[英]loading imageviews of collectionview after the viewcontroller is loaded
所以我正在 swift 中构建一个应用程序,用户可以在其中上传带有图片的产品。 上传完美,但我遇到的问题是图片的下载。 用户获得所有产品的概览并点击它们,这会将他发送到该产品的详细概览。 在该概述中,有一个包含所有图像的集合视图(这是目标)。 我的问题是图片对于收藏视图加载太慢并且没有出现在屏幕上。 我想知道是否有一个选项可以在 function 中提供图像视图并将图像分配给它们,并且在屏幕加载后图片将一张一张地加载?
这是我现在要加载图像的 function:
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)
}
}
}
}
这是我的收藏视图处于活动状态的视图控制器
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)
}
}
希望我最终能解决这个问题。 亲切的问候 B.
我想您面临的问题是您在加载图像后没有更新您的收藏视图。
首先,您的getPictures(...)
方法需要一个 UIImageViews 数组。 但事实上,您不能将它们传递给方法,因为它们是在您的 collectionView 中动态创建的。 相反,您应该在加载图像后返回它们。 问题是图像是异步加载的。 这意味着您需要使用完成处理程序。
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,您需要修改您的 collectionView(numberOfItemsInSection) 方法,以使显示的单元格数等于加载的图像数:
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return images.count
}
最后,您需要在集合视图中的 UIImageViews 中实际显示图像:
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
}
如果您对此有任何疑问,请在评论中提出。
(PS:一个善意的建议:看看 swift 命名约定(这里是一个很好的样式指南)。所有名称,除了类,应该总是以小写字母开头,并且应该描述它们的目的。示例: var TitleLable: UILabel!
-> var titleLable: UILabel!
and: var titleLable = String()
-> var title = String()
这会让你的代码更容易理解!)
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