我的应用程序中存在一个烦人的bug，每次加载UICollectionView控制器时，它都会复制单元格。
这是集合视图首次加载的时间:
我有2个视图控制器，所以这是第二个视图控制器。如果我退回到只有第二个视图控制器只有一个按钮的第一个视图控制器，然后再次触发第二个视图控制器(触发reloadData函数)，则会发生这种情况:
我不太确定为什么会这样，我在缓存图像中使用了Todd Kramer的UICollectionView:http://www.tekramer.com/downloading-images-asynchronously-in-swift-with-alamofire/唯一的区别是，我从JSON异步加载图像url和数据，而不是在模型或plist中静态定义为教程呢。
以下是我在代码中进行了更改的类:
import UIKit
import SwiftyJSON
private let PhotoCollectionViewCellIdentifier = "cell"
class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
@IBOutlet weak var collectionView: UICollectionView!
var index: NSIndexPath!
var names = [String]()
var imgsUrl = [String]()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let photo = PhotosDataManager()
let api = Api()
api.loadJsonData(self.names, imgsUrl: self.imgsUrl, batch: "2016", dept: "dafa") { names, imgsUrl in
self.names = names
self.imgsUrl = imgsUrl
photo.allPhotos(self.names, imgUrls: self.imgsUrl)
self.collectionView.reloadData()
}
}
@IBAction func button(sender: UIButton) {
NSNotificationCenter.defaultCenter().postNotificationName("alert1", object: self, userInfo: nil)
}
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return PhotosDataManager.sharedManager.allPhotos(self.names, imgUrls: self.imgsUrl).count
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(PhotoCollectionViewCellIdentifier, forIndexPath: indexPath) as! CollectionViewCell
dispatch_async(dispatch_get_main_queue(), {
cell.configure(self.glacierScenicAtIndex(indexPath))
})
return cell
}
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
PhotosDataManager.sharedManager.purgeCache()
self.performSegueWithIdentifier("previousViewController", sender: self)
}
func glacierScenicAtIndex(indexPath: NSIndexPath) -> GlacierScenic {
let photos = PhotosDataManager.sharedManager.allPhotos(self.names, imgUrls: self.imgsUrl)
return photos[indexPath.row]
}
}
class PhotosDataManager {
static let sharedManager = PhotosDataManager()
private var photos = [GlacierScenic]()
let decoder = ImageDecoder()
let photoCache = AutoPurgingImageCache(
memoryCapacity: 100 * 1024 * 1024,
preferredMemoryUsageAfterPurge: 60 * 1024 * 1024
)
func allPhotos(names: [String], imgUrls: [String]) -> [GlacierScenic] {
var glacierScenic: GlacierScenic!
for i in 0 ..< names.count {
glacierScenic = GlacierScenic(name: names[i], photoURLString: imgUrls[i])
photos.append(glacierScenic)
}
return photos
}
func getNetworkImage(urlString: String, completion: (UIImage -> Void)) -> (ImageRequest) {
let queue = decoder.queue.underlyingQueue
let request = Alamofire.request(.GET, urlString)
let imageRequest = ImageRequest(request: request)
imageRequest.request.response(
queue: queue,
responseSerializer: Request.imageResponseSerializer(),
completionHandler: { response in
guard let image = response.result.value else {
return
}
let decodeOperation = self.decodeImage(image) { image in
completion(image)
self.cacheImage(image, urlString: urlString)
}
imageRequest.decodeOperation = decodeOperation
}
)
return imageRequest
}
func decodeImage(image: UIImage, completion: (UIImage -> Void)) -> DecodeOperation {
let decodeOperation = DecodeOperation(image: image, decoder: self.decoder, completion: completion)
self.decoder.queue.addOperation(decodeOperation)
return decodeOperation
}
func cacheImage(image: Image, urlString: String) {
photoCache.addImage(image, withIdentifier: urlString)
}
func cachedImage(urlString: String) -> Image? {
return photoCache.imageWithIdentifier(urlString)
}
func purgeCache() {
// photoCache.removeAllImages()
print("memory used: \(photoCache.memoryUsage)")
}
}
class PhotosDataManager {
static let sharedManager = PhotosDataManager()
private var photos = [GlacierScenic]()
let decoder = ImageDecoder()
let photoCache = AutoPurgingImageCache(
memoryCapacity: 100 * 1024 * 1024,
preferredMemoryUsageAfterPurge: 60 * 1024 * 1024
)
func allPhotos(names: [String], imgUrls: [String]) -> [GlacierScenic] {
var glacierScenic: GlacierScenic!
for i in 0 ..< names.count {
glacierScenic = GlacierScenic(name: names[i], photoURLString: imgUrls[i])
photos.append(glacierScenic)
}
return photos
}
func getNetworkImage(urlString: String, completion: (UIImage -> Void)) -> (ImageRequest) {
let queue = decoder.queue.underlyingQueue
let request = Alamofire.request(.GET, urlString)
let imageRequest = ImageRequest(request: request)
imageRequest.request.response(
queue: queue,
responseSerializer: Request.imageResponseSerializer(),
completionHandler: { response in
guard let image = response.result.value else {
return
}
let decodeOperation = self.decodeImage(image) { image in
completion(image)
self.cacheImage(image, urlString: urlString)
}
imageRequest.decodeOperation = decodeOperation
}
)
return imageRequest
}
func decodeImage(image: UIImage, completion: (UIImage -> Void)) -> DecodeOperation {
let decodeOperation = DecodeOperation(image: image, decoder: self.decoder, completion: completion)
self.decoder.queue.addOperation(decodeOperation)
return decodeOperation
}
func cacheImage(image: Image, urlString: String) {
photoCache.addImage(image, withIdentifier: urlString)
}
func cachedImage(urlString: String) -> Image? {
return photoCache.imageWithIdentifier(urlString)
}
func purgeCache() {
// photoCache.removeAllImages()
print("memory used: \(photoCache.memoryUsage)")
}
}
最佳答案
问题
在PhotosDataManager =>中，您正在使用sharedManager引用，该引用将对象引用保存为静态引用，并在所有segues导航中一直重复使用它，因此allPhotos方法始终在旧数组中添加数据。
static let sharedManager = PhotosDataManager()
另一个问题
不要在numberOfItemsInSection中调用allPhotos方法，因为它会被多次调用，这可能会多次追加数据
解决方案
在您的方法中:
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
//USE Instantiated reference
return photos.getPhotosCount()
}
而是在您的类类PhotosDataManager中
class PhotosDataManager {
func getPhotosCount(){
return photos.count
}
}