When I try to tap all collectionViewCells from top to bottom, lower cells which is probably reused can't be tapped.
I guess the cells is reused with selection condition.
How do I fix it?
ViewController.m
- (void)viewDidLoad
{
flowLayout = [[UICollectionViewFlowLayout alloc]init];
flowLayout.itemSize = CGSizeMake(106, 106);
collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, 320, 568) collectionViewLayout:flowLayout];
collectionView.allowsMultipleSelection = YES;
[collectionView registerClass:[CustomCell class] forCellWithReuseIdentifier:kCellIdentifier];
collectionView.delegate = self;
collectionView.dataSource = self;
[self.view addSubview:collectionView];
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 30;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
CustomCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kCellIdentifier forIndexPath:indexPath];
return cell;
}
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
NSLog(#"%#", indexPath);
}
CustomCell.m
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
{
//
}
}
In -collectionView:didSelectItemAtIndexPath:, call [self.collectionView deselectItemAtIndexPath:indexPath animated:YES]; to deselect the cell so that in case it gets reused, the selection won't be passed on to be reused.
Another way of doing this is to have your model track whether it is selected or not so that you can set the selected state in -collectionView:cellForItemAtIndexPath:.
Related
I'm trying to do a UICollectionView of articles that doesn't eats RAM like an elephant. So, the UICollectionView consists of full screen cells that contain one image. If the UICollectionViewCell appears, the content gets loaded in. This is the code:
- (void)viewDidLoad {
UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayout alloc] init];
layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
layout.itemSize = CGSizeMake(self.view.frame.size.width, self.view.frame.size.height);
layout.minimumInteritemSpacing = 0;
layout.minimumLineSpacing = 0;
_collectionView = [[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:layout];
[_collectionView setDataSource:self];
[_collectionView setDelegate:self];
_collectionView.pagingEnabled = YES;
[_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:#"cellIdentifier"];
[_collectionView setBackgroundColor:[UIColor redColor]];
[self.view addSubview:_collectionView];
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
//add UIImageView here
//add UITextView with tag 123 here
return cell;
}
- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell *cell = [_collectionView cellForItemAtIndexPath:indexPath];
UITextView *textView = [cell viewWithTag:123];
textView.text = #"Testing this out.";
}
However, this doesn't do anything. No errors are thrown, it just doesn't do anything. What am I doing wrong?
Although UICollectionViewCells is displayed, [collectionView visibleCells] returns nil.
- (void)viewDidLoad{
self.collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, 320, 568) collectionViewLayout:flowLayout];
self.collectionView.delegate = self;
self.collectionView.dataSource = self;
[self.collectionView registerClass:[CustomCell class] forCellWithReuseIdentifier:#"Cell"];
[self.view addSubview:self.collectionView];
NSLog(#"%d", [[self.collectionView visibleCells] count]);
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
CustomCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"Cell" forIndexPath:indexPath];
return cell;
}
Do you have any idea?
The issue is caused by reload has not been finished.
The solution is ：
1. [collectionView reloadData];
2. **[collectionView layoutIfNeeded];
3. the get your - > [collectionView visibleCells];
Try this in your view controller
- (void) viewDidLayoutSubviews {
NSLog(#"%d", [[self.collectionView visibleCells] count]);
}
Try add this:
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
collectionView?.collectionViewLayout.invalidateLayout()
}
I create one UICollectionView sticky header section with this : sticky header section but when my UICollectionViewCell is 0 number header section in hide like this picture :
in my picture show me one header section (index:2) and other header section is hidden. please guide me !!! I want other show like index 2.
this is my code:
- (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor whiteColor];
Flow *layout=[[Flow alloc] init];
//layout.sectionInset = UIEdgeInsetsMake(20,0,40,0);
//layout.itemSize = CGSizeMake(100,100);
_collect=[[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:layout];
_collect.backgroundColor = [UIColor clearColor];
[_collect setDataSource:self];
[_collect setDelegate:self];
[_collect registerClass:[HeaderView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:#"HeaderView"];
[_collect registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:#"cellIdentifier"];
[self.view addSubview:_collect];
//NSLog(#"%#",self.array);
}
- (NSMutableArray*)array {
if (!_array) {
_array = [NSMutableArray array];
for (NSInteger i=0; i<SectionNum; i++) {
//NSMutableArray *inner = [NSMutableArray arrayWithObject:#"0"];
[_array addObject:#"0"];
}
}
return _array;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return SectionNum;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
if (section == 2) {
return 10;
} else
return 0;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *identifier = #"cellIdentifier";
CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
return cell;
}
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
UICollectionReusableView *reusableview = nil;
if (kind == UICollectionElementKindSectionHeader) {
HeaderView *header = [_collect dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:#"HeaderView" forIndexPath:indexPath];
header.backgroundColor = [UIColor colorWithWhite:0.75 alpha:.9];
header.titleLabel.font = [UIFont systemFontOfSize:24];
header.titleLabel.textAlignment = NSTextAlignmentCenter;
header.titleLabel.text = [NSString stringWithFormat:#"%ld",indexPath.section];
reusableview = header;
}
if (kind == UICollectionElementKindSectionFooter) {
UICollectionReusableView *footerview = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:#"FooterView" forIndexPath:indexPath];
reusableview = footerview;
}
return reusableview;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return CGSizeMake(100,100);
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
CGSize headerSize = CGSizeMake(320, 50);
return headerSize;
}
I have a UIViewController with a UICollectionView on it but Xcode doesn't seem to look like every tutorial I find on the Internet or on YouTube - When I drag a UICollectionViewCell to place in the UICollectionView, it won't let me place it.
Now I'm confused as to how I can link my cell to the UICollectionView.
This is the viewController.h file:
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
return 1;
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
return [self.imagesArray count];
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
ImageViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"imageCell" forIndexPath:indexPath];
NSString *myImageString = [self.imagesArray objectAtIndex:indexPath.row];
cell.imageView.image = [UIImage imageNamed:myImageString];
return cell;
}
-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
return CGSizeMake(100.0, 100.0);
}
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
return UIEdgeInsetsMake(5, 5, 5, 5);
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.collectionView.delegate = self;
self.collectionView.dataSource = self;
//[self.collectionView registerClass:[ImageViewCell class] forCellWithReuseIdentifier:#"imageCell"];
self.imagesArray = #[#"shirt1.PNG", #"pants.png", #"pants2.png"];
}
I'm not using a Storyboard interface but individual xib's. When I run this all that appears is the blank black screen. What am I missing?
-registerNib:forCellWithReuseIdentifier:
If you have your cell defined in a NIB, then you register that NIB with the collection view. That is how the collection view know what to load when -dequeueReusableCellWithReuseIdentifier:forIndexPath: is called.
- (void)viewDidLoad
{
// …
UINib nib = [UINib nibWithNibName:#"<the name of your xib>" bundle:nil];
[self.collectionView registerNib:nib forCellWithReuseIdentifier:#"imageCell"];
// …
}
Because you didn't have new a object of UICollectionViewCell in this method:
-(UICollectionViewCell*)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
The "cell" in your method must be set to nil.
i have multiple image in uicollectionview like grid view. i want select multiple image at a time but not working this code.please any one give idea about this code.
i have already tried this code but not working.
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath: (NSIndexPath *)indexPath
{
NSMutableArray *indexPaths = [NSMutableArray arrayWithObject:indexPath];
if (self.selectedItemIndexPath)
{
// if we had a previously selected cell
if ([indexPath compare:self.selectedItemIndexPath] == NSOrderedSame)
{
// if it's the same as the one we just tapped on, then we're unselecting it
self.selectedItemIndexPath = nil;
}
else
{
// if it's different, then add that old one to our list of cells to reload, and
// save the currently selected indexPath
[indexPaths addObject:self.selectedItemIndexPath];
self.selectedItemIndexPath = indexPath;
}
}
else
{
// else, we didn't have previously selected cell, so we only need to save this indexPath for future reference
self.selectedItemIndexPath = indexPath;
}
// and now only reload only the cells that need updating
[self.collectionView reloadItemsAtIndexPaths:indexPaths];
}
// I Have Drag the UICollectionView Controller in storyboard
static NSString * const reuseIdentifier = #"Cell";
- (void)viewDidLoad
{
[super viewDidLoad];
[self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];
arrImage = [[NSMutableArray alloc]initWithObjects:#"1.jpeg",#"2.jpeg",#"3.jpeg",#"4.jpeg",#"5.jpeg",#"6.jpeg",#"7.jpeg",#"8.jpeg",#"9.jpeg",#"10.jpeg",#"flower.jpeg",#"flower1.jpeg", nil];
[self.collectionView setAllowsMultipleSelection:YES];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark <UICollectionViewDataSource>
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return [arrImage count];
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
UIImageView *recipeImageView = (UIImageView *)[cell viewWithTag:100];
recipeImageView.image = [UIImage imageNamed:[arrImage objectAtIndex:indexPath.row]];
[self.view addSubview:recipeImageView];
cell.backgroundColor=[UIColor colorWithPatternImage:[UIImage imageNamed:[arrImage objectAtIndex:indexPath.row]]];
return cell;
}
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell* cell=[self.collectionView cellForItemAtIndexPath:indexPath];
cell.contentView.backgroundColor = [[UIColor yellowColor] colorWithAlphaComponent:0.15];
}
- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell* cell=[self.collectionView cellForItemAtIndexPath:indexPath];
UIImageView *recipeImageView = (UIImageView *)[cell viewWithTag:100];
recipeImageView.image = [UIImage imageNamed:[arrImage objectAtIndex:indexPath.row]];
}