UICollectionView dynamic number of rows [duplicate] - ios

I would like to have a UICollectionView that, in the first row there is a cell with all the row's width, and the second row has 3 cells.
I have researched the documentation but I'm not able to do it. Something like this:
Thanks in advance

Make 2 Cell prototypes in collection view in your storyboard, and set them reuse identifiers
In your ViewController's .m file implement this functions
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 6;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell;
if (/*condition for small cell*/)// e.g. indexPath.row % 3 != 0
cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"smallCell" forIndexPath:indexPath];
else
cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"bigCell" forIndexPath:indexPath];
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
if (/*condition for small cell*/) // e.g. indexPath.row % 3 != 0
return CGSizeMake(65, 50);
return CGSizeMake(318, 50);
}
After doing this you will have something like this:

Related

UICollectionView Assertion failure in createPreparedCellForItemAtIndexPath

my code is simple,just want to create a flow layout UIColloctionView
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return 7;
}
- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell *cell = [UICollectionViewCell new];
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return CGSizeMake(SCREEN_WIDTH / 2 - 5, 160);
}
and this is the error
*** Assertion failure in -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:isFocused:notify:],
/BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3600.9.1/UICollectionView.m:2115
Try using dequeue reusability of the collection view cell:
- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell * cell=[collectionView dequeueReusableCellWithReuseIdentifier:#"cell" forIndexPath:indexPath];
return cell;
}
as the documentation said
the collection view requires that you always dequeue views, rather than create them explicitly in your code
this is different from UITableView , just deque the cell all the time
wrong:
UICollectionViewCell *cell = [UICollectionViewCell new];
return cell;

UICollectionViewCell goes over sticky header

I've a strange behavior with UICollectionView.
In Figure 1 is shown the correct behavior when the user scroll up the collection: the items goes under header view.
[FIGURE 1]
When I reload Items after a search, some items goes over header during scroll.
I've no idea about the cause...
Any ideas or suggestions?
Thanks.
EDIT
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
return CGSizeMake(CGRectGetWidth([UIScreen mainScreen].bounds), CGRectGetWidth([UIScreen mainScreen].bounds) * 0.612f);
}
What worked for me is to call reloadData() instead of trying to reload with animation (reloadSections()).
In my case, I had a show/hide button to toggle the number of rows in section between item count and 0 (expand the content of the section).
When I replaced
collectionView?.reloadSections([section])
with
collectionView?.reloadData()
I no longer had the issue.
My working code for UICollectionView along with HeaderView inside UIViewController:
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 20;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cell" forIndexPath:indexPath];
cell.backgroundColor = [UIColor blueColor];
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
return CGSizeMake(100, 100);
}
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
UICollectionReusableView *view = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:#"header" forIndexPath:indexPath];
return view;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
return CGSizeMake(self.view.frame.size.width, 100);
}
Storyboard:
Output:
Please check this. Hope this will help you in some other way.
You can try to set sectionHeadersPinToVisibleBounds = true property on your UICollectionViewFlowLayout. Because every UICollectionView has own layout.
Apple doc
A Boolean value indicating whether headers pin to the top of the collection view bounds during scrolling.
Maybe it will help. Add this code into viewDidLoad.
(self.yourCollectionView.collectionViewLayout as! UICollectionViewFlowLayout).sectionHeadersPinToVisibleBounds = true
After trying many solutions in my case that works,
collectionView.clipsToBounds = true

How to add Load more cell in UICollectionView?

I want to add load more cell in UICollectionview ? can anyone tell me how can i add load button ? i have created collectionview that works fine but i want to add Load more button in bottom of collection view cell like this
Here's my collection view
#pragma mark <UICollectionViewDataSource>
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 3;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
switch (section) {
case 0: return 66;
case 1: return 123;
}
return 31;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
NSUInteger row = [indexPath row];
NSUInteger count = [self.stockImages count];
if (row == count) {
//Add load more cell
}
DemoCellView *cell = [collectionView dequeueReusableCellWithReuseIdentifier:[DemoCellView reuseIdentifier] forIndexPath:indexPath];
// Configure the cell
cell.titleLabel.text = [NSString stringWithFormat:#"%ld", (long)indexPath.item + 1];
NSLog(#"%#", self.stockImages[indexPath.item % self.stockImages.count]);
cell.imageView.image = self.stockImages[indexPath.item % self.stockImages.count];
return cell;
}
#pragma mark <DemoLayoutDelegate>
- (void) collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
// Do something
// Insert new cell after clicking load more data
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout: (UICollectionViewLayout *)collectionViewLayout heightForHeaderInSection:(NSInteger)section {
return kFMHeaderFooterHeight;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout heightForFooterInSection:(NSInteger)section {
return kFMHeaderFooterHeight;
}
You can Add a footer
- (UICollectionReusableView *)collectionView:(JSQMessagesCollectionView *)collectionView
viewForSupplementaryElementOfKind:(NSString *)kind
atIndexPath:(NSIndexPath *)indexPath
{
if ([kind isEqualToString:UICollectionElementKindSectionFooter]) {
//load your footer you have registered earlier for load more
[super dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter
withReuseIdentifier:#“load more footer”
forIndexPath:indexPath];
}
return nil;
}
In your cellForItemAtIndexPath method you can check this:
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
ImageCollectionViewCell *cellImage;
AddMoreCollectionViewCell *addMoreCell;
if(indexPath.row < [_dataSource numberOfItems]){
cellImage = [collectionView dequeueReusableCellWithReuseIdentifier:ImageCollectionCellIdentifier
forIndexPath:indexPath];
[cellImage configureForMediaViewModel:[_dataSource mediaViewModelForItemIndex:indexPath.row] delegate:self];
return cellImage;
}else{
addMoreCell = [collectionView dequeueReusableCellWithReuseIdentifier:AddMoreCollectionCellIdentifier
forIndexPath:indexPath];
addMoreCell.delegate = self;
return addMoreCell;
}
}
where ImageCollectionViewCell is the main kind of cells and AddMoreCollectionViewCell is a cell with a plus ('+') symbol and other stuff.
With this method, AddMoreCollectionViewCell always add at end of your collection view.
Hope it helps!

Display different amount of cells in a row within a UICollectionView

I would like to have a UICollectionView that, in the first row there is a cell with all the row's width, and the second row has 3 cells.
I have researched the documentation but I'm not able to do it. Something like this:
Thanks in advance
Make 2 Cell prototypes in collection view in your storyboard, and set them reuse identifiers
In your ViewController's .m file implement this functions
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 6;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell;
if (/*condition for small cell*/)// e.g. indexPath.row % 3 != 0
cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"smallCell" forIndexPath:indexPath];
else
cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"bigCell" forIndexPath:indexPath];
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
if (/*condition for small cell*/) // e.g. indexPath.row % 3 != 0
return CGSizeMake(65, 50);
return CGSizeMake(318, 50);
}
After doing this you will have something like this:

Multiple UICollectionView in the same ViewController

I am using custom UICollectionView layout for having different size of cells and I am not able to have a section in this.
Is it good idea to use multiple UICollectionViews in the same UIViewController? Any suggestion please?
it's simple
for every UICollectionView Delegates
- (NSUInteger)maximumNumberOfColumnsForCollectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout
- (CGFloat)collectionView:(UICollectionView*)collectionView layout:(UICollectionViewLayout*)collectionViewLayout
heightForItemAtIndexPath:(NSIndexPath*)indexPath
- (UICollectionViewCell*)collectionView:(UICollectionView*)collectionView
cellForItemAtIndexPath:(NSIndexPath*)indexPath
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
- (NSInteger)collectionView:(UICollectionView*)collectionView numberOfItemsInSection:(NSInteger)section`
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView*)collectionView`
write condition inside:
if (collectionView == myCollectionView1)
{
// do this
}
else if (collectionView == myCollectionView2)
{
// do this
}
lets say for example in
- (NSInteger)collectionView:(UICollectionView*)collectionView numberOfItemsInSection:(NSInteger)section
{
if (collectionView == myCollectionView1)
{
return 12;
}
else if (collectionView == myCollectionView2)
{
return 7;
}
return 0;
}
Use Tag Property for distinguish between multiple UICollectionView or UITableView in one View Controller.
firstCollectionView.tag = 1;
secondCollectionView.tag = 2;
and so on ...
Now, In delegate methods use if to check UICollectionView
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
if(collectionView.tag == 1)
{
//cell for first UICollectionView or CollectionView with tag equal to 1
}
else if(collection.tag == 2)
{
//cell for second UICollectionView or CollectionView with tag equal to 2
}
}
Use same technique in other delegate methods.

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