How to give width and height programatically for c

问题:

I tried to give the height and width for collectionViewCell , programatically. I used following method:

 func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let viewWidth = self.deviceWidth/3 - 5
        let viewHeight = viewWidth

        return CGSize(width :100,height: 100)
    }

This didn't work. even this method didn't show as a hint. Help me with this. Is there any other delegate method to set the cell width and height programmatically in Swift 3?

回答1:

Method collectionView(_:layout:sizeForItemAt:) is UICollectionViewDelegateFlowLayout protocol's method, so setting delegate and datasource of collectionView is not enough, you need to implement UICollectionViewDelegateFlowLayout with your custom class where you have added collectionView to call UICollectionViewDelegateFlowLayout protocol's methods. So implement UICollectionViewDelegateFlowLayout like below example:

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

回答2:

Pls sure your class must implement UICollectionViewDelegateFlowLayout like this:

class ViewController: UIViewController,UICollectionViewDataSource,UICollectionViewDelegate, UICollectionViewDelegateFlowLayout
{
    ...
}

And then write this delegate method in your class:

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
{
    return CGSize(width: 100, height: 100) // The size of one cell
}

Hope it will help you...

回答3:

This methods always work. Please first ensure that this method is executed ot not. If not, the write delegate UICollectionViewDelegateFlowLayout like this:

class MyViewController: UIViewController , UICollectionViewDelegateFlowLayout, UICollectionViewDelegate, UICollectionViewDataSource{
   :
   :
}

And dont forget to bind the delegate and datasource of UICollectionView either from storyboard or by code collectionView.delegate = self and collectionView.datasource = self