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
感谢@Kushal,这是我实现它的方式
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
loading = true;
}
}
}
}
});
别忘了加上
LinearLayoutManager mLayoutManager;
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);
其他回答
我在我的RecyclerView的onBindViewHolder方法中使用此逻辑实现了无限滚动类型。适配器类。
if (position == mItems.size() - 1 && mCurrentPage <= mTotalPageCount) {
if (mCurrentPage == mTotalPageCount) {
mLoadImagesListener.noMorePages();
} else {
int newPage = mCurrentPage + 1;
mLoadImagesListener.loadPage(newPage);
}
}
使用这段代码,当RecyclerView到达最后一项时,它会增加当前页面和接口上的回调,该接口负责从api加载更多数据并将新结果添加到适配器。
我可以张贴更完整的例子,如果这不是很清楚?
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);
}
}
这个解决方案对我来说非常有效。
//Listener
public abstract class InfiniteScrollListener extendsRecyclerView.OnScrollListener {
public static String TAG = InfiniteScrollListener.class.getSimpleName();
int firstVisibleItem, visibleItemCount, totalItemCount;
private int previousTotal = 0;
private boolean loading = true;
private int visibleThreshold = 1;
private int current_page = 1;
private LinearLayoutManager mLinearLayoutManager;
public InfiniteScrollListener(LinearLayoutManager linearLayoutManager) {
this.mLinearLayoutManager = linearLayoutManager;
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
visibleItemCount = recyclerView.getChildCount();
totalItemCount = mLinearLayoutManager.getItemCount();
firstVisibleItem = mLinearLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
}
}
if (!loading && (totalItemCount - visibleItemCount - firstVisibleItem <= visibleThreshold)) {
current_page++;
onLoadMore(current_page);
loading = true;
}
}
public void resetState() {
loading = true;
previousTotal = 0;
current_page = 1;
}
public abstract void onLoadMore(int current_page);
}
//Implementation into fragment
private InfiniteScrollListener scrollListener;
scrollListener = new InfiniteScrollListener(manager) {
@Override
public void onLoadMore(int current_page) {
//Load data
}
};
rv.setLayoutManager(manager);
rv.addOnScrollListener(scrollListener);
@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;
}
}
}
}
大多数答案是假设RecyclerView使用LinearLayoutManager,或GridLayoutManager,甚至StaggeredGridLayoutManager,或假设滚动是垂直或水平的,但没有人张贴一个完全通用的答案。
使用ViewHolder的适配器显然不是一个好的解决方案。一个适配器可能有超过1个RecyclerView在使用它。它“改编”了它们的内容。它应该是RecyclerView(它是一个负责当前显示给用户的类,而不是适配器,它只负责向RecyclerView提供内容),它必须通知您的系统需要更多的项(加载)。
下面是我的解决方案,只使用了RecyclerView (RecycerView. view)的抽象类。LayoutManager和RecycerView.Adapter):
/**
* Listener to callback when the last item of the adpater is visible to the user.
* It should then be the time to load more items.
**/
public abstract class LastItemListener extends RecyclerView.OnScrollListener {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// init
RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
RecyclerView.Adapter adapter = recyclerView.getAdapter();
if (layoutManager.getChildCount() > 0) {
// Calculations..
int indexOfLastItemViewVisible = layoutManager.getChildCount() -1;
View lastItemViewVisible = layoutManager.getChildAt(indexOfLastItemViewVisible);
int adapterPosition = layoutManager.getPosition(lastItemViewVisible);
boolean isLastItemVisible = (adapterPosition == adapter.getItemCount() -1);
// check
if (isLastItemVisible)
onLastItemVisible(); // callback
}
}
/**
* Here you should load more items because user is seeing the last item of the list.
* Advice: you should add a bollean value to the class
* so that the method {@link #onLastItemVisible()} will be triggered only once
* and not every time the user touch the screen ;)
**/
public abstract void onLastItemVisible();
}
// --- Exemple of use ---
myRecyclerView.setOnScrollListener(new LastItemListener() {
public void onLastItemVisible() {
// start to load more items here.
}
}