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import {
useCallback,
useContext,
useImperativeHandle,
useRef,
useState,
} from 'react'
import {View} from 'react-native'
import {DrawerGestureContext} from 'react-native-drawer-layout'
import {Gesture, GestureDetector} from 'react-native-gesture-handler'
import PagerView, {
type PagerViewOnPageScrollEventData,
type PagerViewOnPageSelectedEvent,
type PagerViewOnPageSelectedEventData,
type PageScrollStateChangedNativeEventData,
} from 'react-native-pager-view'
import Animated, {
runOnJS,
type SharedValue,
useEvent,
useHandler,
useSharedValue,
} from 'react-native-reanimated'
import {useFocusEffect} from '@react-navigation/native'
import {useSetDrawerSwipeDisabled} from '#/state/shell'
import {atoms as a, native} from '#/alf'
export type PageSelectedEvent = PagerViewOnPageSelectedEvent
export interface PagerRef {
setPage: (index: number) => void
}
export interface RenderTabBarFnProps {
selectedPage: number
onSelect?: (index: number) => void
tabBarAnchor?: JSX.Element | null | undefined // Ignored on native.
dragProgress: SharedValue<number> // Ignored on web.
dragState: SharedValue<'idle' | 'dragging' | 'settling'> // Ignored on web.
}
export type RenderTabBarFn = (props: RenderTabBarFnProps) => JSX.Element
interface Props {
ref?: React.Ref<PagerRef>
initialPage?: number
renderTabBar: RenderTabBarFn
// tab pressed, yet to scroll to page
onTabPressed?: (index: number) => void
// scroll settled
onPageSelected?: (index: number) => void
onPageScrollStateChanged?: (
scrollState: 'idle' | 'dragging' | 'settling',
) => void
testID?: string
}
const AnimatedPagerView = Animated.createAnimatedComponent(PagerView)
export function Pager({
ref,
children,
initialPage = 0,
renderTabBar,
onPageSelected: parentOnPageSelected,
onTabPressed: parentOnTabPressed,
onPageScrollStateChanged: parentOnPageScrollStateChanged,
testID,
}: React.PropsWithChildren<Props>) {
const [selectedPage, setSelectedPage] = useState(initialPage)
const pagerView = useRef<PagerView>(null)
const [isIdle, setIsIdle] = useState(true)
const setDrawerSwipeDisabled = useSetDrawerSwipeDisabled()
useFocusEffect(
useCallback(() => {
const canSwipeDrawer = selectedPage === 0 && isIdle
setDrawerSwipeDisabled(!canSwipeDrawer)
return () => {
setDrawerSwipeDisabled(false)
}
}, [setDrawerSwipeDisabled, selectedPage, isIdle]),
)
useImperativeHandle(ref, () => ({
setPage: (index: number) => {
pagerView.current?.setPage(index)
},
}))
const onPageSelectedJSThread = useCallback(
(nextPosition: number) => {
setSelectedPage(nextPosition)
parentOnPageSelected?.(nextPosition)
},
[setSelectedPage, parentOnPageSelected],
)
const onTabBarSelect = useCallback(
(index: number) => {
parentOnTabPressed?.(index)
pagerView.current?.setPage(index)
},
[pagerView, parentOnTabPressed],
)
const dragState = useSharedValue<'idle' | 'settling' | 'dragging'>('idle')
const dragProgress = useSharedValue(selectedPage)
const didInit = useSharedValue(false)
const handlePageScroll = usePagerHandlers(
{
onPageScroll(e: PagerViewOnPageScrollEventData) {
'worklet'
if (didInit.get() === false) {
// On iOS, there's a spurious scroll event with 0 position
// even if a different page was supplied as the initial page.
// Ignore it and wait for the first confirmed selection instead.
return
}
dragProgress.set(e.offset + e.position)
},
onPageScrollStateChanged(e: PageScrollStateChangedNativeEventData) {
'worklet'
runOnJS(setIsIdle)(e.pageScrollState === 'idle')
if (dragState.get() === 'idle' && e.pageScrollState === 'settling') {
// This is a programmatic scroll on Android.
// Stay "idle" to match iOS and avoid confusing downstream code.
return
}
dragState.set(e.pageScrollState)
parentOnPageScrollStateChanged?.(e.pageScrollState)
},
onPageSelected(e: PagerViewOnPageSelectedEventData) {
'worklet'
didInit.set(true)
runOnJS(onPageSelectedJSThread)(e.position)
},
},
[parentOnPageScrollStateChanged],
)
const drawerGesture = useContext(DrawerGestureContext) ?? Gesture.Native() // noop for web
const nativeGesture =
Gesture.Native().requireExternalGestureToFail(drawerGesture)
return (
<View testID={testID} style={[a.flex_1, native(a.overflow_hidden)]}>
{renderTabBar({
selectedPage,
onSelect: onTabBarSelect,
dragProgress,
dragState,
})}
<GestureDetector gesture={nativeGesture}>
<AnimatedPagerView
ref={pagerView}
style={[a.flex_1]}
initialPage={initialPage}
onPageScroll={handlePageScroll}>
{children}
</AnimatedPagerView>
</GestureDetector>
</View>
)
}
function usePagerHandlers(
handlers: {
onPageScroll: (e: PagerViewOnPageScrollEventData) => void
onPageScrollStateChanged: (e: PageScrollStateChangedNativeEventData) => void
onPageSelected: (e: PagerViewOnPageSelectedEventData) => void
},
dependencies: unknown[],
) {
const {doDependenciesDiffer} = useHandler(handlers as any, dependencies)
const subscribeForEvents = [
'onPageScroll',
'onPageScrollStateChanged',
'onPageSelected',
]
return useEvent(
event => {
'worklet'
const {onPageScroll, onPageScrollStateChanged, onPageSelected} = handlers
if (event.eventName.endsWith('onPageScroll')) {
onPageScroll(event as any as PagerViewOnPageScrollEventData)
} else if (event.eventName.endsWith('onPageScrollStateChanged')) {
onPageScrollStateChanged(
event as any as PageScrollStateChangedNativeEventData,
)
} else if (event.eventName.endsWith('onPageSelected')) {
onPageSelected(event as any as PagerViewOnPageSelectedEventData)
}
},
subscribeForEvents,
doDependenciesDiffer,
)
}
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