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
对于那些只想在最后一项完全显示时得到通知的人,可以使用view . canscrollvertical()。
这是我的实现:
public abstract class OnVerticalScrollListener
extends RecyclerView.OnScrollListener {
@Override
public final void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (!recyclerView.canScrollVertically(-1)) {
onScrolledToTop();
} else if (!recyclerView.canScrollVertically(1)) {
onScrolledToBottom();
} else if (dy < 0) {
onScrolledUp();
} else if (dy > 0) {
onScrolledDown();
}
}
public void onScrolledUp() {}
public void onScrolledDown() {}
public void onScrolledToTop() {}
public void onScrolledToBottom() {}
}
注意:如果你想支持API < 14,你可以使用recyclerView.getLayoutManager(). canscrollvertical()。
其他回答
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
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。
我使用了recyclerview。adapter的onBindViewHolder方法。
适配器:
public interface OnViewHolderListener {
void onRequestedLastItem();
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
...
if (position == getItemCount() - 1) onViewHolderListener.onRequestedLastItem();
}
片段(或活动):
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
contentView = inflater.inflate(R.layout.comments_list, container, false);
recyclerView = (RecyclerView) mContentView.findViewById(R.id.my_recycler_view);
adapter = new Adapter();
recyclerView.setAdapter(adapter);
...
adapter.setOnViewHolderListener(new Adapter.OnViewHolderListener() {
@Override
public void onRequestedLastItem() {
//TODO fetch new data from webservice
}
});
return contentView;
}
有一个易于使用的名为paginate的库。支持ListView和RecyclerView(线性布局,GridLayout和StaggeredGridLayout)。
这是该项目在Github上的链接
我已经创建LoadMoreRecyclerView使用Abdulaziz Noor回答
LoadMoreRecyclerView
public class LoadMoreRecyclerView extends RecyclerView {
private boolean loading = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;
//WrapperLinearLayout is for handling crash in RecyclerView
private WrapperLinearLayout mLayoutManager;
private Context mContext;
private OnLoadMoreListener onLoadMoreListener;
public LoadMoreRecyclerView(Context context) {
super(context);
mContext = context;
init();
}
public LoadMoreRecyclerView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
mContext = context;
init();
}
public LoadMoreRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mContext = context;
init();
}
private void init(){
mLayoutManager = new WrapperLinearLayout(mContext,LinearLayoutManager.VERTICAL,false);
this.setLayoutManager(mLayoutManager);
this.setItemAnimator(new DefaultItemAnimator());
this.setHasFixedSize(true);
}
@Override
public void onScrolled(int dx, int dy) {
super.onScrolled(dx, 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("...", "Call Load More !");
if(onLoadMoreListener != null){
onLoadMoreListener.onLoadMore();
}
//Do pagination.. i.e. fetch new data
}
}
}
}
@Override
public void onScrollStateChanged(int state) {
super.onScrollStateChanged(state);
}
public void onLoadMoreCompleted(){
loading = true;
}
public void setMoreLoading(boolean moreLoading){
loading = moreLoading;
}
public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {
this.onLoadMoreListener = onLoadMoreListener;
}
}
WrapperLinearLayout
public class WrapperLinearLayout extends LinearLayoutManager
{
public WrapperLinearLayout(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
try {
super.onLayoutChildren(recycler, state);
} catch (IndexOutOfBoundsException e) {
Log.e("probe", "meet a IOOBE in RecyclerView");
}
}
}
//在xml中添加
<your.package.LoadMoreRecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
</your.package.LoadMoreRecyclerView>
OnCreate或onViewCreated
mLoadMoreRecyclerView = (LoadMoreRecyclerView) view.findViewById(R.id.recycler_view);
mLoadMoreRecyclerView.setOnLoadMoreListener(new OnLoadMoreListener() {
@Override
public void onLoadMore() {
callYourService(StartIndex);
}
});
callYourService
private void callYourService(){
//callyour Service and get response in any List
List<AnyModelClass> newDataFromServer = getDataFromServerService();
//Enable Load More
mLoadMoreRecyclerView.onLoadMoreCompleted();
if(newDataFromServer != null && newDataFromServer.size() > 0){
StartIndex += newDataFromServer.size();
if (newDataFromServer.size() < Integer.valueOf(MAX_ROWS)) {
//StopLoading..
mLoadMoreRecyclerView.setMoreLoading(false);
}
}
else{
mLoadMoreRecyclerView.setMoreLoading(false);
mAdapter.notifyDataSetChanged();
}
}