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Update proposed-offset-calculation algorithm, the result is more accurate.

This commit is contained in:
WenchaoD 2018-10-03 11:55:14 +08:00
parent b5fc6ccbfc
commit c72899860d
1 changed files with 5 additions and 6 deletions
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11
Sources/FSPageViewLayout.swift
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@ -154,9 +154,8 @@ class FSPagerViewLayout: UICollectionViewLayout {
return proposedContentOffset
}
var proposedContentOffset = proposedContentOffset
let touchedContentOffset: CGPoint = collectionView.panGestureRecognizer.location(in: collectionView)
func calculateTargetOffset(by proposedOffset: CGFloat, touchedOffset: CGFloat, boundedOffset: CGFloat) -> CGFloat {
func calculateTargetOffset(by proposedOffset: CGFloat, boundedOffset: CGFloat) -> CGFloat {
var targetOffset: CGFloat
if pagerView.decelerationDistance == FSPagerView.automaticDistance {
if abs(velocity.x) >= 0.3 {
@ -169,9 +168,9 @@ class FSPagerViewLayout: UICollectionViewLayout {
let extraDistance = max(pagerView.decelerationDistance-1, 0)
switch velocity.x {
case 0.3 ... CGFloat.greatestFiniteMagnitude:
targetOffset = ceil(touchedOffset/self.itemSpacing+CGFloat(extraDistance)) * self.itemSpacing
targetOffset = ceil(collectionView.contentOffset.x/self.itemSpacing+CGFloat(extraDistance)) * self.itemSpacing
case -CGFloat.greatestFiniteMagnitude ... -0.3:
targetOffset = floor(touchedOffset/self.itemSpacing-1-CGFloat(extraDistance)) * self.itemSpacing
targetOffset = floor(collectionView.contentOffset.x/self.itemSpacing-CGFloat(extraDistance)) * self.itemSpacing
default:
targetOffset = round(proposedOffset/self.itemSpacing) * self.itemSpacing
}
@ -185,14 +184,14 @@ class FSPagerViewLayout: UICollectionViewLayout {
return proposedContentOffset.x
}
let boundedOffset = collectionView.contentSize.width-self.itemSpacing
return calculateTargetOffset(by: proposedContentOffset.x, touchedOffset: touchedContentOffset.x, boundedOffset: boundedOffset)
return calculateTargetOffset(by: proposedContentOffset.x, boundedOffset: boundedOffset)
}()
let proposedContentOffsetY: CGFloat = {
if self.scrollDirection == .horizontal {
return proposedContentOffset.y
}
let boundedOffset = collectionView.contentSize.height-self.itemSpacing
return calculateTargetOffset(by: proposedContentOffset.y, touchedOffset: touchedContentOffset.y, boundedOffset: boundedOffset)
return calculateTargetOffset(by: proposedContentOffset.y, boundedOffset: boundedOffset)
}()
proposedContentOffset = CGPoint(x: proposedContentOffsetX, y: proposedContentOffsetY)
return proposedContentOffset