所以我在swift中建立一个应用程序，用户可以上传带有图片的产品。上传工作完美，但我遇到的问题是下载图片。用户得到所有产品的概览，并点击它们，然后将其发送到该产品的详细概览。在该概览中，有一个包含所有图片的集合视图（这是目标）。我的问题是，图片的加载速度太慢，无法在屏幕上显示。我想知道是否有一个选项可以在一个函数中给出图像视图，并将图像分配给它们，然后在屏幕已经加载后，图片将一个一个地加载？
这就是我现在用来加载图片的函数。
func getPictures(imageStrings: [String], imageViews: [UIImageView]){
let storage = Storage.storage();
for index in 0...imageStrings.count - 1 {
let gsReference = storage.reference(forURL: imageStrings[index])
gsReference.getData(maxSize: 15 * 1024 * 1024) { data, error in
if let error = error {
// Uh-oh, an error occurred!
print(error)
return
} else {
DispatchQueue.main.async {
imageViews[index].image = UIImage(data: data!)
}
print(UIImage(data: data!) as Any)
}
}
}
}
这是viewcontroller，我的集合视图在这里活动。
import MessageUI
import FirebaseStorage
class ProductDetailViewController: UIViewController, MFMailComposeViewControllerDelegate, UINavigationControllerDelegate, UICollectionViewDelegate, UICollectionViewDataSource {
@IBOutlet var TitleLable: UILabel!
@IBOutlet var PriceLable: UILabel!
@IBOutlet var ProductDate: UILabel!
@IBOutlet var UsernameLable: UILabel!
@IBOutlet var LocationLable: UILabel!
@IBOutlet var Userdate: UILabel!
@IBOutlet var ReserveerButton: UIButton!
@IBOutlet var DescriptionTextView: UITextView!
@IBOutlet var collectionView: UICollectionView!
var titleLable = String()
var priceLable = String()
var productDate = String()
var descriptionLable = String()
var userId = String()
var usernameLable = String()
var locationLable = String()
var userdate = String()
var email = String()
var imageStrings = [String]()
var images = [UIImage]()
var dbhelper = DBHelper()
override func viewDidLoad() {
super.viewDidLoad()
ReserveerButton.layer.cornerRadius = 20
loadUser(id: userId)
TitleLable.text = titleLable
PriceLable.text = priceLable
ProductDate.text = productDate
DescriptionTextView.text = descriptionLable
UsernameLable.text = usernameLable
loadImages()
// Do any additional setup after loading the view.
}
private func loadUser(id: String){
let dbhelper = DBHelper()
dbhelper.getUserbyUserID(id: id){ success in
if(dbhelper.users[0].Bedrijf != "NULL"){
self.UsernameLable.text = dbhelper.users[0].Bedrijf
} else {
self.UsernameLable.text = dbhelper.users[0].Voornaam + " " + dbhelper.users[0].Familienaam
}
self.Userdate.text = dbhelper.users[0].Added_on
self.LocationLable.text = dbhelper.users[0].Stad
self.email = dbhelper.users[0].Email
}
}
@IBAction func ReserveerProduct(_ sender: Any) {
if !MFMailComposeViewController.canSendMail() {
print("Mail services are not available")
return
}
let composeVC = MFMailComposeViewController()
composeVC.mailComposeDelegate = self
// Configure the fields of the interface.
composeVC.setToRecipients([self.email])
composeVC.setSubject(self.titleLable)
composeVC.setMessageBody("Beste " + self.usernameLable + ", \n\nIk zou graag het zoekertje " + self.titleLable + " reserveren. Is dit nog steeds mogelijk? \n\nMet vriendelijke groet" , isHTML: false)
// Present the view controller modally.
self.present(composeVC, animated: true, completion: nil)
}
func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {
switch result.rawValue {
case MFMailComposeResult.cancelled.rawValue :
print("Cancelled")
case MFMailComposeResult.failed.rawValue :
print("Failed")
case MFMailComposeResult.saved.rawValue :
print("Saved")
case MFMailComposeResult.sent.rawValue :
print("Sent")
default: break
}
self.dismiss(animated: true, completion: nil)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return imageStrings.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ImageCollectionViewCell", for: indexPath) as! ImageCollectionViewCell
cell.contentMode = .scaleAspectFill
return cell
}
func loadImages(){
let dbhelper = DBHelper()
//dbhelper.getPictures2(imageStrings: self.imageStrings, imageViews: self.images)
}
}
希望我可以最终解决这个问题！Kind regardsB。
我想你面临的问题是你在加载图片后没有更新你的收藏视图。
首先，你的 getPictures(...) 方法期望一个UIImageViews数组。但事实上，你不能将它们传递给该方法，因为它们是在你的collectionView中动态创建的。相反，你应该返回图像，一旦它们被加载。问题是图像是异步加载的。这意味着你需要使用一个完成处理程序。
func getPictures(imageStrings: [String], completionHandler: @escaping (UIImage) -> ()) {
let storage = Storage.storage();
for index in 0...imageStrings.count - 1 {
let gsReference = storage.reference(forURL: imageStrings[index])
gsReference.getData(maxSize: 15 * 1024 * 1024) { data, error in
if let error = error {
// Uh-oh, an error occurred!
print(error)
return
} else {
completionHandler(UIImage(data: data!))
print(UIImage(data: data!) as Any)
}
}
}
}
然后你需要修改你的 loadImages() 方法。
func loadImages() {
let dbhelper = DBHelper()
dbhelpergetPictures(imageStrings: [""]) { (loadedImage) in
DispatchQueue.main.async {
self.images.append(loadedImage)
self.collectionView.reloadData()
}
}
}
之后你需要修改你的collectionView(numberOfItemsInSection)方法，以使显示的单元格数量等于加载的图片数量。
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return images.count
}
最后，你需要在你的集合视图中实际显示UIImageViews中的图片。
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ImageCollectionViewCell", for: indexPath) as! ImageCollectionViewCell
cell.contentMode = .scaleAspectFill
cell.imageView.image = images[indexPath.row]
return cell
}
如果你有任何关于这方面的问题，就在评论中提出来吧。
(PS：一个善意的建议：看看swift的命名惯例(这里有一个很好的风格指南). 除了来自类的名称外，所有的名称都应该以小写字母开头，并且应该描述它们的用途.示例: var TitleLable: UILabel! 例如：-> var titleLable: UILabel!和: var titleLable = String() ->.这将使你的代码更容易理解！）。var title = String()这将使你的代码更容易理解！）。)