Ability to get occurred exception (#1615)

Author: PatilShreyas

app/src/main/java/com/firebase/uidemo/database/firestore/FirestorePagingActivity.java

@@ -111,6 +111,12 @@ protected void onLoadingStateChanged(@NonNull LoadingState state) {
                                 break;
                         }
                     }
+
+                    @Override
+                    protected void onError(@NonNull Exception e) {
+                        mSwipeRefreshLayout.setRefreshing(false);
+                        Log.e(TAG, e.getMessage(), e);
+                    }
                 };
 
         mRecycler.setLayoutManager(new LinearLayoutManager(this));

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

@@ -48,6 +48,7 @@ public DataSource<PageKey, DocumentSnapshot> create() {
     }
 
     private final MutableLiveData<LoadingState> mLoadingState = new MutableLiveData<>();
+    private final MutableLiveData<Exception> mException = new MutableLiveData<>();
 
     private final Query mBaseQuery;
     private final Source mSource;
@@ -133,6 +134,11 @@ public LiveData<LoadingState> getLoadingState() {
         return mLoadingState;
     }
 
+    @NonNull
+    public LiveData<Exception> getLastError() {
+        return mException;
+    }
+
     public void retry() {
         LoadingState currentState = mLoadingState.getValue();
         if (currentState != LoadingState.ERROR) {
@@ -216,6 +222,9 @@ public void onFailure(@NonNull Exception e) {
 
             // Set the retry action
             mRetryRunnable = getRetryRunnable();
+
+            //Set to the MutableLiveData to determine Latest Error
+            mException.postValue(e);
         }
 
         protected abstract Runnable getRetryRunnable();

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

@@ -32,6 +32,7 @@ public abstract class FirestorePagingAdapter<T, VH extends RecyclerView.ViewHold
 
     private final LiveData<PagedList<DocumentSnapshot>> mSnapshots;
     private final LiveData<LoadingState> mLoadingState;
+    private final LiveData<Exception> mException;
     private final LiveData<FirestoreDataSource> mDataSource;
 
     /*
@@ -45,6 +46,14 @@ public void onChanged(@Nullable FirestoreDataSource source) {
         }
     };
 
+    //Error observer to determine last occurred Error
+    private final Observer<Exception> mErrorObserver = new Observer<Exception>() {
+        @Override
+        public void onChanged(@Nullable Exception e) {
+            onError(e);
+        }
+    };
+
     private final Observer<LoadingState> mStateObserver =
             new Observer<LoadingState>() {
                 @Override
@@ -94,6 +103,15 @@ public FirestoreDataSource apply(PagedList<DocumentSnapshot> input) {
                     }
                 });
 
+        mException = Transformations.switchMap(mSnapshots,
+                new Function<PagedList<DocumentSnapshot>, LiveData<Exception>>() {
+                    @Override
+                    public LiveData<Exception> apply(PagedList<DocumentSnapshot> input) {
+                        FirestoreDataSource dataSource = (FirestoreDataSource) input.getDataSource();
+                        return dataSource.getLastError();
+                    }
+                });
+
         mParser = options.getParser();
 
         if (options.getOwner() != null) {
@@ -135,6 +153,7 @@ public void startListening() {
         mSnapshots.observeForever(mDataObserver);
         mLoadingState.observeForever(mStateObserver);
         mDataSource.observeForever(mDataSourceObserver);
+        mException.observeForever(mErrorObserver);
     }
 
     /**
@@ -146,6 +165,7 @@ public void stopListening() {
         mSnapshots.removeObserver(mDataObserver);
         mLoadingState.removeObserver(mStateObserver);
         mDataSource.removeObserver(mDataSourceObserver);
+        mException.removeObserver(mErrorObserver);
     }
 
     @Override
@@ -169,4 +189,13 @@ public void onBindViewHolder(@NonNull VH holder, int position) {
     protected void onLoadingStateChanged(@NonNull LoadingState state) {
         // For overriding
     }
+
+    /**
+     * Called whenever the {@link Exception} is caught.
+     *
+     * When {@link Exception} is caught the adapter will stop loading any data
+     */
+    protected void onError(@NonNull Exception e) {
+        // For overriding
+    }
 }