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ios: equal scrolling speed to top/bottom and fix of scroll loop (#5649)

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This commit is contained in:
Stanislav Dmitrenko
2025-02-21 03:46:22 +07:00
committed by GitHub
parent 676583d3c3
commit ca3687488f
1 changed files with 21 additions and 9 deletions
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30
apps/ios/Shared/Views/Chat/EndlessScrollView.swift
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@@ -107,7 +107,7 @@ class EndlessScrollView<ScrollItem>: UIScrollView, UIScrollViewDelegate, UIGestu
var averageItemHeight: CGFloat = 30
/// This is used as a multiplier for difference between current index and scrollTo index using [averageItemHeight] as well. Increase it to get faster speed
var scrollStepMultiplier: CGFloat = 0.6
var scrollStepMultiplier: CGFloat = 0.37
/// Adds content padding to top
var insetTop: CGFloat = 100
@@ -324,6 +324,8 @@ class EndlessScrollView<ScrollItem>: UIScrollView, UIScrollViewDelegate, UIGestu
var shouldBeFirstVisible = items.firstIndex(where: { item in item.id == listState.firstVisibleItemId as! ScrollItem.ID }) ?? 0
var wasFirstVisibleItemOffset = listState.firstVisibleItemOffset
var alreadyChangedIndexWhileScrolling = false
var allowOneMore = false
var nextOffsetY: CGFloat = 0
var i = shouldBeFirstVisible
@@ -343,16 +345,24 @@ class EndlessScrollView<ScrollItem>: UIScrollView, UIScrollViewDelegate, UIGestu
}
if shouldBeFirstVisible == i {
if let vis = visible {
let oldHeight = vis.view.frame.height
vis.view.frame.origin.y += oldHeight - vis.view.frame.height
// the fist visible item previously is hidden now, remove it and move on
if !isVisible(vis.view) {
if // there is auto scroll in progress and the first item has a higher offset than bottom part
// of the screen. In order to make scrolling down & up equal in time, we treat this as a sign to
// re-make the first visible item
(listState.isScrolling && vis.view.frame.origin.y + vis.view.bounds.height < contentOffsetY + bounds.height) ||
// the fist visible item previously is hidden now, remove it and move on
!isVisible(vis.view) {
let newIndex: Int
if listState.isScrolling {
// skip many items to make the scrolling take less time
var indexDiff = Int(ceil(abs(offsetsDiff / averageItemHeight)))
var indexDiff = !alreadyChangedIndexWhileScrolling ? Int(ceil(abs(offsetsDiff / averageItemHeight))) : 0
// if index was already changed, no need to change it again. Otherwise, the scroll will overscoll and return back animated. Because it means the whole screen was scrolled
alreadyChangedIndexWhileScrolling = true
indexDiff = offsetsDiff <= 0 ? indexDiff : -indexDiff
newIndex = max(0, min(items.count - 1, i + indexDiff))
// offset for the first visible item can now be 0 because the previous first visible item doesn't exist anymore
wasFirstVisibleItemOffset = 0
} else {
// don't skip multiple items if it's manual scrolling gesture
newIndex = i + (offsetsDiff <= 0 ? 1 : -1)
@@ -370,7 +380,7 @@ class EndlessScrollView<ScrollItem>: UIScrollView, UIScrollViewDelegate, UIGestu
vis = VisibleItem(index: i, item: item, view: visible.view, offset: offsetToBottom(visible.view))
} else {
let cell = createCell(i, items, &cellsToReuse)!
cell.frame.origin.y = bottomY + listState.firstVisibleItemOffset - cell.frame.height
cell.frame.origin.y = bottomY + wasFirstVisibleItemOffset - cell.frame.height
vis = VisibleItem(index: i, item: item, view: cell, offset: offsetToBottom(cell))
}
if vis.view.superview == nil {
@@ -499,7 +509,7 @@ class EndlessScrollView<ScrollItem>: UIScrollView, UIScrollViewDelegate, UIGestu
let firstOrLastIndex = up ? listState.visibleItems.last?.index ?? 0 : listState.firstVisibleItemIndex
let step: CGFloat = max(0.1, CGFloat(abs(index - firstOrLastIndex)) * scrollStepMultiplier) * stepSlowdownMultiplier
let offsetToScroll = (up ? -averageItemHeight : averageItemHeight) * step * stepSlowdownMultiplier
let offsetToScroll = (up ? -averageItemHeight : averageItemHeight) * step
adjustedOffset += offsetToScroll
if let item = listState.visibleItems.first(where: { $0.index == index }) {
let y = if top {
@@ -544,7 +554,9 @@ class EndlessScrollView<ScrollItem>: UIScrollView, UIScrollViewDelegate, UIGestu
let firstOrLastIndex = up ? listState.visibleItems.last?.index ?? 0 : listState.firstVisibleItemIndex
let step: CGFloat = max(0.1, CGFloat(abs(index - firstOrLastIndex)) * scrollStepMultiplier) * stepSlowdownMultiplier
let offsetToScroll = (up ? -averageItemHeight : averageItemHeight) * step * stepSlowdownMultiplier
//println("Scrolling step \(step) \(stepSlowdownMultiplier) index \(index) \(firstOrLastIndex) \(index - firstOrLastIndex) \(adjustedOffset), up \(up), i \(i)")
let offsetToScroll = (up ? -averageItemHeight : averageItemHeight) * step
adjustedOffset += offsetToScroll
if let item = listState.visibleItems.first(where: { $0.index == index }) {
let y = if top {