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To create a UICollectionView programmatically, I will create a new instance of UICollectionView by giving it a UICollectionViewFlowLayout as a parameter. var myCollectionView:UICollectionView? The above collection view will not display any items however.
Add a UICollectionView to your view controller using the story board or programmatically. Add constraints to the newly added UICollectionView. It's important to have a fixed height for this collection view as it will scroll in one direction. Set the scroll direction to horizontal.
Tableiw is a simple list, which displays single-dimensional rows of data. It's smooth because of cell reuse and other magic. 2. UICollectionView is the model for displaying multidimensional data .
An object that manages an ordered collection of data items and presents them using customizable layouts.
Header file:--
@interface ViewController : UIViewController<UICollectionViewDataSource,UICollectionViewDelegateFlowLayout>
{
UICollectionView *_collectionView;
}
Implementation File:--
- (void)viewDidLoad
{
[super viewDidLoad];
self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayout alloc] init];
_collectionView=[[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:layout];
[_collectionView setDataSource:self];
[_collectionView setDelegate:self];
[_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cellIdentifier"];
[_collectionView setBackgroundColor:[UIColor redColor]];
[self.view addSubview:_collectionView];
// Do any additional setup after loading the view, typically from a nib.
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 15;
}
// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cellIdentifier" forIndexPath:indexPath];
cell.backgroundColor=[UIColor greenColor];
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
return CGSizeMake(50, 50);
}
Output---
For swift4 user:--
class TwoViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, UICollectionViewDelegate {
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView = UICollectionView(frame: self.view.bounds, collectionViewLayout: flowLayout)
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
collectionView.delegate = self
collectionView.dataSource = self
collectionView.backgroundColor = UIColor.cyan
self.view.addSubview(collectionView)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 20
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
var cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)
cell.backgroundColor = UIColor.green
return cell
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
return CGSize(width: 50, height: 50)
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAtIndex section: Int) -> UIEdgeInsets {
return UIEdgeInsets(top: 5, left: 5, bottom: 5, right: 5)
}
}
For Swift 2.0
Instead of implementing the methods that are required to draw the CollectionViewCells:
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize
{
return CGSizeMake(50, 50);
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAtIndex section: Int) -> UIEdgeInsets
{
return UIEdgeInsetsMake(5, 5, 5, 5); //top,left,bottom,right
}
Use UICollectionViewFlowLayout
func createCollectionView() {
let flowLayout = UICollectionViewFlowLayout()
// Now setup the flowLayout required for drawing the cells
let space = 5.0 as CGFloat
// Set view cell size
flowLayout.itemSize = CGSizeMake(50, 50)
// Set left and right margins
flowLayout.minimumInteritemSpacing = space
// Set top and bottom margins
flowLayout.minimumLineSpacing = space
// Finally create the CollectionView
let collectionView = UICollectionView(frame: CGRectMake(10, 10, 300, 400), collectionViewLayout: flowLayout)
// Then setup delegates, background color etc.
collectionView?.dataSource = self
collectionView?.delegate = self
collectionView?.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "cellID")
collectionView?.backgroundColor = UIColor.whiteColor()
self.view.addSubview(collectionView!)
}
Then implement the UICollectionViewDataSource methods as required:
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 20;
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
var cell:UICollectionViewCell=collectionView.dequeueReusableCellWithReuseIdentifier("collectionCell", forIndexPath: indexPath) as UICollectionViewCell;
cell.backgroundColor = UIColor.greenColor();
return cell;
}
func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
Swift 3
class TwoViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, UICollectionViewDelegate {
override func viewDidLoad() {
super.viewDidLoad()
let flowLayout = UICollectionViewFlowLayout()
let collectionView = UICollectionView(frame: self.view.bounds, collectionViewLayout: flowLayout)
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
collectionView.delegate = self
collectionView.dataSource = self
collectionView.backgroundColor = UIColor.cyan
self.view.addSubview(collectionView)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
return 20
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)
cell.backgroundColor = UIColor.green
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
{
return CGSize(width: 50, height: 50)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets
{
return UIEdgeInsets(top: 5, left: 5, bottom: 5, right: 5)
}
}
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