Ravindra Kushwaha Ravindra Kushwaha -4 years ago 188
Android Question

Get the data from the Firebase in limit to perform pull to refresh and load more functionality

Yet now i am getting the all data from the

FireBase
at one time.What i want to do that getting data in LIMITS like 15 records at a time. Like in first time user get the 15 records from the
Firebase
and when user load more data at the bottom/TOP of the screen than 15 more records should come from
Firebase
and added to the bottom/TOP of the list.



I have implemented the logic to get the 15 records at a top OR bottom of the database from
Firebase
like below:-

public class ChatActivity extends AppCompatActivity implements FirebaseAuth.AuthStateListener {

private FirebaseAuth mAuth;
private DatabaseReference mChatRef;

private Query postQuery;
private String newestPostId;
private String oldestPostId;
private int startAt = 0;
private SwipeRefreshLayout swipeRefreshLayout;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat);

mAuth = FirebaseAuth.getInstance();
mAuth.addAuthStateListener(this);

mChatRef = FirebaseDatabase.getInstance().getReference();
mChatRef = mChatRef.child("chats");

/////GETTING THE VIEW ID OF SWIPE LAYOUT
swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipeRefreshLayout);

/////GETTING FIRST 10 RECORDS FROM THE FIREBASE HERE
mChatRef.limitToFirst(10).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot child : dataSnapshot.getChildren()) {
oldestPostId = child.getKey();
System.out.println("here si the data==>>" + child.getKey());
}
}

@Override
public void onCancelled(DatabaseError databaseError) {

}
});

//////FOR THE PULL TO REFRESH CODE IS HERE
swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
// Refresh items

System.out.println("Here==>>> "+oldestPostId);

///HERE "oldestPostId" IS THE KEY WHICH I GET THE LAST RECORDS FROM THE FIREBASE

mChatRef.startAt(oldestPostId).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot child : dataSnapshot.getChildren()) {

System.out.println("here AFTER data added==>>" + child.getKey());
}
}

@Override
public void onCancelled(DatabaseError databaseError) {

}
});

}
});
}


I have searched here on SO for it , but did not get the expected result, below link which i have searched for it


1. First Link

2. Second Link

3. Third Link

4. Forth Link


Please look at my firebase data structure in image.
Data of firebase

I have implemented the logic for the getting 15 OR 10 records at first time and it works..and also implemented the logic for loading more records in limits but not getting proper solution (NOT WORKING) , please help and let me know where am i doing wrong..Thanks :)

Answer Source

You are missing orderByKey(). For any filtering queries you must use the ordering functions. Refer to the documentation

In your onRefresh method you need to set the limit:

 public void onRefresh() {
     // Refresh items  
     ///HERE "oldestPostId" IS THE KEY WHICH I GET THE LAST RECORDS FROM THE FIREBASE
                mChatRef.orderByKey().startAt(oldestPostId).limitToFirst(10).addListenerForSingleValueEvent(new ValueEventListener() {
.....

So the data you retrieve is the only 10 new records after you got your first 10 records.

Make sure to save the oldest key of the newly retrieved data so that on next refresh new data from this key is only retrieved.

Suggestion: Instead of adding a child value listener to find the last key, you can just use the value listener and get the last data snapshot with the size to get the last record's key.

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