我正在从云存储下载图像,它们在我的应用程序中使用。我把它们缓存了但是当我的表滚动或重新加载时我仍然看到一些闪烁。
这是我尝试过的:
我的缓存代码:
import UIKit
class ImageService {
static let cache = NSCache<NSString, UIImage>()
static func downloadImage(withURL url:URL, completion: @escaping (_ image:UIImage?)->()) {
let dataTask = URLSession.shared.dataTask(with: url) { data, responseURL, error in
var downloadedImage: UIImage?
downloadedImage = nil
if let data = data {
downloadedImage = UIImage(data: data)
}
if downloadedImage != nil {
cache.setObject(downloadedImage!, forKey: url.absoluteString as NSString)
}
DispatchQueue.main.async {
completion(downloadedImage)
}
}
dataTask.resume()
}
static func getImage(withURL url:URL, completion: @escaping (_ image:UIImage?)->()) {
if let image = cache.object(forKey: url.absoluteString as NSString) {
print("IMAGE IS LOADED FROM CACHE!!!!")
DispatchQueue.main.async {
completion(image)
}
} else {
print("IMAGE IS LOADED FROM DOWNLOAD!!!!")
downloadImage(withURL: url, completion: completion)
}
}
}
这是我的一个表中的一个例子:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
cell.imageView.image = nil
let storage = Storage.storage()
let storageRef = storage.reference()
let imageRef = storageRef.child(String(format: "images/%@.jpg", id))
imageRef.downloadURL { (URL, error) in
if error == nil {
DispatchQueue.main.async {
ImageService.getImage(withURL: URL!, completion: { image in
cell.imageView.image = image
})
}
} else {
cell.imageView.image = UIImage (named: "placeholder")
}
}
}
我看到,当我第一次加载我的应用程序时,图像被下载,然后从缓存加载。但我仍然看到它们闪烁。有关更新上述内容以缓存内存和磁盘或修复闪烁问题的建议吗?
解:
我正在使用FirebaseUI,它具有SDWebImage的修改版本,可根据存储参考进行缓存。
TBH我不知道这是否有效。但我遇到了同样的问题,你需要将cell.imageview设置为nil
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
// cell.imageView.image = nil (remove)
let storage = Storage.storage()
let storageRef = storage.reference()
let imageRef = storageRef.child(String(format: "images/%@.jpg", id))
imageRef.downloadURL { (URL, error) in
if error == nil {
DispatchQueue.main.async {
ImageService.getImage(withURL: URL!, completion: { image in
cell.imageView.image = nil //add
cell.imageView.image = image
})
}
} else {
cell.imageView.image = nil // Add
cell.imageView.image = UIImage (named: "placeholder")
}
}
}
您应该从UITableView
委托方法中删除以下行。
let storage = Storage.storage()
let storageRef = storage.reference()
并使它们成为类变量。