With the image above, I would like to know/detect if the UIView 3 has reached the top of the UIScrollView.
What I did so far is to get the offSet of the UIView within the UIScrollView then check if it's less than or equal to 0 (zero).
let offsetY = scrollView.convert(myView.frame, to: nil).origin.y
if offsetY <= 0 {
print("myView is at Top")
}
But the code above is surely wrong! anybody who has an idea?
TIA!
Just convert the top of the scroll view and the top of v3 to the same coordinate system and now you can simply look to see which one is higher.
Let sv be the scroll view and v3 be view 3. Then:
func scrollViewDidScroll(_ sv: UIScrollView) {
let svtop = sv.frame.origin.y
let v3top = sv.superview!.convert(v3.bounds.origin, from:v3).y
if v3top < svtop { print("now") }
}
I'm actually not seeing anything wrong with your approach. Since according to the documentation, when view is nil, the method converts to window based coordinates:
Parameters
rect
A rectangle specified in the local coordinate system (bounds) of the receiver.
view
The view that is the target of the conversion operation. If view
is nil, this method instead converts to window base coordinates.
Otherwise, both view and the receiver must belong to the same
UIWindow object.
Another option if you don't want to assume the scroll view has a superview.
func scrollViewDidScroll(_ sv: UIScrollView) {
// The view we want to check if it's at the top of the scroll view
//let viewThatMayBeAtTop = UIView()
// get how far in the scroll view this view is
let yInScrollViewWithoutScroll = sv.convert(viewThatMayBeAtTop.bounds, from: viewThatMayBeAtTop).minY
// How far we've scrolled down
let scrolledAmount = sv.adjustedContentInset.top + sv.contentOffset.y
// If how far we've scrolled is equal or greater than the y position of the view, then it's at the top or higher
let isScrolledToTopOrHigher = scrolledAmount >= yInScrollViewWithoutScroll
if isScrolledToTopOrHigher {
print("now")
}
}
Related
My thoughts are to put a function in the viewController, but when I call it, I just get 0 for both x and y instead of the window position, obviously I am messing up somewhere any ideas?
class ViewController: NSViewController {
func getCoordinate() {
let x = self.view.frame.origin.x
let y = self.view.frame.origin.y
print (x)
print (y)
}
}
You need to get the view.window.frame, rather than view.frame.
if let window = view.window {
print(window.frame.origin)
} else {
print("The view is not in a window yet!")
}
Remember to do this only after view is added to the window, such as in viewDidAppear.
The view's frame is relative to view's superview's origin, not the screen's origin. and it just so happens that in this case, view is positioned exactly at the origin of its superview (whatever view that is), hence (0, 0).
I'd like to implement a nav style like what is found in the "Add Reminder" view controller from Apple's Reminders (iOS 14). I've tried hooking into the scrollview delegate methods but I'm not sure how to change the alpha of the default nav bar background/shadow image.
I've tried changing the nav bar style on scroll and, while that works, it doesn't fade in/out like in the example. That makes me think the answer lies manipulating the alpha value. Thanks in advance!
I've found a (hacky) solution that works in iOS 14 (untested in other versions). It makes an assumption about the private view structure of UINavigationBar, so there's no guarantee that it will work in future iOS versions, but it's unlikely to crash - the worst that should happen is that the bar will fail to hide, or only partially hide.
Assuming that you are placing the code inside a UIViewController subclass that it acting as the delegate for a UITableView, UICollectionView or UIScrollView, the following should work:
override func viewDidLoad() {
super.viewDidLoad()
// this hides the bar initially
self.navigationController?.navigationBar.subviews.first?.alpha = 0
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
guard let navigationController = self.navigationController else { return }
let navBarHeight = navigationController.navigationBar.frame.height
let threshold: CGFloat = 20 // distance from bar where fade-in begins
let alpha = (scrollView.contentOffset.y + navBarHeight + threshold) / threshold
navigationController.navigationBar.subviews.first?.alpha = alpha
}
The magic threshold value is a little hard to explain, but it's basically the distance from the bar at which the fade in will start. A value of 20 means the bar starts to fade in when the scrollView content is 20 points away. A value of 0 would mean the bar snaps straight from fully transparent to fully opaque the moment the scrollView content touches it.
I'm working with Cocoa and I create my views in code (no IB) and I'm hitting an issue with NSSplitView.
I have a NSSplitView that I configure in the following way in my view controller, in Swift:
override func viewDidLoad() {
super.viewDidLoad()
let splitView = NSSplitView()
splitView.isVertical = true
splitView.addArrangedSubview(self.createLeftPanel())
splitView.addArrangedSubview(self.createRightPanel())
splitView.adjustSubviews()
self.view.addSubview(splitView)
...
}
The resulting view shows the two subviews and the divider for the NSSplitView, and one view is wider than the other. When I drag the diver to change the width, as soon as I release the mouse, the divider goes back to its original position, as if pulled back by a "spring".
I can't resize the two subviews; the right one always keeps a fixed size. However, nowhere in the code I fix the width of that subview, or any of its content, to a constant.
What I would like to achieve instead is that the right view size is not fixed, and that if I drag the divider at halfway through, the subviews will resize accordingly and end up with the same width.
This is a screen recording of the problem:
Edit: here is how I set the constraints. I'm using Carthography, because otherwise setting constraints in code is extremely verbose beyond the most simple cases.
private func createLeftPanel() -> NSView {
let view = NSView()
let table = self.createTable()
view.addSubview(table)
constrain(view, table) { view, table in // Cartography magic.
table.edges == view.edges // this just constraints table.trailing to
// view.trailing, table.top to view.top, etc.
}
return view
}
private func createRightPanel() -> NSView {
let view = NSView()
let label = NSTextField(labelWithString: "Name of item")
view.addSubview(label)
constrain(view, label) { view, label in
label.edges == view.edges
}
return view
}
I have a NSTableView and want to track the position of its containing NSCells when the tableView got scrolled by the user.
I couldn’t find anything helpful. Would be great if someone can lead me into the right direction!
EDIT:
Thanks to #Ken Thomases and #Code Different, I just realized that I am using a view-based tableView, using tableView(_ tableView:viewFor tableColumn:row:), which returns a NSView.
However, that NSView is essentially a NSCell.
let cell = myTableView.make(withIdentifier: "customCell", owner: self) as! MyCustomTableCellView // NSTableCellView
So I really hope my initial question wasn’t misleading. I am still searching for a way how to track the position of the individual cells/views.
I set the behaviour of the NSScrollView (which contains the tableView) to Copy on Scroll in IB.
But when I check the x and y of the view/cells frame (within viewWillDraw of my MyCustomTableCellView subclass) it remains 0, 0.
NSScrollView doesn't use delegate. It uses the notification center to inform an observer that a change has taken place. The solution below assume vertical scrolling.
override func viewDidLoad() {
super.viewDidLoad()
// Observe the notification that the scroll view sends out whenever it finishes a scroll
let notificationName = NSNotification.Name.NSScrollViewDidLiveScroll
NotificationCenter.default.addObserver(self, selector: #selector(scrollViewDidScroll(_:)), name: notificationName, object: scrollView)
// Post an intial notification to so the user doesn't have to start scrolling to see the effect
scrollViewDidScroll(Notification(name: notificationName, object: scrollView, userInfo: nil))
}
// Whenever the scroll view finished scrolling, we will start coloring the rows
// based on how much they are visible in the scroll view. The idea is we will
// perform hit testing every n-pixel in the scroll view to see what table row
// lies there and change its color accordingly
func scrollViewDidScroll(_ notification: Notification) {
// The data's part of a table view begins with at the bottom of the table's header
let topEdge = tableView.headerView!.frame.height
let bottomEdge = scrollView.bounds.height
// We are going to do hit-testing every 10 pixel. For best efficiency, set
// the value to your typical row's height
let step = CGFloat(10.0)
for y in stride(from: topEdge, to: bottomEdge, by: step) {
let point = NSPoint(x: 10, y: y) // the point, in the coordinates of the scrollView
let hitPoint = scrollView.convert(point, to: tableView) // the same point, in the coordinates of the tableView
// The row that lies that the hitPoint
let row = tableView.row(at: hitPoint)
// If there is a row there
if row > -1 {
let rect = tableView.rect(ofRow: row) // the rect that contains row's view
let rowRect = tableView.convert(rect, to: scrollView) // the same rect, in the scrollView's coordinates system
let visibleRect = rowRect.intersection(scrollView.bounds) // the part of the row that visible from the scrollView
let visibility = visibleRect.height / rowRect.height // the percentage of the row that is visible
for column in 0..<tableView.numberOfColumns {
// Now iterate through every column in the row to change their color
if let cellView = tableView.view(atColumn: column, row: row, makeIfNecessary: true) as? NSTableCellView {
let color = cellView.textField?.textColor
// The rows in a typical text-only tableView is 17px tall
// It's hard to spot their grayness so we exaggerate the
// alpha component a bit here:
let alpha = visibility == 1 ? 1 : visibility / 3
cellView.textField?.textColor = color?.withAlphaComponent(alpha)
}
}
}
}
}
Result:
Update based on edited question:
First, just so you're aware, NSTableCellView is not an NSCell nor a subclass of it. When you are using a view-based table, you are not using NSCell for the cell views.
Also, a view's frame is always relative to the bounds of its immediate superview. It's not an absolute position. And the superview of the cell view is not the table view nor the scroll view. Cell views are inside of row views. That's why your cell view's origin is at 0, 0.
You could use NSTableView's frameOfCell(atColumn:row:) to determine where a given cell view is within the table view. I still don't think this is a good approach, though. Please see the last paragraph of my original answer, below:
Original answer:
Table views do not "contain" a bunch of NSCells as you seem to think. Also, NSCells do not have a position. The whole point of NSCell-based compound views is that they're much lighter-weight than an architecture that uses a separate object for each cell.
Usually, there's one NSCell for each table column. When the table view needs to draw the cells within a column, it configures that column's NSCell with the data for one cell and tells it to draw at that cell's position. Then, it configures that same NSCell with the data for the next cell and tells it to draw at the next position. Etc.
To do what you want, you could configure the scroll view to not copy on scroll. Then, the table view will be asked to draw everything whenever it is scrolled. Then, you would implement the tableView(_:willDisplayCell:for:row:) delegate method and apply the alpha value to the cells at the top and bottom edges of the scroll view.
But that's probably not a great approach.
I think you may have better luck by adding floating subviews to the scroll view that are partially transparent, with a gradient from fully opaque to fully transparent in the background color. So, instead of the cells fading out and letting the background show through, you put another view on top which only lets part of the cells show through.
I just solved the issue by myself.
Just set the contents view postsBoundsChangedNotifications to true and added an observer to NotificationCenter for NSViewBoundsDidChange. Works like a charm!
I have a UIView, in which I have arranged UIButtons. I want to find the positions of those UIButtons.
I am aware that buttons.frame will give me the positions, but it will give me positions only with respect to its immediate superview.
Is there is any way we can find the positions of those buttons, withe respect to UIButtons superview's superview?
For instance, suppose there is UIView named "firstView".
Then, I have another UIView, "secondView". This "SecondView" is a subview of "firstView".
Then I have UIButton as a subview on the "secondView".
->UIViewController.view
--->FirstView A
------->SecondView B
------------>Button
Now, is there any way we can find the position of that UIButton, with respect to "firstView"?
You can use this:
Objective-C
CGRect frame = [firstView convertRect:buttons.frame fromView:secondView];
Swift
let frame = firstView.convert(buttons.frame, from:secondView)
Documentation reference:
https://developer.apple.com/documentation/uikit/uiview/1622498-convert
Although not specific to the button in the hierarchy as asked I found this easier to visualize and understand:
From here: original source
ObjC:
CGPoint point = [subview1 convertPoint:subview2.frame.origin toView:viewController.view];
Swift:
let point = subview1.convert(subview2.frame.origin, to: viewControll.view)
Updated for Swift 3
if let frame = yourViewName.superview?.convert(yourViewName.frame, to: nil) {
print(frame)
}
UIView extension for converting subview's frame (inspired by #Rexb answer).
extension UIView {
// there can be other views between `subview` and `self`
func getConvertedFrame(fromSubview subview: UIView) -> CGRect? {
// check if `subview` is a subview of self
guard subview.isDescendant(of: self) else {
return nil
}
var frame = subview.frame
if subview.superview == nil {
return frame
}
var superview = subview.superview
while superview != self {
frame = superview!.convert(frame, to: superview!.superview)
if superview!.superview == nil {
break
} else {
superview = superview!.superview
}
}
return superview!.convert(frame, to: self)
}
}
// usage:
let frame = firstView.getConvertedFrame(fromSubview: buttonView)
Frame: (X,Y,width,height).
Hence width and height wont change even wrt the super-super view. You can easily get the X, Y as following.
X = button.frame.origin.x + [button superview].frame.origin.x;
Y = button.frame.origin.y + [button superview].frame.origin.y;
If there are multiple views stacked and you don't need (or want) to know any possible views between the views you are interested in, you could do this:
static func getConvertedPoint(_ targetView: UIView, baseView: UIView)->CGPoint{
var pnt = targetView.frame.origin
if nil == targetView.superview{
return pnt
}
var superView = targetView.superview
while superView != baseView{
pnt = superView!.convert(pnt, to: superView!.superview)
if nil == superView!.superview{
break
}else{
superView = superView!.superview
}
}
return superView!.convert(pnt, to: baseView)
}
where targetView would be the Button, baseView would be the ViewController.view.
What this function is trying to do is the following:
If targetView has no super view, it's current coordinate is returned.
If targetView's super view is not the baseView (i.e. there are other views between the button and viewcontroller.view), a converted coordinate is retrieved and passed to the next superview.
It continues to do the same through the stack of views moving towards the baseView.
Once it reaches the baseView, it does one last conversion and returns it.
Note: it doesn't handle a situation where targetView is positioned under the baseView.
You can easily get the super-super view as following.
secondView -> [button superview]
firstView -> [[button superview] superview]
Then, You can get the position of the button..
You can use this:
xPosition = [[button superview] superview].frame.origin.x;
yPosition = [[button superview] superview].frame.origin.y;
Please note that the following code works regardless of how deep (nested) is the view you need the location for in the view hierarchy.
Let's assume that you need the location of myView which is inside myViewsContainer and which is really deep in the view hierarchy, just follow the following sequence.
let myViewLocation = myViewsContainer.convert(myView.center, to: self.view)
myViewsContainer: the view container where the view you need the location for is located.
myView: the view you need the location for.
self.view : the main view