I have a Pagination recycler view inside my app and i'm loading 3 post every time the user scrolls down. But i want to display the items from the database, from last child to first child. I'm beginner on firebase querying and i don't know how to do something like this
My HomeFragment:
package com.george.socialmeme.Fragments;
public class HomeFragment extends Fragment {
LoadingDialog progressDialog;
final DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
boolean isSearchOpen = false;
private EditText searchView;
ArrayList<PostModel> postModelArrayList;
RecyclerView recyclerView;
PostRecyclerAdapter recyclerAdapter;
final int ITEM_LOAD_COUNT = 3;
int totalItems = 0, lastVisibleItem = 0;
boolean isLoading = false, isMaxData = false;
String lastKey = "", lastNode = "";
void getLastKeyFromFirebase() {
Query getLastKey = FirebaseDatabase.getInstance().getReference()
.child("posts")
.orderByKey()
.limitToLast(1);
getLastKey.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
for (DataSnapshot last_Key : snapshot.getChildren()) {
lastKey = last_Key.getKey();
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
isLoading = false;
Toast.makeText(getContext(), "Error: " + error.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}
void loadPosts(View fragmentView, FirebaseUser user, boolean isRefresh, boolean getDataFromDB) {
if (isRefresh) {
fragmentView.findViewById(R.id.constraintLayout2).setVisibility(View.GONE);
((HomeActivity) getContext()).findViewById(R.id.bottom_nav).setVisibility(View.VISIBLE);
}
if (getDataFromDB) {
getLastKeyFromFirebase();
if (!isMaxData) {
Query query;
if (TextUtils.isEmpty(lastNode))
query = FirebaseDatabase.getInstance().getReference()
.child("posts")
.orderByKey()
.limitToFirst(ITEM_LOAD_COUNT);
else
query = FirebaseDatabase.getInstance().getReference()
.child("posts")
.orderByKey()
.startAt(lastNode)
.limitToFirst(ITEM_LOAD_COUNT);
query.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
if (snapshot.hasChildren()) {
new Handler().postDelayed(() -> {
fragmentView.findViewById(R.id.constraintLayout2).setVisibility(View.GONE);
HomeActivity.bottomNavBar.setVisibility(View.VISIBLE);
HomeActivity.showLoadingScreen = false;
}, 1200);
ArrayList<PostModel> newPosts = new ArrayList<>();
for (DataSnapshot userSnapshot : snapshot.getChildren()) {
PostModel postModel = new PostModel();
postModel.setId(userSnapshot.child("id").getValue(String.class));
postModel.setImgUrl(userSnapshot.child("imgUrl").getValue(String.class));
postModel.setLikes(userSnapshot.child("likes").getValue(String.class));
postModel.setName(userSnapshot.child("name").getValue(String.class));
postModel.setProfileImgUrl(userSnapshot.child("authorProfilePictureURL").getValue(String.class));
postModel.setPostType(userSnapshot.child("postType").getValue(String.class));
// Show post in recycler adapter only if the user is not blocked
if (!snapshot.child("users").child(user.getUid()).child("blockedUsers").child(userSnapshot.child("name").getValue(String.class)).exists()) {
//postModelArrayList.add(postModel);
newPosts.add(postModel);
//postModelArrayList.add(postModel);
recyclerAdapter.notifyDataSetChanged();
}
}
lastNode = newPosts.get(newPosts.size() - 1).getId();
if (!lastNode.equals(lastKey))
newPosts.remove(newPosts.size() - 1);
else
lastNode = "end"; // Avoiding infinity load
recyclerAdapter.addAll(newPosts);
isLoading = false;
} else {
isLoading = false;
isMaxData = true;
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
} else {
Toast.makeText(getContext(), "Hello3", Toast.LENGTH_SHORT).show();
isLoading = false;
isMaxData = true;
}
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_home, container, false);
AdView mAdView = view.findViewById(R.id.adView);
AdRequest adRequest = new AdRequest.Builder().build();
if (isAdded()) {
mAdView.loadAd(adRequest);
}
SwipeRefreshLayout swipeRefreshLayout = view.findViewById(R.id.root_view);
TextView usernameLoadingScreen = view.findViewById(R.id.textView40);
ImageButton searchUserBtn = view.findViewById(R.id.searchPersonButton);
ImageButton notificationsBtn = view.findViewById(R.id.notificationsButton);
ImageButton searchUserButton = view.findViewById(R.id.enter_search_button);
View postsOfTheMonthBtn = view.findViewById(R.id.posts_of_the_month_btn);
searchView = view.findViewById(R.id.search_view);
DatabaseReference usersRef = FirebaseDatabase.getInstance().getReference("users");
FirebaseAuth auth = FirebaseAuth.getInstance();
FirebaseUser user = auth.getCurrentUser();
if (!HomeActivity.anonymous) {
usernameLoadingScreen.setText(user.getDisplayName());
if (user.getPhotoUrl() != null) {
Glide.with(getContext()).load(user.getPhotoUrl().toString()).into((ImageView) view.findViewById(R.id.my_profile_image));
}
} else {
searchUserBtn.setVisibility(View.GONE);
notificationsBtn.setVisibility(View.GONE);
usernameLoadingScreen.setText("Anonymous User");
}
recyclerView = view.findViewById(R.id.home_recycler_view);
if (HomeActivity.savedPostsModelArrayList == null) {
postModelArrayList = new ArrayList<>();
} else {
postModelArrayList = HomeActivity.savedPostsModelArrayList;
}
final LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
recyclerAdapter = new PostRecyclerAdapter(postModelArrayList, getContext(), getActivity());
//layoutManager.setReverseLayout(true);
//layoutManager.setStackFromEnd(true);
recyclerView.setAdapter(recyclerAdapter);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(layoutManager);
progressDialog = LoadingDialog.Companion.get(getActivity());
searchView.setVisibility(View.GONE);
searchUserButton.setVisibility(View.GONE);
if (HomeActivity.showWhatsNewMessage) {
FirebaseInAppMessaging.getInstance().triggerEvent("new_version_open");
}
// Avoid data refresh on every swipe down
//RelativeLayout scrollView = view.findViewById(R.id.scrollView3);
recyclerView.setOnScrollChangeListener((v, scrollX, scrollY, oldScrollX, oldScrollY) ->
swipeRefreshLayout.setEnabled(scrollY <= 5));
// Re-load data
swipeRefreshLayout.setOnRefreshListener(() -> {
swipeRefreshLayout.setRefreshing(true);
loadPosts(view, user, true, true);
swipeRefreshLayout.setRefreshing(false);
});
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
totalItems = layoutManager.getItemCount();
lastVisibleItem = layoutManager.findLastVisibleItemPosition();
if (!isLoading && totalItems <= ((lastVisibleItem + ITEM_LOAD_COUNT))) {
loadPosts(view, user, false, true);
isLoading = true;
}
}
});
HomeActivity.bottomNavBar.setVisibility(View.GONE);
loadPosts(view, user, !HomeActivity.showLoadingScreen, true);
postsOfTheMonthBtn.setOnClickListener(view13 -> {
Intent intent = new Intent(getActivity(), PostsOfTheMonthActivity.class);
startActivity(intent);
CustomIntent.customType(getContext(), "left-to-right");
});
searchUserButton.setOnClickListener(v -> usersRef.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
boolean userFound = false;
for (DataSnapshot snap : snapshot.getChildren()) {
if (snap.child("name").getValue().toString().equals(searchView.getText().toString())) {
userFound = true;
UserProfileActivity.username = searchView.getText().toString();
UserProfileActivity.userID = snap.child("id").getValue().toString();
Intent intent = new Intent(getActivity(), UserProfileActivity.class);
getActivity().startActivity(intent);
CustomIntent.customType(getActivity(), "left-to-right");
break;
}
}
if (!userFound) {
new AlertDialog.Builder(getActivity())
.setTitle("User not found")
.setMessage("We cannot find a user with this username")
.setPositiveButton("ok", (dialog, which) -> dialog.dismiss())
.show();
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
Toast.makeText(getActivity(), "Error: " + error.getMessage(), Toast.LENGTH_SHORT).show();
}
}));
notificationsBtn.setOnClickListener(view12 -> {
startActivity(new Intent(getActivity(), NotificationsActivity.class));
CustomIntent.customType(getContext(), "left-to-right");
});
searchUserBtn.setOnClickListener(view1 -> {
if (isSearchOpen) {
// search is closed
searchUserBtn.setImageResource(R.drawable.ic_search);
isSearchOpen = false;
// animate button
YoYo.with(Techniques.FadeInUp)
.duration(500)
.repeat(0)
.playOn(searchUserBtn);
// hide and animate search view
YoYo.with(Techniques.FadeInUp)
.duration(500)
.repeat(0)
.playOn(searchView);
YoYo.with(Techniques.FadeInUp)
.duration(500)
.repeat(0)
.playOn(searchUserButton);
searchView.setVisibility(View.GONE);
searchUserButton.setVisibility(View.GONE);
} else {
// search is open
searchUserBtn.setImageResource(R.drawable.ic_close);
isSearchOpen = true;
// animate button
YoYo.with(Techniques.FadeInDown)
.duration(500)
.repeat(0)
.playOn(searchUserBtn);
// show and animate search view
searchView.setVisibility(View.VISIBLE);
searchUserButton.setVisibility(View.VISIBLE);
YoYo.with(Techniques.FadeInDown)
.duration(500)
.repeat(0)
.playOn(searchView);
YoYo.with(Techniques.FadeInDown)
.duration(500)
.repeat(0)
.playOn(searchUserButton);
// display keyboard to type
((InputMethodManager) getContext().getSystemService(Context.INPUT_METHOD_SERVICE))
.showSoftInput(searchView, InputMethodManager.SHOW_FORCED);
}
});
return view;
}
}
