I do have a UIScrollView with a single customContentView as subview. This is returned as the viewForZoomingInScrollView: . But this way, every subview of my customContentView is zoomed: I would like to have some zoomed, others not (e.g. labels), but of course the relative position should remain. Is there a way to achieve this?
You need apply inverse scale transform to the label as below,
func scrollViewDidZoom(_ scrollView: UIScrollView) {
sampleLabel.transform = CGAffineTransform(scaleX: 1/scrollView.zoomScale, y: 1/scrollView.zoomScale)
}
Before Zoom,
After Zoom,
Related
I have a scroll view and inside the scrollview I am having a content view with few subview inside this content view. My requirement is to zoom the content view but not the subview of content view.
Can anyone faced this before, or did the same. Any help would be appreciated.
Thanks in advance.
Scroll view just apply transform to contentView. This transform applied to all children in contentView. So you can apply inverted transform to children to negate parent transform.
func scrollViewDidZoom(_ scrollView: UIScrollView) {
guard let content = viewForZooming(in: scrollView) else {
return
}
let t = content.transform.inverted()
for v in content.subviews {
v.transform = t
}
}
I’m trying to implement a custom top bar that behaves similarly to the iOS 11+ large title navigation bar, where the large title section of the bar collapses when scrolling down the content:
The difference is that my bar needs a custom height and also a bottom section that doesn’t collapse when scrolled. I managed to get that part working:
The bar is implemented using a UIStackView & with some non-required layout constraints, but I believe its internal implementation is not relevant. The most important thing is that the height of the bar is tied to scrollview's top contentInset. These are driven by scrollview's contentOffset in UIScrollViewDelegate.scrollViewDidScroll method:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let topInset = (-scrollView.contentOffset.y).limitedBy(topBarHeightRange)
// changes both contentInset and scrollIndicatorInsets
adjustTopContentInset(topInset)
// changes top bar height
heightConstraint?.constant = topInset
adjustSmallTitleAlpha()
}
topBarHeightRange stores the minimum and maximum bar height
One thing that I'm having a problem with is that when the user stops scrolling the scrollview, it's possible that the bar will end up in a semi-collapsed state. Again, let's look at the desired behavior:
Content offset is snapped to either the compact or expanded height, whichever is "closer". I'm trying to achieve the same in UIScrollViewDelegate.scrollViewWillEndDragging method:
func scrollViewWillEndDragging(_ scrollView: UIScrollView,
withVelocity velocity: CGPoint,
targetContentOffset: UnsafeMutablePointer<CGPoint>) {
let targetY = targetContentOffset.pointee.y
// snaps to a "closer" value
let snappedTargetY = targetY.snappedTo([topBarHeightRange.lowerBound, topBarHeightRange.upperBound].map(-))
targetContentOffset.pointee.y = snappedTargetY
print("Snapped: \(targetY) -> \(snappedTargetY)")
}
The effect is far from perfect:
When I look at the printout it shows that the targetContentOffset is modified correctly. However, visually in the app the content offset is snapped only to the compact height but not to the expanded height (you can observe that the large "Title" label ends up being cut in half instead of back to the "expanded" position.
I suspect this issue has something to do with changing the contentInset.top while the user is scrolling, but I can't figure out how to fix this behavior.
It's a bit hard to explain the problem, so I hope the GIFs help. Here's the repo: https://github.com/AleksanderMaj/ScrollView
Any ideas how to make the scrollview/bar combo snap to compact/expanded height properly?
I took a look at your project and liked your implementation.
I came up with a solution in your scrollViewWillEndDragging method by adding the following code at the end of method:
if abs(targetY) < abs(snappedTargetY) {
scrollView.setContentOffset(CGPoint(x: 0, y: snappedTargetY), animated: true)
}
Basically, if the scroll down amount is not worth hiding the large title (it happens if targetY is less than snappedTargetY) then just scroll to value of snappedTargetY to show the large title back.
Seems to be working for now, but let me know if you encounter any bugs or find a way to improve.
Whole scrollViewWillEndDragging method:
func scrollViewWillEndDragging(_ scrollView: UIScrollView,
withVelocity velocity: CGPoint,
targetContentOffset: UnsafeMutablePointer<CGPoint>) {
let targetY = targetContentOffset.pointee.y
// snaps to a "closer" value
let snappedTargetY = targetY.snappedTo([topBarHeightRange.lowerBound, topBarHeightRange.upperBound].map(-))
targetContentOffset.pointee.y = snappedTargetY
if abs(targetY) < abs(snappedTargetY) {
scrollView.setContentOffset(CGPoint(x: 0, y: snappedTargetY), animated: true)
}
print("Snapped: \(targetY) -> \(snappedTargetY)")
}
I have a view and within an image that works as a button. I would like to know if there is a way to lock the size of the button so that when I zoom in, the view remains small and does not enlarge with the view..
I thought it was hard to manager in the beginning. But finally, if you put the imageView in a UIScrollView, It's not hard to achieve.
The idea is move the buttonView outside of imageView during zooming and when zoom is over, put it back to imageView to pretend nothing happened. I know it's too verbose in programming but actually it works perfectly for your case.
var originalCenter : CGPoint! // The center of ButtonView in imageView.
//All functions are from the UIScrollViewDelegate.
func viewForZooming(in scrollView: UIScrollView) -> UIView?{
originalCenter = buttonView.center // remember the original position.
return imageView
}
func scrollViewWillBeginZooming(_ scrollView: UIScrollView, with view: UIView?) {
buttonView.frame = imageView.convert(buttonView.frame, to: scrollView)
scrollView.addSubview(buttonView)//add to superView of imageImage.
}
func scrollViewDidZoom(_ scrollView: UIScrollView){
buttonView.center = imageView.convert(originalCenter, to: scrollView) //During Zooming, update the buttonView in ScrollView.
}
func scrollViewDidEndZooming(_ scrollView: UIScrollView, with view: UIView?, atScale scale: CGFloat){
buttonView.frame = imageView.convert(buttonView.frame, from: scrollView)
imageView.addSubview(buttonView) //put it back.
}
I know it's better to use a parameter to control such operation. But I have-not found one according to public APIs. Maybe there is a better way, hope this one is your answer too.
Because you called transform for superView. It will make all subViews inside transform together.
You need to remake you views:
SuperView:
- Content view (the image view)
- Border view
- Button close
When you want to zoom the image, you only need to reset the superview frame.
You found a git SPUserResizableView.
One of the cells in a UITableView contains a scroll view. I want to be able to scroll the content in the cell horizontally, but NOT vertically.
How can I achieve this?
Additionally, the scroll view is a subview of UIWebView, so I cannot control its content size.
I have tried setting the content offset directly, but this prevents the entire table from being scrolled. I want the table to scroll vertically, but not the content in the cell.
func scrollViewDidScroll(_ scrollView: UIScrollView) {
DispatchQueue.main.async {
scrollView.contentOffset = CGPoint(x: scrollView.contentOffset.x, y: 0)
}
}
You will have to ensure the content is smaller than the vertical bounds of the UIScrollView to prevent vertical scrolling, and in addition you'll need to set scrollView.alwaysBounceVertical = false.
I have a scroll view with several elements (textview, label, image view...), I need to display an uiview when my label appears on the screen when I'm scrolling.
How can I do ?
Make sure your view controller is the scroll view delegate. Implement the scrollViewDidScroll method, and check whether the scroll view's frame, offset by the contentOffset, overlaps the label's frame.
func scrollViewDidScroll(scrollView: UIScrollView) {
let offset = self.scrollView.contentOffset
let onScreen = CGRectOffset(self.scrollView.frame, offset.x, offset.y)
if CGRectIntersectsRect(onScreen, self.label.frame) {
NSLog("Overlap")
}
}
If you want to detect when the label is fully on the screen, use CGRectContainsRect instead of CGRectIntersectsRect.