问题
I want to implement an endless RecyclerView but so far all the implementations and tutorials I have come across describe loading data off a server then loading it or dynamically adding elements using a loop.
In my case, I already have a large ArrayList containing the data I want to display in the RecyclerView.
What I need is to say, display the first 10 items of the array, and on loading more, display the next batch of 10.
回答1:
This could achieve your goal.
public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener {
public static String TAG = EndlessRecyclerOnScrollListener.class.getSimpleName();
private int previousTotal = 0; // The total number of items in the dataset after the last load
private boolean loading = true; // True if we are still waiting for the last set of data to load.
private int visibleThreshold = 5; // The minimum amount of items to have below your current scroll position before loading more.
int firstVisibleItem, visibleItemCount, totalItemCount;
private int current_page = 1;
private LinearLayoutManager mLinearLayoutManager;
public EndlessRecyclerOnScrollListener(LinearLayoutManager linearLayoutManager) {
this.mLinearLayoutManager = linearLayoutManager;
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
visibleItemCount = recyclerView.getChildCount();
totalItemCount = mLinearLayoutManager.getItemCount();
firstVisibleItem = mLinearLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
}
}
if (!loading && (totalItemCount - visibleItemCount)
<= (firstVisibleItem + visibleThreshold)) {
// End has been reached
// Do something
current_page++;
onLoadMore(current_page);
loading = true;
}
}
public abstract void onLoadMore(int current_page);
}
And sample activity
public class SampleActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sample);
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.list);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setOnScrollListener(new EndlessRecyclerOnScrollListener(linearLayoutManager) {
@Override
public void onLoadMore(int current_page) {
// do something...
}
});
}
}
Edit: See here: Endless Scrolling with AdapterViews
回答2:
You can use this Endless Adapter
- It is generic, you give it (You model, Recycler.ViewHolder)
- You can set the adapter either show loading or not.
- Have Listeners to check when loading finished, and when loading starts.
You can check also the sample for more info
回答3:
Try using:
recyclerView.addOnScrollListener (recyclerViewOnScrollListener);
private RecyclerView.OnScrollListener recyclerViewOnScrollListener = new RecyclerView.OnScrollListener () {
private final String LOG_TAG = "PAGINATION_";
boolean isIdle;
@Override
public void onScrollStateChanged (RecyclerView recyclerView, int newState) {
try {
super.onScrollStateChanged (recyclerView, newState);
isIdle = (newState == RecyclerView.SCROLL_STATE_IDLE);
}
catch (Exception e) {
e.printStackTrace ();
}
}
@Override
public void onScrolled (RecyclerView recyclerView, int dx, int dy) {
firstVisibleItemPosition = layoutManager.findFirstVisibleItemPosition ();
super.onScrolled (recyclerView, dx, dy);
if (!isIdle dy > 0) {
int totalItems = yourList.size()();
totalItemCount = layoutManager.getItemCount ();
visibleItemCount = layoutManager.getChildCount ();
Log.i (LOG_TAG, "Max: " + totalItems + ", Total: " + totalItemCount + ", Previous Total: " + previousTotal + ", Visible: " + visibleItemCount + ", First: " + firstVisibleItemPosition);
if (isLoading) {
if (totalItemCount != previousTotal) {
isLoading = false;
previousTotal = totalItemCount;
}
}
isLastPage = (totalItemCount >= totalItems);
Log.i (LOG_TAG, "DETAILS: currentPage: " + currentPage + ", isLoading: " + isLoading + ", isLast: " + isLastPage);
if (!isLoading && !isLastPage) {
if ((visibleItemCount + firstVisibleItemPosition) >= totalItemCount && firstVisibleItemPosition >= 0 && totalItems >= (currentPage * PAGE_LIMIT) && totalItems > totalItemCount) {
if (totalItems > (currentPage * PAGE_LIMIT)) {
currentPage = (totalItemCount / PAGE_LIMIT) + 1;
isLoading = true;
//load more data using currentPage and PAGE_LIMIT
}
}
}
}
previousTotal = totalItemCount;
}
catch (Exception e) {
e.printStackTrace ();
}
}
}
}
};
回答4:
try using this class it help me alot :
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(GridLayoutManager layoutManager) {
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);
}
reference :
- https://gist.github.com/nesquena/d09dc68ff07e845cc622
- https://guides.codepath.com/android/Endless-Scrolling-with-AdapterViews-and-RecyclerView
来源：https://stackoverflow.com/questions/37004131/implementing-endless-recyclerview