UICollectionView full screen zoom on UICollectionViewCell - ios

Question

How can you zoom in on a UICollectionViewCell so that it will be displayed full screen? I have extended UICollectionViewFlowLayout and in my view controller when a cell is tapped I'm doing this:
CGPoint pointInCollectionView = [gesture locationInView:self.collectionView];
NSIndexPath *selectedIndexPath = [self.collectionView indexPathForItemAtPoint:pointInCollectionView];
UICollectionViewCell *selectedCell = [self.collectionView cellForItemAtIndexPath:selectedIndexPath];
NSLog(#"Selected cell %#", selectedIndexPath);
Not really sure where to go from here. Should the UICollectionView be responsible of showing the zoomed in cell? Or should I create a new view controller that displays the content of the cell (an image) in full screen?

Answer 1

I took the solution here and modified it slightly to work with a collection view instead. I also added a transparent gray background to hide the original view a bit (assuming the image doesn't take up the entire frame).
#implementation CollectionViewController
{
UIImageView *fullScreenImageView;
UIImageView *originalImageView;
}
...
// in whatever method you're using to detect the cell selection
CGPoint pointInCollectionView = [gesture locationInView:self.collectionView];
NSIndexPath *selectedIndexPath = [self.collectionView indexPathForItemAtPoint:pointInCollectionView];
UICollectionViewCell *selectedCell = [self.collectionView cellForItemAtIndexPath:selectedIndexPath];
originalImageView = [selectedCell imageView]; // or whatever cell element holds your image that you want to zoom
fullScreenImageView = [[UIImageView alloc] init];
[fullScreenImageView setContentMode:UIViewContentModeScaleAspectFit];
fullScreenImageView.image = [originalImageView image];
// ***********************************************************************************
// You can either use this to zoom in from the center of your cell
CGRect tempPoint = CGRectMake(originalImageView.center.x, originalImageView.center.y, 0, 0);
// OR, if you want to zoom from the tapped point...
CGRect tempPoint = CGRectMake(pointInCollectionView.x, pointInCollectionView.y, 0, 0);
// ***********************************************************************************
CGRect startingPoint = [self.view convertRect:tempPoint fromView:[self.collectionView cellForItemAtIndexPath:selectedIndexPath]];
[fullScreenImageView setFrame:startingPoint];
[fullScreenImageView setBackgroundColor:[[UIColor lightGrayColor] colorWithAlphaComponent:0.9f]];
[self.view addSubview:fullScreenImageView];
[UIView animateWithDuration:0.4
animations:^{
[fullScreenImageView setFrame:CGRectMake(0,
0,
self.view.bounds.size.width,
self.view.bounds.size.height)];
}];
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(fullScreenImageViewTapped:)];
singleTap.numberOfTapsRequired = 1;
singleTap.numberOfTouchesRequired = 1;
[fullScreenImageView addGestureRecognizer:singleTap];
[fullScreenImageView setUserInteractionEnabled:YES];
...
- (void)fullScreenImageViewTapped:(UIGestureRecognizer *)gestureRecognizer {
CGRect point=[self.view convertRect:originalImageView.bounds fromView:originalImageView];
gestureRecognizer.view.backgroundColor=[UIColor clearColor];
[UIView animateWithDuration:0.5
animations:^{
[(UIImageView *)gestureRecognizer.view setFrame:point];
}];
[self performSelector:#selector(animationDone:) withObject:[gestureRecognizer view] afterDelay:0.4];
}
-(void)animationDone:(UIView *)view
{
[fullScreenImageView removeFromSuperview];
fullScreenImageView = nil;
}

Answer 2

You can simply use another layout (similar to the one you already have) wherein the item size is larger, and then do setCollectionViewLayout:animated:completion: on the collectionView.
You don't need a new view controller. Your datasource remains the same. You can even use the same cell Class, just make sure that it knows when to layout things for a larger cell content size, and when not to.
I'm quite sure that's how Facebook does it in Paper, as there is no reloading of the content, i.e. [collectionView reloadData] never seems to be called (would have caused flickering and resetting of the scroll offset, etc). This seems to be the most straight forward possible solution.
CGPoint pointInCollectionView = [gesture locationInView:self.collectionView];
NSIndexPath *selectedIndexPath = [self.collectionView indexPathForItemAtPoint:pointInCollectionView];
UICollectionViewCell *selectedCell = [self.collectionView cellForItemAtIndexPath:selectedIndexPath];
NSLog(#"Selected cell %#", selectedIndexPath);
__weak typeof(self) weakSelf = self;
[self.collectionView setCollectionViewLayout:newLayout animated:YES completion:^{
[weakSelf.collectionView scrollToItemAtIndexPath:selectedIndexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:NO];
}];

Answer 3

You can use MWPhotoBrowser, which is suitable for your problem. It supports Grid with Tap to Zoom functionality. you can get it from here
Grid
In order to properly show the grid of thumbnails, you must ensure the property enableGrid is set to YES, and implement the following delegate method:
(id <MWPhoto>)photoBrowser:(MWPhotoBrowser *)photoBrowser thumbPhotoAtIndex:(NSUInteger)index;
The photo browser can also start on the grid by enabling the startOnGrid property.