Programatically constraint doesn't work inside UICollectionViewCell Swift

Question

I tried to make a programatically view inside UICollectionViewCell, and I think it will be wise to put the "programatically view code" inside UICollectionViewCell.

So here is my code:

override func awakeFromNib() {
        super.awakeFromNib()

        let view = UIView()
        view.frame = CGRect.zero
        view.backgroundColor = UIColor.black

        self.contentView.addSubview(view)
        self.contentView.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate([
            view.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 0),
            view.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: 0),
            view.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: 25),
            view.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 25),
            ])

        self.contentView.layoutIfNeeded()
    }

I was wondering why the auto layout does not work, instead if I use manual CGRect, the view did appeared.

Mohamed Obaya · Accepted Answer · 2019-02-06 10:00:15Z

1

This Solve it just needs to set view.translatesAutoresizingMaskIntoConstraints = false not The contenView

override func awakeFromNib() {
    super.awakeFromNib()

    let view = UIView()
    view.frame = CGRect.zero
    view.backgroundColor = UIColor.black


    self.contentView.addSubview(view)
    view.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        view.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 0),
        view.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: 0),
        view.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: 25),
        view.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 25),
        ])
}

edited Feb 6, 2019 at 10:00

answered Feb 6, 2019 at 9:54

Mohamed Obaya

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Comments

Tieda Wei · Accepted Answer · 2019-02-06 09:56:11Z

1

Try to change self.contentView.translatesAutoresizingMaskIntoConstraints = false to: view.translatesAutoresizingMaskIntoConstraints = false

You'd like to turn off the translatesAutoresizingMaskIntoConstraints of your view since we want to apply autolayout to it.

answered Feb 6, 2019 at 9:56

Tieda Wei

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LowKostKustomz · Accepted Answer · 2019-02-06 10:06:03Z

1

First: You should not call layoutIfNeeded method, the auto layout cycle will do this for you after you change the rules (constraints)

Second: You should set translatesAutoresizingMaskIntoConstraints property to false for the view that will be layed out, so you should not do this

self.contentView.translatesAutoresizingMaskIntoConstraints = false

but you should do this

view.translatesAutoresizingMaskIntoConstraints = false

That's because autoresizing mask constraints are applied to your view with constraints that you've set. This may and probably will cause constraints break.

If this won't help then provide console output with autolayout errors.

answered Feb 6, 2019 at 10:06

LowKostKustomz

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1 Comment

Wendy Liga Over a year ago

noted. the thing that layoutIfNeeded is pretty crucial , thanks man

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