我已使用Recycler视图成功实施了Endless Scrolling。我正在使用this代码，这完全有效但除了以下情况
案例1：当列表中有2个项目小于屏幕大小时，它看起来像OnLoadMore再次调用，因为它发现自己到达列表的末尾
我在做什么：我从1个片段中获取列表然后将此列表发送到另一个片段，在该片段中有一个带有onScroll列表器的RecyclerView，如下所示：
recyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager) {
@Override
public void onLoadMore(int page, int totalItemsCount) {
// do something...
currentVisiblePosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstCompletelyVisibleItemPosition();
pageNumber = pageNumber + 1;
CallingMyApi();
}
});
混淆：
所以我可以猜测它是问题，因为列表视图中的项目较少如何控制，请帮帮我？
更新1：我的片段代码
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
mAdapter = new EnrollmentSearchAdapter(getActivity(), parentList);
rvSearchEnrollments.addOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager) {
@Override
public void onLoadMore(int page, int totalItemsCount) {
// do something...
if(parentList!=null && parentList.size()>3) { // just checking my own that 3 items should not be minimum to screen size , where as here it should be more flexible solution
currentVisiblePosition = ((LinearLayoutManager) rvSearchEnrollments.getLayoutManager()).findFirstCompletelyVisibleItemPosition();
pageNumber = pageNumber + 1;
SearchSundaySchoolParentsCouples searchSundaySchoolParentsCouples = new SearchSundaySchoolParentsCouples(keyword, 20, pageNumber, getActivity());
searchSundaySchoolParentsCouples.execute();
}
}
});
rvSearchEnrollments.addItemDecoration(new SimpleDividerItemDecoration(getActivity()));
rvSearchEnrollments.setAdapter(mAdapter);
}
答案 0 :(得分：4)
使用EndlessRecyclerViewScrollListener OnScrollListener子类（来自流行的Gist）。当列表中的项目小于屏幕尺寸时，您需要更改一些内容才能使无尽的Scrolling RecyclerView正常工作。
以下是您需要添加到EndlessRecyclerViewScrollListener课程的内容：
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState)
{
super.onScrollStateChanged(recyclerView, newState);
// Don't do any work until after the ScrollEvent has ended, so do the following check.
if (newState == RecyclerView.SCROLL_STATE_IDLE)
{
// supply a positive number to recyclerView.canScrollVertically(int direction) to check if scrolling down.
boolean canScrollDownMore = recyclerView.canScrollVertically(1);
// If recyclerView.canScrollVertically(1) returns false it means you're at the end of the list.
if (!canScrollDownMore)
{
//call the overridden onScrolled() method in our EndlessRecyclerViewScrollListener class.
// supply any positive number to the third argument to indicate that we've scrolled downward.
onScrolled(recyclerView, 0, 1);
}
}
}
说明：我们需要实现onScrollStateChanged()方法，因为在列表末尾没有调用onScrolled()，或者至少它没有被调用当列表中的项目小于屏幕大小时调用。
以下是整个EndlessRecyclerViewScrollListener课程，其中包含您需要的更新内容：
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;
private RecyclerView.LayoutManager layoutManager;
public void setLayoutManager(RecyclerView.LayoutManager layoutManager)
{
this.layoutManager = layoutManager;
}
public RecyclerView.LayoutManager getLayoutManager()
{
return layoutManager;
}
public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager)
{
this.layoutManager = layoutManager;
}
public EndlessRecyclerViewScrollListener(GridLayoutManager layoutManager, int visibleThreshold)
{
this.layoutManager = layoutManager;
this.visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
}
public EndlessRecyclerViewScrollListener(
StaggeredGridLayoutManager layoutManager,
int visibleThreshold)
{
this.layoutManager = layoutManager;
this.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)
{
if (dy < 1)
{
// don't do anything when scrolling up.
return;
}
int lastVisibleItemPosition = 0;
int totalItemCount = layoutManager.getItemCount();
if (layoutManager instanceof StaggeredGridLayoutManager)
{
int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) layoutManager).findLastVisibleItemPositions(null);
// get maximum element within the list
lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions);
}
else if (layoutManager instanceof GridLayoutManager)
{
lastVisibleItemPosition = ((GridLayoutManager) layoutManager).findLastVisibleItemPosition();
}
else if (layoutManager instanceof LinearLayoutManager)
{
lastVisibleItemPosition = ((LinearLayoutManager) layoutManager).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, view);
loading = true;
}
}
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState)
{
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_IDLE)
{
// supply a positive number to recyclerView.canScrollVertically(int direction) to check if scrolling down.
boolean canScrollDownMore = recyclerView.canScrollVertically(1);
// If recyclerView.canScrollVertically(1) returns false it means you're at the end of the list.
if (!canScrollDownMore)
{
onScrolled(recyclerView, 0, 1);
}
}
}
// Call this method whenever performing new searches on in onRefresh() if using SwipeRefresh
public void resetState()
{
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = 0;
this.loading = true;
}
// Defines the process for actually loading more data based on page
public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view);
}
简要使用示例：（more info here）
public class MainActivity extends Activity {
// Store a member variable for the listener
private EndlessRecyclerViewScrollListener scrollListener;
@Override
protected void onCreate(Bundle savedInstanceState) {
// Configure the RecyclerView
RecyclerView rvItems = (RecyclerView) findViewById(R.id.rvContacts);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
rvItems.setLayoutManager(linearLayoutManager);
// Retain an instance so that you can call `resetState()` for fresh searches
scrollListener = new EndlessRecyclerViewScrollListener(linearLayoutManager) {
@Override
public void onLoadMore(int page, int totalItemsCount, RecyclerView view) {
// 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
loadNextDataFromApi(page);
}
};
// Adds the scroll listener to RecyclerView
rvItems.addOnScrollListener(scrollListener);
}
// Append the next page of data into the adapter
// This method probably sends out a network request and appends new data items to your adapter.
public void loadNextDataFromApi(int offset) {
// Send an API request to retrieve appropriate paginated data
// --> Send the request including an offset value (i.e `page`) as a query parameter.
// --> Deserialize and construct new model objects from the API response
// --> Append the new data objects to the existing set of items inside the array of items
// --> Notify the adapter of the new items made with `notifyItemRangeInserted()`
}
}
您可能需要稍微修改一下以使其在您的方案中正常工作，但所提供的代码是一个很好的起点。
答案 1 :(得分：1)
如果列表小于屏幕尺寸
，您可以在recyclerview中加载更多类似的任务@Override
public void onBindViewHolder(DataObjectHolder holder, int position) {
holder.label.setText(mDataset.get(position).getmText1());
holder.dateTime.setText(mDataset.get(position).getmText2());
if (position == this.getItemCount() - 1 && !loading){
// do your load more task here
}
}
答案 2 :(得分：-1)
private boolean loading = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener()
{
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy)
{
if(dy > 0) //check for scroll down
{
visibleItemCount = mLayoutManager.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
if (loading)
{
if ( (visibleItemCount + pastVisiblesItems) >= totalItemCount)
{
loading = false;
Log.v("...", "Last Item Wow !");
//Do pagination.. i.e. fetch new data
}
}
}
}
});
//Don't forgot to implement this
LinearLayoutManager mLayoutManager;
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);