Creating a Uicollectionview Programmatically

How to create UICollectionViewCell programmatically

Your problem lies here. In your viewDidLoad(), you're registering your collectionView cell twice. You are registering the collectionview's cell to your custom cell class in the first line and then in the second line you are registering it to the class UICollectionViewCell.

 collectionView.registerClass(MyCollectionViewCell.self, forCellWithReuseIdentifier: cellReuseIdentifier)
 collectionView.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")

Just remove the second line and your code should work.

Creating a UICollectionView programmatically

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---

How can I programmatically make a UICollectionView fill a UITableViewCell?

In your code you have added just 1 constraint - bottomAnchor. Autolayout doesn't work like that. Just add all the required constraints after adding UICollectionView as subview of UITableViewCell, i.e.

override init(style: UITableViewCellStyle, reuseIdentifier: String?)
{
    super.init(style: style, reuseIdentifier: reuseIdentifier)

    self.collectionViewLayout = UICollectionViewFlowLayout()
    self.collectionViewLayout.sectionInset = UIEdgeInsets(top: 1.0, left: 1.0, bottom: 1.0, right: 1.0)
    self.collectionViewLayout.scrollDirection = .vertical

    let frame = CGRect(x: 0.0, y: 0.0, width: self.frame.width, height: self.frame.height)
    self.collectionView = UICollectionView(frame: frame, collectionViewLayout: self.collectionViewLayout)
    self.collectionView?.translatesAutoresizingMaskIntoConstraints = false
    self.addSubview(self.collectionView!)

    NSLayoutConstraint.activate([
        self.collectionView!.topAnchor.constraint(equalTo: self.topAnchor),
        self.collectionView!.bottomAnchor.constraint(equalTo: self.bottomAnchor),
        self.collectionView!.leftAnchor.constraint(equalTo: self.leftAnchor),
        self.collectionView!.rightAnchor.constraint(equalTo: self.rightAnchor),
        ])

    self.collectionView?.dataSource = self
    self.collectionView?.delegate = self
}

UICollectionView Programmatically

You need to use UICollectionViewController's designated intialiser as below.

let layout = UICollectionViewLayout()
let homeViewController = HomeController(collectionViewLayout: layout)
window?.rootViewController = UINavigationController(rootViewController: homeViewController)

Along with that, you will need to modify you HomeViewController to implement UICollectionViewDataSource required methods.

override func viewDidLoad() {
        super.viewDidLoad()

        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        // Register cell classes
        self.collectionView!.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")

        // Do any additional setup after loading the view.
    }


// MARK: UICollectionViewDataSource

    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        // #warning Incomplete implementation, return the number of sections
        return 0
    }


    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of items
        return 0
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)

        // Configure the cell

        return cell
    }

Creating UICollectionView programmatically (outside of UIViewController)

You can declare your CollectionView as

class AlbumPlayerProgressBar: UICollectionView, UICollectionViewDataSource {
    var progressBarType :ProgressBarType = .Player
    var numOfSlides: Int = 0
    var numOfPlayingSlide: Int = 0

    override func awakeFromNib() {
        super.awakeFromNib()
        //gets called when you instantiate your collectionView from xib
        self.register(UINib(nibName: NSStringFromClass(ProgressBarCell.self), bundle: nil), forCellWithReuseIdentifier: NSStringFromClass(ProgressBarCell.self))
        self.dataSource = self
    } 

    override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
        super.init(frame: frame, collectionViewLayout: layout)
        self.register(UINib(nibName: NSStringFromClass(ProgressBarCell.self), bundle: nil), forCellWithReuseIdentifier: NSStringFromClass(ProgressBarCell.self))
        self.dataSource = self
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.register(UINib(nibName: NSStringFromClass(ProgressBarCell.self), bundle: nil), forCellWithReuseIdentifier: NSStringFromClass(ProgressBarCell.self))
        self.dataSource = self
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return numOfSlides
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: NSStringFromClass(ProgressBarCell.self), for: indexPath) as! ProgressBarCell

        cell.setType(self.progressBarType)

        if (indexPath.row < numOfPlayingSlide)
        {
            cell.setPlayed()
        }
        else if (indexPath.row == numOfPlayingSlide)
        {
            cell.setPlaying()
        }
        else
        {
            cell.setUnplayed()
        }
        return cell
    }
}

Depending on how would you initialize/instantiate collectionView decide where would like to register your nib and setting data source as self.

Hope it helps

How to create and use UIcollectionView programmatically?

There is not alternative to create or allocate cells in itemAtIndex method. We need to register the customised class to create any views inside the custom class. something like this :

[UICollectionView registerClass:[CustomCollectionViewClass class] forCellWithReuseIdentifier:@"cellIdentifier"];

here is the best link which I found useful. Hope it helps others

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