onChangeIndex() doesn't always fire when using swipe feature

[curtismenmuir]

Description

• When user manually swipes item to side numerous times, onChangeIndex callback occasionally is not fired.
• I have stripped back the props I was passing to <SwiperFlatList> to the bare minimum (see code example below) and issue still seen.
• Issue only seen with manual swipe

Info

• Issue seen on Android + iOS
• RN Version: 0.63.4 (also seen in v0.62.2)
• react-native-swiper-flatlist version: 3.0.14 (also seen in v3.0.8)

Code Example:

const LIST_ITEMS = [
  { title: 'Title 1 },
  { title: 'Title 2' },
  { title: 'Title 3' },
  { title: 'Title 4' },
];

export default class SwipeView extends Component {
  constructor(props) {
      super(props);
    }

  onChangeIndex({ index, prevIndex }) {
      console.log('New Index: ' + index);
    }
  
  renderItem = ({ item }) => {
      return <SwipeListItem item={item} />;
    };
  
  render() {
    return (
      <SwiperFlatList
        autoplay={false}
        data={LIST_ITEMS}
        renderItem={this.renderItem}
        showPagination={false}
        onChangeIndex={this.onChangeIndex.bind(this)}
      />
    )
  }
}

Steps to recreate

• Render list with 4 items
• Swipe forward to index 1
• Swipe back to index 0
• Repeat swiping between index 0 & 1 many times
• onChangeIndex callback not always fired

[curtismenmuir]

I have found a work-around by also implementing onMomentumScrollEnd callback. Leaving this issue open incase you want to track the onChangeIndex issue.

[curtismenmuir]

Done a bit of digging into onChangeIndex issue and it looks like _onChangeIndex() in SwiperFlatList.tsx (line 77) receives the same value for _index and _prevIndex and this causes the onChangeIndex callback not to fire.

From a quick look, it seems like _onViewableItemsChanged() (line 181) is not setting the index on the swipe previous to the swipe which does not fire onChangeIndex callback. EG:

if (newItem.isViewable) {
  setCurrentIndexes((prevState) => ({ ...prevState, index: nextIndex }));
}

I just had a quick look, I will try do some more investigation when I have some free time.

[gusgard]

@curtismenmuir thanks for reporting the issue and the work-around, if you could take a deep look at it, it would be great 🙌

[gusgard]

@curtismenmuir thanks for reporting the issue and the work-around, if you could take a deep look at it, it would be great 🙌

[PaperMonster]

I also faced this issue. I noticed paginationIndex props of PaginationComponent always gives correct index. I found the value can be derived from parameters of onViewableItemsChanged. So here is my current workaround:

 onViewableItemsChanged={(params) => console.log('index', params.changed?.[0]?.index)}

[arcsoftanil]

Same issue persist for me also. I have noticed that onchange index trigger after some delay. Any luck ?

[Priyadharshini-max]

I'm facing this issue , only when I swipe manually

[Priyadharshini-max]

It show half image, I need to show like this when i swipe manuall

y

[iortega-dev]

Same issue persist for me also. I have noticed that onchange index trigger after some delay. Any luck ?

I'm facing the same delay issue... :(

[zachnicoll]

+1 experiencing this issue!

[ShobanaBohs100]

+1 having the same issue when swipe manually.

[ShobanaBohs100]

figured out onMomentumScrollEnd solves the problem for now. Thanks @curtismenmuir

Instead this,
onChangeIndex={({ index }) => { setListIndex(index); }}
we can use this prop to get the index
onMomentumScrollEnd={({ index }: any) => setListIndex(index)}

[garrettg123]

onMomentumScrollEnd doesn't work on Android

[apethree]

+1 having issues where onChangeIndex doesn't update the index.

[varunkukade]

@ShobanaBohs100 onMomentumScrollEnd={({ index }: any) => setListIndex(index)} Thanks!!! this perfectly worked for IOS. but android still having same issue. What did you use for android?

[DanielRiera]

+1

[gusgard]

I did a few improvements (removing re-renders and adding support for getItemLayout), please use version 3.2.2 and let me know. Thanks

[bravecode]

@gusgard Still the same issue on 3.2.2 :(

[gusgard]

I wasn't able to reproduce it with Expo v48, is there an example or steps you can provide me ? @bravecode

[kishanvaghera]

i achieve this design and also created this code blog.
https://buzzstuck.com/react-native-swiper-component-implemented-with-flatlist/

[Riuhou]

/node_modules/react-native-swiper-flatlist/src/components/SwiperFlatList/SwiperFlatList.tsx      

     const _onChangeIndex = React.useCallback(
       ({ index: _index, prevIndex: _prevIndex }: { index: number; prevIndex: number }) => {
       	
         // -> Moving it out of the condition can temporarily solve the issue. Another problem is that _onChangeIndex cannot be triggered immediately after the swipe, but needs to wait for a moment.
        onChangeIndex?.({ index: _index, prevIndex: _prevIndex });

         //  -> First swipe right, then swipe left will not trigger _onChangeIndex.
         if (_index !== _prevIndex) {
          onChangeIndex?.({ index: _index, prevIndex: _prevIndex });
         // onChangeIndex?.({ index: _index, prevIndex: _prevIndex });
         }
       },
       [onChangeIndex]

[iamsaadMehmood]

+1

I have 6 items onChnageIndex is not firing after 3rd Index.

  const renderItem = ({item, index}: {item: IHome; index: number}) => {
    return (
      <View height={height * 0.9} width={width}>
        <Video
          source={{
            uri: item.attachmentUrl,
          }}
          paused={currentIndex !== index}
          style={styles.video}
          resizeMode="stretch"
          // controls
          onLoad={() => setLoading(false)}
          onLoadStart={() => setLoading(true)}
          onError={() => setLoading(false)}
          repeat
        />
        <View position={'absolute'} bottom={height * 0.1} right={5}>
          <Pressable>
            {item.is_Liked ? (
              <SelectedLike height={7} width={7} />
            ) : (
              <Likes height={7} width={7} />
            )}
            <Text
              style={[
                styles.text,
                styles.count,
                theme === 'light' ? styles.countLight : styles.countDark,
              ]}>
              {formatCount(item.total_likes)}
            </Text>
          </Pressable>
          <Pressable mt={5}>
            <MessageGrey height={7} width={7} />
            <Text
              style={[
                styles.text,
                styles.count,
                theme === 'light' ? styles.countLight : styles.countDark,
              ]}>
              {formatCount(item.total_comments)}
            </Text>
          </Pressable>
          <Pressable mt={5}>
            <FavoritesWhite height={7} width={7} />
          </Pressable>
        </View>
        <View
          position={'absolute'}
          bottom={height * 0.1}
          left={5}
          width={widthToDp(65)}>
          <HStack>
            <FastImage
              style={styles.profilePic}
              source={{uri: item.profile_pic}}
            />
            <View ml={3}>
              <Text
                style={[
                  styles.text,
                  styles.fullName,
                  theme === 'light' ? styles.countLight : styles.countDark,
                ]}>
                {item.full_name}
              </Text>
              <Text
                style={[
                  styles.text,
                  styles.bio,
                  theme === 'light' ? styles.bioLight : styles.bioDark,
                ]}>
                {item.user_bio}
              </Text>
            </View>
          </HStack>
          <Text
            style={[
              styles.text,
              styles.bio,
              theme === 'light' ? styles.countLight : styles.countDark,
            ]}>
            {item.description}
          </Text>
        </View>
      </View>
    );
  };
  
<SwiperFlatList
            vertical
            ref={flatListRef}
            data={reels}
            autoplay={false}
            
            renderItem={renderItem}
            onChangeIndex={({index, prevIndex}) => {
              console.log('prev=>', prevIndex, 'current index=>', index);
              setCurrentIndex(index);
            }}
            keyExtractor={item => item.id}
          />
          

[dprajapati1179]

If any one have any other work around for getting the index of current visible item then please let me know

[douglas-esportudo]

I did a few improvements (removing re-renders and adding support for getItemLayout), please use version 3.2.2 and let me know. Thanks

This worked for me! I was having this issue with onChangeIndex function, it would reach the third item in the array and stop counting. I'm using the list vertically and have a fixed header at the top with a height of 90px. I believe in this part of the code

if (props.getItemLayout === undefined) {
      const itemDimension = vertical ? height : width;
      flatListProps.getItemLayout = (__data, ItemIndex: number) => ({
        length: itemDimension,
        offset: itemDimension * ItemIndex,
        index: ItemIndex,
      });
    }

the offset didn't match the height of the images in the list. I just needed to provide this information in the SwiperFlatList:

<SwiperFlatList
        data={content}
        renderItem={({index, item}) => renderItem({index, item})}
        vertical
        keyExtractor={item => item.itemId.toString()}
        getItemLayout={(_d, i) => ({
          length: Dimensions.get('window').height,
          index: i,
          offset: (Dimensions.get('window').height - 90) * i,
        })}
        onChangeIndex={({index, prevIndex}) => console.log(index)}
      />

Now the onChangeIndex function is correctly returning the visible index.
I'm not sure if it applies to everyone here, but it worked for my case.

[devakrishna33]

I can confirm that setting getItemLayout with correct dimensions triggers the onChangeIndex correctly, can it be added to the docs?

[lsps9150414]

hey @devakrishna33 could you kindly share your code snippet?

[BLOCKMATERIAL]

same

[gusgard]

Should be fixed in 3.2.4

[Qurat-ul-ainn]

I also faced this issue. I noticed paginationIndex props of PaginationComponent always gives correct index. I found the value can be derived from parameters of onViewableItemsChanged. So here is my current workaround:

 onViewableItemsChanged={(params) => console.log('index', params.changed?.[0]?.index)}

by using this getting an error "Changing onViewableChanged on the fly is not supported"