在所有UICollectionViewCells上应用手势

Question

in my app i have a UICollectionView. i want to apply to it's cells a long pressure gesture. i implemented that but when i run the app only the last cell works and the others do not respond. what it wrong? here is my code.

    @interface
@property (nonatomic, strong) UILongPressGestureRecognizer *longPressure;

in view did load:

self.longPressure = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handlePressue:)];

self.longPressure.delegate = self;

[self.collectionView addGestureRecognizer:self.longPressure];

gesture handler:

- (void)handlePressue:(UILongPressGestureRecognizer*)gesture{

    [[gesture.view viewWithTag:1] setBackgroundColor:[UIColor yellowColor]];
}

in collectionView:cellforitemAtIndexPAth:

UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 75, 75)];
    imageView.tag = 1;
    [imageView setBackgroundColor:[UIColor redColor]];
    [cell addGestureRecognizer:self.longPressure];
    [cell addSubview:imageView];
    return cell;

is there anything wrong?

Answer 1

you need to add gesture on the each cell not for the UICollection View. that might be your problem.the last cell works because the gesture is added to the last cell only.

Answer 2

You need to creat long press gesture for each cell. Because gesture like other ui control,only one in the project.If you want add it to other view,you need copy another one.

Answer 3

Have a look at following Code snippet

MyFlowLayout *myLayout = [[MyFlowLayout alloc]init];
[self.collectionView setCollectionViewLayout:myLayout animated:YES];
UIGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc]
}
initWithTarget:self action:@selector(handlePinch:)];
[self.collectionView addGestureRecognizer:pinchRecognizer];

Handling the Pinch:

- (IBAction)handlePinch:(UIPinchGestureRecognizer *)sender {
    // Get a reference to the flow layout
    MyFlowLayout *layout =
          (MyFlowLayout
*)self.collectionView.collectionViewLayout;
// If this is the start of the gesture
if (sender.state == UIGestureRecognizerStateBegan) {
    // Get the initial location of the pinch?
    CGPoint initialPinchPoint =
[sender locationInView:self.collectionView]; //Convert pinch location into a specific cell
NSIndexPath *pinchedCellPath =
             [self.collectionView
indexPathForItemAtPoint:initialPinchPoint];
        // Store the indexPath to cell
layout.currentCellPath = pinchedCellPath; }
else if (sender.state == UIGestureRecognizerStateChanged) {
// Store the new center location of the selected cell layout.currentCellCenter =
[sender locationInView:self.collectionView]; // Store the scale value
layout.currentCellScale = sender.scale; }
else {
[self.collectionView performBatchUpdates:^{ layout.currentCellPath = nil;
layout.currentCellScale = 1.0;
        } completion:nil];
} }

Answer 4

For performance reasons I suggest you to avoid adding subviews and/or gestures to every single cell. Instead, add a singe longPressureGesture to your collectionView and on the gesture selector handle your per-cell switch business logic. Something as follow:

On your viewDidLoad or where you setup your collection, add the following gesture:

UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(showDeleteActions:)];
longPress.delegate = self;
[_aCollectionView addGestureRecognizer:longPress];

then on the selector do the single-cell handling:

- (void)showDeleteActions:(UILongPressGestureRecognizer*)gesture {
    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        NSIndexPath *indexPath = [_aCollectionView indexPathForItemAtPoint:[gesture locationInView:_aCollectionView]];
        UICollectionViewCell *cell = [_aCollectionView cellForItemAtIndexPath:indexPath];
        NSLog(@"cell to delete at IndexPath: %@", indexPath);
    }
}

this approach is much more efficient abd far more stable.

Answer 5

Here what it is causing that your UILongPressGestureRecognizer getting overwrite to last cell. So you need to create UILongPressGestureRecognizer for each cell in cellForRowAtIndexPath:

Here is a small code snippet that can help you out

    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 75, 75)];
    imageView.tag = 1;
    [imageView setBackgroundColor:[UIColor redColor]];
    UILongPressGestureRecognizer *longPressure =[[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handlePressue:)];
    longPressure.delegate = self;
    cell.userInteractionEnabled = YES; // Make userInteractionEnabled enable so it can detect touch
    [cell addGestureRecognizer:self.longPressure];
    [cell addSubview:imageView];
    return cell;

There is no need to create any property for the UILongPressGestureRecognizer in .h file. And also remove code to add userInteractionEnabled on whole UICollectionView.