memorizing scrolls

src/components/posts/container/postsContainer.js

@@ -86,11 +86,11 @@ const PostsContainer = ({
   const [recommendedUsers, setRecommendedUsers] = useState([]);
   const [recommendedCommunities, setRecommendedCommunities] = useState([]);
 
-  const _setFeedPosts = (_posts) => {
+  const _setFeedPosts = (_posts, scrollPos = 0) => {
     if (isFeedScreen) {
-      dispatch(setFeedPosts(_posts));
+      dispatch(setFeedPosts(_posts, scrollPos));
     } else {
-      dispatch(setOtherPosts(_posts));
+      dispatch(setOtherPosts(_posts, scrollPos));
     }
   };
 
@@ -110,6 +110,7 @@ const PostsContainer = ({
           startAuthor: '',
           startPermlink: '',
           isLoading: false,
+          scrollPosition: 0,
         };
       }
     });
@@ -213,7 +214,8 @@ const PostsContainer = ({
         state.currentFilter = filter;
         console.log('New state:', state);
 
-        _setFeedPosts(state.cachedData[filter !== 'feed' ? filter : state.currentSubFilter].posts);
+        const data = state.cachedData[filter !== 'feed' ? filter : state.currentSubFilter];
+        _setFeedPosts(data.posts, data.scrollPosition);
 
         return state;
       }
@@ -223,7 +225,19 @@ const PostsContainer = ({
         state.currentSubFilter = filter;
         console.log('New state:', state);
         //dispatch to redux;
-        _setFeedPosts(state.cachedData[filter].posts);
+        const data = state.cachedData[filter];
+        _setFeedPosts(data.posts, data.scrollPosition);
+        return state;
+      }
+
+      case 'scroll-position-change': {
+        const scrollPosition = action.payload.scrollPosition || 0;
+        const filter = state.currentFilter;
+        const subFilter = state.currentSubFilter;
+
+        const cacheFilter = filter !== 'feed' ? filter : subFilter;
+
+        state.cachedData[cacheFilter].scrollPosition = scrollPosition;
         return state;
       }
 
@@ -697,12 +711,30 @@ const PostsContainer = ({
     );
   };
 
+  const _handleOnScroll = (event) => {
+    if (handleOnScroll) {
+      handleOnScroll();
+    }
+
+    //memorize filter position
+    const scrollPosition = event.nativeEvent.contentOffset.y;
+    if (scrollPosition == 0) {
+      Alert.alert('Scroll positionsing failed', JSON.stringify(event));
+    }
+    cacheDispatch({
+      type: 'scroll-position-change',
+      payload: {
+        scrollPosition,
+      },
+    });
+  };
+
   return (
     <PostsView
       ref={elem}
       filterOptions={filterOptions}
       handleImagesHide={_handleImagesHide}
-      handleOnScroll={handleOnScroll}
+      handleOnScroll={_handleOnScroll}
       isHideImage={isHideImages}
       isLoggedIn={isLoggedIn}
       isAnalytics={isAnalytics}

src/components/posts/view/postsView.js

@@ -238,12 +238,6 @@ const PostsView = ({
     );
   };
 
-  const _handleOnScroll = () => {
-    if (handleOnScroll) {
-      handleOnScroll();
-    }
-  };
-
   const _scrollTop = () => {
     postsList.current.scrollToTop();
   };
@@ -330,7 +324,7 @@ const PostsView = ({
             onRefresh={handleOnRefreshPosts}
             onEndReachedThreshold={1}
             ListFooterComponent={_renderFooter}
-            onScrollEndDrag={_handleOnScroll}
+            onScrollEndDrag={handleOnScroll}
             ListEmptyComponent={_renderEmptyContent}
             refreshControl={
               <RefreshControl

src/components/postsList/container/postsListContainer.tsx

@@ -24,12 +24,38 @@ const postsListContainer = ({
         : state.posts.otherPosts
     });
 
+    const scrollPosition = useSelector((state) => {
+      return isFeedScreen
+      ? state.posts.feedScrollPosition
+      : state.posts.otherScrollPosition
+  });
+
     useImperativeHandle(ref, () => ({
         scrollToTop() {
             flatListRef.current?.scrollToOffset({ x: 0, y: 0, animated: true });
         },
       }));
 
+    useEffect(() => {
+      console.log("Scroll Position: ", scrollPosition)
+      if(posts.length == 0){
+        flatListRef.current?.scrollToOffset({
+          offset: 0, 
+          animated: false 
+        });
+      }
+      
+    }, [posts])
+
+    useEffect(() => {
+      console.log("Scroll Position: ", scrollPosition)
+      flatListRef.current?.scrollToOffset({
+        offset: posts.length == 0?0:scrollPosition, 
+        animated: false 
+      });
+      
+    }, [scrollPosition])
+
     const _renderItem = ({ item, index }:{item:any, index:number}) => {
         const e = [];
         if (index % 3 === 0) {

src/redux/actions/postsAction.js

@@ -8,16 +8,22 @@ import {
   SET_INIT_POSTS,
 } from '../constants/constants';
 
-export const setFeedPosts = (payload) => ({
-  payload,
+export const setFeedPosts = (posts, scrollPosition = 0) => ({
+  payload: {
+    posts,
+    scrollPosition,
+  },
   type: SET_FEED_POSTS,
 });
 export const setInitPosts = (payload) => ({
   payload,
   type: SET_INIT_POSTS,
 });
-export const setOtherPosts = (payload) => ({
-  payload,
+export const setOtherPosts = (posts, scrollPosition = 0) => ({
+  payload: {
+    posts,
+    scrollPosition,
+  },
   type: SET_OTHER_POSTS,
 });
 export const fetchPosts = (payload) => ({

src/redux/reducers/postsReducer.js

@@ -22,7 +22,8 @@ export default function (state = initialState, action) {
     case SET_FEED_POSTS:
       return {
         ...state,
-        feedPosts: action.payload,
+        feedPosts: action.payload.posts,
+        feedScrollPosition: action.payload.scrollPosition,
         posts: action.payload,
       };
     case SET_INIT_POSTS:
@@ -33,7 +34,8 @@ export default function (state = initialState, action) {
     case SET_OTHER_POSTS:
       return {
         ...state,
-        otherPosts: action.payload,
+        otherPosts: action.payload.posts,
+        otherScrollPosition: action.payload.scrollPosition,
         posts: action.payload,
       };
     case FILTER_SELECTED: {