cellForItemAt indexPath在使用UICollectionViewDelegateFlowLayout时不会调用。
在这种情况下：
class Something: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
}
它调用我的cellforItemAtIndexPath，但不调用我的
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
}
但如果我包括UICollectionViewDelegateFlowLayout:
class Something: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
}
它将调用：
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
}
但不会调用CCD_ 5。我不理解这个问题。这是iOS的错误还是我什么都没看到？
对我来说，在创建带有布局的collectionView时，应该是let layout = UICollectionViewFlowLayout()，而不是容易被忽略的let layout = UICollectionViewLayout()。我不止两次陷入这种困境。
试试这个代码。
import UIKit
let kSCREENWIDTH = UIScreen.main.bounds.size.width
let kSCREENHEIGHT = UIScreen.main.bounds.size.height
let COLLECTION_CELL = "collectionCell"
class DemoController: UIViewController {
var collectionView : UICollectionView!
override func viewDidLoad() {
super.viewDidLoad()
setupCollectionView()
}
/// create programatically collection view
fileprivate func setupCollectionView() {
let layout = UICollectionViewFlowLayout()
// layout.itemSize = CGSize(width:(kSCREENWIDTH-20)/2,height:150)
layout.sectionInset = UIEdgeInsetsMake(5, 7, 5, 7)
layout.minimumLineSpacing = 5
layout.minimumInteritemSpacing = 1
collectionView = UICollectionView.init(frame: self.view.bounds, collectionViewLayout: layout)
collectionView.delegate = self
collectionView.dataSource = self
collectionView.backgroundColor = UIColor.white
self.view .addSubview(collectionView)
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: COLLECTION_CELL)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
//MARK: UICollectionViewDelegate
extension DemoController : UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 10
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
// add your code here
}
}
//MARK: UICollectionViewDataSource
extension DemoController : UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
/// add your code here
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: COLLECTION_CELL, for: indexPath)
cell.backgroundColor = UIColor.lightGray
print("Here cellForItemAt Works")
return cell
}
}
//MARK: UICollectionViewDelegateFlowLayout
extension DemoController : UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
print("Here sizeForItemAt Works")
return CGSize(width: 150, height: 150)
}
}
在我的例子中，contentInset不适合UICollectionView子类。尝试在你的子类中添加以下代码
override func layoutSubviews() {
super.layoutSubviews()
self.contentInset = UIEdgeInsetsMake(0, 0, 0, 0)
}
override func reloadData() {
DispatchQueue.main.async {
super.reloadData()
}
}
希望这能帮助到别人！
返回CGSize(width: 0, height: 0)的大小导致在我的情况下没有调用委托cellForItemAt。
例如：
这将导致这个问题。
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 0, height: 0)
}
因为这不会。
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 10, height: 10)
}