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
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);
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.
}
}
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();
}
}
我是这样做的,简单而简短:
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener()
{
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy)
{
if(!recyclerView.canScrollVertically(1) && dy != 0)
{
// Load more results here
}
}
});
对我来说,这很简单:
private boolean mLoading = false;
mList.setOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int totalItem = mLinearLayoutManager.getItemCount();
int lastVisibleItem = mLinearLayoutManager.findLastVisibleItemPosition();
if (!mLoading && lastVisibleItem == totalItem - 1) {
mLoading = true;
// Scrolled to bottom. Do something here.
mLoading = false;
}
}
});
小心异步作业:mLoading必须在异步作业结束时更改。希望对大家有所帮助!