UITableview、SDWebImage、单元格重用和UIImage问题
UITableview, SDWebImage, cell reuse and UIImage problems
在此处查看视频示例：
https://imgur.com/a/vSBPjlP
有一个表格视图，其中包含我从 Internet 异步下载的图像。我能够让它们正确填充，并且我自己的代码或 SDWebImage 都没有问题。当我将更多数据分页到表格视图的末尾时，我的问题就开始了。分页确实有效。与所有文本数据一样，它在整个表视图中都能正常工作并保持正确。我遇到的问题是我的 ImageView。正如您在视频中看到的那样，分页后，UIImageViews 图像将上一次调用中的所有单元格更改为表格视图末尾最新单元格中的图像。是什么导致了这种行为？为什么它只发生在我的图像视图中？我该如何解决？
我试过在 prepareForReuse 中将 imageview 图像设置为 nil（反对 Apple 的建议），它产生了相同的结果。
相关代码
API 通话
func downloadGamesByPlatformIDJSON(platformID: Int?, fields: String?, include: String?, pageURL: String?, completed: @escaping () -> () ) {
var urlString : String?
if pageURL == nil {
urlString = "https://api.thegamesdb.net/v1/Games/ByPlatformID?apikey=\(apiKey)&id=\(platformID!)"
if fields != nil {
urlString = urlString! + "&fields=" + fields!
}
if include != nil {
urlString = urlString! + "&include=" + include!
}
} else {
urlString = pageURL!
}
let url = URL(string: "\(urlString!)")!
var requestHeader = URLRequest.init(url: url)
requestHeader.httpMethod = "GET"
requestHeader.setValue("application/json", forHTTPHeaderField: "Accept")
URLSession.shared.dataTask(with: requestHeader) { (data, response, error) in
if error != nil {
print("error = \(error)")
completed()
}
if error == nil {
do {
print("error = nil")
let json = String(data: data!, encoding: .utf8)
print(json)
if let jsonDecodedPlatforms = try JSONDecoder().decode(ByPlatformIDData?.self, from: data!) {
let decodedJSON = jsonDecodedPlatforms.data?.games
self.boxart = jsonDecodedPlatforms.include.boxart
self.baseURL = jsonDecodedPlatforms.include.boxart.baseURL
self.page = jsonDecodedPlatforms.pages
self.games.append(contentsOf: decodedJSON!
}
DispatchQueue.main.async {
completed()
}
} catch {
print(error)
}
}
}.resume()
}
分页
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offsetY = scrollView.contentOffset.y
let contentHeight = scrollView.contentSize.height
if offsetY > contentHeight - scrollView.frame.size.height {
if !fetchingMore {
beginBatchFetch()
}
}
}
func beginBatchFetch() {
fetchingMore = true
print("fetching data")
network.downloadGamesByPlatformIDJSON(platformID: nil, fields: nil, include: nil, pageURL: network.page?.next) {
print("pagination successful")
self.fetchingMore = false
self.tableView.reloadData()
}
}
cellForRowAt
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! ViewControllerTableViewCell
cell.configureCells()
//creating game object
let game1 : GDBGamesPlatform?
game1 = network.games[indexPath.row]
//retrieving the filename information based on the game id
if network.boxart?.data["\(game1!.id!)"]?[0].side == .front {
print(network.boxart?.data["\(game1!.id!)"]?[0].filename)
frontImageName = network.boxart?.data["\(game1!.id!)"]?[0].filename as! String
} else if network.boxart?.data["\(game1!.id!)"]?[0].side == .back {
backImageName = network.boxart?.data["\(game1!.id!)"]?[0].filename as! String
}
if network.boxart?.data["\(game1!.id!)"]?.count == 2 {
if network.boxart?.data["\(game1!.id!)"]?[1].side == .front {
frontImageName = network.boxart?.data["\(game1!.id!)"]?[1].filename as! String
} else if network.boxart?.data["\(game1!.id!)"]?[1].side == .back {
backImageName = network.boxart?.data["\(game1!.id!)"]?[1].filename as! String
}
}
//creating image url string
var imageUrlString = network.baseURL!.small + frontImageName
print(imageUrlString)
let imageURL = URL(string: imageUrlString)
//if data exists for the front cover image download it, otherwise show default image
if frontImageName != nil {
cell.loadCoverImageWith(urlString: imageUrlString)
} else {
cell.tableViewCoverImage.image = UIImage(named: "noArtNES")
}
return cell
}
import UIKit
import SDWebImage
class ViewControllerTableViewCell: UITableViewCell {
@IBOutlet weak var tableViewCoverImage: UIImageView!
@IBOutlet weak var tableViewGameName: UILabel!
@IBOutlet weak var tableViewGenreLabel: UILabel!
@IBOutlet weak var tableViewAgeRatingLabel: UILabel!
@IBOutlet weak var tableViewCompanyLabel: UILabel!
@IBOutlet weak var tableViewReleaseDateLabel: UILabel!
@IBOutlet weak var backgroundCell: UIView!
@IBOutlet weak var tableViewCoverRearImage: UIImageView!
@IBOutlet weak var gameCartImage: UIImageView!
override func prepareForReuse() {
super.prepareForReuse()
tableViewCoverImage.sd_cancelCurrentImageLoad()
tableViewCoverImage.image = nil
}
override func awakeFromNib() {
super.awakeFromNib()
// Initialization code
}
override func setSelected(_ selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
// Configure the view for the selected state
}
func loadCoverImageWith(urlString: String) {
let imageURL = URL(string: urlString)
self.tableViewCoverImage.sd_setImage(with: imageURL, placeholderImage: UIImage(named: "noArtNES"), options: SDWebImageOptions.highPriority) { (image, error, cacheType, url) in
if let error = error {
print("Error downloading the image. Error Description: \(error.localizedDescription)")
} else {
let edgeColor = self.tableViewCoverImage.image?.edgeColor()
self.tableViewCoverImage.layer.shadowColor = edgeColor!.cgColor
}
}
}
func configureCells() {
tableViewCoverImage.layer.shadowOffset = CGSize(width: -5, height: 8)
tableViewCoverImage.layer.shadowRadius = 8
tableViewCoverImage.layer.shadowOpacity = 0.8
tableViewCoverImage.layer.cornerRadius = 10
tableViewCoverImage.clipsToBounds = false
tableViewCoverImage.layer.masksToBounds = false
backgroundCell.layer.shadowOffset = CGSize(width: 0, height: 5)
backgroundCell.layer.shadowRadius = 5
backgroundCell.layer.shadowOpacity = 0.1
backgroundCell.layer.cornerRadius = 10
if self.traitCollection.userInterfaceStyle == .light {
backgroundCell.layer.shadowColor = UIColor.black.cgColor
backgroundCell.layer.backgroundColor = UIColor.white.cgColor
} else {
backgroundCell.layer.shadowColor = UIColor.white.cgColor
backgroundCell.layer.backgroundColor = UIColor.black.cgColor
}
}
}
这是一个可重用性问题。尝试更改 cellForRowAtIndex 中的这一行。
tableview.register(UINib(nibName: "TableViewCell", bundle: nil), forCellReuseIdentifier: "cell\(indexPath.row)")
let cell = tableView.dequeueReusableCell(withIdentifier: "cell\(indexPath.row)", for: indexPath) as! ViewControllerTableViewCell
第二次及以后对 API 的调用将游戏的结果附加到数组中，但会覆盖 boxart 的结果。后面几页的结果将不包括前面几页的 boxart。
因此，您的 boxart 数据不再包含早期页面的艺术。您从最后一项获取图像的原因是变量 frontImageName 和 backImageName 的范围错误，它们应该是 tableView(:cellForRowAt:)
的局部变量
您需要通过调用 Dictionary.merge(_:uniquingKeysWith:)，将 API 调用的结果与现有的 boxart 字典合并。详情见https://developer.apple.com/documentation/swift/dictionary/3127171-merge
在此处查看视频示例： https://imgur.com/a/vSBPjlP
有一个表格视图，其中包含我从 Internet 异步下载的图像。我能够让它们正确填充，并且我自己的代码或 SDWebImage 都没有问题。当我将更多数据分页到表格视图的末尾时，我的问题就开始了。分页确实有效。与所有文本数据一样，它在整个表视图中都能正常工作并保持正确。我遇到的问题是我的 ImageView。正如您在视频中看到的那样，分页后，UIImageViews 图像将上一次调用中的所有单元格更改为表格视图末尾最新单元格中的图像。是什么导致了这种行为？为什么它只发生在我的图像视图中？我该如何解决？
我试过在 prepareForReuse 中将 imageview 图像设置为 nil（反对 Apple 的建议），它产生了相同的结果。
相关代码
API 通话
func downloadGamesByPlatformIDJSON(platformID: Int?, fields: String?, include: String?, pageURL: String?, completed: @escaping () -> () ) {
var urlString : String?
if pageURL == nil {
urlString = "https://api.thegamesdb.net/v1/Games/ByPlatformID?apikey=\(apiKey)&id=\(platformID!)"
if fields != nil {
urlString = urlString! + "&fields=" + fields!
}
if include != nil {
urlString = urlString! + "&include=" + include!
}
} else {
urlString = pageURL!
}
let url = URL(string: "\(urlString!)")!
var requestHeader = URLRequest.init(url: url)
requestHeader.httpMethod = "GET"
requestHeader.setValue("application/json", forHTTPHeaderField: "Accept")
URLSession.shared.dataTask(with: requestHeader) { (data, response, error) in
if error != nil {
print("error = \(error)")
completed()
}
if error == nil {
do {
print("error = nil")
let json = String(data: data!, encoding: .utf8)
print(json)
if let jsonDecodedPlatforms = try JSONDecoder().decode(ByPlatformIDData?.self, from: data!) {
let decodedJSON = jsonDecodedPlatforms.data?.games
self.boxart = jsonDecodedPlatforms.include.boxart
self.baseURL = jsonDecodedPlatforms.include.boxart.baseURL
self.page = jsonDecodedPlatforms.pages
self.games.append(contentsOf: decodedJSON!
}
DispatchQueue.main.async {
completed()
}
} catch {
print(error)
}
}
}.resume()
}
分页
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offsetY = scrollView.contentOffset.y
let contentHeight = scrollView.contentSize.height
if offsetY > contentHeight - scrollView.frame.size.height {
if !fetchingMore {
beginBatchFetch()
}
}
}
func beginBatchFetch() {
fetchingMore = true
print("fetching data")
network.downloadGamesByPlatformIDJSON(platformID: nil, fields: nil, include: nil, pageURL: network.page?.next) {
print("pagination successful")
self.fetchingMore = false
self.tableView.reloadData()
}
}
cellForRowAt
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! ViewControllerTableViewCell
cell.configureCells()
//creating game object
let game1 : GDBGamesPlatform?
game1 = network.games[indexPath.row]
//retrieving the filename information based on the game id
if network.boxart?.data["\(game1!.id!)"]?[0].side == .front {
print(network.boxart?.data["\(game1!.id!)"]?[0].filename)
frontImageName = network.boxart?.data["\(game1!.id!)"]?[0].filename as! String
} else if network.boxart?.data["\(game1!.id!)"]?[0].side == .back {
backImageName = network.boxart?.data["\(game1!.id!)"]?[0].filename as! String
}
if network.boxart?.data["\(game1!.id!)"]?.count == 2 {
if network.boxart?.data["\(game1!.id!)"]?[1].side == .front {
frontImageName = network.boxart?.data["\(game1!.id!)"]?[1].filename as! String
} else if network.boxart?.data["\(game1!.id!)"]?[1].side == .back {
backImageName = network.boxart?.data["\(game1!.id!)"]?[1].filename as! String
}
}
//creating image url string
var imageUrlString = network.baseURL!.small + frontImageName
print(imageUrlString)
let imageURL = URL(string: imageUrlString)
//if data exists for the front cover image download it, otherwise show default image
if frontImageName != nil {
cell.loadCoverImageWith(urlString: imageUrlString)
} else {
cell.tableViewCoverImage.image = UIImage(named: "noArtNES")
}
return cell
}
import UIKit
import SDWebImage
class ViewControllerTableViewCell: UITableViewCell {
@IBOutlet weak var tableViewCoverImage: UIImageView!
@IBOutlet weak var tableViewGameName: UILabel!
@IBOutlet weak var tableViewGenreLabel: UILabel!
@IBOutlet weak var tableViewAgeRatingLabel: UILabel!
@IBOutlet weak var tableViewCompanyLabel: UILabel!
@IBOutlet weak var tableViewReleaseDateLabel: UILabel!
@IBOutlet weak var backgroundCell: UIView!
@IBOutlet weak var tableViewCoverRearImage: UIImageView!
@IBOutlet weak var gameCartImage: UIImageView!
override func prepareForReuse() {
super.prepareForReuse()
tableViewCoverImage.sd_cancelCurrentImageLoad()
tableViewCoverImage.image = nil
}
override func awakeFromNib() {
super.awakeFromNib()
// Initialization code
}
override func setSelected(_ selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
// Configure the view for the selected state
}
func loadCoverImageWith(urlString: String) {
let imageURL = URL(string: urlString)
self.tableViewCoverImage.sd_setImage(with: imageURL, placeholderImage: UIImage(named: "noArtNES"), options: SDWebImageOptions.highPriority) { (image, error, cacheType, url) in
if let error = error {
print("Error downloading the image. Error Description: \(error.localizedDescription)")
} else {
let edgeColor = self.tableViewCoverImage.image?.edgeColor()
self.tableViewCoverImage.layer.shadowColor = edgeColor!.cgColor
}
}
}
func configureCells() {
tableViewCoverImage.layer.shadowOffset = CGSize(width: -5, height: 8)
tableViewCoverImage.layer.shadowRadius = 8
tableViewCoverImage.layer.shadowOpacity = 0.8
tableViewCoverImage.layer.cornerRadius = 10
tableViewCoverImage.clipsToBounds = false
tableViewCoverImage.layer.masksToBounds = false
backgroundCell.layer.shadowOffset = CGSize(width: 0, height: 5)
backgroundCell.layer.shadowRadius = 5
backgroundCell.layer.shadowOpacity = 0.1
backgroundCell.layer.cornerRadius = 10
if self.traitCollection.userInterfaceStyle == .light {
backgroundCell.layer.shadowColor = UIColor.black.cgColor
backgroundCell.layer.backgroundColor = UIColor.white.cgColor
} else {
backgroundCell.layer.shadowColor = UIColor.white.cgColor
backgroundCell.layer.backgroundColor = UIColor.black.cgColor
}
}
}
这是一个可重用性问题。尝试更改 cellForRowAtIndex 中的这一行。
tableview.register(UINib(nibName: "TableViewCell", bundle: nil), forCellReuseIdentifier: "cell\(indexPath.row)")
let cell = tableView.dequeueReusableCell(withIdentifier: "cell\(indexPath.row)", for: indexPath) as! ViewControllerTableViewCell
第二次及以后对 API 的调用将游戏的结果附加到数组中，但会覆盖 boxart 的结果。后面几页的结果将不包括前面几页的 boxart。
因此，您的 boxart 数据不再包含早期页面的艺术。您从最后一项获取图像的原因是变量 frontImageName 和 backImageName 的范围错误，它们应该是 tableView(:cellForRowAt:)
的局部变量您需要通过调用 Dictionary.merge(_:uniquingKeysWith:)，将 API 调用的结果与现有的 boxart 字典合并。详情见https://developer.apple.com/documentation/swift/dictionary/3127171-merge