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
Create an abstract class and extends RecyclerView.OnScrollListener public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener { private int previousTotal = 0; private boolean loading = true; private int visibleThreshold; private int firstVisibleItem, visibleItemCount, totalItemCount; private RecyclerView.LayoutManager layoutManager; public EndlessRecyclerOnScrollListener(RecyclerView.LayoutManager layoutManager, int visibleThreshold) { this.layoutManager = layoutManager; this.visibleThreshold = visibleThreshold; } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); visibleItemCount = recyclerView.getChildCount(); totalItemCount = layoutManager.getItemCount(); firstVisibleItem = ((LinearLayoutManager)layoutManager).findFirstVisibleItemPosition(); if (loading) { if (totalItemCount > previousTotal) { loading = false; previousTotal = totalItemCount; } } if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) { onLoadMore(); loading = true; } } public abstract void onLoadMore();} in activity (or fragment) add addOnScrollListener to recyclerView LinearLayoutManager mLayoutManager = new LinearLayoutManager(this); recyclerView.setLayoutManager(mLayoutManager); recyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager, 3) { @Override public void onLoadMore() { //TODO ... } });
其他回答
if (layoutManager.findLastCompletelyVisibleItemPosition() ==
recyclerAdapter.getItemCount() - 1) {
//load more items.
}
公平而简单。 这是可行的。
正如约翰·T所建议的。只需使用下面的代码块,真的很简短,美观简单:D
public void loadMoreOnRecyclerView() {
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(@NonNull @NotNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (!recyclerView.canScrollVertically(1) && dy != 0) {
//Load more items here
}
}
});
}
你可以跟随我的回购来了解它的工作方式。
https://github.com/Nghien-Nghien/PokeAPI-Java/blob/0d8d69d348e068911b883f0ae7791d904cc75cb5/app/src/main/java/com/example/pokemonapi/MainActivity.java
关于应用程序的描述信息如下:https://github.com/skydoves/Pokedex#readme
我检测加载事件的方法不是检测滚动,而是监听最后一个视图是否附加。如果附加了最后一个视图,我认为这是加载更多内容的时机。
class MyListener implements RecyclerView.OnChildAttachStateChangeListener {
RecyclerView mRecyclerView;
MyListener(RecyclerView view) {
mRecyclerView = view;
}
@Override
public void onChildViewAttachedToWindow(View view) {
RecyclerView.Adapter adapter = mRecyclerView.getAdapter();
RecyclerView.LayoutManager mgr = mRecyclerView.getLayoutManager();
int adapterPosition = mgr.getPosition(view);
if (adapterPosition == adapter.getItemCount() - 1) {
// last view was attached
loadMoreContent();
}
@Override
public void onChildViewDetachedFromWindow(View view) {}
}
试试下面:
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.LayoutManager;
/**
* Abstract Endless ScrollListener
*
*/
public abstract class EndlessScrollListener extends
RecyclerView.OnScrollListener {
// The minimum amount of items to have below your current scroll position
// before loading more.
private int visibleThreshold = 10;
// The current offset index of data you have loaded
private int currentPage = 1;
// True if we are still waiting for the last set of data to load.
private boolean loading = true;
// The total number of items in the data set after the last load
private int previousTotal = 0;
private int firstVisibleItem;
private int visibleItemCount;
private int totalItemCount;
private LayoutManager layoutManager;
public EndlessScrollListener(LayoutManager layoutManager) {
validateLayoutManager(layoutManager);
this.layoutManager = layoutManager;
}
public EndlessScrollListener(int visibleThreshold,
LayoutManager layoutManager, int startPage) {
validateLayoutManager(layoutManager);
this.visibleThreshold = visibleThreshold;
this.layoutManager = layoutManager;
this.currentPage = startPage;
}
private void validateLayoutManager(LayoutManager layoutManager)
throws IllegalArgumentException {
if (null == layoutManager
|| !(layoutManager instanceof GridLayoutManager)
|| !(layoutManager instanceof LinearLayoutManager)) {
throw new IllegalArgumentException(
"LayoutManager must be of type GridLayoutManager or LinearLayoutManager.");
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
visibleItemCount = recyclerView.getChildCount();
totalItemCount = layoutManager.getItemCount();
if (layoutManager instanceof GridLayoutManager) {
firstVisibleItem = ((GridLayoutManager) layoutManager)
.findFirstVisibleItemPosition();
} else if (layoutManager instanceof LinearLayoutManager) {
firstVisibleItem = ((LinearLayoutManager) layoutManager)
.findFirstVisibleItemPosition();
}
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
}
}
if (!loading
&& (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
// End has been reached do something
currentPage++;
onLoadMore(currentPage);
loading = true;
}
}
// Defines the process for actually loading more data based on page
public abstract void onLoadMore(int page);
}
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.
}
}