Automatically Scroll a tableview when another scrollView goes to a certain contentOffset - ios

Question

There are two scrollView in the View: mainScrollView(red) and listTable(yellow). I want to set that mainScrollView scrolls first and does the following actions:
When the topView disappears and top of the listTable reaches top of the screen, the listTable scrolls up automatically.
If the top of listTable is at the top of screen, the mainScrollView scroll down first when user scrolls down.
func detectScrollView(_ scrollView: UIScrollView){
if scrollView.tag == 1{
if scrollView.contentOffset.y >= 100{
mainScrollView.isScrollEnabled = false
mainScrollView.contentOffset.y = 100
mainScrollView.panGestureRecognizer.isEnabled = false
listTable.isScrollEnabled = true
listTable.panGestureRecognizer.isEnabled = true
}
}else{
//.....
}
}
By now, I just try the codes of scrolling up action, and it can runs part of my need. Problem is that the listTable cannot scrolls automatically when it's top reaches top of the screen. I have to make it works by releasing my finger from the screen and starting a new drag.
How can I continue the panGesture using on the listTable?
======= Update 2017-7-3 =======
I temporarily use the following codes:
var lastContentOffset:CGFloat = 0
func detectScrollView(){
if (self.lastContentOffset > mainScrollView.contentOffset.y) {
// move up
listTable.isScrollEnabled = true
}
else if (self.lastContentOffset < mainScrollView.contentOffset.y) {
// move down
if mainScrollView.contentOffset.y >= 110{
mainScrollView.setContentOffset(CGPoint(x:0, y:110), animated: true)
listTable.isScrollEnabled = true
}else{
listTable.isScrollEnabled = false
}
}
// update the new position acquired
self.lastContentOffset = mainScrollView.contentOffset.y
}
Moving up is solved, and still moving down needs retouching the screen so as to scroll the listTable.