When we make a UIButton programmatically and add a target for its click action.
And for the selector we need a function with "#objc" reference, even if we are working in a purely swift project.
override func viewDidLoad() {
let requiredButton = UIButton(frame: CGRect(x: 100, y: 100, width: 50, height: 30))
self.view.addSubview(requiredButton)
requiredButton.addTarget(self, action: #selector(self.buttonTapAction(sender:)), for: UIControl.Event.touchUpInside)
}
#objc func buttonTapAction(sender:UIButton) {
// button action implementation here
}
Is there a way to do this without the "#objC" reference???
If you target iOS 14+ there is new API that you can use without "#objc" references:
override func viewDidLoad() {
let requiredButton = UIButton(frame: CGRect(x: 100, y: 100, width: 50, height: 30), primaryAction: .init(handler: { _ in
// button action implementation here
}))
self.view.addSubview(requiredButton)
}
If you target iOS 13+ you can build UI using SwiftUI with Button controls. SwiftUI is currently internally based on UIKit, but you can write whole apps in swift using SwiftUI without a single "#objc" reference
UIButton is a foundation object from NSObject subclass so it executes on the Objective-c runtime, so you need to tell Swift to expose the code to objective-c
Reference: https://craiggrummitt.com/2016/09/16/any-vs-anyobject-vs-nsobject-in-swift-3/
Related
I'm working on a swiftUI app where I have to display multiple PDF files in one screen.
I've created a PDFView:
struct PDFKitRepresentedView: UIViewRepresentable {
let url: URL
init(_ url: URL) {
self.url = url
}
func makeUIView(context: UIViewRepresentableContext<PDFKitRepresentedView>) -> PDFKitRepresentedView.UIViewType {
let pdfView = PDFView()
let pdfDocument = PDFDocument(url: self.url)
pdfView.document = pdfDocument
return pdfView
}
func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext<PDFKitRepresentedView>) {
// Update the view.
}
}
struct PDFKitView: View {
var url: URL
var body: some View {
PDFKitRepresentedView(url)
}
}
The PDF is created here:
if let url = attachment.path {
PDFKitView(url: url)
.frame(width: UIScreen.screenWidth - 40, height: UIScreen.screenHeight - 40, alignment: .center)
.padding()
}
The problem I'm having is that, whenever the first document is multipage, in order to see the other documents the user has first to pinch to zoom out completely and the other PDF's are shown in sequence.
I've tried to add this values, but that just makes the content of the PDF to disappear
I was wondering if setting the frame on the PDFKitView directly could be causing the issue, but no.
Anyone has any suggestions on how to make this work? I assume that if I could make the pdf to show already with a min zoom it would display the view correctly.
I finally found the answer on this post How to detect where NaN is passing to CoreGraphics API on Mac OS X 10.9
I have to replace an existing SwiftUI List of views with a UICollectionView(because the app designs were updated and the new designs are pretty complex for SwiftUI so it that had to be implemented as a custom UICollectionViewFlowLayout)
So the views(which now will be (or a part of)UICollectionViewCell) are already implemented in SwiftUI, and i didn't want to re-write them in Swift. The view are complex in terms of writing down the Layout Code, which apparently was pretty easy using SwiftUI.
I could find some help wrapping up a collection view like this one but little on how to host an existing swift ui view inside a UICollectionViewCell
Any help/suggestions/links would be appreciated.
Thanks
I did get that working. But not sure if that's the correct solution. If anyone has a better solution please add your answer.
So i created a UICollectionViewCell sub-class.
final class HostingCollectionViewCell: UICollectionViewCell {
func host<Content: View>(_ hostingController: UIHostingController<Content>) {
backgroundColor = .clear
hostingController.view.translatesAutoresizingMaskIntoConstraints = false
hostingController.view.backgroundColor = .clear
addSubview(hostingController.view)
let constraints = [
hostingController.view.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 0),
hostingController.view.leftAnchor.constraint(equalTo: contentView.leftAnchor, constant: 0),
hostingController.view.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: 0),
hostingController.view.rightAnchor.constraint(equalTo: contentView.rightAnchor, constant: 0),
]
NSLayoutConstraint.activate(constraints)
}
}
And used it like..
func makeUIView(context: Context) -> UICollectionView {
let collectionView = UICollectionView(
frame: .zero,
collectionViewLayout: MyCustomCollectionViewLayout()
)
collectionView.register(HostingCollectionViewCell.self, forCellWithReuseIdentifier: "HostingCell")
let dataSource = UICollectionViewDiffableDataSource<Section, Member>(collectionView: collectionView) { collectionView, indexPath, member in
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "HostingCell", for: indexPath) as? HostingCollectionViewCell
for subview in cell?.contentView.subviews ?? [] {
subview.removeFromSuperview()
}
let swiftUIView = SomeSwiftUIView()
.onTapGesture {
// Equivalent of didTapItemAt...
}
cell?.host(UIHostingController(rootView: firefighterView))
return cell
}
context.coordinator.dataSource = dataSource
collectionView.clipsToBounds = false
collectionView.backgroundColor = .clear
collectionView.showsVerticalScrollIndicator = false
// Populated Datasource
return collectionView
}
This makeUIView is part of the struct SwiftUICollectionView: UIViewRepresentable view.
How do I change the height of an iOS 10 extension in compact mode? Or more broadly, how do I change the height of an extension without using widgetActiveDisplayModeDidChange?
I'm using like this, maybe this will help your problem :
override func viewDidLoad() {
super.viewDidLoad()
self.preferredContentSize = CGSize(width:self.view.frame.size.width, height:210)
if #available(iOSApplicationExtension 10.0, *) {
self.extensionContext?.widgetLargestAvailableDisplayMode = .expanded
}
}
height as 210 how I prefer, you can use any height of course...
UPDATE :
If you want to use a fixed size you can use NCWidgetDisplayMode's second option "compact":
#available(iOS 10.0, *)
public enum NCWidgetDisplayMode : Int {
case compact // Fixed height
case expanded // Variable height
}
you can update your code like below :
if #available(iOSApplicationExtension 10.0, *) {
self.extensionContext?.widgetLargestAvailableDisplayMode = .compact
}
I want to use This library in swift. It's written in Obj-C.
I've added header and Bridging and etc, now, I don't know what is equivalent of this statement :
//Color did change block declaration
NKOColorPickerDidChangeColorBlock colorDidChangeBlock = ^(UIColor *color){
//Your code handling a color change in the picker view.
};
NKOColorPickerView *colorPickerView = [[NKOColorPickerView alloc] initWithFrame:CGRectMake(0, 0, 300, 340) color:[UIColor blueColor] andDidChangeColorBlock:colorDidChangeBlock];
//Add color picker to your view
[self.view addSubview:colorPickerView];
let colorPickerView = NKOColorPickerView(frame: CGRect(x: 0, y: 0, width: 300, height: 340), color: UIColor.blueColor()) { (color) -> Void in
// Your code handling a color change in the picker view.
}
view.addSubview(colorPickerView)
or
var colorDidChangeBlock: NKOColorPickerDidChangeColorBlock = { (color) in
// Your code handling a color change in the picker view.
}
let colorPickerView = NKOColorPickerView(frame: CGRect(x: 0, y: 0, width: 300, height: 340), color: UIColor.blueColor(), andDidChangeColorBlock: colorDidChangeBlock)
view.addSubview(colorPickerView)
I prefer the first way. Its more clear and easier to read.
I have done a View in CollectionView with CustomLayout. In iOS6 it worked great but iOS7 it throws an exception like this.
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason:
'layout attributes for supplementary item at index path ( {length = 2, path = 0 - 0}) changed from CustomSupplementaryAttributes: 0xd1123a0 index path: (NSIndexPath: 0xd112580 {length = 2, path = 0 - 0}); element kind: (identifier); frame = (0 0; 1135.66 45); zIndex = -1; to CustomSupplementaryAttributes: 0xd583c80 index path: (NSIndexPath: 0xd583c70 {length = 2, path = 0 - 0}); element kind: (identifier); frame = (0 0; 1135.66 45); zIndex = -1; without invalidating the layout'
iOS 10
At iOS 10, a new feature is introduced, it is Cell Prefetching. It will let dynamic position of SupplementaryView crash. In order to run in the old behavior, it needs to disable prefetchingEnabled. It's true by default at iOS 10.
// Obj-C
// This function is available in iOS 10. Disable it for dynamic position of `SupplementaryView `.
if ([self.collectionView respondsToSelector:#selector(setPrefetchingEnabled:)]) {
self.collectionView.prefetchingEnabled = false;
}
// Swift
if #available(iOS 10, *) {
// Thanks #maksa
collectionView.prefetchingEnabled = false
// Swift 3 style
colView.isPrefetchingEnabled = false
}
I hate this problem. I spend 2 days for this problem.
A reference about Cell Pre-fetch #iOS 10.
iOS 9 and before ...
#Away Lin is right.. I solve the same problem by implementing that delegate method.
My Custom UICollectionViewLayout will modify the attributes in layoutAttributesForElementsInRect. The section position is dynamic, not static. So, I obtain warnings about the layout attributes for supplementary item at index path ... changed from ... to .... Before the changes, invalideLayout related methods should be called.
And, after implementing this delegate method to return true, the method invalidateLayoutWithContext: will be called when scrolling the UICollectionViewLayout. By default, it returns false.
- (BOOL) shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
return YES;
}
From Apple Docs
Return Value
true if the collection view requires a layout update or false if the
layout does not need to change.
Discussion The default implementation of this method returns false.
Subclasses can override it and return an appropriate value based on
whether changes in the bounds of the collection view require changes
to the layout of cells and supplementary views.
If the bounds of the collection view change and this method returns
true, the collection view invalidates the layout by calling the
invalidateLayoutWithContext: method.
Availability Available in iOS 6.0 and later.
And more ...
A nice example project on GitHub, for custom UICollectionViewLayout.
You need to invalidate the existing layout before updating, see the end of the error message:
without invalidating the layout'
[collectionViewLayout invalidateLayout];
Apple Documentation for UICollectionViewLayout
I had the same exception: in iOS 7, you need now to override the inherited isEqual: in your UICollectionViewLayoutAttributes subclass as stated in Apple documentation here.
I solved my problem by override the method at the subclase of UICollectionViewFlowLayout:
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBound
return YES
I'm not entirely certain how or why, but this appears to be fixed in iOS 12, supporting both supplementary view resizing and prefetching. The trick for me was to make sure things are happening in the correct order.
Here is a working implementation of a stretchable header view. Notice the implementation of the header resizing happening in layoutAttributesForElements(in rect: CGRect):
class StretchyHeaderLayout: UICollectionViewFlowLayout {
var cache = [UICollectionViewLayoutAttributes]()
override func prepare() {
super.prepare()
cache.removeAll()
guard let collectionView = collectionView else { return }
let sections = [Int](0..<collectionView.numberOfSections)
for section in sections {
let items = [Int](0..<collectionView.numberOfItems(inSection: section))
for item in items {
let indexPath = IndexPath(item: item, section: section)
if let attribute = layoutAttributesForItem(at: indexPath) {
cache.append(attribute)
}
}
}
if let header = layoutAttributesForSupplementaryView(ofKind: StretchyCollectionHeaderKind, at: IndexPath(item: 0, section: 0)) {
cache.append(header)
}
}
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
return true
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
let visibleAttributes = cache.filter { rect.contains($0.frame) || rect.intersects($0.frame) }
guard let collectionView = collectionView else { return visibleAttributes }
// Find the header and stretch it while scrolling.
guard let header = visibleAttributes.filter({ $0.representedElementKind == StretchyCollectionHeaderKind }).first else { return visibleAttributes }
header.frame.origin.y = collectionView.contentOffset.y
header.frame.size.height = headerHeight.home - collectionView.contentOffset.y
header.frame.size.width = collectionView.frame.size.width
return visibleAttributes
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let attributes = super.layoutAttributesForItem(at: indexPath as IndexPath)?.copy() as! UICollectionViewLayoutAttributes
guard collectionView != nil else { return attributes }
attributes.frame.origin.y = headerHeight.home + attributes.frame.origin.y
return attributes
}
override func layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: StretchyCollectionHeaderKind, with: indexPath)
}
override var collectionViewContentSize: CGSize {
get {
guard let collectionView = collectionView else { return .zero }
let numberOfSections = collectionView.numberOfSections
let lastSection = numberOfSections - 1
let numberOfItems = collectionView.numberOfItems(inSection: lastSection)
let lastItem = numberOfItems - 1
guard let lastCell = layoutAttributesForItem(at: IndexPath(item: lastItem, section: lastSection)) else { return .zero }
return CGSize(width: collectionView.frame.width, height: lastCell.frame.maxY + sectionInset.bottom)
}
}
}
P.S.: I'm aware the cache doesn't actually serve any purpose at this point :)
I had this problem too, because I had code that depended on the content size of the collection view. My code was accessing the content size via the collectionView!.contentSize instead of collectionViewContentSize.
The former uses the collectionView property of UICollectionViewLayout, while the latter uses the custom-implemented layout property. In my code, the first time the layout was asked for attributes, contentSize had not been set yet.
Select the CollectionView and Goto Attribute Inspector. Uncheck The Prefetching Enabled CheckBox. This is Fixed my Issue. Screenshot