308 lines
11 KiB
JavaScript
308 lines
11 KiB
JavaScript
/**
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow strict-local
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* @format
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*/
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import type {LayoutEvent} from '../../Types/CoreEventTypes';
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import Animated from '../../Animated/Animated';
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import {isPublicInstance as isFabricPublicInstance} from '../../Renderer/public/ReactFabricPublicInstanceUtils';
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import StyleSheet from '../../StyleSheet/StyleSheet';
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import Platform from '../../Utilities/Platform';
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import useMergeRefs from '../../Utilities/useMergeRefs';
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import * as React from 'react';
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import {useCallback, useEffect, useMemo, useRef, useState} from 'react';
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export type Props = $ReadOnly<{
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children?: React.Element<$FlowFixMe>,
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nextHeaderLayoutY: ?number,
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onLayout: (event: LayoutEvent) => void,
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scrollAnimatedValue: Animated.Value,
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// Will cause sticky headers to stick at the bottom of the ScrollView instead
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// of the top.
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inverted: ?boolean,
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// The height of the parent ScrollView. Currently only set when inverted.
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scrollViewHeight: ?number,
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nativeID?: ?string,
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hiddenOnScroll?: ?boolean,
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}>;
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type Instance = {
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...React.ElementRef<typeof Animated.View>,
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setNextHeaderY: number => void,
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...
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};
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const ScrollViewStickyHeaderWithForwardedRef: React.AbstractComponent<
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Props,
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Instance,
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> = React.forwardRef(function ScrollViewStickyHeader(props, forwardedRef) {
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const {
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inverted,
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scrollViewHeight,
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hiddenOnScroll,
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scrollAnimatedValue,
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nextHeaderLayoutY: _nextHeaderLayoutY,
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} = props;
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const [measured, setMeasured] = useState<boolean>(false);
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const [layoutY, setLayoutY] = useState<number>(0);
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const [layoutHeight, setLayoutHeight] = useState<number>(0);
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const [translateY, setTranslateY] = useState<?number>(null);
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const [nextHeaderLayoutY, setNextHeaderLayoutY] =
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useState<?number>(_nextHeaderLayoutY);
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const [isFabric, setIsFabric] = useState<boolean>(false);
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const callbackRef = (ref: Instance | null): void => {
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if (ref == null) {
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return;
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}
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ref.setNextHeaderY = value => {
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setNextHeaderLayoutY(value);
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};
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setIsFabric(isFabricPublicInstance(ref));
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};
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const ref: (React.ElementRef<typeof Animated.View> | null) => void =
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// $FlowFixMe[incompatible-type] - Ref is mutated by `callbackRef`.
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useMergeRefs<Instance | null>(callbackRef, forwardedRef);
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const offset = useMemo(
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() =>
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hiddenOnScroll === true
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? Animated.diffClamp(
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scrollAnimatedValue
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.interpolate({
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extrapolateLeft: 'clamp',
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inputRange: [layoutY, layoutY + 1],
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outputRange: ([0, 1]: Array<number>),
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})
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.interpolate({
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inputRange: [0, 1],
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outputRange: ([0, -1]: Array<number>),
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}),
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-layoutHeight,
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0,
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)
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: null,
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[scrollAnimatedValue, layoutHeight, layoutY, hiddenOnScroll],
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);
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const [animatedTranslateY, setAnimatedTranslateY] = useState<Animated.Node>(
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() => {
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const inputRange: Array<number> = [-1, 0];
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const outputRange: Array<number> = [0, 0];
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const initialTranslateY = scrollAnimatedValue.interpolate({
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inputRange,
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outputRange,
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});
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if (offset != null) {
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return Animated.add(initialTranslateY, offset);
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}
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return initialTranslateY;
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},
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);
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const _haveReceivedInitialZeroTranslateY = useRef<boolean>(true);
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const _timer = useRef<?TimeoutID>(null);
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useEffect(() => {
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if (translateY !== 0 && translateY != null) {
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_haveReceivedInitialZeroTranslateY.current = false;
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}
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}, [translateY]);
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// This is called whenever the (Interpolated) Animated Value
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// updates, which is several times per frame during scrolling.
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// To ensure that the Fabric ShadowTree has the most recent
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// translate style of this node, we debounce the value and then
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// pass it through to the underlying node during render.
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// This is:
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// 1. Only an issue in Fabric.
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// 2. Worse in Android than iOS. In Android, but not iOS, you
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// can touch and move your finger slightly and still trigger
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// a "tap" event. In iOS, moving will cancel the tap in
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// both Fabric and non-Fabric. On Android when you move
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// your finger, the hit-detection moves from the Android
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// platform to JS, so we need the ShadowTree to have knowledge
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// of the current position.
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const animatedValueListener = useCallback(
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({value}: $FlowFixMe) => {
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const _debounceTimeout: number = Platform.OS === 'android' ? 15 : 64;
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// When the AnimatedInterpolation is recreated, it always initializes
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// to a value of zero and emits a value change of 0 to its listeners.
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if (value === 0 && !_haveReceivedInitialZeroTranslateY.current) {
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_haveReceivedInitialZeroTranslateY.current = true;
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return;
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}
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if (_timer.current != null) {
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clearTimeout(_timer.current);
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}
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_timer.current = setTimeout(() => {
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if (value !== translateY) {
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setTranslateY(value);
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}
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}, _debounceTimeout);
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},
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[translateY],
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);
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useEffect(() => {
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const inputRange: Array<number> = [-1, 0];
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const outputRange: Array<number> = [0, 0];
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if (measured) {
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if (inverted === true) {
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// The interpolation looks like:
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// - Negative scroll: no translation
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// - `stickStartPoint` is the point at which the header will start sticking.
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// It is calculated using the ScrollView viewport height so it is a the bottom.
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// - Headers that are in the initial viewport will never stick, `stickStartPoint`
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// will be negative.
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// - From 0 to `stickStartPoint` no translation. This will cause the header
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// to scroll normally until it reaches the top of the scroll view.
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// - From `stickStartPoint` to when the next header y hits the bottom edge of the header: translate
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// equally to scroll. This will cause the header to stay at the top of the scroll view.
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// - Past the collision with the next header y: no more translation. This will cause the
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// header to continue scrolling up and make room for the next sticky header.
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// In the case that there is no next header just translate equally to
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// scroll indefinitely.
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if (scrollViewHeight != null) {
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const stickStartPoint = layoutY + layoutHeight - scrollViewHeight;
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if (stickStartPoint > 0) {
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inputRange.push(stickStartPoint);
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outputRange.push(0);
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inputRange.push(stickStartPoint + 1);
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outputRange.push(1);
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// If the next sticky header has not loaded yet (probably windowing) or is the last
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// we can just keep it sticked forever.
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const collisionPoint =
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(nextHeaderLayoutY || 0) - layoutHeight - scrollViewHeight;
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if (collisionPoint > stickStartPoint) {
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inputRange.push(collisionPoint, collisionPoint + 1);
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outputRange.push(
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collisionPoint - stickStartPoint,
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collisionPoint - stickStartPoint,
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);
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}
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}
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}
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} else {
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// The interpolation looks like:
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// - Negative scroll: no translation
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// - From 0 to the y of the header: no translation. This will cause the header
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// to scroll normally until it reaches the top of the scroll view.
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// - From header y to when the next header y hits the bottom edge of the header: translate
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// equally to scroll. This will cause the header to stay at the top of the scroll view.
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// - Past the collision with the next header y: no more translation. This will cause the
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// header to continue scrolling up and make room for the next sticky header.
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// In the case that there is no next header just translate equally to
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// scroll indefinitely.
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inputRange.push(layoutY);
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outputRange.push(0);
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// If the next sticky header has not loaded yet (probably windowing) or is the last
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// we can just keep it sticked forever.
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const collisionPoint = (nextHeaderLayoutY || 0) - layoutHeight;
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if (collisionPoint >= layoutY) {
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inputRange.push(collisionPoint, collisionPoint + 1);
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outputRange.push(collisionPoint - layoutY, collisionPoint - layoutY);
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} else {
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inputRange.push(layoutY + 1);
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outputRange.push(1);
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}
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}
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}
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let newAnimatedTranslateY: Animated.Node = scrollAnimatedValue.interpolate({
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inputRange,
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outputRange,
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});
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if (offset != null) {
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newAnimatedTranslateY = Animated.add(newAnimatedTranslateY, offset);
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}
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// add the event listener
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let animatedListenerId;
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if (isFabric) {
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animatedListenerId = newAnimatedTranslateY.addListener(
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animatedValueListener,
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);
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}
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setAnimatedTranslateY(newAnimatedTranslateY);
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// clean up the event listener and timer
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return () => {
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if (animatedListenerId) {
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newAnimatedTranslateY.removeListener(animatedListenerId);
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}
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if (_timer.current != null) {
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clearTimeout(_timer.current);
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}
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};
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}, [nextHeaderLayoutY, measured, layoutHeight, layoutY, scrollViewHeight, scrollAnimatedValue, inverted, offset, animatedValueListener, isFabric]);
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const _onLayout = (event: LayoutEvent) => {
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setLayoutY(event.nativeEvent.layout.y);
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setLayoutHeight(event.nativeEvent.layout.height);
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setMeasured(true);
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props.onLayout(event);
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const child = React.Children.only<$FlowFixMe>(props.children);
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if (child.props.onLayout) {
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child.props.onLayout(event);
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}
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};
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const child = React.Children.only<$FlowFixMe>(props.children);
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// TODO T68319535: remove this if NativeAnimated is rewritten for Fabric
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const passthroughAnimatedPropExplicitValues =
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isFabric && translateY != null
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? {
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style: {transform: [{translateY: translateY}]},
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}
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: null;
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return (
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/* $FlowFixMe[prop-missing] passthroughAnimatedPropExplicitValues isn't properly
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included in the Animated.View flow type. */
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<Animated.View
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collapsable={false}
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nativeID={props.nativeID}
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onLayout={_onLayout}
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ref={ref}
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style={[
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child.props.style,
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styles.header,
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{transform: [{translateY: animatedTranslateY}]},
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]}
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passthroughAnimatedPropExplicitValues={
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passthroughAnimatedPropExplicitValues
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}>
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{React.cloneElement(child, {
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style: styles.fill, // We transfer the child style to the wrapper.
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onLayout: undefined, // we call this manually through our this._onLayout
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})}
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</Animated.View>
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);
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});
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const styles = StyleSheet.create({
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header: {
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zIndex: 10,
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position: 'relative',
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},
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fill: {
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flex: 1,
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},
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});
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export default ScrollViewStickyHeaderWithForwardedRef;
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