I'm developing app which contains 3 UICollectionViews in one ViewController.
I can know if UICollectionView is scrolled or not with this code
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
let isScrolling: Bool = colView.isDragging || colView.isDecelerating
}
Specifically I want to know if which UICollectionView did scroll in scrollViewDidEndDragging.
But the problem is that I can't know if which collectionview is scrolled before.
Like I want to know if colview2 is scrolling or not.
Is there anybody who knows this solution? I searched solution on Google and Stackoverflow but I don't think there's such a solution for this problem.
Help will be much appreciated.
You can Do it by set tag to CollectionView And Scroll View Delegate method scrollViewDidEndDecelerating Here is the Code :
First Set tag top your CollectionView in your ViewDidLoad method :
firstCollectionView.tag = 1
secondCollectionView.tag = 2
thirdCollectionView.tag = 3
2.Create three Property Observer variable like this upside of your viewDidload:
var whichCollectionViewScrolled = "" {
willSet{
print(newValue)
}
}
var isFirstCollectionViewScrolled = false {
willSet{
print("First CollectionView Scrolled : \(newValue)")
}
}
var isSecondCollectionViewScrolled = false {
willSet{
print("Second CollectionView Scrolled : \(newValue)")
}
}
var isthirdCollectionViewScrolled = false {
willSet{
print("Third CollectionView Scrolled : \(newValue)")
}
}
1.lastly inside of your scrollViewDelegate method cast your scrollview instance and check the tag value like this :
extension ViewController: UIScrollViewDelegate {
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
if let collectionView = scrollView as? UICollectionView {
switch collectionView.tag {
case 1:
whichCollectionViewScrolled = "First"
isFirstCollectionViewScrolled = true
isSecondCollectionViewScrolled = false
isthirdCollectionViewScrolled = false
case 2:
whichCollectionViewScrolled = "second"
isFirstCollectionViewScrolled = false
isSecondCollectionViewScrolled = true
isthirdCollectionViewScrolled = false
case 3:
whichCollectionViewScrolled = "Third"
isFirstCollectionViewScrolled = false
isSecondCollectionViewScrolled = false
isthirdCollectionViewScrolled = true
default:
whichCollectionViewScrolled = "unknown"
}
} else{
print("cant cast")
}
}
Hope it will help You .
Scroll view is the superClass of UICollectionView. Just check that scroll view and collection view you are storing are the same instance.
if collectionView === scrollView {
}
Like this.
I have an infoButton UIButton outlet in my swift file. This button is originally placed in the storyboard with the following constraints:
I want to move this button down by 50 pixels depending if NoAds boolean is true or false.
I have tried doing this, but I can't seem to move it.
if NoAds{
print("No Ads")
infoButton.center.y = infoButton.center.y - 50
}else{
print("Ads")
loadBanner()
}
I assume this should be an easy fix?
EDIT: The ad is a standard google ad banner which is 320 wide and 50 high.
have an outlet for the top constraint
change the topConstraint.constant
like this:
if NoAds{
print("No Ads")
//topConstraint.constant -= 50
topConstraint.constant = 50 // Avoid using -= or += if this func will call a lot of time
}else{
print("Ads")
// set the default constant you want
topConstraint.constant = 100
loadBanner()
}
Use an IBOutlet to connect to the constraint as #wilson-xj describes.
Then use the following code to animate the change to the constraint. This will add some polish and allow the ad to slide in/out nicely instead of jarring the user by instantly shifting content they may be interacting with.
view.layoutIfNeeded()
UIView.animateWithDuration(0.30) { () -> Void in
self.topConstraint.constant = constraintConstant // 50 or 100 etc
self.view.layoutIfNeeded()
}
The best way would probably be to add the constraints and dynamically change the button, but if you didn't want to add another outlet and wanted to do this dynamically you could change the position of the button frame like so:
var X_Position:CGFloat? = startButton.frame.origin.x + 50 //add 50 to move button down page
var Y_Position:CGFloat? = startButton.frame.origin.y
startButton.frame = CGRectMake(X_Position, Y_Position, startButton.frame.width, startButton.frame.height)
This will redraw the button in the new position.
Try this i hope it would be helpful This is mine code i am using!!
and i Assume that you all set the constraints like Top,Bottom,leading,Trailing space
if NoAds
{
print("No Ads")
for item in self.view.constraints
{
if item.firstItem .isKindOfClass(UIButton)
{
let newField = item.firstItem as! UIButton
if newField == buttonName && item.firstAttribute == NSLayoutAttribute.Top
{
item.constant = -50
self.view .layoutIfNeeded()
}
}
}
}else{
print("Ads")
for item in self.view.constraints
{
if item.firstItem .isKindOfClass(UIButton)
{
let newField = item.firstItem as! UIButton
if newField == buttonName && item.firstAttribute == NSLayoutAttribute.Top
{
item.constant = 0
self.view .layoutIfNeeded()
}
}
}
loadBanner()
}
I have a background which is also a UIView, on which has 3 UIViews as its subviews.
I added a UIPanGestureRecognizer to each of them, hoping when the user drags a view to the left, the corresponding UIView expands horizontally.
Heres my code:
func labelPanned(sender:UIPanGestureRecognizer!){
self.labelBeingMoved = sender.view.tag
if(sender.state == UIGestureRecognizerState.Began || sender.state == UIGestureRecognizerState.Changed){
var translation:CGPoint = sender.translationInView(self.background)
self.labelCurrWidth += translation.x
NSLog("self.labelCurrWidth is now %f", self.labelCurrWidth)
if(self.labelCurrWidth <= self.labelOriginalWidth || self.labelCurrWidth >= self.labelMaxWidth){self.labelCurrWidth -= translation.x}
sender.setTranslation(CGPointZero, inView: self.background)
dispatch_async(dispatch_get_main_queue(), {
self.background.setNeedsLayout()
})
}
}
And in the layoutSubviews() call I have:
func layoutSubviews(){
NSLog("layoutSubviews called")
switch self.labelBeingMoved{
case 1:
NSLog("CASE 1")
self.labelbg.frame = CGRectMake(self.labelbg.frame.origin.x, self.labelbg.frame.origin.y, self.labelCurrWidth, self.labelbg.frame.height)
case 2:
NSLog("CASE 2")
self.label1bg.frame = CGRectMake(self.label1bg.frame.origin.x, self.label1bg.frame.origin.y, self.labelCurrWidth, self.label1bg.frame.height)
case 3:
NSLog("CASE 3")
self.label2bg.frame = CGRectMake(self.label2bg.frame.origin.x, self.label2bg.frame.origin.y, self.labelCurrWidth, self.label2bg.frame.height)
default:
NSLog("An unknown error occurred")
}
}
Pretty simple, but it somehow doesn't work and I couldn't figure out whats wrong. I've also tried self.view.setNeedsLayout() but no luck either.
*The labelbg's are UIViews, not UILabels.
Thanks in advance!
You might forgot to add 'override' keyword at the front of layoutSubviews method
I just like to ask how can I implement the same behavior of UITableView`s swipe to delete in UICollectionView. I am trying to find a tutorial but I cannot find any.
Also, I am using PSTCollectionView wrapper to support iOS 5.
Thank you!
Edit:
The swipe recognizer is already good.
What I need now is the same functionality as UITableView's when cancelling the Delete mode, e.g. when user taps on a cell or on a blank space in the table view (that is, when user taps outside of the Delete button).
UITapGestureRecognizer won't work, since it only detects taps on release of a touch.
UITableView detects a touch on begin of the gesture (and not on release), and immediately cancels the Delete mode.
There is a simpler solution to your problem that avoids using gesture recognizers. The solution is based on UIScrollView in combination with UIStackView.
First, you need to create 2 container views - one for the visible part of the cell and one for the hidden part. You’ll add these views to a UIStackView. The stackView will act as a content view. Make sure that the views have equal widths with stackView.distribution = .fillEqually.
You’ll embed the stackView inside a UIScrollView that has paging enabled. The scrollView should be constrained to the edges of the cell. Then you’ll set the stackView’s width to be 2 times the scrollView’s width so each of the container views will have the width of the cell.
With this simple implementation, you have created the base cell with a visible and hidden view. Use the visible view to add content to the cell and in the hidden view you can add a delete button. This way you can achieve this:
I've set up an example project on GitHub. You can also read more about this solution here.
The biggest advantage of this solution is the simplicity and that you don't have to deal with constraints and gesture recognizers.
Its very simple..You need to add a customContentView and customBackgroundView behind the customContentView.
After that and you need to shift the customContentViewto the left as user swipes from right to left. Shifting the view makes visible to the customBackgroundView.
Lets Code:
First of all you need to add panGesture to your UICollectionView as
override func viewDidLoad() {
super.viewDidLoad()
self.panGesture = UIPanGestureRecognizer(target: self, action: #selector(self.panThisCell))
panGesture.delegate = self
self.collectionView.addGestureRecognizer(panGesture)
}
Now implement the selector as
func panThisCell(_ recognizer:UIPanGestureRecognizer){
if recognizer != panGesture{ return }
let point = recognizer.location(in: self.collectionView)
let indexpath = self.collectionView.indexPathForItem(at: point)
if indexpath == nil{ return }
guard let cell = self.collectionView.cellForItem(at: indexpath!) as? CustomCollectionViewCell else{
return
}
switch recognizer.state {
case .began:
cell.startPoint = self.collectionView.convert(point, to: cell)
cell.startingRightLayoutConstraintConstant = cell.contentViewRightConstraint.constant
if swipeActiveCell != cell && swipeActiveCell != nil{
self.resetConstraintToZero(swipeActiveCell!,animate: true, notifyDelegateDidClose: false)
}
swipeActiveCell = cell
case .changed:
let currentPoint = self.collectionView.convert(point, to: cell)
let deltaX = currentPoint.x - cell.startPoint.x
var panningleft = false
if currentPoint.x < cell.startPoint.x{
panningleft = true
}
if cell.startingRightLayoutConstraintConstant == 0{
if !panningleft{
let constant = max(-deltaX,0)
if constant == 0{
self.resetConstraintToZero(cell,animate: true, notifyDelegateDidClose: false)
}else{
cell.contentViewRightConstraint.constant = constant
}
}else{
let constant = min(-deltaX,self.getButtonTotalWidth(cell))
if constant == self.getButtonTotalWidth(cell){
self.setConstraintsToShowAllButtons(cell,animate: true, notifyDelegateDidOpen: false)
}else{
cell.contentViewRightConstraint.constant = constant
cell.contentViewLeftConstraint.constant = -constant
}
}
}else{
let adjustment = cell.startingRightLayoutConstraintConstant - deltaX;
if (!panningleft) {
let constant = max(adjustment, 0);
if (constant == 0) {
self.resetConstraintToZero(cell,animate: true, notifyDelegateDidClose: false)
} else {
cell.contentViewRightConstraint.constant = constant;
}
} else {
let constant = min(adjustment, self.getButtonTotalWidth(cell));
if (constant == self.getButtonTotalWidth(cell)) {
self.setConstraintsToShowAllButtons(cell,animate: true, notifyDelegateDidOpen: false)
} else {
cell.contentViewRightConstraint.constant = constant;
}
}
cell.contentViewLeftConstraint.constant = -cell.contentViewRightConstraint.constant;
}
cell.layoutIfNeeded()
case .cancelled:
if (cell.startingRightLayoutConstraintConstant == 0) {
self.resetConstraintToZero(cell,animate: true, notifyDelegateDidClose: true)
} else {
self.setConstraintsToShowAllButtons(cell,animate: true, notifyDelegateDidOpen: true)
}
case .ended:
if (cell.startingRightLayoutConstraintConstant == 0) {
//Cell was opening
let halfOfButtonOne = (cell.swipeView.frame).width / 2;
if (cell.contentViewRightConstraint.constant >= halfOfButtonOne) {
//Open all the way
self.setConstraintsToShowAllButtons(cell,animate: true, notifyDelegateDidOpen: true)
} else {
//Re-close
self.resetConstraintToZero(cell,animate: true, notifyDelegateDidClose: true)
}
} else {
//Cell was closing
let buttonOnePlusHalfOfButton2 = (cell.swipeView.frame).width
if (cell.contentViewRightConstraint.constant >= buttonOnePlusHalfOfButton2) {
//Re-open all the way
self.setConstraintsToShowAllButtons(cell,animate: true, notifyDelegateDidOpen: true)
} else {
//Close
self.resetConstraintToZero(cell,animate: true, notifyDelegateDidClose: true)
}
}
default:
print("default")
}
}
Helper methods to update constraints
func getButtonTotalWidth(_ cell:CustomCollectionViewCell)->CGFloat{
let width = cell.frame.width - cell.swipeView.frame.minX
return width
}
func resetConstraintToZero(_ cell:CustomCollectionViewCell, animate:Bool,notifyDelegateDidClose:Bool){
if (cell.startingRightLayoutConstraintConstant == 0 &&
cell.contentViewRightConstraint.constant == 0) {
//Already all the way closed, no bounce necessary
return;
}
cell.contentViewRightConstraint.constant = -kBounceValue;
cell.contentViewLeftConstraint.constant = kBounceValue;
self.updateConstraintsIfNeeded(cell,animated: animate) {
cell.contentViewRightConstraint.constant = 0;
cell.contentViewLeftConstraint.constant = 0;
self.updateConstraintsIfNeeded(cell,animated: animate, completionHandler: {
cell.startingRightLayoutConstraintConstant = cell.contentViewRightConstraint.constant;
})
}
cell.startPoint = CGPoint()
swipeActiveCell = nil
}
func setConstraintsToShowAllButtons(_ cell:CustomCollectionViewCell, animate:Bool,notifyDelegateDidOpen:Bool){
if (cell.startingRightLayoutConstraintConstant == self.getButtonTotalWidth(cell) &&
cell.contentViewRightConstraint.constant == self.getButtonTotalWidth(cell)) {
return;
}
cell.contentViewLeftConstraint.constant = -self.getButtonTotalWidth(cell) - kBounceValue;
cell.contentViewRightConstraint.constant = self.getButtonTotalWidth(cell) + kBounceValue;
self.updateConstraintsIfNeeded(cell,animated: animate) {
cell.contentViewLeftConstraint.constant = -(self.getButtonTotalWidth(cell))
cell.contentViewRightConstraint.constant = self.getButtonTotalWidth(cell)
self.updateConstraintsIfNeeded(cell,animated: animate, completionHandler: {(check) in
cell.startingRightLayoutConstraintConstant = cell.contentViewRightConstraint.constant;
})
}
}
func setConstraintsAsSwipe(_ cell:CustomCollectionViewCell, animate:Bool,notifyDelegateDidOpen:Bool){
if (cell.startingRightLayoutConstraintConstant == self.getButtonTotalWidth(cell) &&
cell.contentViewRightConstraint.constant == self.getButtonTotalWidth(cell)) {
return;
}
cell.contentViewLeftConstraint.constant = -self.getButtonTotalWidth(cell) - kBounceValue;
cell.contentViewRightConstraint.constant = self.getButtonTotalWidth(cell) + kBounceValue;
self.updateConstraintsIfNeeded(cell,animated: animate) {
cell.contentViewLeftConstraint.constant = -(self.getButtonTotalWidth(cell))
cell.contentViewRightConstraint.constant = self.getButtonTotalWidth(cell)
self.updateConstraintsIfNeeded(cell,animated: animate, completionHandler: {(check) in
cell.startingRightLayoutConstraintConstant = cell.contentViewRightConstraint.constant;
})
}
}
func updateConstraintsIfNeeded(_ cell:CustomCollectionViewCell, animated:Bool,completionHandler:#escaping ()->()) {
var duration:Double = 0
if animated{
duration = 0.1
}
UIView.animate(withDuration: duration, delay: 0, options: [.curveEaseOut], animations: {
cell.layoutIfNeeded()
}, completion:{ value in
if value{ completionHandler() }
})
}
I have created a sample project here in Swift 3.
It is a modified version of this tutorial.
In the Collection View Programming Guide for iOS, in the section Incorporating Gesture Support, the docs read:
You should always attach your gesture recognizers to the collection view itself and not to a specific cell or view.
So, I think it's not a good practice to add recognizers to UICollectionViewCell.
I followed a similar approach to #JacekLampart, but decided to add the UISwipeGestureRecognizer in the UICollectionViewCell's awakeFromNib function so it is only added once.
UICollectionViewCell.m
- (void)awakeFromNib {
UISwipeGestureRecognizer* swipeGestureRecognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(swipeToDeleteGesture:)];
swipeGestureRecognizer.direction = UISwipeGestureRecognizerDirectionLeft;
[self addGestureRecognizer:swipeGestureRecognizer];
}
- (void)swipeToDeleteGesture:(UISwipeGestureRecognizer *)swipeGestureRecognizer {
if (swipeGestureRecognizer.state == UIGestureRecognizerStateEnded) {
// update cell to display delete functionality
}
}
As for exiting delete mode, I created a custom UIGestureRecognizer with an NSArray of UIViews. I borrowed the idea from #iMS from this question: UITapGestureRecognizer - make it work on touch down, not touch up?
On touchesBegan, if the touch point isn't within any of the UIViews, the gesture succeeds and delete mode is exited.
In this way, I am able to pass the delete button within the cell (and any other views) to the UIGestureRecognizer and, if the touch point is within the button's frame, delete mode will not exit.
TouchDownExcludingViewsGestureRecognizer.h
#import <UIKit/UIKit.h>
#interface TouchDownExcludingViewsGestureRecognizer : UIGestureRecognizer
#property (nonatomic) NSArray *excludeViews;
#end
TouchDownExcludingViewsGestureRecognizer.m
#import "TouchDownExcludingViewsGestureRecognizer.h"
#import <UIKit/UIGestureRecognizerSubclass.h>
#implementation TouchDownExcludingViewsGestureRecognizer
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
if (self.state == UIGestureRecognizerStatePossible) {
BOOL touchHandled = NO;
for (UIView *view in self.excludeViews) {
CGPoint touchLocation = [[touches anyObject] locationInView:view];
if (CGRectContainsPoint(view.bounds, touchLocation)) {
touchHandled = YES;
break;
}
}
self.state = (touchHandled ? UIGestureRecognizerStateFailed : UIGestureRecognizerStateRecognized);
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
self.state = UIGestureRecognizerStateFailed;
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
self.state = UIGestureRecognizerStateFailed;
}
#end
Implementation (in the UIViewController containing UICollectionView):
#import "TouchDownExcludingViewsGestureRecognizer.h"
TouchDownExcludingViewsGestureRecognizer *touchDownGestureRecognizer = [[TouchDownExcludingViewsGestureRecognizer alloc] initWithTarget:self action:#selector(exitDeleteMode:)];
touchDownGestureRecognizer.excludeViews = #[self.cellInDeleteMode.deleteButton];
[self.view addGestureRecognizer:touchDownGestureRecognizer];
- (void)exitDeleteMode:(TouchDownExcludingViewsGestureRecognizer *)touchDownGestureRecognizer {
// exit delete mode and disable or remove TouchDownExcludingViewsGestureRecognizer
}
You can try adding a UISwipeGestureRecognizer to each collection cell, like this:
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
CollectionViewCell *cell = ...
UISwipeGestureRecognizer* gestureRecognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(userDidSwipe:)];
[gestureRecognizer setDirection:UISwipeGestureRecognizerDirectionRight];
[cell addGestureRecognizer:gestureRecognizer];
}
followed by:
- (void)userDidSwipe:(UIGestureRecognizer *)gestureRecognizer {
if (gestureRecognizer.state == UIGestureRecognizerStateEnded) {
//handle the gesture appropriately
}
}
With iOS 14, you can use UICollectionViewLayoutListConfiguration in conjunction with UICollectionViewCompositionalLayout to get this functionality natively for free, no custom cells or gesture recognizes needed.
If your minimum deploy target is >= iOS 14.x, this is probably the preferred method from now on, and it will also let you to adopt modern cell configuration with UIContentView and UIContentConfiguration to boot.
There is a more standard solution to implement this feature, having a behavior very similar to the one provided by UITableView.
For this, you will use a UIScrollView as the root view of the cell, and then position the cell content and the delete button inside the scroll view. The code in your cell class should be something like this:
override init(frame: CGRect) {
super.init(frame: frame)
addSubview(scrollView)
scrollView.addSubview(viewWithCellContent)
scrollView.addSubview(deleteButton)
scrollView.isPagingEnabled = true
scrollView.showsHorizontalScrollIndicator = false
}
In this code we set the property isPagingEnabled to true to make the scroll view to stop scrolling only at the boundaries of its content. The layout subviews for this cell should be something like:
override func layoutSubviews() {
super.layoutSubviews()
scrollView.frame = bounds
// make the view with the content to fill the scroll view
viewWithCellContent.frame = scrollView.bounds
// position the delete button just at the right of the view with the content.
deleteButton.frame = CGRect(
x: label.frame.maxX,
y: 0,
width: 100,
height: scrollView.bounds.height
)
// update the size of the scrolleable content of the scroll view
scrollView.contentSize = CGSize(width: button.frame.maxX, height: scrollView.bounds.height)
}
With this code in place, if you run the app you will see that the swipe to delete is working as expected, however, we lost the ability to select the cell. The problem is that since the scroll view is filling the whole cell, all the touch events are processed by it, so the collection view will never have the opportunity to select the cell (this is similar to when we have a button inside a cell, since touches on that button don't trigger the selection process but are handled directly by the button.)
To fix this problem we just have to indicate the scroll view to ignore the touch events that are processed by it and not by one of its subviews. To achieve this just create a subclass of UIScrollView and override the following function:
override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
let result = super.hitTest(point, with: event)
return result != self ? result : nil
}
Now in your cell you should use an instance of this new subclass instead of the standard UIScrollView.
If you run the app now you will see that we have the cell selection back, but this time the swipe isn't working 😳. Since we are ignoring touches that are handled directly by the scroll view, then its pan gesture recognizer won't be able to start recognizing touch events. However, this can be easily fixed by indicating to the scroll view that its pan gesture recognizer will be handled by the cell and not by the scroll. You do this adding the following line at the bottom of your cell's init(frame: CGRect):
addGestureRecognizer(scrollView.panGestureRecognizer)
This may look like a bit hacky, but it isn't. By design, the view that contains a gesture recognizer and the target of that recognizer don't have to be the same object.
After this change all should be working as expected. You can see a full implementation of this idea in this repo
I'm implementing UIScrollViewDelegate and doing a lot of stuff with it. However, I just found an annoying issue.
I expect scrollViewDidEndDecelerating: to be called always after scrollViewWillBeginDecelerating:. However, if I simply touch my ScrollView (actually I'm touching a button inside the scrollView), scrollViewDidEndDecelerating: gets called and scrollViewWillBeginDecelerating: was not called.
So how can I avoid scrollViewDidEndDecelerating: being called when I simply press a button inside my UIScrollView?
Thank you!
Create a member BOOL called buttonPressed or similar and initialise this to false in your init: method.
Set the BOOL to true whenever your button/s are hit, and then perform the following check:
-(void)scrollViewDidEndDecelerating: (UIScrollView*)scrollView
{
if (!buttonPressed)
{
// resume normal processing
}
else
{
// you will need to decide on the best place to reset this variable.
buttonPressed = NO;
}
}
I had the same problem I fixed it by making a variable that hold the current page num and compare it with the local current page variable if they r equal then don't proceed.
var currentPage : CGFloat = 0.0
var oldPage : CGFloat = 0.0
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView){
// Test the offset and calculate the current page after scrolling ends
let pageWidth:CGFloat = scrollView.frame.width
let currentPage:CGFloat = floor((scrollView.contentOffset.x-pageWidth/2)/pageWidth)+1
// Change the indicator
print("that's the self.currentPage \(self.currentPage) and that's the current : \(currentPage)")
guard self.currentPage != currentPage else { return }
oldPage = self.currentPage
self.currentPage = currentPage;
print("that's the old \(oldPage) and that's the current : \(currentPage)")
//Do something
}