I have a small collectionView with 2 cells. That is centred on the screen vertically. When user selects a cell a new cell appears in the collection view and collection view changes its insets accordingly to middle 3 cells vertically in the screen. However this change is not smooth, it is jumpy. Is there any way to animate collectionView inset change ?
-(NSArray*)layoutAttributesForElementsInRect:(CGRect)rect {
NSArray* array = [super layoutAttributesForElementsInRect:rect];
UICollectionViewLayoutAttributes* att = [array lastObject];
if (att){
CGFloat lastY = att.frame.origin.y + att.frame.size.height;
CGFloat diff = self.collectionView.frame.size.height - lastY;
if (diff > 0){
UIEdgeInsets contentInsets = UIEdgeInsetsMake(diff/2, 0.0, 0.0, 0.0);
self.collectionView.contentInset = contentInsets;
}
self.diff = diff;
}
return array;
}
It did not seem possible to animate the collectionView insets without creating custom UICollectionViewLayout so I changed the logic and implemented changing position of the cell instead of changing the insets of collection view. This gives real smooth animation !
-(NSArray*)layoutAttributesForElementsInRect:(CGRect)rect {
NSArray* array = [super layoutAttributesForElementsInRect:rect];
UICollectionViewLayoutAttributes* att = [array lastObject];
if (att){
CGFloat lastY = att.frame.origin.y + att.frame.size.height;
CGFloat diff = self.collectionView.frame.size.height - lastY;
if (diff > 0){
for (UICollectionViewLayoutAttributes* a in array){
a.frame = CGRectMake(a.frame.origin.x, a.frame.origin.y + diff/2, a.frame.size.width, a.frame.size.height) ;
}
}
}
return array;
}
It appears that ila's answer is no longer accurate as of iOS 12 - the following code shows the inset change animating for me:
if !disableCustomInsets {
UIView.animate(withDuration: 0.2, animations: {
self.disableCustomInsets = true
self.collectionViewLayout.invalidateLayout()
}, completion: nil)
}
Related
I have a UICollectionView which expands on clicking a cell and once the screen fills it becomes scrollable.
Now when I scroll down I need my header view to scroll down with it and for that I've implemented the logic in the layoutAttributesForSupplementaryViewOfKind method in my custom UICollectionViewLayout class.
This works fine but now the issue is that when I the content becomes scrollable and I scroll down few cells and immediately click on a cell to shrink the content back to one screen at that point the header view doesn't gets arranged, i.e it still remains in the last scrolled position.
But there after if I perform any other action like cell tap it gets arranged properly.
I've tried calling setNeedsLayout, setNeedsDisplay and layoutSubviews where I reload my UICollectionView but the header still doesn't updates to its proper position.
Below is the code for my layoutAttributesForSupplementaryViewOfKind method.
Any help is appreciated.
- (UICollectionViewLayoutAttributes *)layoutAttributesForSupplementaryViewOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
if (![kind isEqualToString:[myGridHeaderView kind]]) {
return nil;
}
myGridHeaderPosition headerPosition = [[self collectionView] headerPositionAtIndexPath:indexPath];
CGRect cellRect = [[self delegate] getRectForHeaderAtIndex:indexPath headerPosition:headerPosition];
if (CGRectEqualToRect(cellRect, CGRectZero)) {
return nil;
}
myGridHeaderLayoutAttribute* attributes = [myGridHeaderLayoutAttribute layoutAttributesForSupplementaryViewOfKind:kind withIndexPath:indexPath];
CGPoint centerPoint = CGPointMake(CGRectGetMidX(cellRect), CGRectGetMidY(cellRect));
CGSize size = cellRect.size;
UICollectionView * const cv = self.collectionView;
NSInteger zIndex = 1;
CGPoint const contentOffset = cv.contentOffset;
if (contentOffset.x > 0)
{
if (headerPosition != myGridHeaderPositionColumn)
{
centerPoint.x += contentOffset.x;
}
zIndex = 1005;
}
if (contentOffset.y > 0)
{
if (headerPosition != myGridHeaderPositionRow)
{
centerPoint.y += contentOffset.y;
}
zIndex = 1005;
}
if (headerPosition == myGridHeaderPositionCommon) {
zIndex = 1024;
}
attributes.zIndex = zIndex;
attributes.headerPosition = headerPosition;
attributes.center = centerPoint;
attributes.size = size;
attributes.alpha = 1.0;
return attributes;
}
When you scroll up and down , header will be visible and hidden , for use this code.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
isScrollingStart=YES;
NSLog(#"scrollViewDidScroll %f , %f",scrollView.contentOffset.x,scrollView.contentOffset.y);
if (scrollView.contentOffset.y<=124) {
_img_top_header.alpha=scrollView.contentOffset.y/124;
}
else
{
_img_top_header.alpha=1.0;
}
}
must be set image in header.
I am using UICollectionView in such a way that collection view cell will be in centre of the screen and left and right cells are partially visible. Infect, UICollectionView width is equal to screen width and cell width is lesser so that left and right cells should partially visible.
For enabling pagination, I had implement custom code that sets the centre cell in centre of the screen. Now its creating some issues; I want to get any default way to avoid custom implementation that causing the issue.
I want to enable pagination in such a way that I can achieve described behaviour in following image.
If I disable custom implementation and enable default pagination then two cells are partially shown but its not expected behaviour as i want.
Thanks
As far as I know, you can't do this by "default", you need to customise your collectionView. The way I achieved this is by subclassing the collectionView's flow layout and implementing the following method like this:
- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity
{
CGFloat offSetAdjustment = MAXFLOAT;
CGFloat horizontalCenter = (CGFloat) (proposedContentOffset.x + (self.collectionView.bounds.size.width / 2.0));
CGRect targetRect = CGRectMake(proposedContentOffset.x, 0.0, self.collectionView.bounds.size.width, self.collectionView.bounds.size.height);
NSArray *array = [self layoutAttributesForElementsInRect:targetRect];
UICollectionViewLayoutAttributes *currentAttributes;
for (UICollectionViewLayoutAttributes *layoutAttributes in array)
{
if(layoutAttributes.representedElementCategory == UICollectionElementCategoryCell)
{
CGFloat itemHorizontalCenter = layoutAttributes.center.x;
if (ABS(itemHorizontalCenter - horizontalCenter) < ABS(offSetAdjustment))
{
currentAttributes = layoutAttributes;
offSetAdjustment = itemHorizontalCenter - horizontalCenter;
}
}
}
CGFloat nextOffset = proposedContentOffset.x + offSetAdjustment;
proposedContentOffset.x = nextOffset;
CGFloat deltaX = proposedContentOffset.x - self.collectionView.contentOffset.x;
CGFloat velX = velocity.x;
// detection form gist.github.com/rkeniger/7687301
// based on http://stackoverflow.com/a/14291208/740949
if(deltaX == 0.0 || velX == 0 || (velX > 0.0 && deltaX > 0.0) || (velX < 0.0 && deltaX < 0.0)) {
} else if(velocity.x > 0.0) {
for (UICollectionViewLayoutAttributes *layoutAttributes in array)
{
if(layoutAttributes.representedElementCategory == UICollectionElementCategoryCell)
{
CGFloat itemHorizontalCenter = layoutAttributes.center.x;
if (itemHorizontalCenter > proposedContentOffset.x) {
proposedContentOffset.x = nextOffset + (currentAttributes.frame.size.width / 2) + (layoutAttributes.frame.size.width / 2);
break;
}
}
}
} else if(velocity.x < 0.0) {
for (UICollectionViewLayoutAttributes *layoutAttributes in array)
{
if(layoutAttributes.representedElementCategory == UICollectionElementCategoryCell)
{
CGFloat itemHorizontalCenter = layoutAttributes.center.x;
if (itemHorizontalCenter > proposedContentOffset.x) {
proposedContentOffset.x = nextOffset - ((currentAttributes.frame.size.width / 2) + (layoutAttributes.frame.size.width / 2));
break;
}
}
}
}
proposedContentOffset.y = 0.0;
return proposedContentOffset;
}
(This piece of code is inspired heavily from something else I found here on SO, but I can't find the reference now).
In my case, the collection view isn't paginated, but this method makes it behave like it is.
Also, if you want to make the first cell of the collection view to start at the center of the screen (and same for the last one), you will have to override this method in the UICollectionViewDelegateFlowLayout
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
CGFloat leftInset = (self.view.bounds.size.width - CELL_WIDTH) / 2; // CELL_WIDTH is the width of your cell
return UIEdgeInsetsMake(0, leftInset, 0, leftInset);
}
This method assumes that the collectionView is as wide as the screen. If this is not the case for you, adapt it to your needs by computing the left and right insets for the collectionView.
I have a UICollectionView that uses a UICollectionViewLayout subclass for its layout. The layout is a simple grid.
When I zoom the collection view in or out, the positions of the cells on the screen change. In some cases, when zooming in, cells move off the screen entirely. I zoom the cells with a pinch gesture recognizer that sends x and y scale values to the layout class and then invalidates the layout.
As the cells get bigger, they move because their origins are calculated relative to the 0,0 position of the collection view.
I want to be able to zoom the collection view in, while having as many of the cells that were originally on the screen stay there. A good solution would be to have the cell in the center of the screen stay in the center as it becomes larger. Cells around the center cell would grow, and that might push them off the screen.
I've tried adjusting the collection view's content offset, but I haven't achieved what I want. I'm not quite sure how to calculate its new value, and I've learned that the changes caused by invalidateLayout do not happen immediately.
I tried a key value observer for the collection view's content size, but that caused stuttering because the changes in the KVO method happened well after the original zooming.
I've also worked a little bit with scrollToItemAtIndexPath, but the code in my full app is not guaranteed to have a cell at the exact center of the screen. That solution is less desirable for me.
Here is the code where the pinch recognizer sends changes to the layout class:
[self.gridLayout updateCellWidthScale:xScale];
[self.gridLayout updateCellHeightScale:yScale];
[self.gridLayout invalidateLayout];
Here is the code in the layout class
(numberOfRows and numberOfColumns are both set to 20):
-(id)initWithNumberOfRows:(NSUInteger)numberOfRows
andNumberOfColumns:(NSUInteger)numberOfColumns
{
self = [super init];
if (self)
{
_numberOfRows = numberOfRows;
_numberOfColumns = numberOfColumns;
_cellWidth = 80.0f;
_cellHeight = 80.0f;
_cellWidthScale = 1.0f;
_cellHeightScale = 1.0f;
}
return self;
}
-(void)updateCellWidthScale:(CGFloat)newWidthScale
{
self.cellWidthScale *= newWidthScale;
}
-(void)updateCellHeightScale:(CGFloat)newHeightScale
{
self.cellHeightScale *= newHeightScale;
}
-(CGSize)collectionViewContentSize
{
CGSize returnValue = CGSizeMake(self.numberOfColumns * self.cellWidth * self.cellWidthScale,
self.numberOfRows * self.cellHeight * self.cellHeightScale);
return returnValue;
}
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)path
{
UICollectionViewLayoutAttributes* attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:path];
CGRect rect = [self frameForItemAtIndexPath:path];
attributes.size = CGSizeMake(rect.size.width, rect.size.height);
attributes.center = CGPointMake(rect.origin.x + (0.5f * rect.size.width),
rect.origin.y + (0.5f * rect.size.height));
return attributes;
}
-(NSArray*)layoutAttributesForElementsInRect:(CGRect)rect
{
NSMutableArray *returnValue = [[NSMutableArray alloc] init];
for (NSInteger i=0; i < self.numberOfRows; i++)
{
for (NSInteger j=0; j < self.numberOfColumns; j++)
{
NSIndexPath* indexPath = [NSIndexPath indexPathForItem:j inSection:i];
CGRect frame = [self frameForItemAtIndexPath:indexPath];
if (CGRectIntersectsRect(frame, rect))
{
[returnValue addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];
}
}
}
return returnValue;
}
- (CGRect)frameForItemAtIndexPath:(NSIndexPath *)indexPath
{
CGRect returnValue = CGRectMake(indexPath.section * self.cellWidth * self.cellWidthScale,
indexPath.row * self.cellHeight * self.cellHeightScale,
self.cellWidth * self.cellWidthScale,
self.cellHeight * self.cellHeightScale);
return returnValue;
}
You need to set your collectionView contentOffset to the value it was before starting to zoom multiplied the gestures scale.
Your pinch recognizer method should look like this (you need to add some more code to stop changing contentOffset when reaching the MAXIMUM_SCALE or MINIMUM_SCALE).
- (void)didReceivePinchGesture:(UIPinchGestureRecognizer*)gesture
{
static CGFloat scaleStart;
static CGPoint p;
if (gesture.state == UIGestureRecognizerStateBegan)
{
scaleStart = self.scale;
p = self.collectionView.contentOffset;
}
else if (gesture.state == UIGestureRecognizerStateChanged)
{
CGFloat tempScale = scaleStart * gesture.scale;
if (tempScale < MINMUM_SCALE)
{
self.scale = MINMUM_SCALE;
}
else if (tempScale > MAXIMUM_SCALE)
{
self.scale = MAXIMUM_SCALE;
}
else
{
self.scale = tempScale ;
}
dispatch_async(dispatch_get_main_queue(), ^{
[self.collectionView.collectionViewLayout invalidateLayout];
self.collectionView.contentOffset = CGPointMake(0, p.y * gesture.scale);
});
}
}
I've been working on trying to recreate the stretchy collection view that Evernote uses in iOS 7 and I'm really close to having it working. I've managed to create a custom collection view flow layout that modifies the layout attribute transforms when the content offset y value lies outside collection view bounds. I'm modifying the layout attributes in the layoutAttributesForElementsInRect method and it behaves as expected except that the bottom cells can disappear when you hit the bottom of the scroll view. The further you pull the content offset the more cells can disappear. I think the cells basically get clipped off. It doesn't happen at the top though and I'd expect to see the same behavior in both places. Here's what my flow layout implementation looks like right now.
#implementation CNStretchyCollectionViewFlowLayout
{
BOOL _transformsNeedReset;
CGFloat _scrollResistanceDenominator;
}
- (id)init
{
self = [super init];
if (self)
{
// Set up the flow layout parameters
self.minimumInteritemSpacing = 10;
self.minimumLineSpacing = 10;
self.itemSize = CGSizeMake(320, 44);
self.sectionInset = UIEdgeInsetsMake(10, 0, 10, 0);
// Set up ivars
_transformsNeedReset = NO;
_scrollResistanceDenominator = 800.0f;
}
return self;
}
- (void)prepareLayout
{
[super prepareLayout];
}
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
// Set up the default attributes using the parent implementation
NSArray *items = [super layoutAttributesForElementsInRect:rect];
// Compute whether we need to adjust the transforms on the cells
CGFloat collectionViewHeight = self.collectionViewContentSize.height;
CGFloat topOffset = 0.0f;
CGFloat bottomOffset = collectionViewHeight - self.collectionView.frame.size.height;
CGFloat yPosition = self.collectionView.contentOffset.y;
// Update the transforms if necessary
if (yPosition < topOffset)
{
// Compute the stretch delta
CGFloat stretchDelta = topOffset - yPosition;
NSLog(#"Stretching Top by: %f", stretchDelta);
// Iterate through all the visible items for the new bounds and update the transform
for (UICollectionViewLayoutAttributes *item in items)
{
CGFloat distanceFromTop = item.center.y;
CGFloat scrollResistance = distanceFromTop / 800.0f;
item.transform = CGAffineTransformMakeTranslation(0, -stretchDelta + (stretchDelta * scrollResistance));
}
// Update the ivar for requiring a reset
_transformsNeedReset = YES;
}
else if (yPosition > bottomOffset)
{
// Compute the stretch delta
CGFloat stretchDelta = yPosition - bottomOffset;
NSLog(#"Stretching bottom by: %f", stretchDelta);
// Iterate through all the visible items for the new bounds and update the transform
for (UICollectionViewLayoutAttributes *item in items)
{
CGFloat distanceFromBottom = collectionViewHeight - item.center.y;
CGFloat scrollResistance = distanceFromBottom / 800.0f;
item.transform = CGAffineTransformMakeTranslation(0, stretchDelta + (-stretchDelta * scrollResistance));
}
// Update the ivar for requiring a reset
_transformsNeedReset = YES;
}
else if (_transformsNeedReset)
{
NSLog(#"Resetting transforms");
_transformsNeedReset = NO;
for (UICollectionViewLayoutAttributes *item in items)
item.transform = CGAffineTransformIdentity;
}
return items;
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
// Compute whether we need to adjust the transforms on the cells
CGFloat collectionViewHeight = self.collectionViewContentSize.height;
CGFloat topOffset = 0.0f;
CGFloat bottomOffset = collectionViewHeight - self.collectionView.frame.size.height;
CGFloat yPosition = self.collectionView.contentOffset.y;
// Handle cases where the layout needs to be rebuilt
if (yPosition < topOffset)
return YES;
else if (yPosition > bottomOffset)
return YES;
else if (_transformsNeedReset)
return YES;
return NO;
}
#end
I also zipped up the project for people to try out. Any help would be greatly appreciated as I'm pretty new to creating custom collection view layouts. Here's the link to it:
https://dl.dropboxusercontent.com/u/2975688/StackOverflow/stretchy_collection_view.zip
Thanks everyone!
I was able to solve the problem. I'm not sure if there's actually a bug in iOS or not, but the issue was that the cells were actually getting translated outside the content view of the collection view. Once the cell would get translated far enough, it would get clipped off. I find it interesting that this does not happen in the simulator for non-retina displays, but does with retina displays which is why I feel this may actually be a bug.
With that in mind, a workaround for now is to add padding to the top and bottom of the collection view by overriding the collectionViewContentSize method. Once you do this, if you add padding to the top, you need to adjust the layout attributes for the cells as well so they are in the proper location. The final step is to set the contentInset on the collection view itself to adjust for the padding. Leave the scroll indicator insets alone since those are fine. Here's the implementation of my final collection view controller and the custom flow layout.
CNStretchyCollectionViewController.m
#implementation CNStretchyCollectionViewController
static NSString *CellIdentifier = #"Cell";
- (void)viewDidLoad
{
// Register the cell
[self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:CellIdentifier];
// Tweak out the content insets
CNStretchyCollectionViewFlowLayout *layout = (CNStretchyCollectionViewFlowLayout *) self.collectionViewLayout;
self.collectionView.contentInset = layout.bufferedContentInsets;
// Set the delegate for the collection view
self.collectionView.delegate = self;
self.collectionView.clipsToBounds = NO;
// Customize the appearance of the collection view
self.collectionView.backgroundColor = [UIColor whiteColor];
self.collectionView.indicatorStyle = UIScrollViewIndicatorStyleDefault;
}
#pragma mark - UICollectionViewDataSource Methods
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 20;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
if ([indexPath row] % 2 == 0)
cell.backgroundColor = [UIColor orangeColor];
else
cell.backgroundColor = [UIColor blueColor];
return cell;
}
#end
CNStretchyCollectionViewFlowLayout.m
#interface CNStretchyCollectionViewFlowLayout ()
- (CGSize)collectionViewContentSizeWithoutOverflow;
#end
#pragma mark -
#implementation CNStretchyCollectionViewFlowLayout
{
BOOL _transformsNeedReset;
CGFloat _scrollResistanceDenominator;
UIEdgeInsets _contentOverflowPadding;
}
- (id)init
{
self = [super init];
if (self)
{
// Set up the flow layout parameters
self.minimumInteritemSpacing = 10;
self.minimumLineSpacing = 10;
self.itemSize = CGSizeMake(320, 44);
self.sectionInset = UIEdgeInsetsMake(10, 0, 10, 0);
// Set up ivars
_transformsNeedReset = NO;
_scrollResistanceDenominator = 800.0f;
_contentOverflowPadding = UIEdgeInsetsMake(100.0f, 0.0f, 100.0f, 0.0f);
_bufferedContentInsets = _contentOverflowPadding;
_bufferedContentInsets.top *= -1;
_bufferedContentInsets.bottom *= -1;
}
return self;
}
- (void)prepareLayout
{
[super prepareLayout];
}
- (CGSize)collectionViewContentSize
{
CGSize contentSize = [super collectionViewContentSize];
contentSize.height += _contentOverflowPadding.top + _contentOverflowPadding.bottom;
return contentSize;
}
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
// Set up the default attributes using the parent implementation (need to adjust the rect to account for buffer spacing)
rect = UIEdgeInsetsInsetRect(rect, _bufferedContentInsets);
NSArray *items = [super layoutAttributesForElementsInRect:rect];
// Shift all the items down due to the content overflow padding
for (UICollectionViewLayoutAttributes *item in items)
{
CGPoint center = item.center;
center.y += _contentOverflowPadding.top;
item.center = center;
}
// Compute whether we need to adjust the transforms on the cells
CGFloat collectionViewHeight = [self collectionViewContentSizeWithoutOverflow].height;
CGFloat topOffset = _contentOverflowPadding.top;
CGFloat bottomOffset = collectionViewHeight - self.collectionView.frame.size.height + _contentOverflowPadding.top;
CGFloat yPosition = self.collectionView.contentOffset.y;
// Update the transforms if necessary
if (yPosition < topOffset)
{
// Compute the stretch delta
CGFloat stretchDelta = topOffset - yPosition;
NSLog(#"Stretching Top by: %f", stretchDelta);
// Iterate through all the visible items for the new bounds and update the transform
for (UICollectionViewLayoutAttributes *item in items)
{
CGFloat distanceFromTop = item.center.y - _contentOverflowPadding.top;
CGFloat scrollResistance = distanceFromTop / _scrollResistanceDenominator;
item.transform = CGAffineTransformMakeTranslation(0, -stretchDelta + (stretchDelta * scrollResistance));
}
// Update the ivar for requiring a reset
_transformsNeedReset = YES;
}
else if (yPosition > bottomOffset)
{
// Compute the stretch delta
CGFloat stretchDelta = yPosition - bottomOffset;
NSLog(#"Stretching bottom by: %f", stretchDelta);
// Iterate through all the visible items for the new bounds and update the transform
for (UICollectionViewLayoutAttributes *item in items)
{
CGFloat distanceFromBottom = collectionViewHeight + _contentOverflowPadding.top - item.center.y;
CGFloat scrollResistance = distanceFromBottom / _scrollResistanceDenominator;
item.transform = CGAffineTransformMakeTranslation(0, stretchDelta + (-stretchDelta * scrollResistance));
}
// Update the ivar for requiring a reset
_transformsNeedReset = YES;
}
else if (_transformsNeedReset)
{
NSLog(#"Resetting transforms");
_transformsNeedReset = NO;
for (UICollectionViewLayoutAttributes *item in items)
item.transform = CGAffineTransformIdentity;
}
return items;
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
return YES;
}
#pragma mark - Private Methods
- (CGSize)collectionViewContentSizeWithoutOverflow
{
return [super collectionViewContentSize];
}
#end
CNStretchyCollectionViewFlowLayout.h
#interface CNStretchyCollectionViewFlowLayout : UICollectionViewFlowLayout
#property (assign, nonatomic) UIEdgeInsets bufferedContentInsets;
#end
I'm actually going to through this onto Github and I'll post a link to the project once it's up. Thanks again everyone!
I have a custom horizontal collection view that has 1 row and I want to add pull to refresh functionality which, by default, appears above my row of cells. I would like the user to be able to pull the collection view from left to right to activate the UIRefreshControl. Any ideas?
Thanks in advance.
Basically the response above tells you how to do in Objective-C a load more in a UICollectionView. However, I believe the question was how to do pull to refresh horizontally on that component.
I don't think you can add a UIRefreshControl horizontally but taking into consideration the previous code and making a conversion to Swift I came up with the following one
DON'T FORGET TO SET YOUR UICollectionView bounce property TO TRUE
func scrollViewDidScroll(scrollView: UIScrollView) {
let offset = scrollView.contentOffset
let inset = scrollView.contentInset
let y: CGFloat = offset.x - inset.left
let reload_distance: CGFloat = -75
if y < reload_distance{
scrollView.bounces = false
UIView.animateWithDuration(0.3, animations: { () -> Void in
scrollView.setContentOffset(CGPointMake(0, 0), animated: false)
}, completion: { (Bool) -> Void in
scrollView.bounces = true
})
}
}
Also and in order to avoid issues with the continuous pulling I added some code to remove the bouncing temporarily, animate de scroll back to the right and then enabling the bouncing again. That will give you the same effect as the UIRefreshControl.
Finally, if you want to have a loading icon my suggestion is to add it behind the controller so when you pull you can see it behind
Just adding the Obj-C version of Julio Bailon's answer, which works for pulling the collectionView from its Top i.e. Left to Right
CGPoint offset = scrollView.contentOffset;
CGRect bounds = scrollView.bounds;
CGSize size = scrollView.contentSize;
UIEdgeInsets inset = scrollView.contentInset;
float y = offset.x - inset.left;
float h = size.width;
float reload_distance = -75; //distance for which you want to load more
if(y < reload_distance) {
// write your code getting the more data
NSLog(#"load more rows");
}
For this you need to implement the UIScrollViewDelegate method
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGPoint offset = scrollView.contentOffset;
CGRect bounds = scrollView.bounds;
CGSize size = scrollView.contentSize;
UIEdgeInsets inset = scrollView.contentInset;
float y = offset.x + bounds.size.width - inset.right;
float h = size.width;
float reload_distance = 75; //distance for which you want to load more
if(y > h + reload_distance) {
// write your code getting the more data
NSLog(#"load more rows");
}
}