scrollTo works improperly

sowf commented 3 years ago

Which OS ?

Windows 10 x64

Version

Which versions I am using:

react-native-swiper v 1.6.0-rc.3?
react-native v0.63.2

Expected behaviour

When using inside onIndexChanged() it lags behind by 1 slide.

const MyScreen= () => {
const [currentIndex, setCurrentIndex] = useState(0);
const swiper = React.createRef();
const onIndexChanged = (index) => {
    console.log('Changed to ' + index);
    console.log(swiper.current.state.index);
    if (index > currentIndex) {
      console.log('Inside');
      swiper.current.scrollTo(currentIndex);
    }
  };
return (
    <Swiper
      ref={swiper}
      onIndexChanged={onIndexChanged}
      paginationStyle={styles.swiperPagination}
      dotColor={appColors.primary.dark}
      activeDotColor={appColors.primary.light}
      buttonWrapperStyle={{borderColor: 'white'}}
      loop={false}
      showsButtons
      nextButton={<Text style={styles.swiperButton}>›</Text>}
      prevButton={<Text style={styles.swiperButton}>‹</Text>}>
      {slides}
    </Swiper>

If I swipe left index changes to 1 (initial index = 0) and condition (index > currentIndex = true) is met, so it should be scrolled to slide with index 0

Actual behaviour

After left swipe condition (index > currentIndex = true) is met, so console logs 'Inside', but swiper.current.scrollTo(currentIndex) doesn't work. It happens because swiper state index value is one unit behind real index value and scrollTo function checks whether is it on the same slide, state says yes and nothing changes.

START! SWIPE! SWIPE!

So instead of immediate scrolling scrollTo function waits untill its state changes, and then it scrolls to slide with 0 index. As I have already mentioned it happens because swiper state index value is one unit behind real index value