I was wondering how to detect if the UITableView is scrolled (up or down).
I want to hide the keyboard when the UITableView is scrolled with self.view.endEditing(true).
Thanks in advance
You can set property of UITable view (XCode 7+)
In Storyboard:
in Code:
tableView.keyboardDismissMode = .onDrag
You can add UIScrollViewDelegate. After that you can implement scrollViewDidScroll method.
I believe the complete solution would be the following:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if scrollView == feedTableView {
let contentOffset = scrollView.contentOffset.y
print("contentOffset: ", contentOffset)
if (contentOffset > self.lastKnowContentOfsset) {
print("scrolling Down")
print("dragging Up")
} else {
print("scrolling Up")
print("dragging Down")
}
}
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if scrollView == feedTableView {
self.lastKnowContentOfsset = scrollView.contentOffset.y
print("lastKnowContentOfsset: ", scrollView.contentOffset.y)
}
}
The previous answers weren't 100% accurate.
Explanation: scrollViewDidEndDragging will be called when the scrolling stops, therefore we save the last know offset. After that we compare it with the current offset in the delegate method scrollViewDidScroll.
override func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
if(velocity.y>0){
NSLog("dragging Up");
}else{
NSLog("dragging Down");
}
}
Related
I have a UIViewController that has UITableView and UICollectionView. I want to do certain tasks when UICollectionView is scrolled.
I've extended UIScrollViewDelegate and wrote my code in
func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView)
But this method is called when both UITableView and UICollectionView are scrolled. How do I differentiate between the two views here? I tried
func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
if let cv = scrollView as? UICollectionView {
}
}
But it's not working. I tried po scrollView and the output is <uninitialized>.
// Say tv and cv are outlets to table View and Collection View
Objective c
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if (scrollView == self.tv) {
self.tv.contentOffset = self.tv.contentOffset;
} else if (scrollView == self.cv) {
self.cv.contentOffset = self.cv.contentOffset;
}
}
Swift
func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
if let scrollView == tv {
//do whatever you need with tableView
}
if let scrollView == cv {
//do whatever you need with collectionView
}
}
It was a mistake on my end but for others here I'll post the answer.
I needed to execute my code when slider has finished dragging/scrolling. To achieve that I had
func scrollViewDidScroll(_ scrollView: UIScrollView) {
NSObject.cancelPreviousPerformRequests(withTarget: self)
perform(#selector(UIScrollViewDelegate.scrollViewDidEndScrollingAnimation), with: nil, afterDelay: 0.3)
}
Problem was in line
perform(#selector(UIScrollViewDelegate.scrollViewDidEndScrollingAnimation), with: nil, afterDelay: 0.3)
Instead of passing nil, I wrote
perform(#selector(UIScrollViewDelegate.scrollViewDidEndScrollingAnimation), with: scrollView afterDelay: 0.3)
and that resolved it. I wasn't getting scrollView <uninitialized> anymore and my
if let cv = scrollView as? UICollectionView {
}
worked fine.
How can I detect when the user scrolled to the very top of my collectionView?
I tried to use this code:
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if collectionView.contentOffset.y <= collectionView.contentSize.height - collectionView.frame.size.height {
print("top")
}
}
But it prints "top" even if I didn't get to the top.
scrollViewDidEndDragging means the user's finger lifted, but because it has physics to simulate inertia, the view may continue to move. There is another delegate method for exactly what you are looking for: scrollViewDidScrollToTop which as the name implies fires when you get to the top of the scrollview.
EDIT:
you can also try:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if scrollView.contentOffset.y <= 0 {
print("top!")
}
}
EDIT third time's the charm? This one only fires once, after the scroll view has stopped moving, if you are at the top.
override func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
if scrollView.contentOffset.y == 0 {
print("top!")
}
}
You can try
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if scrollView.contentOffset.y == 0 {
// top
}
}
Right now I have a UICollectionView set up with horizontal paging. I have sized my cells to fit the screen so that there is only ever one visible(unless you are scrolling).
What I wish to do is get the index path of the cell that is in view once you have stopped scrolling. This is because other parts of the view are dependent on the information that is currently visible.
I have set up a function in the scrollViewWillBeginDecelerating function and I am close but I still don't seem to understand how it is grabbing the cells.
func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) {
if( lastContentOffset > scrollView.contentOffset.x && lastPointVisited > 0)
{
lastPointVisited -= 1
print("Scrolling Right")
}
else if(lastContentOffset < scrollView.contentOffset.x && lastPointVisited < myPoints.count - 1)
{
lastPointVisited += 1
print("Scrolling Left")
}
lastContentOffset = scrollView.contentOffset.x
}
This gets me accurate results if I am very careful about scrolling. Going fast or only half scrolling a page so that it snaps back seems to throw everything off.
You can use following code to get page number
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let pageWidth = scrollView.frame.size.width
let page = Int(floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1)
print("Page Number : \(page)")
}
It works for me If I put the same code in these two delegates at same time
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
//code here
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
//code here
}
instead of writing it in
func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView)
It gives me the exact value of index whether it is scrolling fast or half scrolled.
Hope it helps!
try this,
func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) {
let cellObj = collectionViewDemo.visibleCells[0]
print(collectionViewDemo.indexPath(for: cellObj))
}
You can use the below code it will be always effective to find the visible collectionView page
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let pageWidth = scrollview.frame.width
let pageIndex = scrollview.frame.width
let indexTemp = Int((scrollview.contentOffset.x +
pageWidth / 2) / pageWidth)
print(pageIndex)
}
I want to stop backward scrolling on ScrollView after user scrolls to the next page. How can I do that.
I tried the following two codes, but the first one does not have any effect
self.scrollView.contentOffset = CGPointMake(self.view.frame.width,0)
and the second only disables the forward scrolling.
self.scrollView.contentSize = CGSizeMake( 2 * scrollWidth, scrollHeight);
To disable scrolling in one direction you implement the UIScrollViewDelegate method scrollViewDidScroll and put your logic there. For instance this TableViewController can only ever scroll down, because if the user tries to scroll up, we just overwrite the contentOffset, effectively undoing their scroll before they see it.
class ViewController: UITableViewController {
var lastScrollPosition = CGPoint.zero
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard scrollView.contentOffset.y > lastScrollPosition.y else {
scrollView.setContentOffset(lastScrollPosition, animated: false)
return
}
lastScrollPosition = scrollView.contentOffset
}
}
If your cell is equal in size to your screen, you can apply the following option, which is very smooth:
var lastScrollPosition = CGPoint.zero
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
if scrollView.contentOffset.x == lastScrollPosition.x + UIScreen.main.bounds.width {
lastScrollPosition.x += UIScreen.main.bounds.width
}
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard scrollView.contentOffset.x > lastScrollPosition.x else {
scrollView.setContentOffset(lastScrollPosition, animated: false)
return
}
}
I am trying to set the content offset in my uiscrollview. I have tried the following, and none of it works. None of the following affect my scrollView in any way, it simple appears on the screen as normal.:
let point = CGPoint(x: 0, y: self.view.frame.height / 2)
self.scrollView.setContentOffset(point, animated: true)
and:
self.scrollView.contentOffset.y = self.view.frame.size.height / 2
and:
self.scrollView.contentOffset = CGPointMake(0, self.view.frame.size.height / 2)
and:
self.scrollView.contentOffset = CGPointMake(0, scrollView.frame.size.height / 2)
I have a scroll view that is 2 times the height of my view. They are essentially separated into 2 different view that I can page between. I want the scrollview to start on the bottom part.
You should try them in the viewDidLayoutSubviews
Ref: iOS 9 scroll UITextView to top
I was really scratching my head when I found that setting scrollView.contentOffset to any value was not working. Eventually I realized that I was calling the scrollView delegate message 'scrollViewDidScroll' to manage scroll dragging peculiarities.
It turns out that 'scrollViewDidScroll' is called whenever the scrollView contentOffset is changed, and my code to manage drag issues was changing the contentOffset. I just made a 'BOOL isDragging' variable to only make changes to the contentOffset when dragging:
private var isDragging : Bool = false
private var initialContentOffset = CGPoint.zero
public func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
isDragging = true
...
}
public func scrollViewDidScroll(_ scrollView: UIScrollView) {
// need to keep track if we are dragging with isDragging
// since this 'scrollViewDidScroll' API is called with ANY contentOffset change
if (isDragging == true){
// do stuff to contentOffset to manage dragging peculiarities
...
}
}
public func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if (decelerate == false){
scrollViewDidEndScrollingAnimation(scrollView)
}
}
public func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
scrollViewDidEndScrollingAnimation(scrollView)
}
public func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
isDragging = false
}