35. Swipe to delete

Quite a complicated example that combines layout animations, useAnimation(), and info provided by an onDragEnd() event.

Code component

A few details in the Item() component:

• When the dragging stops (onDragEnd()), the handleDragEnd() function looks at the current offset or velocity.
• When one of those is high enough:
  • an useAnimation() animation will slide the item offscreen,
  • and the onDelete() function in the parent component is called.
• The items have a layout property (so that they animate to their new position automatically) and springy transition settings.

const initialItems = [0, 1, 2, 3, 4]
const height = 70
const padding = 10
const size = 150

function Item({ total, index, onDelete }) {
    const controls = useAnimation()

    async function handleDragEnd(event, info) {
        const offset = info.offset.x
        const velocity = info.velocity.x

        if (offset < -100 || velocity < -500) {
            await controls.start({ x: "-100%", transition: { duration: 0.2 } })
            onDelete(index)
        } else {
            controls.start({ x: 0, opacity: 1, transition: { duration: 0.5 } })
        }
    }

    return (
        <motion.div
            style={{
                width: 150,
                height: height,
                borderRadius: 20,
                overflow: "hidden",
                marginBottom: total - 1 === index ? 0 : 10,
                willChange: "transform",
                cursor: "grab",
            }}
            whileTap={{ cursor: "grabbing" }}
            layout
            transition={{ type: "spring", stiffness: 600, damping: 30 }}
        >
            <motion.div
                style={{
                    width: size,
                    height: height,
                    borderRadius: 20,
                    backgroundColor: "#fff",
                }}
                drag="x"
                dragDirectionLock
                onDragEnd={handleDragEnd}
                animate={controls}
            />
        </motion.div>
    )
}

export default function CC_35_Swipe_to_delete(props) {
    const y = useMotionValue(0)

    const [items, setItems] = useState(initialItems)
    const { top, bottom } = useConstraints(items)
    const controls = useAnimation()
    const totalScroll = getHeight(items)
    const scrollContainer = 150

    function onDelete(index) {
        const newItems = [...items]
        newItems.splice(index, 1)

        const newScrollHeight = getHeight(newItems)
        const bottomOffset = -y.get() + scrollContainer
        const bottomWillBeVisible = newScrollHeight < bottomOffset
        const isScrollHeightLarger = newScrollHeight >= scrollContainer

        if (bottomWillBeVisible && isScrollHeightLarger) {
            controls.start({ y: -newScrollHeight + scrollContainer })
        }

        setItems(newItems)
    }

    return (
        <div
            style={{
                width: 400,
                height: 400,
                ...props.style,
                display: "flex",
                placeItems: "center",
                placeContent: "center",
            }}
        >
            <div
                style={{
                    width: size,
                    height: size,
                    borderRadius: 30,
                    background: "transparent",
                    overflow: "hidden",
                    position: "relative",
                    transform: "translateZ(0)",
                }}
            >
                <motion.div
                    style={{ y: y, height: totalScroll }}
                    drag="y"
                    dragDirectionLock
                    dragConstraints={{ top, bottom }}
                    animate={controls}
                >
                    {items.map((value, index) => {
                        return (
                            <Item
                                total={items.length}
                                index={index}
                                onDelete={onDelete}
                                key={value}
                            />
                        )
                    })}
                </motion.div>
            </div>
        </div>
    )
}

function getHeight(items) {
    const totalHeight = items.length * height
    const totalPadding = (items.length - 1) * padding
    const totalScroll = totalHeight + totalPadding
    return totalScroll
}

function useConstraints(items) {
    const [constraints, setConstraints] = useState({ top: 0, bottom: 0 })

    useEffect(() => {
        setConstraints({ top: size - getHeight(items), bottom: 0 })
    }, [items])

    return constraints
}

Some more details in the main CC_35_Swipe_to_delete() component:

• The onDelete() function also checks for empty space at the bottom (occurs when you delete the bottommost item) and will move the items down when needed (with a useAnimation()).
• A reference to this onDelete() function is passed down to every <Item>.

Code override

While it might be possible to create this interaction with overrides, it would be way more complicated. Not really worth the effort.