With UIScrollView, it's possible to programmatically move to an offset, with setContentOffset:animated: for exemple.
I'm trying to add a bounce effect when the offset is set programmatically. I think I should use a UIAttachmentBehavior, but I don't really know how to use it.
When should it be declared ? When the user finish dragging, in the scrollViewDidEndDragging function ? Or when the offset is the same than the final offset ?
For exemple, I'm at offset 10 and I want to go to offset 50. Maybe I should go to offset 60 and set a UIAttachmentBehavior at offset 50 ? Or maybe there's an other way ?
Thanks for your help
From my understanding, you want to enable bouncing when you get to the edge of a scroll view.
If you want the default of the scrollview to be that it doesn't bounce, then use this code:
override func viewDidLoad() {
super.viewDidLoad()
self.scrollview.bounces = false
}
Then, if you want to enable bouncing at any point, just add the line:
self.scrollview.bounces = true
If you know that you always want to scrollview to bounce you can set the following properties:
self.scrollview.alwaysBounceVertical = true
self.scrollview.alwaysBounceHorizontal = true
See this link for more information.
Related
i have view with `UIProgressView` and 3 dot-view. It's like a page control. Each page - the video. `progressView` displays progress of video playback
ok. I do not use constraints for left and right anchors, because my progressView should swap places with dot-view. For example, when current video is ended and next start play, we should swap positions of `progressView` with next dot-view. For swap i just change frames
and the problem is: when i move app to background and returns back, my `progressView` loses his old frame. It attaches to the left side, because `.frame.minX` is 0
and the last one: this problem occurs only after first returns from background
what i tried to do:
save progressView frames before app is going to background and restore it when app comes to foreground: progressView.frame = progressViewOldFrames and call setNeedsDisplay()
add constraint to leftAnchor with constant (frame.minX) before background and remove it after foreground
combine these 2 tries
so now it looks like
func appWillMoveInBackground() {
progressBarXConstraint = progressBar.leftAnchor.constraint(equalTo: self.leftAnchor, constant: progressBar.frame.minX)
progressBarXConstraint?.isActive = true
progressBarFrame = progressBar.frame
}
func updateProgressWidth() {
progressBarXConstraint?.isActive = false
// here i use constraints because my width and height also disables
// and only constraints helps me
progressBar.widthAnchor.constraint(equalToConstant: 32).isActive = true
progressBar.heightAnchor.constraint(equalToConstant: 6).isActive = true
progressBar.frame = progressBarFrame
progressBar.setNeedsDisplay()
}
UPDATE
ok, i should explain more. I guess i cant use constraints because we have some animation while we are scrolling. When we scroll to right - we should move our progressView to some points at right. And in this moment we should move right dot-view to the left. I mean, we do not scroll page by page, we can scroll to a half on the right, then we can return to the initial position.
this code of block did change frames of progressView and dot-view. Formulas are not important. Please, just understand the behavior of this view
func scrollViewDidScroll(_ scrollView: UIScrollView) {
// calc some math variables
// and call method that make changes in frames
pageControl.moveBetweenPages(atPercentValue: distInPercents - 100)
}
// its part of body moveBetweenPages() func
progressBar.frame = CGRect(x: progStartX + progAddDist, y: 0,
width: SizeConstants.progressBarWidth.value,
height: SizeConstants.height.value)
let dotStartX: CGFloat = SizeConstants.progressBarWidth.value + SizeConstants.itemsSpacing.value + (CGFloat(currentPageNum) * dotSectionSize)
dots[currentPageNum].view.frame = CGRect(x: dotStartX - dotAddDist, y: 0,
width: SizeConstants.dotWidth.value,
height: SizeConstants.height.value)
images shows how it looks before background and after
matt from comments suggested me use constraints instead of frames and yes, it helps and it works
only thing i can say is dont forget call setNeedsLayout() after constraints update
So heres my issue, the 4 orange rectangles you see on the gif are a single vertical UICollectionView = orangeCollectionView.
The Green and Purple "card" views are part of another UICollectionView = overlayCollectionView.
overlayCollectionView has 3 cells, one of which is just a blank UICollectionViewCell, the other 2 are the cards.
When the overlayCollectionView is showing the blank UICollectionViewCell, I want to be able to scroll the orangeCollectionView.
override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
guard let superr = superview else { return true}
for view in superr.subviews {
if view.isKind(of: OrangeCollectionView.self) {
view.point(inside: point, with: event)
return false
}
}
return true
}
This allows me to scroll the orangeCollectionView HOWEVER this doesn't actually work to fix my issue. I need to be able to scroll left and right to show the cards, however this blocks all touches becuase the point always falls on the OrangeCollectionView.
How can I check to see if they are scrolling left/right to show the cards? Otherwise if they are on the blank cell, scroll the orangeViewController up and down.
Had this issue as well... Didn't find a nice way to do it, but this works.
First, you need to access the scroll view delegate method scrollViewDidScroll(). There you call:
if scrollView == overlayScrollView {
if scrollView.contentOffset.x == self.view.frame.width { // don't know which coordinate you need
self.overlayScrollView.alpa = 0
}
}
After that, you add a blank view onto of the orange collection view. The view's alpha is 0 (I think, maybe the color is just clear; try it out if it works).
In the code, you then add a UISwipeGestureRecognizer to the view you just created and and detect whether there's a swipe to the left or to the right.
By detecting the direction of that swipe, you can simply change the contentOffset.x axis of your overlayScrollView to 0 or self.view.frame.width * 2.
Sorry I can't provide my working sample code, I'm answering from my mobile. It's not the proper solution, but when I made a food app for a big client it worked perfectly and no one ever complained :)
I've tried a lot of things but couldn't come up with a solution. Any words of thought can help me evaluate on this. I made a full view DrawBoard class which is inherited from a UITextView class.When the switch on the view controller is on the user can type and scroll, when it is off the user can draw on the Drawboard.
#IBAction func changeSwitch(sender: UISwitch) {
if sender.on{
drawBoard.setNeedsDisplay()
drawBoard.scrollEnabled = true
drawBoard.editable = true
drawBoard.selectable = true
drawBoard.switchBool = false
}else if !sender.on {
drawBoard.switchBool=true
let a:CGPoint = drawBoard.contentOffset
drawBoard.scrollEnabled = false
drawBoard.setContentOffset(a, animated: false)
drawBoard.editable = false
drawBoard.selectable=false
}
}
It updates the scrolling but scrollEnabled= false just saves the text that is in the first page range of the textview so that it scrolls to the top automatically and disable the scrolling there.Then when I do the setContentOffset the drawable view of the background is visible and it draws on the right place of the textview. However the text that should be on top of it is not visible. This only happens when the switch button is set to off while I am out of the first page's range.How do I also make the text at that range visible?
Sorry if it's a really easy question I'm new to programming and got stuck for a considerable amount of time for this.Thank you.
You have to update the content size of the UIScrollView.
Like this:
scrollView.contentSize = CGSize(width: 100, height: 100)
"Content Size" determines the size of scrollable content, if it's not large enough to cover new views, you won't be able to see it in your scroll view.
I want to lock the scrollView when my segmented Control comes to top of the screen. How can I do this in swift? What's the code of this? How to compute the distance between the top of the segmented control and top of the view controller? It means how can I find the true place for locking scrollView?
After Swift 4.0 it has changed to
scrollView.isScrollEnabled = false
and
scrollView?.isScrollEnabled = true
Just flip the scrollEnabled boolean:
yourScrollView.scrollEnabled = false
To make it scroll again:
yourScrollView.scrollEnabled = true
I have a horizontal UICollectionView with a custom UICollectionViewFlowLayout that has a UIAttachmentBehavior set on each cell to give it a bouncy feel when scrolling left and right. The behavior has the following properties:
attachmentBehavior.length = 1.0f;
attachmentBehavior.damping = 0.5f;
attachmentBehavior.frequency = 1.9f;
When a new cell is added to the collection view it's added at the bottom and then animated to its position also using a UIAttachmentBehavior. Naturally it bounces up and down a bit till it rests in its position. Everything is working as expected till now.
The problem I have starts appearing when the collection view is scrolled left or right before the newly added cell has come to rest. The adds left and right bounciness to the up and down one the cell already has from being added. This results in a very weird circular motion in the cell.
My question is, is it possible to stop the vertical motion of a UIAttachmentBehavior while the collection view is being scrolled? I've tried different approaches like using multiple attachment behaviors and disabling scrolling in the collection view till the newly added cell has come to rest, but non of them seem to stop this.
One way to solve this is to use the inherited .action property of the attachment behavior.
You will need to set up a couple of variables first, something like (going from memory, untested code):
BOOL limitVerticalMovement = TRUE;
CGFloat staticCenterY = CGRectGetHeight(self.collectionView.frame) / 2;
Set these as properties of your custom UICollectionViewFlowLayout
When you create your attachment behavior:
UIAttachmentBehavior *attachment = [[UIAttachmentBehavior alloc] initWithItem:item attachedToAnchor:center];
attachment.damping = 1.0f;
attachment.frequency = 1.5f;
attachment.action = ^{
if (!limitVerticalMovement) return;
CGPoint center = item.center;
center.y = staticCenterY;
item.center = center;
};
Then you can turn the limiting function on and off by setting limitVerticalMovement as appropriate.
Have you tried manually removing animations from cells with CALayer's removeAllAnimations?
You'll want to remove the behaviour when the collection view starts scrolling, or perhaps greatly reduce the springiness so that it comes to rest smoothly, but quickly. If you think about it, what you're seeing is a realistic movement for the attachment behaviour you've described.
To keep the vertical bouncing at the same rate but prevent horizontal bouncing, you'd need to add other behaviours - like a collision behaviour with boundaries to the left and right of each added cell. This is going to increase the complexity of the physics a little, and may affect scrolling performance, but it would be worth a try.
Here's how I managed to do it.
The FloatRange limits the range of the attachment, so if you want it to go all the way up and down the screen you just set really large numbers.
This goes inside func recognizePanGesture(sender: UIPanGestureRecognizer) {}
let location = sender.location(in: yourView.superview)
var direction = "Y"
var center = CGPoint(x: 0, y: 0)
if self.direction == "Y" {center.y = 1}
if self.direction == "X" {center.x = 1}
let sliding = UIAttachmentBehavior.slidingAttachment(with: youView, attachmentAnchor: location, axisOfTranslation: CGVector(dx: center.x, dy: center.y))
sliding.attachmentRange = UIFloatRange(minimum: -2000, maximum: 2000)
animator = UIDynamicAnimator(referenceView: self.superview!)
animator.addBehavior(sliding)
If you're using iOS 9 and above then sliding function within attachment class will work perfectly for that job:
class func slidingAttachmentWithItem(_ item: UIDynamicItem,
attachmentAnchor point: CGPoint,
axisOfTranslation axis: CGVector) -> Self
it can be used easily, and it's very effective for sliding Apple documentation
I've resorted to disabling scrolling in the collection view for a specific amount of time after a new cell is added, then removing the attachment behavior after that time has passed using its action property, then adding a new attachment behavior again immediately.
That way I make sure the upwards animation stops before the collection view is scrolled left or right, but also the left/right bounciness is still there when scrolling.
Certainly not the most elegant solution but it works.