Implement startAfter and endBefore for RTDB queries (#2277)

Author: jmwski

firebase-database/CHANGELOG.md

@@ -4,6 +4,7 @@
 - [added] Added `Query.get()`, which allows users to receive a single data
   snapshot. `Query.get()` returns the latest value even if an older value
   already exists in cache.
+- [added] Added `Query.startAfter()` filter for paginating RTDB queries.
 
 # 19.5.1
 - [fixed] Fixes a regression in v19.4 that may cause assertion failures,

firebase-database/api.txt

@@ -154,7 +154,6 @@ package com.google.firebase.database {
 
   public class Query {
     method @NonNull public com.google.firebase.database.ChildEventListener addChildEventListener(@NonNull com.google.firebase.database.ChildEventListener);
-    method @NonNull public com.google.android.gms.tasks.Task<com.google.firebase.database.DataSnapshot> get();
     method public void addListenerForSingleValueEvent(@NonNull com.google.firebase.database.ValueEventListener);
     method @NonNull public com.google.firebase.database.ValueEventListener addValueEventListener(@NonNull com.google.firebase.database.ValueEventListener);
     method @NonNull public com.google.firebase.database.Query endAt(@Nullable String);
@@ -163,12 +162,19 @@ package com.google.firebase.database {
     method @NonNull public com.google.firebase.database.Query endAt(@Nullable String, @Nullable String);
     method @NonNull public com.google.firebase.database.Query endAt(double, @Nullable String);
     method @NonNull public com.google.firebase.database.Query endAt(boolean, @Nullable String);
+    method @NonNull public com.google.firebase.database.Query endBefore(@Nullable String);
+    method @NonNull public com.google.firebase.database.Query endBefore(double);
+    method @NonNull public com.google.firebase.database.Query endBefore(boolean);
+    method @NonNull public com.google.firebase.database.Query endBefore(@Nullable String, @Nullable String);
+    method @NonNull public com.google.firebase.database.Query endBefore(double, @Nullable String);
+    method @NonNull public com.google.firebase.database.Query endBefore(boolean, @Nullable String);
     method @NonNull public com.google.firebase.database.Query equalTo(@Nullable String);
     method @NonNull public com.google.firebase.database.Query equalTo(double);
     method @NonNull public com.google.firebase.database.Query equalTo(boolean);
     method @NonNull public com.google.firebase.database.Query equalTo(@Nullable String, @Nullable String);
     method @NonNull public com.google.firebase.database.Query equalTo(double, @Nullable String);
     method @NonNull public com.google.firebase.database.Query equalTo(boolean, @Nullable String);
+    method @NonNull public com.google.android.gms.tasks.Task<com.google.firebase.database.DataSnapshot> get();
     method @NonNull public com.google.firebase.database.DatabaseReference getRef();
     method public void keepSynced(boolean);
     method @NonNull public com.google.firebase.database.Query limitToFirst(int);
@@ -179,6 +185,12 @@ package com.google.firebase.database {
     method @NonNull public com.google.firebase.database.Query orderByValue();
     method public void removeEventListener(@NonNull com.google.firebase.database.ValueEventListener);
     method public void removeEventListener(@NonNull com.google.firebase.database.ChildEventListener);
+    method @NonNull public com.google.firebase.database.Query startAfter(@Nullable String);
+    method @NonNull public com.google.firebase.database.Query startAfter(double);
+    method @NonNull public com.google.firebase.database.Query startAfter(boolean);
+    method @NonNull public com.google.firebase.database.Query startAfter(@Nullable String, @Nullable String);
+    method @NonNull public com.google.firebase.database.Query startAfter(double, @Nullable String);
+    method @NonNull public com.google.firebase.database.Query startAfter(boolean, @Nullable String);
     method @NonNull public com.google.firebase.database.Query startAt(@Nullable String);
     method @NonNull public com.google.firebase.database.Query startAt(double);
     method @NonNull public com.google.firebase.database.Query startAt(boolean);