Once again auto layout has me scratching my head. I define a UIView and UITextField at the top of my class:
var urlField = UITextField(frame: .zero)
var barView = UIView(frame: .zero)
I call my configuration method from viewWillAppear (so I know that self.view is all set):
override func viewWillAppear(_ animated: Bool) {
configureURLBar()
}
And I'm doing nothing special there.
func configureURLBar() {
barView.translatesAutoresizingMaskIntoConstraints = false
barView.topAnchor.constraint(equalTo: self.view.layoutMarginsGuide.topAnchor).isActive = true
barView.heightAnchor.constraint(equalToConstant: 30).isActive = true
}
When it gets to the topAnchor constraint I get the exception, and I don't understand why. If I reverse the 2nd and 3rd lines it doesn't blow up until it gets to the .topAnchor line, so that's the problem. I can ask a second question once I understand the reason for this exception (in case you're wondering what I'm trying to do): how do I add a user input (url) bar at the top of my UIWebView. (that didn't work either - same results if I try to constrain against my self.webView which is displaying perfectly) Also: I call self.view.setNeedsDisplay() before viewWillAppear() is called.
You have to add your view to parent view first. After that you can add constraints.
Try this:
override func viewWillAppear(_ animated: Bool)
{
self.view.addSubview(barView)
configureURLBar()
}
Include your logic in viewDidLayoutSubviews instead of in viewWillAppear...
viewDidLayoutSubviews is a much better place to handle geometry
Related
I am workin on a messaging client for macOS, written in Swift. I use an NSScrollView with an NSCollectionView as the documentView to present the messages. Currently, I have implemented infinite scrolling, but now the problem is that the collectionView loads the cells starting at the top and works its way down – the default behavior for an NSCollectionView. Instead, I need it to start at the bottom and work its way up – the way that a typical messaging application displays messages.
Solutions I have tried:
Scrolling to the bottom of the collectionView as soon as the view loads or the user selects a different conversation. This solution is visibly janky and truly messes up infinite scrolling.
Overriding the isFlipped variable in the scrollView, the scrollView's contentView, and the collectionView. Doing this has had zero visible effect on any of the views.
Rotating the entire scrollView, collectionView, contentView, or collectionView cells by pi radians. As a desperate measure, I attempted to rotate the entire scrollView and was not able to do that nor rotate any of the collectionView items. I did something along the lines of wantsLayer = true
layer!.setAffineTransform(CGAffineTransform(rotationAngle: .pi))
updateLayer()
setNeedsDisplay(frameRect). This again has no visible affect.
What's the best way to go about getting the NSCollectionView to go from bottom to top? By the way, I am not using Storyboards.
Hi #will i am not sure if this code will help you, because i have used it for iPhone chat application and it works for me. In my case i have simply put collectionView in view controller.
//MARK:- View Controller life cycle method
override func viewDidLoad() {
chatCollectionView.addObserver(self, forKeyPath: "contentSize", options: .new, context: nil)
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if(keyPath == "contentSize"){
if let newvalue = change?[.newKey] {
let contentHeight: CGFloat = chatCollectionView.contentSize.height
let collectionHeight = chatCollectionView.frame.size.height
if contentHeight < collectionHeight {
var insets: UIEdgeInsets = chatCollectionView.contentInset
insets.top = collectionHeight - contentHeight
chatCollectionView.contentInset = insets
} else {
chatCollectionView.contentInset = .zero
}
}
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
chatCollectionView.removeObserver(self, forKeyPath: "contentSize")
}
For the following viewController hierarchy, isUserInteractionEnabled doesn't appear to be working as expected.
NavigationController(ViewController A) --- pushes to ---> NavigationController(ViewController B)
In ViewController A's viewDidAppear method I set navigationController?.navigationBar.isUserInteractionEnabled to false and set it to true in ViewController B's viewDidAppear method. However, upon popping ViewController B and returning to ViewController A, the navigation bar remains enabled for user interaction. Any thoughts as why this may be happening are greatly appreciated, thanks in advance!
That seems to be a bug for which you could get around by doing that on the main thread:
override func viewDidAppear(_ animated: Bool) {
//...
DispatchQueue.main.async {
self.navigationController?.navigationBar.isUserInteractionEnabled = false
}
}
But this still leaves a millisecond window where the navigationBar's interaction is enabled.
You have to be really quick.
However...
I wouldn't recommend what you're doing; i.e. disabling the navigationBar.
You could lose the back ability, if it had one, because you're just disabling the navigationBar entirely.
Suggestion:
Since every viewController in the navigation stack has it's own navigationItem, that contains it's own set of barButtonItems, I would recommend you keep references of the UIBarButtonItem and enable/disable them explicitly.
i.e.
#IBOutlet var myBarButtonItem: UIBarButtonItem!
override func viewDidAppear(_ animated: Bool) {
//...
myBarButtonItem.isEnabled = false
}
Furthermore, the state of this barButtonItem is handled in this viewController itself and you need not do things like self.navigationController?.navigationBar.isUserInteractionEnabled = true elsewhere.
When I open my app I have this label that animates in from outside the screen. When I open the view controller for the first time it works. However, when I go to another view controller and then go back to the initial view controller this label will just be there and not animate in.
levelsLabel.center = CGPoint(x:levelsLabel.center.x - 500, y:levelsLabel.center.y)
UIView.animate(withDuration: 2) {
self.levelsLabel.center = CGPoint(x:self.levelsLabel.center.x + 500, y:self.levelsLabel.center.y)
}
Anyone have any suggestions?? Thank You!
Putting your block of code in viewWillAppear rather than viewDidLoad will make it work. However, according to Apple Doc.
viewDidAppear: Use this method to trigger any operations that need
to occur as soon as the view is presented onscreen, such as fetching
data or showing an animation.
The following is what I'd recommend you to do.
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
levelsLabel.center = CGPoint(x:levelsLabel.center.x - 500, y:levelsLabel.center.y)
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
UIView.animate(withDuration: 2) {
self.levelsLabel.center = CGPoint(x:self.levelsLabel.center.x + 500, y:self.levelsLabel.center.y)
}
}
I have read multiple places with suggestions on how to accomplish this. I went with adding a UI view in the background and setting it to disable and then after showing the popover, setting the view to enable.
As you can see it looks to work nicely:
But I do have two problems. The first one is once the popover is presented, you can tap anywhere on the background to dismiss the popover. Is there anywhere to block this from happening? I assumed my background UIView would block any inputs.
Also, after the popover is dismissed, the screen is still dim. I tried the following but neither of them load after dismissing the popover so the View never gets set back to disable:
override func viewDidAppear(_ animated: Bool) {
dimView.isHidden = true
}
override func viewWillAppear(_ animated: Bool) {
dimView.isHidden = true
}
EDIT:
This is the code that I use to present the popover:
let popover = storyboard?.instantiateViewController(withIdentifier: "PopoverVC")
popover?.modalPresentationStyle = .popover
popover?.popoverPresentationController?.delegate = self as? UIPopoverPresentationControllerDelegate
popover?.popoverPresentationController?.sourceView = self.view
popover?.popoverPresentationController?.sourceRect = CGRect(x: self.view.bounds.midX, y: self.view.bounds.midY, width: 0, height: 0)
popover?.popoverPresentationController?.permittedArrowDirections = UIPopoverArrowDirection(rawValue: 0)
dimView.isHidden = false
self.present(popover!, animated: false)
I realize that, dimView is not in PopoverVC, add it into PopoverVC and handle dismiss when tap on it.After the popover is dismissed viewDidAppear and viewWillAppear will not be called. So your screen is still blurry.If you add dimView into Popover, hope you can solve these issuses
I think you could solve your two problems with the UIPopoverPresentationControllerDelegate and a protocol/ delegate to tell the presenting viewcontroller when your are dismissing and hide your dimView.
The first issue can be implemented like this:
extension YourViewController: UIPopoverPresentationControllerDelegate {
func popoverPresentationControllerShouldDismissPopover(_ popoverPresentationController: UIPopoverPresentationController) -> Bool {
return false
}
For the second issue you can pass a function through delegation. Hopefully this link will help with that.
https://matteomanferdini.com/how-ios-view-controllers-communicate-with-each-other/
Cheers
I have a little problem with an ULlabel. All I want to do is to move a UIlabel outside the view's bounds before it loads and then, when the view is loaded, show with a little animation.
So I have done this:
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
self.lblQuestion.hidden = true
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
self.lblQuestion.center.y = -(self.view.bounds.height + 100)
}
It seems to be all ok because if I put a print("\\(self.lblQuestion.center.y)") in the viewDidAppear function I can see that the position is ok and the UIlabel is outside the bounds, like I want.
But if I wait 2 seconds and check with a new print("\\(self.lblQuestion.center.y)") inside a timer (for example) I see that the y position of the UIlabel is changed.
Does the UIView change its bounds after some event?
Can someone tell me what is happening, please?