我正在制作一个信使应用程序，例如电报，我想实现无限滚动，我JSQMessageViewController用于聊天。
这是无限滚动的代码：
override func scrollViewDidScroll(scrollView: UIScrollView) {
if(scrollView.contentOffset.y >= 0.0 && scrollView.contentOffset.y <= 30.0 && loading == true){
self.loading = false
self.loadMore()
}
}
然后我调用这个函数：
func loadMore() {
//Controllo se nell'array sono presenti altri messaggi
if ((chatList?.messages.count)!-1) != self.messages.count{
//
CATransaction.begin()
CATransaction.setDisableActions(true)
let oldBottomOffset = self.collectionView!.contentSize.height - self.collectionView!.contentOffset.y
UIView.performWithoutAnimation({ () -> Void in
self.collectionView!.performBatchUpdates({ () -> Void in
let idInit = (self.lastMessageId-self.messagePerPage<0) ? 0 : self.lastMessageId-1-self.messagePerPage
let idEnd = self.lastMessageId-1
var indexPaths: [NSIndexPath] = []
for(var i = 0; i<idEnd-idInit; i++){
print("Creo indexpath \(i)")
indexPaths.append(NSIndexPath(forItem: i, inSection: 0))
}
self.collectionView!.insertItemsAtIndexPaths(indexPaths)
let msg = self.chatList?.messages
var i = idEnd
repeat {
let mg = msg![i]
let messagechat:JSQMessage = JSQMessage(senderId: mg.sender, senderDisplayName: "", date:mg.time, text: mg.message)
messagechat.xmppMessageID = mg.messageID
messagechat.status = mg.messageStatus
self.messages.insert(messagechat, atIndex: 0)
self.lastMessageId = i
i--
} while i > idInit
// invalidate layout
self.collectionView!.collectionViewLayout.invalidateLayoutWithContext(JSQMessagesCollectionViewFlowLayoutInvalidationContext())
}, completion: {(finished) in
//scroll back to current position
self.finishReceivingMessageAnimated(false)
self.collectionView!.layoutIfNeeded()
self.collectionView!.contentOffset = CGPointMake(0, self.collectionView!.contentSize.height - oldBottomOffset)
CATransaction.commit()
})
})
}
else {
print("No more messages to load.")
}
}
一切正常，但scrolling滚动停止 1 秒。我想是CATransaction这样做的，有时我会看到跳转效果，如果我添加 10 条新消息，我会在第一时间看到 10 条消息中的第一条消息，然后将偏移量正确设置为旧位置。我怎样才能解决这个问题？我看到电报scrolling很完美，加载旧消息时没有跳转效果。