集合视图中的单元格中的 UIButton 未接收内部事件的修饰

Question

The following code expresses my problem: (It's self-contained in that you could create a Xcode project with an empty template, replace the contents of the main.m file, delete the AppDelegate.h/.m files and build it)

//
//  main.m
//  CollectionViewProblem
//


#import <UIKit/UIKit.h>

@interface Cell : UICollectionViewCell

@property (nonatomic, strong) UIButton *button;
@property (nonatomic, strong) UILabel *label;

@end

@implementation Cell
 - (id)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame])
    {
        self.label = [[UILabel alloc] initWithFrame:self.bounds];
        self.label.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
        self.label.backgroundColor = [UIColor greenColor];
        self.label.textAlignment = NSTextAlignmentCenter;

        self.button = [UIButton buttonWithType:UIButtonTypeInfoLight]; 
        self.button.frame = CGRectMake(-frame.size.width/4, -frame.size.width/4, frame.size.width/2, frame.size.width/2);
        self.button.backgroundColor = [UIColor redColor];
        [self.button addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];
        [self.contentView addSubview:self.label];
        [self.contentView addSubview:self.button];
    }
    return self;
}


// Overriding this because the button's rect is partially outside the parent-view's bounds:
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
    if ([super pointInside:point withEvent:event])
    {
        NSLog(@"inside cell");
        return YES;
    }
    if ([self.button
         pointInside:[self convertPoint:point
                                 toView:self.button] withEvent:nil])
    {
        NSLog(@"inside button");
        return YES;
    }

    return NO;
}


- (void)buttonClicked:(UIButton *)sender
{
    NSLog(@"button clicked!");
}
@end

@interface ViewController : UICollectionViewController

@end

@implementation ViewController

// (1a) viewdidLoad:

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self.collectionView registerClass:[Cell class] forCellWithReuseIdentifier:@"ID"];
}

// collection view data source methods ////////////////////////////////////

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 100;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    Cell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"ID" forIndexPath:indexPath];
    cell.label.text = [NSString stringWithFormat:@"%d", indexPath.row];
    return cell;
}
///////////////////////////////////////////////////////////////////////////

// collection view delegate methods ////////////////////////////////////////

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSLog(@"cell #%d was selected", indexPath.row);
}
////////////////////////////////////////////////////////////////////////////
@end


@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
    ViewController *vc = [[ViewController alloc] initWithCollectionViewLayout:layout];


    layout.itemSize = CGSizeMake(128, 128);
    layout.minimumInteritemSpacing = 64;
    layout.minimumLineSpacing = 64;
    layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    layout.sectionInset = UIEdgeInsetsMake(32, 32, 32, 32);


    self.window.rootViewController = vc;

    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}

@end


int main(int argc, char *argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

Basically I'm creating a Springboard-type UI using collection views. My UICollectionViewCell subclass ( Cell ) has a button which lies partially outside the cell's contentView (ie its superview's) bounds.

The problem is that clicking on any part of the button outside of the contentView bounds (basically 3/4th of the button) doesn't invoke the button action. Only when clicking on the portion of the button that overlaps the contentView is the button's action method called.

I've even overridden -pointInside:withEvent: method in Cell so that touches in the button will be acknowledged. But that hasn't helped with the button clicking problem.

I'm guessing it might be something to do with how collectionView handles touches, but I don't know what. I know that UICollectionView is a UIScrollView subclass and I've actually tested that overriding -pointInside:withEvent: on a view (made subview to a scroll view) containing a partially overlapping button solves the button clicking problem, but it hasn't worked here.

Any help?

** Added: For the record, my current solution to the problem involves insetting a smaller subview to contentView which gives the cell its appearance. The delete button is added to the contentView such that its rect actually lies within the bounds of contentView but only partially overlaps the visible part of the cell (ie the inset subview). So I've got the effect I wanted, and the button is working properly. But I'm still curious about the problem with the original implementation above.

Answer 1

The problem appears to be with hitTest/pointInside. I'm guessing the cell is returning NO from pointInside if the touch is on the part of the button that is outside the cell and thus the button doesn't get hit tested. To fix this you have to override pointInside on your UICollectionViewCell subclass to take the button into account. You also need to override hitTest to return the button if the touch is inside the button. Here are example implementations assuming your button is in a property in the UICollectionViewCell subclass called deleteButton.

-(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    UIView *view = [self.deleteButton hitTest:[self.deleteButton convertPoint:point fromView:self] withEvent:event];
    if (view == nil) {
        view = [super hitTest:point withEvent:event];
    }
    return view;
}

-(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    if ([super pointInside:point withEvent:event]) {
        return YES;
    }
    //Check to see if it is within the delete button
    return !self.deleteButton.hidden && [self.deleteButton pointInside:[self.deleteButton convertPoint:point fromView:self] withEvent:event];
}

Note that because hitTest and pointInside expect the point to be in the coordinate space of the receiver you have to remember to convert the point before calling those methods on the button.

Answer 2

In Interface Builder do you have set the object as UICollectionViewCell? Because erroneously one time I set a UIView and after assign to it the correct UICollectionViewCell class...but doing this things (buttons, labels, ecc.) are not added tor the contentView so they don't respond as they would...

So, remind in IB to take the UICollectionViewCell Object when drawing the interface :)

Answer 3

Swift version:

override func hitTest(point: CGPoint, withEvent event: UIEvent?) -> UIView? {

    //From higher z- order to lower except base view;

    for (var i = subviews.count-2; i >= 0 ; i--){
        let newPoint = subviews[i].convertPoint(point, fromView: self)
        let view = subviews[i].hitTest(newPoint, withEvent: event)
        if view != nil{
            return view
        }
    }

    return super.hitTest(point, withEvent: event)

}

that's it ... for all subViews

Answer 4

I am successfully receiving touches to a button created as follows in the subclassed UICollectionViewCell.m file;

- (id)initWithCoder:(NSCoder *)aDecoder
    {
    self = [super initWithCoder:aDecoder];
    if (self)
    {

    // Create button

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake(0, 0, 100, 100); // position in the parent view and set the size of the button
    [button setTitle:@"Title" forState:UIControlStateNormal];
    [button setImage:[UIImage imageNamed:@"animage.png"] forState:UIControlStateNormal];
    [button addTarget:self action:@selector(button:) forControlEvents:UIControlEventTouchUpInside];

    // add to contentView
    [self.contentView addSubview:button];
    }
    return self;
}

I added the button in code after realising that buttons added in Storyboard did not work, not sure if this is fixed in latest Xcode.

Hope that helps.

Answer 5

As accepted answer requested, we should make a hitTest in order to recieve touches inside the cell. Here is the Swift 4 code for hit test:

override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
  for i in (0..<subviews.count-1).reversed() {
    let newPoint = subviews[i].convert(point, from: self)
    if let view = subviews[i].hitTest(newPoint, with: event) {
        return view
    }
  }
  return super.hitTest(point, with: event)
}

Answer 6

I had a similar problem trying to place a deletion button outside the bounds of a uicollectionview cell and it didn't seam to respond to tap events.

the way i solved it was to place a UITapGestureRecognizer on the collection and when a tap happend preform the following code

//this works also on taps outside the cell bouns, im guessing by getting the closest cell to the point of click.

NSIndexPath* tappedCellPath = [self.collectionView indexPathForItemAtPoint:[tapRecognizer locationInView:self.collectionView]]; 

if(tappedCellPath) {
    UICollectionViewCell *tappedCell = [self.collectionView cellForItemAtIndexPath:tappedCellPath];
    CGPoint tapInCellPoint = [tapRecognizer locationInView:tappedCell];
    //if the tap was outside of the cell bounds then its in negative values and it means the delete button was tapped
    if (tapInCellPoint.x < 0) [self deleteCell:tappedCell]; 
}

Answer 7

I see two swift conversions of the original answer that aren't exactly swift conversions. So I just want to give the Swift 4 conversion of the original answer so everyone who wants to can use it. You can just paste the code into your subclassed UICollectionViewCell . Just make sure that you change closeButton with your own button.

override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
    var view = closeButton.hitTest(closeButton.convert(point, from: self), with: event)
    if view == nil {
        view = super.hitTest(point, with: event)
    }

    return view
}

override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
    if super.point(inside: point, with: event) {
        return true
    }

    return !closeButton.isHidden && closeButton.point(inside: closeButton.convert(point, from: self), with: event)
}

Answer 8

Honus has the best answer here in my opinion. In fact the only one that worked for me so I've been answering other similar questions and sending them this way:

I spent hours scouring the web for a solution to my UIButton's inside UICollectionView's not working. Driving me nuts until I finally found a solution that works for me. And I believe it's also the proper way to go: hacking the hit tests. It's a solution that can go a lot deeper (pun intended) than fixing the UICollectionView Button issues as well, as it can help you get the click event to any button buried under other views that are blocking your events from getting through:

UIButton in cell in collection view not receiving touch up inside event

Since that SO answer was in Objective C, I followed the clues from there to find a swift solution:

http://khanlou.com/2018/09/hacking-hit-tests/

--

When I would disable user interaction on the cell, or any other variety of answers I tried, nothing worked.

The beauty of the solution I posted above is that you can leave your addTarget's and selector functions how you are used to doing them since they were most likey never the problem. You need only override one function to help the touch event make it to its destination.

Why the solution works:

For the first few hours I figured the gesture wasn't being registered properly with my addTarget calls. It turns out the targets were registering fine. The touch events were simply never reaching my buttons.

The reality seems to be from any number of SO posts and articles I read, that UICollectionView Cells were meant to house one action, not multiple for a variety of reasons. So you were only supposed to be using the built in selection actions. With that in mind, I believe the proper way around this limitation is not to hack UICollectionView to disable certain aspects of scrolling or user interaction. UICollectionView is only doing its job. The proper way is to hack the hit tests to intercept the tap before it gets to UICollectionView and figure out which items they were tapping on. Then you simply send a touch event to the button they were tapping on, and let your normal stuff do the work.

---

My final solution (from the khanlou.com article) is to put my addTarget declaration and my selector function wherever I like (in the cell class or the cellForItemAt override), and in the cell class overriding the hitTest function.

In my cell class I have:

@objc func didTapMyButton(sender:UIButton!) {
    print("Tapped it!")
}

and

override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {

    guard isUserInteractionEnabled else { return nil }

    guard !isHidden else { return nil }

    guard alpha >= 0.01 else { return nil }

    guard self.point(inside: point, with: event) else { return nil }


    // add one of these blocks for each button in our collection view cell we want to actually work
    if self.myButton.point(inside: convert(point, to: myButton), with: event) {
        return self.myButton
    }

    return super.hitTest(point, with: event)
}

And in my cell class init I have:

self.myButton.addTarget(self, action: #selector(didTapMyButton), for: .touchUpInside)

Answer 9

I found this from here py4u.net

tried the solution that was at the very bottom. (the whole stuff was collected from this page, as I understand)

In my case the colution also worked. and then I just checked wether the User Interaction Enabled checkmark is checked on Collection view in xib and in it's contentView . Guess what. the contentView`s UserInteraction was disabled.

Enabling it fixed the issue with button's touchUpInside event and there was no need to override hitTest method.

Answer 10

You might not have to override hit test or do any of the complicated solutions above.

This issue can also be caused if you are using a custom button with lots of subviews.

What happens is when the button is hit tested, one of its subviews is being returned.

A cleaner solution here is just to set userInteractionEnabled = false on all of your button's subviews.

That way, hit testing your button will only ever return the button itself and none of the views on it.