我想把ListView改为RecyclerView。我想在RecyclerView中使用OnScrollListener的onScroll来确定用户是否滚动到列表的末尾。
我如何知道用户是否滚动到列表的末尾以便我可以从REST服务获取新数据?
我想把ListView改为RecyclerView。我想在RecyclerView中使用OnScrollListener的onScroll来确定用户是否滚动到列表的末尾。
我如何知道用户是否滚动到列表的末尾以便我可以从REST服务获取新数据?
当前回答
这里我的解决方案使用AsyncListUtil,在网络上说: 注意,这个类使用一个线程来加载数据,所以它适合从二级存储(如磁盘)加载数据,但不适合从网络加载数据。 但是我使用odata来读取数据并工作良好。 我在示例中遗漏了数据实体和网络方法。 我只包括示例适配器。
public class AsyncPlatoAdapter extends RecyclerView.Adapter {
private final AsyncPlatoListUtil mAsyncListUtil;
private final MainActivity mActivity;
private final RecyclerView mRecyclerView;
private final String mFilter;
private final String mOrderby;
private final String mExpand;
public AsyncPlatoAdapter(String filter, String orderby, String expand, RecyclerView recyclerView, MainActivity activity) {
mFilter = filter;
mOrderby = orderby;
mExpand = expand;
mRecyclerView = recyclerView;
mActivity = activity;
mAsyncListUtil = new AsyncPlatoListUtil();
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).
inflate(R.layout.plato_cardview, parent, false);
// Create a ViewHolder to find and hold these view references, and
// register OnClick with the view holder:
return new PlatoViewHolderAsync(itemView, this);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
final Plato item = mAsyncListUtil.getItem(position);
PlatoViewHolderAsync vh = (PlatoViewHolderAsync) holder;
if (item != null) {
Integer imagen_id = item.Imagen_Id.get();
vh.getBinding().setVariable(BR.plato, item);
vh.getBinding().executePendingBindings();
vh.getImage().setVisibility(View.VISIBLE);
vh.getProgress().setVisibility(View.GONE);
String cacheName = null;
String urlString = null;
if (imagen_id != null) {
cacheName = String.format("imagenes/imagen/%d", imagen_id);
urlString = String.format("%s/menusapi/%s", MainActivity.ROOTPATH, cacheName);
}
ImageHelper.downloadBitmap(mActivity, vh.getImage(), vh.getProgress(), urlString, cacheName, position);
} else {
vh.getBinding().setVariable(BR.plato, item);
vh.getBinding().executePendingBindings();
//show progress while loading.
vh.getImage().setVisibility(View.GONE);
vh.getProgress().setVisibility(View.VISIBLE);
}
}
@Override
public int getItemCount() {
return mAsyncListUtil.getItemCount();
}
public class AsyncPlatoListUtil extends AsyncListUtil<Plato> {
/**
* Creates an AsyncListUtil.
*/
public AsyncPlatoListUtil() {
super(Plato.class, //my data class
10, //page size
new DataCallback<Plato>() {
@Override
public int refreshData() {
//get count calling ../$count ... odata endpoint
return countPlatos(mFilter, mOrderby, mExpand, mActivity);
}
@Override
public void fillData(Plato[] data, int startPosition, int itemCount) {
//get items from odata endpoint using $skip and $top
Platos p = loadPlatos(mFilter, mOrderby, mExpand, startPosition, itemCount, mActivity);
for (int i = 0; i < Math.min(itemCount, p.value.size()); i++) {
data[i] = p.value.get(i);
}
}
}, new ViewCallback() {
@Override
public void getItemRangeInto(int[] outRange) {
//i use LinearLayoutManager in the RecyclerView
LinearLayoutManager layoutManager = (LinearLayoutManager) mRecyclerView.getLayoutManager();
outRange[0] = layoutManager.findFirstVisibleItemPosition();
outRange[1] = layoutManager.findLastVisibleItemPosition();
}
@Override
public void onDataRefresh() {
mRecyclerView.getAdapter().notifyDataSetChanged();
}
@Override
public void onItemLoaded(int position) {
mRecyclerView.getAdapter().notifyItemChanged(position);
}
});
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
onRangeChanged();
}
});
}
}
}
其他回答
检查的每一件事都有详细的解释: 使用RecyclerView从A到Z分页
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView,
int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int visibleItemCount = mLayoutManager.getChildCount();
int totalItemCount = mLayoutManager.getItemCount();
int firstVisibleItemPosition = mLayoutManager.findFirstVisibleItemPosition();
if (!mIsLoading && !mIsLastPage) {
if ((visibleItemCount + firstVisibleItemPosition) >= totalItemCount
&& firstVisibleItemPosition >= 0) {
loadMoreItems();
}
}
}
})
loadMoreItems ():
private void loadMoreItems() {
mAdapter.removeLoading();
//load data here from the server
// in case of success
mAdapter.addData(data);
// if there might be more data
mAdapter.addLoading();
}
在MyAdapter中:
private boolean mIsLoadingFooterAdded = false;
public void addLoading() {
if (!mIsLoadingFooterAdded) {
mIsLoadingFooterAdded = true;
mLineItemList.add(new LineItem());
notifyItemInserted(mLineItemList.size() - 1);
}
}
public void removeLoading() {
if (mIsLoadingFooterAdded) {
mIsLoadingFooterAdded = false;
int position = mLineItemList.size() - 1;
LineItem item = mLineItemList.get(position);
if (item != null) {
mLineItemList.remove(position);
notifyItemRemoved(position);
}
}
}
public void addData(List<YourDataClass> data) {
for (int i = 0; i < data.size(); i++) {
YourDataClass yourDataObject = data.get(i);
mLineItemList.add(new LineItem(yourDataObject));
notifyItemInserted(mLineItemList.size() - 1);
}
}
我有一个关于如何使用RecyclerView进行分页的非常详细的示例。在高层次,我有一个设置PAGE_SIZE,让我们说30。所以我请求30个项目,如果我得到30个,我就请求下一页。如果我得到的条目少于30个,我就标记一个变量来指示已经到达最后一页,然后停止请求更多的页面。看看吧,告诉我你的想法。
https://medium.com/@etiennelawlor/pagination-with-recyclerview-1cb7e66a502b
@kushal @abdulaziz
为什么不使用这个逻辑呢?
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
int totalItemCount, lastVisibleItemPosition;
if (dy > 0) {
totalItemCount = _layoutManager.getItemCount();
lastVisibleItemPosition = _layoutManager.findLastVisibleItemPosition();
if (!_isLastItem) {
if ((totalItemCount - 1) == lastVisibleItemPosition) {
LogUtil.e("end_of_list");
_isLastItem = true;
}
}
}
}
有一个方法public void setOnScrollListener (RecyclerView。OnScrollListener监听器)在https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html#setOnScrollListener%28android.support.v7.widget.RecyclerView.OnScrollListener%29。使用这个
编辑:
在onScrollListener中重写onScrollStateChanged方法并执行此操作
boolean loadMore = firstVisibleItem + visibleItemCount >= totalItemCount;
//loading is used to see if its already loading, you have to manually manipulate this boolean variable
if (loadMore && !loading) {
//end of list reached
}
Create an abstract class and extends RecyclerView.OnScrollListener public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener { private int previousTotal = 0; private boolean loading = true; private int visibleThreshold; private int firstVisibleItem, visibleItemCount, totalItemCount; private RecyclerView.LayoutManager layoutManager; public EndlessRecyclerOnScrollListener(RecyclerView.LayoutManager layoutManager, int visibleThreshold) { this.layoutManager = layoutManager; this.visibleThreshold = visibleThreshold; } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); visibleItemCount = recyclerView.getChildCount(); totalItemCount = layoutManager.getItemCount(); firstVisibleItem = ((LinearLayoutManager)layoutManager).findFirstVisibleItemPosition(); if (loading) { if (totalItemCount > previousTotal) { loading = false; previousTotal = totalItemCount; } } if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) { onLoadMore(); loading = true; } } public abstract void onLoadMore();} in activity (or fragment) add addOnScrollListener to recyclerView LinearLayoutManager mLayoutManager = new LinearLayoutManager(this); recyclerView.setLayoutManager(mLayoutManager); recyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager, 3) { @Override public void onLoadMore() { //TODO ... } });