Creating a UICollectionView programmatically

Question

I'm looking for a guide or tutorial that will show me how to set up a simple UICollectionView using only code.

I'm wading through the documentation on Apples site, and I'm using the reference manual as well.

But I would really benefit from a simple guide that can show me how to set up a UICollectionView without having to use Storyboards or XIB/NIB files - but unfortunately when I search about, all I can find is tutorials that feature the Storyboard.

Solution 1

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---

Solution 2

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)
    }
}

Solution 3

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
}

Solution 4

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)
    }

}

Solution 5

You can handle custom cell in uicollection view see below code.

- (void)viewDidLoad
{
  UINib *nib2 = [UINib nibWithNibName:@"YourCustomCell" bundle:nil];
    [CollectionVW registerNib:nib2 forCellWithReuseIdentifier:@"YourCustomCell"];


    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    [flowLayout setItemSize:CGSizeMake(200, 230)];
    flowLayout.minimumInteritemSpacing = 0;
    [flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
    [CollectionVW setCollectionViewLayout:flowLayout];

    [CollectionVW reloadData];
}

#pragma mark - COLLECTIONVIEW
#pragma mark Collection View CODE

-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return Array.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier = @"YourCustomCell";
    YourCustomCell *cell = (YourCustomCell *)[collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

    cell.MainIMG.image=[UIImage imageNamed:[Array objectAtIndex:indexPath.row]];


    return cell;
}

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
}

#pragma mark Collection view layout things
// Layout: Set cell size
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    CGSize mElementSize;
    mElementSize=CGSizeMake(kScreenWidth/3.4, 150);
    return mElementSize;
}


- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 5.0;
}

// Layout: Set Edges
- (UIEdgeInsets)collectionView: (UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    if (isIphone5 || isiPhone4)
    {
        return UIEdgeInsetsMake(15,15,5,15);  // top, left, bottom, right
    }
    else if (isIphone6)
    {
        return UIEdgeInsetsMake(15,15,5,15);  // top, left, bottom, right
    }
    else if (isIphone6P)
    {
        return UIEdgeInsetsMake(15,15,5,15);  // top, left, bottom, right
    }

    return UIEdgeInsetsMake(15,15,5,15);  // top, left, bottom, right
}

View more solutions

Comments

[A-Live]

At the documentation there's a single initializer which you should use instead of any superclass initializer, where do you have problems exactly ?

[Jimmery]

Really? Ive got as far as the section "Configuring Cells and Supplimentary Views" - have I been a dumb ass and missed this line? Or have I yet to reach it?

[A-Live]

The first task is Initializing a Collection View, are you using initializer from there ?

[Jimmery]

Yes, but this in itself is not enough. I will also need to set up a datasource as well or the App crashes.

[ArgaPK]

@Jimmery Now how to add image in the cell in this collectionview?

[zontragon]

You should add the collection view as property in IOS7 @property (strong, nonatomic) UICollectionView *collectionView;

[Pétur Ingi Egilsson]

The setup should happen in -(void)loadView, not in viewDidLoad. As for why it works, the controller first loads default views in its super. Its better to overload loadview and assign your custom views directly.

[Rob]

Also, if you're programmatically adding any subviews to the UICollectionViewCell, you really don't want to be registering UICollectionViewCell, but rather you want to subclass it, do your configuration of the cell in the initWithFrame method, and then register this subclass with the cell identifier, not UICollectionViewCell.

[shrishaster]

Has anyone else had an error with the above code? It's giving me EXC_BAD_ACCESS error on the line _collectionView=[[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:layout];

[shrishaster]

'self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];' this was missing.

[JakubKnejzlik]

it should be placed in -loadView, not in -viewDidLoad

[artud2000]

You should never add any code before the call of the super class method in this case [super viewDidLoad]; that's a bad practice read apple documentation

[hzxu]

But I've read in the apple doc that The layout object to use for organizing items. The collection view stores a strong reference to the specified object. Must not be nil.

[Rambatino]

why are we adding this line in? self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

[Prince Kumar Sharma]

hi @Rambatino just set frame to main screen bounds , no need to alloc until it is not attached with outlet.

[Prince Kumar Sharma]

hi @artud2000, at your suggestion I am editing my answer to get super call first executed. Thanks for suggestion.

[Stephen Rauch]

How does this differ from the 6 others answers already here? When giving an answer it is preferable to give some explanation as to WHY your answer is the one.

[ArgaPK]

@Warewolf could you please tell me, How to change the direction of collection view to horizontal??

[ArgaPK]

Now how to add image in this programmatically collectionView ?

[shvets]

@ArgaPK sure, just add flowLayout.scrollDirection = .horizontal after you instantiate the flowLayout :)

[Prince Kumar Sharma]

@ArgaPK adding subview to cell in cellForItem method

[andrewz]

How are you binding this view controller as a delegate to the collection view layout?