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
对于使用StaggeredGridLayoutManager的人,这是我的实现,它适用于我。
private class ScrollListener extends RecyclerView.OnScrollListener {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
firstVivisibleItems = mLayoutManager.findFirstVisibleItemPositions(firstVivisibleItems);
if(!recyclerView.canScrollVertically(1) && firstVivisibleItems[0]!=0) {
loadMoreImages();
}
}
private boolean loadMoreImages(){
Log.d("myTag", "LAST-------HERE------");
return true;
}
}
其他回答
没有重复调用,但你滚动。fetchData只会在您位于列表的末尾并且有更多数据要获取时调用
关于我的代码: 1.fetchData()每次调用取10个项。 2.isScrolling是一个类成员变量 3.previousTotalCount也是类成员。它存储以前访问过的最后一个项目
recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
isScrolling = true
}
}
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
val visibleItemCount = layoutManager.childCount
val totalItemCount = layoutManager.itemCount
val scrolledOutItems = layoutManager.findFirstVisibleItemPosition()
if (isScrolling && (visibleItemCount + scrolledOutItems == totalItemCount)
&& (visibleItemCount + scrolledOutItems != previousTotalCount)) {
previousTotalCount = totalItemCount
isScrolling = false
fetchData() //fetches 10 new items from Firestore
pagingProgressBar.visibility = View.VISIBLE
}
}
})
我的答案是一个改良版的努尔。我从一个ListView,在那里我有EndlessScrollListener(你可以很容易地在SO上找到许多答案)到一个RecyclerView,所以我想要一个endlessrecyscrolllistener轻松地更新我过去的监听器。
下面是代码,希望能有所帮助:
public abstract class EndlessScrollRecyclListener extends RecyclerView.OnScrollListener
{
// The total number of items in the dataset after the last load
private int previousTotalItemCount = 0;
private boolean loading = true;
private int visibleThreshold = 5;
int firstVisibleItem, visibleItemCount, totalItemCount;
private int startingPageIndex = 0;
private int currentPage = 0;
@Override
public void onScrolled(RecyclerView mRecyclerView, int dx, int dy)
{
super.onScrolled(mRecyclerView, dx, dy);
LinearLayoutManager mLayoutManager = (LinearLayoutManager) mRecyclerView
.getLayoutManager();
visibleItemCount = mRecyclerView.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();
onScroll(firstVisibleItem, visibleItemCount, totalItemCount);
}
public void onScroll(int firstVisibleItem, int visibleItemCount, int totalItemCount)
{
// 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;
currentPage++;
}
// 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.
if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem +
visibleThreshold))
{
onLoadMore(currentPage + 1, totalItemCount);
loading = true;
}
}
// Defines the process for actually loading more data based on page
public abstract void onLoadMore(int page, int totalItemsCount);
}
做这些变量。
private int previousTotal = 0;
private boolean loading = true;
private int visibleThreshold = 5;
int firstVisibleItem, visibleItemCount, totalItemCount;
设置为滚动回收视图。
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
visibleItemCount = mRecyclerView.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
}
}
if (!loading && (totalItemCount - visibleItemCount)
<= (firstVisibleItem + visibleThreshold)) {
// End has been reached
Log.i("Yaeye!", "end called");
// Do something
loading = true;
}
}
});
注意:确保你使用LinearLayoutManager作为RecyclerView的布局管理器。
LinearLayoutManager mLayoutManager;
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);
对于网格来说
GridLayoutManager mLayoutManager;
mLayoutManager = new GridLayoutManager(getActivity(), spanCount);
mRecyclerView.setLayoutManager(mLayoutManager);
有乐趣与你无尽的卷轴!!^ ^。
更新:mRecyclerView.setOnScrollListener()已弃用,只需替换为mRecyclerView.addOnScrollListener(),警告将消失!你可以从这个SO问题中读到更多。
由于Android现在正式支持Kotlin,这里是相同的更新-
使OnScrollListener
class OnScrollListener(val layoutManager: LinearLayoutManager, val adapter: RecyclerView.Adapter<RecyclerAdapter.ViewHolder>, val dataList: MutableList<Int>) : RecyclerView.OnScrollListener() {
var previousTotal = 0
var loading = true
val visibleThreshold = 10
var firstVisibleItem = 0
var visibleItemCount = 0
var totalItemCount = 0
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
visibleItemCount = recyclerView.childCount
totalItemCount = layoutManager.itemCount
firstVisibleItem = layoutManager.findFirstVisibleItemPosition()
if (loading) {
if (totalItemCount > previousTotal) {
loading = false
previousTotal = totalItemCount
}
}
if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
val initialSize = dataList.size
updateDataList(dataList)
val updatedSize = dataList.size
recyclerView.post { adapter.notifyItemRangeInserted(initialSize, updatedSize) }
loading = true
}
}
}
然后像这样把它添加到你的RecyclerView中
recyclerView.addOnScrollListener(OnScrollListener(layoutManager, adapter, dataList))
要获得完整的代码示例,请参阅Github repo。
我让你接近我。对我来说没问题。
我希望这对你有所帮助。
/**
* Created by Daniel Pardo Ligorred on 03/03/2016.
*/
public abstract class BaseScrollListener extends RecyclerView.OnScrollListener {
protected RecyclerView.LayoutManager layoutManager;
public BaseScrollListener(RecyclerView.LayoutManager layoutManager) {
this.layoutManager = layoutManager;
this.init();
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
this.onScroll(recyclerView, this.getFirstVisibleItem(), this.layoutManager.getChildCount(), this.layoutManager.getItemCount(), dx, dy);
}
private int getFirstVisibleItem(){
if(this.layoutManager instanceof LinearLayoutManager){
return ((LinearLayoutManager) this.layoutManager).findFirstVisibleItemPosition();
} else if (this.layoutManager instanceof StaggeredGridLayoutManager){
int[] spanPositions = null; //Should be null -> StaggeredGridLayoutManager.findFirstVisibleItemPositions makes the work.
try{
return ((StaggeredGridLayoutManager) this.layoutManager).findFirstVisibleItemPositions(spanPositions)[0];
}catch (Exception ex){
// Do stuff...
}
}
return 0;
}
public abstract void init();
protected abstract void onScroll(RecyclerView recyclerView, int firstVisibleItem, int visibleItemCount, int totalItemCount, int dx, int dy);
}
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);
}
}