
  private boolean mLoading = false; 
  private Items mItems; 
  private final LoadMore mLoadMore = new LoadMore(); 
  private LinearLayoutManager mLinearLayoutManager; 
  private OnLoadMoreListener mOnLoadMoreListener; 
  private MultiTypeAdapter mMultiTypeAdapter; 
  ScrollListener(MultiTypeAdapter multiTypeAdapter, Items datas, LinearLayoutManager linearLayoutManager, OnLoadMoreListener onLoadMoreListener) { 
  mItems = datas; 
  mMultiTypeAdapter = multiTypeAdapter; 
  this.mLinearLayoutManager = linearLayoutManager; 
  this.mOnLoadMoreListener = onLoadMoreListener; 
  } 
  @Override 
  public void onScrolled(RecyclerView recyclerView, int dx, int dy) { 
  if (dy < 0) {//下滑忽略 
  return; 
  } 
  int totalNum = mLinearLayoutManager.getItemCount(); 
  int lastVisiblePosition = mLinearLayoutManager.findLastCompletelyVisibleItemPosition(); 
  if (!mLoading &;&; lastVisiblePosition == totalNum - size) {//最后可见的view的位置为倒数第size个,触发加载更多 
  mLoading = true; 
  mItems.add(mLoadMore); 
  mMultiTypeAdapter.notifyItemInserted(mItems.size() - 1); 
  mOnLoadMoreListener.onLoadMore(); 
  } 
  } 
  void setLoading(boolean loading) { 
  this.mLoading = loading; 
  } 
  } 
  } 
  

  这里提下有些加载更多只是简单的直接使用 notifyDataSetChanged() 方法,效率上我没有研究过,不敢说哪个效率更好,但至少 RecycleView 给我们提供的动画效果没有了,所以建议还是采用 notifyItemInserted().

  
  

  完整示例:multitypeloadmore

  
  public class PullUpTestActivity extends AppCompatActivity implements LoadMoreDelegate.OnLoadMoreListener { 
  private Items mItems = new Items(); 
  private LoadMoreDelegate mLoadMoreDelegate; 
  @Bind(R.id.show) 
  RecyclerView mShow; 
  
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.activity_pull_up); 
  ButterKnife.bind(this); 
  for (int i = 0; i < 20; i++) { 
  mItems.add("data***" + i); 
  } 
  
  MultiTypeAdapter multiTypeAdapter = new MultiTypeAdapter(mItems); 
  multiTypeAdapter.register(String.class, new NormalViewProvider()); 
  multiTypeAdapter.register(LoadMore.class, new LoadMoreViewProvider()); 
  mShow.setLayoutManager(new LinearLayoutManager(this)); 
  mShow.setAdapter(multiTypeAdapter); 
  mLoadMoreDelegate = new LoadMoreDelegate(multiTypeAdapter, mItems, this); 
  mLoadMoreDelegate.attach(mShow); 
  } 
  @Override 
  public void onLoadMore() { 
  getMore(); 
  } 
  private void getMore() { 
  new Thread(new Runnable() { 
  @Override 
  public void run() { 
  try { 
  Thread.sleep(2000); 
  runOnUiThread(new Runnable() { 
  @Override 
  public void run() { 
  Items strings = new Items(); 
  for (int i = 0; i < 20; i++) { 
  strings.add("data***more" + i); 
  } 
  mLoadMoreDelegate.addData(strings); 
  mLoadMoreDelegate.loadMoreComplete(); 
  } 
  }); 
  } catch (InterruptedException e) { 
  e.printStackTrace(); 
  } 
  
  } 
  }).start(); 
  } 
  } 
  

  还有一点提一下,这样的必须需要滑动界面才可以触发加载更多,如果第一屏数据不超过一屏,将没法触发加载更多.但这样我认为是合理的,如果第一页数据的请求就不满一屏,所以后面应该是在没有数据的.有些加载更多的实现是一到最后一个数据,就开始加载更多.但在第一页数据不满一屏的情况下,触发了加载很多,很违背直觉. BaseRecyclerViewAdapterHelper 就采用了这种实现,大家可以去看源码. 而且一般第一页的请求,我们一般会有自己的一个 loading 视图,这样不满一屏的情况下,还有一个加载更多的视图,这是不太合理的.

  
  

  以上 demo 仅供参考,大家可以进一步自己封装和实现.可以自己实现个 MultiTypeAdapter 并把代码整合到里面去,这样用起来可能会更方便点.

  
  

  效果图

  
   
  loadmore.gif