我对无尽的滚动有问题。每次加载更多数据时，它都会返回顶部视图。我想要的是 RecyclerView 在加载新数据时保持在最后一个位置。我正在尝试实现此代码https://github.com/codepath/android_guides/wiki/Endless-Scrolling-with-AdapterViews-and-RecyclerView
这是无尽的滚动代码
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 = 30;
// 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 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 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);
}
OnCreateView
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
View view = inflater.inflate(R.layout.booking_fragment, container, false);
recyclerView = (RecyclerView) view.findViewById(R.id.bookingRecyclerView);
linearLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setHasFixedSize(true);
scrollListener = new EndlessRecyclerViewScrollListener(linearLayoutManager) {
@Override
public void onLoadMore(int page, int totalItemsCount, RecyclerView view) {
// Triggered only when new data needs to be appended to the list
// Add whatever code is needed to append new items to the bottom of the list
if(CurrentStatus.equals("notSearch")){
if (current < Integer.parseInt(TP)) {
current++;
loadMoreBookings(sort);
}
else if(current == Integer.parseInt(TP)){
Toast.makeText(getActivity(),"No More Data to Load", Toast.LENGTH_SHORT).show();
}
}else{
if (current < Integer.parseInt(TP)) {
current++;
searchMoreBookings(search, sort);
}
else if(current == Integer.parseInt(TP)){
Toast.makeText(getActivity(),"No More Data to Be Load", Toast.LENGTH_SHORT).show();
}
}
}
加载更多预订
private void loadMoreBookings(final String sort){
CurrentStatus = "notSearch";
final ProgressDialog progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("Please Wait While Retrieving Data");
progressDialog.setCancelable(false);
progressDialog.show();
StringRequest requesting = new StringRequest(Request.Method.POST, URL,
new Response.Listener<String>() {
@Override
public void onResponse(String JSONString) {
progressDialog.dismiss();
try{
JSONObject jsonTP = new JSONObject(JSONString);
JSONArray jsonArrayB = jsonTP.getJSONArray("Data");
for(int i = 0; i < jsonArrayB.length(); i++){
JSONObject o = jsonArrayB.getJSONObject(i);
Booking list = new Booking(
o.getString("bookID"),
o.getString("userEmail"),
o.getString("paymentMethod"),
o.getString("paymentStatus"),
o.getString("totalPrice"),
o.getString(String.valueOf("securityCode")),
o.getString(String.valueOf("travelDate")),
o.getString("paymentID"),
o.getString("userFN"),
o.getString("userLN"),
o.getString(String.valueOf("createdAt")),
o.getString("tTM"),
o.getString("messageToCustomer"),
o.getString("messageFromMerchant"),
o.getString("wCN"),
o.getString("wLocation"),
o.getString("wWebsite")
);
listBooking.add(list);
count++;
}
Toast.makeText(getActivity(), "Data : "+count, Toast.LENGTH_SHORT).show();
adapter = new BookingAdapter(listBooking,getActivity());
recyclerView.setAdapter(adapter);
} catch (JSONException e) {
loadMoreBookings(sort);
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
progressDialog.dismiss();
Toast.makeText(getActivity().getApplicationContext(), "Failed To Retrieve Data. Please Try Again.",Toast.LENGTH_LONG).show();
}
}
){
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String,String> params = new HashMap<String, String>();
String user = getActivity().getIntent().getStringExtra("username");
params.put("username", user);
params.put("currentpage", String.valueOf(current));
params.put("sorting", sort);
return params;
}
};
RequestQueue requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
requestQueue.add(requesting);
}