1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
import React, {forwardRef} from 'react'
import {View} from 'react-native'
import PagerView, {
PagerViewOnPageScrollEvent,
PagerViewOnPageSelectedEvent,
PageScrollStateChangedNativeEvent,
} from 'react-native-pager-view'
import {LogEvents} from '#/lib/statsig/events'
import {atoms as a, native} from '#/alf'
export type PageSelectedEvent = PagerViewOnPageSelectedEvent
export interface PagerRef {
setPage: (
index: number,
reason: LogEvents['home:feedDisplayed']['reason'],
) => void
}
export interface RenderTabBarFnProps {
selectedPage: number
onSelect?: (index: number) => void
tabBarAnchor?: JSX.Element | null | undefined // Ignored on native.
}
export type RenderTabBarFn = (props: RenderTabBarFnProps) => JSX.Element
interface Props {
initialPage?: number
renderTabBar: RenderTabBarFn
onPageSelected?: (index: number) => void
onPageSelecting?: (
index: number,
reason: LogEvents['home:feedDisplayed']['reason'],
) => void
onPageScrollStateChanged?: (
scrollState: 'idle' | 'dragging' | 'settling',
) => void
testID?: string
}
export const Pager = forwardRef<PagerRef, React.PropsWithChildren<Props>>(
function PagerImpl(
{
children,
initialPage = 0,
renderTabBar,
onPageScrollStateChanged,
onPageSelected,
onPageSelecting,
testID,
}: React.PropsWithChildren<Props>,
ref,
) {
const [selectedPage, setSelectedPage] = React.useState(0)
const lastOffset = React.useRef(0)
const lastDirection = React.useRef(0)
const scrollState = React.useRef('')
const pagerView = React.useRef<PagerView>(null)
React.useImperativeHandle(ref, () => ({
setPage: (
index: number,
reason: LogEvents['home:feedDisplayed']['reason'],
) => {
pagerView.current?.setPage(index)
onPageSelecting?.(index, reason)
},
}))
const onPageSelectedInner = React.useCallback(
(e: PageSelectedEvent) => {
setSelectedPage(e.nativeEvent.position)
onPageSelected?.(e.nativeEvent.position)
},
[setSelectedPage, onPageSelected],
)
const onPageScroll = React.useCallback(
(e: PagerViewOnPageScrollEvent) => {
const {position, offset} = e.nativeEvent
if (offset === 0) {
// offset hits 0 in some awkward spots so we ignore it
return
}
// NOTE
// we want to call `onPageSelecting` as soon as the scroll-gesture
// enters the "settling" phase, which means the user has released it
// we can't infer directionality from the scroll information, so we
// track the offset changes. if the offset delta is consistent with
// the existing direction during the settling phase, we can say for
// certain where it's going and can fire
// -prf
if (scrollState.current === 'settling') {
if (lastDirection.current === -1 && offset < lastOffset.current) {
onPageSelecting?.(position, 'pager-swipe')
setSelectedPage(position)
lastDirection.current = 0
} else if (
lastDirection.current === 1 &&
offset > lastOffset.current
) {
onPageSelecting?.(position + 1, 'pager-swipe')
setSelectedPage(position + 1)
lastDirection.current = 0
}
} else {
if (offset < lastOffset.current) {
lastDirection.current = -1
} else if (offset > lastOffset.current) {
lastDirection.current = 1
}
}
lastOffset.current = offset
},
[lastOffset, lastDirection, onPageSelecting],
)
const handlePageScrollStateChanged = React.useCallback(
(e: PageScrollStateChangedNativeEvent) => {
scrollState.current = e.nativeEvent.pageScrollState
onPageScrollStateChanged?.(e.nativeEvent.pageScrollState)
},
[scrollState, onPageScrollStateChanged],
)
const onTabBarSelect = React.useCallback(
(index: number) => {
pagerView.current?.setPage(index)
onPageSelecting?.(index, 'tabbar-click')
},
[pagerView, onPageSelecting],
)
return (
<View testID={testID} style={[a.flex_1, native(a.overflow_hidden)]}>
{renderTabBar({
selectedPage,
onSelect: onTabBarSelect,
})}
<PagerView
ref={pagerView}
style={[a.flex_1]}
initialPage={initialPage}
onPageScrollStateChanged={handlePageScrollStateChanged}
onPageSelected={onPageSelectedInner}
onPageScroll={onPageScroll}>
{children}
</PagerView>
</View>
)
},
)
|
