[英]Detect when RecyclerView reaches the bottom most position while scrolling
我有一個 RecyclerView 的代碼。
recyclerView = (RecyclerView)rootview.findViewById(R.id.fabric_recyclerView);
recyclerView.setLayoutManager(layoutManager);
recyclerView.addItemDecoration(new RV_Item_Spacing(5));
FabricAdapter fabricAdapter=new FabricAdapter(ViewAdsCollection.getFabricAdsDetailsAsArray());
recyclerView.setAdapter(fabricAdapter);
我需要知道滾動時 RecyclerView 何時到達最底部 position。 可能嗎? 如果是,如何?
還有一個簡單的方法來做到這一點
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (!recyclerView.canScrollVertically(1)) {
Toast.makeText(YourActivity.this, "Last", Toast.LENGTH_LONG).show();
}
}
});
方向整數:-1 向上,1 向下,0 將始終返回 false。
使用此代碼避免重復調用
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (!recyclerView.canScrollVertically(1) && newState==RecyclerView.SCROLL_STATE_IDLE) {
Log.d("-----","end");
}
}
});
只需在您的 recyclerview 上實現 addOnScrollListener() 即可。 然后在滾動監聽器內部實現下面的代碼。
RecyclerView.OnScrollListener mScrollListener = new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (mIsLoading)
return;
int visibleItemCount = mLayoutManager.getChildCount();
int totalItemCount = mLayoutManager.getItemCount();
int pastVisibleItems = mLayoutManager.findFirstVisibleItemPosition();
if (pastVisibleItems + visibleItemCount >= totalItemCount) {
//End of list
}
}
};
答案是在 Kotlin 中,它將在 Java 中工作。 如果您復制和粘貼,IntelliJ 應該為您轉換它。
recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener(){
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
// 3 lines below are not needed.
Log.d("TAG","Last visible item is: ${gridLayoutManager.findLastVisibleItemPosition()}")
Log.d("TAG","Item count is: ${gridLayoutManager.itemCount}")
Log.d("TAG","end? : ${gridLayoutManager.findLastVisibleItemPosition() == gridLayoutManager.itemCount-1}")
if(gridLayoutManager.findLastVisibleItemPosition() == gridLayoutManager.itemCount-1){
// We have reached the end of the recycler view.
}
super.onScrolled(recyclerView, dx, dy)
}
})
這也適用於LinearLayoutManager
,因為它具有上面使用的相同方法。 即findLastVisibleItemPosition()
和getItemCount()
(Kotlin 中的itemCount
)。
在對該線程中的大多數其他答案不滿意之后,我發現了一些我認為更好的東西,而且這里沒有任何地方。
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (!recyclerView.canScrollVertically(1) && dy > 0)
{
//scrolled to BOTTOM
}else if (!recyclerView.canScrollVertically(-1) && dy < 0)
{
//scrolled to TOP
}
}
});
這很簡單,並且當您滾動到頂部或底部時,在所有條件下都會恰好點擊一次。
通過上述答案,我沒有得到完美的解決方案,因為即使在onScrolled
上它也會觸發兩次
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
if( !recyclerView.canScrollVertically(RecyclerView.FOCUS_DOWN))
context?.toast("Scroll end reached")
}
我幾天前發現的替代解決方案,
rv_repatriations.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (!recyclerView.canScrollVertically(RecyclerView.FOCUS_DOWN) && recyclerView.scrollState == RecyclerView.SCROLL_STATE_IDLE
&& !isLoaded
) {
isLoaded = true
//do what you want here and after calling the function change the value of boolean
Log.e("RepatriationFragment", "Scroll end reached")
}
}
})
使用布爾值來確保當我們觸底時它不會被多次調用。
我已經使用了上面的答案,當您在回收站視圖結束時,它總是運行,
如果您只想檢查一次它是否在底部? 示例:-如果我在底部時有 10 個項目的列表,它會顯示我,如果我從上到下滾動它不會再次打印,如果你添加更多列表並且你去那里它會再次顯示。
注意:-當您處理命中 API 的偏移時使用此方法
創建一個名為 EndlessRecyclerViewScrollListener 的類
import android.support.v7.widget.GridLayoutManager; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.support.v7.widget.StaggeredGridLayoutManager; public abstract class EndlessRecyclerViewScrollListener extends RecyclerView.OnScrollListener { // The minimum amount of items to have below your current scroll position // before loading more. private int visibleThreshold = 5; // The current offset index of data you have loaded private int currentPage = 0; // The total number of items in the dataset after the last load private int previousTotalItemCount = 0; // True if we are still waiting for the last set of data to load. private boolean loading = true; // Sets the starting page index private int startingPageIndex = 0; RecyclerView.LayoutManager mLayoutManager; public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager) { this.mLayoutManager = layoutManager; } // public EndlessRecyclerViewScrollListener() { // this.mLayoutManager = layoutManager; // visibleThreshold = visibleThreshold * layoutManager.getSpanCount(); // } public EndlessRecyclerViewScrollListener(StaggeredGridLayoutManager layoutManager) { this.mLayoutManager = layoutManager; visibleThreshold = visibleThreshold * layoutManager.getSpanCount(); } public int getLastVisibleItem(int[] lastVisibleItemPositions) { int maxSize = 0; for (int i = 0; i < lastVisibleItemPositions.length; i++) { if (i == 0) { maxSize = lastVisibleItemPositions[i]; } else if (lastVisibleItemPositions[i] > maxSize) { maxSize = lastVisibleItemPositions[i]; } } return maxSize; } // This happens many times a second during a scroll, so be wary of the code you place here. // We are given a few useful parameters to help us work out if we need to load some more data, // but first we check if we are waiting for the previous load to finish. @Override public void onScrolled(RecyclerView view, int dx, int dy) { int lastVisibleItemPosition = 0; int totalItemCount = mLayoutManager.getItemCount(); if (mLayoutManager instanceof StaggeredGridLayoutManager) { int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastVisibleItemPositions(null); // get maximum element within the list lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions); } else if (mLayoutManager instanceof GridLayoutManager) { lastVisibleItemPosition = ((GridLayoutManager) mLayoutManager).findLastVisibleItemPosition(); } else if (mLayoutManager instanceof LinearLayoutManager) { lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition(); } // 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; } // 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. // threshold should reflect how many total columns there are too if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) { currentPage++; onLoadMore(currentPage, totalItemCount, view); loading = true; } } // Call this method whenever performing new searches public void resetState() { this.currentPage = this.startingPageIndex; this.previousTotalItemCount = 0; this.loading = true; } // Defines the process for actually loading more data based on page public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view); }
像這樣使用這個類
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity()); recyclerView.setLayoutManager(linearLayoutManager); recyclerView.addOnScrollListener(new EndlessRecyclerViewScrollListener( linearLayoutManager) { @Override public void onLoadMore(int page, int totalItemsCount, RecyclerView view) { Toast.makeText(getActivity(),"LAst",Toast.LENGTH_LONG).show(); } });
它在我的最后運行完美,如果您遇到任何問題,請評論我
有我的實現,它對StaggeredGridLayout
非常有用。
用法 :
private EndlessScrollListener scrollListener =
new EndlessScrollListener(new EndlessScrollListener.RefreshList() {
@Override public void onRefresh(int pageNumber) {
//end of the list
}
});
rvMain.addOnScrollListener(scrollListener);
監聽器實現:
class EndlessScrollListener extends RecyclerView.OnScrollListener {
private boolean isLoading;
private boolean hasMorePages;
private int pageNumber = 0;
private RefreshList refreshList;
private boolean isRefreshing;
private int pastVisibleItems;
EndlessScrollListener(RefreshList refreshList) {
this.isLoading = false;
this.hasMorePages = true;
this.refreshList = refreshList;
}
@Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
StaggeredGridLayoutManager manager =
(StaggeredGridLayoutManager) recyclerView.getLayoutManager();
int visibleItemCount = manager.getChildCount();
int totalItemCount = manager.getItemCount();
int[] firstVisibleItems = manager.findFirstVisibleItemPositions(null);
if (firstVisibleItems != null && firstVisibleItems.length > 0) {
pastVisibleItems = firstVisibleItems[0];
}
if (visibleItemCount + pastVisibleItems >= totalItemCount && !isLoading) {
isLoading = true;
if (hasMorePages && !isRefreshing) {
isRefreshing = true;
new Handler().postDelayed(new Runnable() {
@Override public void run() {
refreshList.onRefresh(pageNumber);
}
}, 200);
}
} else {
isLoading = false;
}
}
public void noMorePages() {
this.hasMorePages = false;
}
void notifyMorePages() {
isRefreshing = false;
pageNumber = pageNumber + 1;
}
interface RefreshList {
void onRefresh(int pageNumber);
} }
我也在尋找這個問題,但我沒有找到讓我滿意的答案,所以我創建了自己的recyclerView實現。
其他解決方案不如我的精確。 例如:如果最后一項非常大(大量文本),那么其他解決方案的回調將早得多,然后 recyclerView 真正達到底部。
我的解決方案解決了這個問題。
class CustomRecyclerView: RecyclerView{
abstract class TopAndBottomListener{
open fun onBottomNow(onBottomNow:Boolean){}
open fun onTopNow(onTopNow:Boolean){}
}
constructor(c:Context):this(c, null)
constructor(c:Context, attr:AttributeSet?):super(c, attr, 0)
constructor(c:Context, attr:AttributeSet?, defStyle:Int):super(c, attr, defStyle)
private var linearLayoutManager:LinearLayoutManager? = null
private var topAndBottomListener:TopAndBottomListener? = null
private var onBottomNow = false
private var onTopNow = false
private var onBottomTopScrollListener:RecyclerView.OnScrollListener? = null
fun setTopAndBottomListener(l:TopAndBottomListener?){
if (l != null){
checkLayoutManager()
onBottomTopScrollListener = createBottomAndTopScrollListener()
addOnScrollListener(onBottomTopScrollListener)
topAndBottomListener = l
} else {
removeOnScrollListener(onBottomTopScrollListener)
topAndBottomListener = null
}
}
private fun createBottomAndTopScrollListener() = object :RecyclerView.OnScrollListener(){
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
checkOnTop()
checkOnBottom()
}
}
private fun checkOnTop(){
val firstVisible = linearLayoutManager!!.findFirstCompletelyVisibleItemPosition()
if(firstVisible == 0 || firstVisible == -1 && !canScrollToTop()){
if (!onTopNow) {
onTopNow = true
topAndBottomListener?.onTopNow(true)
}
} else if (onTopNow){
onTopNow = false
topAndBottomListener?.onTopNow(false)
}
}
private fun checkOnBottom(){
var lastVisible = linearLayoutManager!!.findLastCompletelyVisibleItemPosition()
val size = linearLayoutManager!!.itemCount - 1
if(lastVisible == size || lastVisible == -1 && !canScrollToBottom()){
if (!onBottomNow){
onBottomNow = true
topAndBottomListener?.onBottomNow(true)
}
} else if(onBottomNow){
onBottomNow = false
topAndBottomListener?.onBottomNow(false)
}
}
private fun checkLayoutManager(){
if (layoutManager is LinearLayoutManager)
linearLayoutManager = layoutManager as LinearLayoutManager
else
throw Exception("for using this listener, please set LinearLayoutManager")
}
private fun canScrollToTop():Boolean = canScrollVertically(-1)
private fun canScrollToBottom():Boolean = canScrollVertically(1)
}
然后在您的活動/片段中:
override fun onCreate() {
customRecyclerView.layoutManager = LinearLayoutManager(context)
}
override fun onResume() {
super.onResume()
customRecyclerView.setTopAndBottomListener(this)
}
override fun onStop() {
super.onStop()
customRecyclerView.setTopAndBottomListener(null)
}
希望它會幫助某人;-)
使用 Kotlin
recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
if (!recyclerView.canScrollVertically(1)) {
Toast.makeText(context, "Last", Toast.LENGTH_LONG).show();
}
}
})
科特林答案
您可以使用此 Kotlin 函數來實現底部滾動跟隨的最佳實踐,以創建無限或無限滾動。
// Scroll listener.
private fun setupListenerPostListScroll() {
val scrollDirectionDown = 1 // Scroll down is +1, up is -1.
var currentListSize = 0
mRecyclerView.addOnScrollListener(
object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (!recyclerView.canScrollVertically(scrollDirectionDown)
&& newState == RecyclerView.SCROLL_STATE_IDLE
) {
val listSizeAfterLoading = recyclerView.layoutManager!!.itemCount
// List has more item.
if (currentListSize != listSizeAfterLoading) {
currentListSize = listSizeAfterLoading
// Get more posts.
postListScrollUpAction(listSizeAfterLoading)
}
else { // List comes limit.
showToastMessageShort("No more items.")
}
}
}
})
}
我已經看到很多關於這個問題的回答,我認為他們都沒有給出准確的行為作為結果。 但是,如果您遵循這種方法,我很肯定您將獲得最佳行為。
rvCategories是你的 RecyclerView
categoriesList是傳遞給您的適配器的列表
binding.rvCategories.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
val position = (recyclerView.layoutManager as LinearLayoutManager).findLastCompletelyVisibleItemPosition()
if (position + 1 == categoriesList.size) {
// END OF RECYCLERVIEW IS REACHED
} else {
// END OF RECYCLERVIEW IS NOT REACHED
}
}
})
你可以使用這個,如果你放 1 那將在你停留在列表末尾時顯示,如果你現在想要當你停留在列表的開頭時,你將 1 更改為 -1
recyclerChat.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (!recyclerView.canScrollVertically(1)) {
}
}
})
這是我在閱讀了這篇文章中的所有答案后的解決方案。 我只想在最后一項顯示在列表末尾並且listview
長度大於屏幕高度時顯示loading
,這意味着如果列表中只有一個或兩個項目,則不會顯示loading
。
private var isLoadMoreLoading: Boolean = false
mRecyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (!isLoadMoreLoading) {
if (linearLayoutManager.findLastCompletelyVisibleItemPosition() == (list.size-1)) {
if (recyclerView.canScrollVertically(-1)) {
adapter?.addLoadMoreView()
loadMore()
}
}
}
}
})
private fun loadMore() {
isLoadMoreLoading = true
//call loadMore api
}
由於這個linearLayoutManager.findLastCompletelyVisibleItemPosition() == (list.size-1)
,我們可以知道最后一個項目是否顯示,但我們還需要知道 listview 是否可以滾動。
因此我添加了recyclerView.canScrollVertically(-1)
。 一旦你點擊列表的底部,它就不能再向下滾動了。 -1
表示列表可以向上滾動。 這意味着listview
長度大於屏幕高度。
這個答案在 kotlin 中。
最簡單的方法是在這樣的適配器中:
@Override
public void onBindViewHolder(HistoryMessageListAdapter.ItemViewHolder holder, int position) {
if (position == getItemCount()-1){
listener.onLastItemReached();
}
}
因為一旦最后一個項目被回收,監聽器就會被觸發。
大多數答案的結構都很差,並且存在一些問題。 一個常見的問題是,如果用戶快速滾動,到達結束塊會執行多次我找到了一個解決方案,其中結束塊只運行 1 次。
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
if (yourLayoutManager.findLastVisibleItemPosition() ==
yourLayoutManager.itemCount - 1 && !recyclerView.canScrollVertically(1)) {
Logger.log("End reached")
// Do your operations
}
super.onScrolled(recyclerView, dx, dy)
}
PS 有時如果RecyclerView
變空,最終的監聽器可能會被調用。 作為解決方案,您還可以在上述代碼中添加此檢查。
if (recyclerView.adapter?.itemCount!! > 0)
這是我的解決方案:
val onScrollListener = object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView?, dx: Int, dy: Int) {
directionDown = dy > 0
}
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
if (recyclerView.canScrollVertically(1).not()
&& state != State.UPDATING
&& newState == RecyclerView.SCROLL_STATE_IDLE
&& directionDown) {
state = State.UPDATING
// TODO do what you want when you reach bottom, direction
// is down and flag for non-duplicate execution
}
}
}
我們可以使用接口來獲取位置
接口:為監聽器創建一個接口
public interface OnTopReachListener { void onTopReached(int position);}
活動 :
mediaRecycleAdapter = new MediaRecycleAdapter(Class.this, taskList); recycle.setAdapter(mediaRecycleAdapter); mediaRecycleAdapter.setOnSchrollPostionListener(new OnTopReachListener() {
@Override
public void onTopReached(int position) {
Log.i("Position","onTopReached "+position);
}
});
適配器 :
public void setOnSchrollPostionListener(OnTopReachListener topReachListener) {
this.topReachListener = topReachListener;}@Override public void onBindViewHolder(MyViewHolder holder, int position) {if(position == 0) {
topReachListener.onTopReached(position);}}
我的水平LinearLayoutManager(Kotlin)解決方案:
recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx:Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
if (dx == 0 && !recyclerView.canScrollHorizontally(1)) {
//add here your code
recyclerView.removeOnScrollListener(this)//remove this listener to prevent leaks
}
}
})
recyclerView.layoutManager?.scrollToPosition(recyclerView.adapter?.itemCount?.minus(1)!!)//scroll to last item position to trigger OnScrollListener
在使用適配器聲明和初始化您的 recyclerView 后使用此方法
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if(dy > 0){ // Scrolling Down
**Look at the condition inside if, this is how you can check, either you have scrolled till last element of your recyclerView or not.**
//------------------------------------------------------------------------------
LinearLayoutManager linearLayoutManager =
(LinearLayoutManager) recyclerView.getLayoutManager();
if (linearLayoutManager != null &&
linearLayoutManager.findLastCompletelyVisibleItemPosition() ==
recyclerViewList.size() - 1) {
//bottom of list!
}
//------------------------------------------------------------------------------
}else if(dy < 0){
// Scrolling Up
}
}
});
經過長時間的搜索,我找到了完美的解決方案,它只在您需要時滾動到底部,並且還保持了您通過使用 ListAdapter 獲得的平滑滾動行為:
adapter.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() {
override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
super.onItemRangeInserted(positionStart, itemCount)
scrollToBottomIfUserIsAtTheBottom(linearLayoutManager, positionStart)
}
})
private fun scrollToBottomIfUserIsAtTheBottom(linearLayout: LinearLayoutManager, positionStart: Int) {
val messageCount = adapter.itemCount
val lastVisiblePosition = linearLayout.findLastCompletelyVisibleItemPosition()
if (lastVisiblePosition == -1 ||
(positionStart >= (messageCount - 1) &&
lastVisiblePosition == (positionStart - 1)))
{
recyclerView.scrollToPosition(positionStart)
}
}
一些注意事項:
smoothScrollToPosition
與 ListAdapter 一起使用。 它破壞了 ListAdapter 的“更平滑”行為,這種行為在 diff 運行良好時發生,並且它檢測到新舊列表之間的變化是在新添加的項目中。adapter.layoutManager as LinearLayoutManager
試試這個,
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int visibleItemCount = recyclerView.getLayoutManager().getChildCount();
int totalItemCount = recyclerView.getLayoutManager().getItemCount();
int firstVisibleItem = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstVisibleItemPosition();
final int lastItem = firstVisibleItem + visibleItemCount;
if(lastItem == totalItemCount) {
if(previousLast != lastItem) {
previousLast = lastItem;
load();
}
}
}
});
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.