Reduce complexity of factory

Change-Id: I823555e51436bd72fb0a6118aa0a36df71517ff2

Author: samtstern

firestore/src/main/java/com/firebase/ui/firestore/paging/FirestoreDataSource.java

@@ -29,21 +29,14 @@ public class FirestoreDataSource extends PageKeyedDataSource<PageKey, DocumentSn
     public static class Factory extends DataSource.Factory<PageKey, DocumentSnapshot> {
 
         private final Query mQuery;
-        private final MutableLiveData<FirestoreDataSource> mDataSource = new MutableLiveData<>();
 
         public Factory(Query query) {
             mQuery = query;
         }
 
         @Override
         public DataSource<PageKey, DocumentSnapshot> create() {
-            FirestoreDataSource source = new FirestoreDataSource(mQuery);
-            mDataSource.postValue(source);
-            return source;
-        }
-
-        public LiveData<FirestoreDataSource> getDataSource() {
-            return mDataSource;
+            return new FirestoreDataSource(mQuery);
         }
     }
 

firestore/src/main/java/com/firebase/ui/firestore/paging/PagingData.java

@@ -5,6 +5,7 @@
 import android.arch.lifecycle.Transformations;
 import android.arch.paging.LivePagedListBuilder;
 import android.arch.paging.PagedList;
+import android.support.annotation.NonNull;
 import android.support.annotation.RestrictTo;
 
 import com.google.firebase.firestore.DocumentSnapshot;
@@ -18,16 +19,17 @@ public class PagingData {
     private final LiveData<PagedList<DocumentSnapshot>> mSnapshots;
     private final LiveData<LoadingState> mLoadingState;
 
-    public PagingData(FirestoreDataSource.Factory factory,
-                      PagedList.Config config) {
+    public PagingData(@NonNull FirestoreDataSource.Factory factory,
+                      @NonNull PagedList.Config config) {
 
         mSnapshots = new LivePagedListBuilder<>(factory, config).build();
 
-        mLoadingState = Transformations.switchMap(factory.getDataSource(),
-                new Function<FirestoreDataSource, LiveData<LoadingState>>() {
+        mLoadingState = Transformations.switchMap(mSnapshots,
+                new Function<PagedList<DocumentSnapshot>, LiveData<LoadingState>>() {
                     @Override
-                    public LiveData<LoadingState> apply(FirestoreDataSource input) {
-                        return input.getLoadingState();
+                    public LiveData<LoadingState> apply(PagedList<DocumentSnapshot> input) {
+                        FirestoreDataSource dataSource = (FirestoreDataSource) input.getDataSource();
+                        return dataSource.getLoadingState();
                     }
                 });
     }