我正在尝试设置一个只显示特定数量单元格的表格视图 . 一旦显示该单元格,用户就可以继续滚动以显示更多单元格 . 截至目前,我正在检索要在viewDidLoad中显示的所有JSON数据并将它们存储在数组中 . 仅举例来说,我试图仅首先显示2个单元格,一个用户滚动到屏幕底部,下一个单元格将出现 . 到目前为止这是我的代码:
class DrinkViewController: UIViewController {
@IBOutlet weak var drinkTableView: UITableView!
private let networkManager = NetworkManager.sharedManager
fileprivate var totalDrinksArray: [CocktailModel] = []
fileprivate var drinkImage: UIImage?
fileprivate let DRINK_CELL_REUSE_IDENTIFIER = "drinkCell"
fileprivate let DRINK_SEGUE = "detailDrinkSegue"
var drinksPerPage = 2
var loadingData = false
override func viewDidLoad() {
super.viewDidLoad()
drinkTableView.delegate = self
drinkTableView.dataSource = self
networkManager.getJSONData(function: urlFunction.search, catagory: urlCatagory.cocktail, listCatagory: nil, drinkType: "margarita", isList: false, completion: { data in
self.parseJSONData(data)
})
}
}
extension DrinkViewController {
//MARK: JSON parser
fileprivate func parseJSONData(_ jsonData: Data?){
if let data = jsonData {
do {
let jsonDictionary = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.mutableContainers) as? [String : AnyObject]//Parses data into a dictionary
// print(jsonDictionary!)
if let drinkDictionary = jsonDictionary!["drinks"] as? [[String: Any]] {
for drink in drinkDictionary {
let drinkName = drink["strDrink"] as? String ?? ""
let catagory = drink["strCategory"] as? String
let drinkTypeIBA = drink["strIBA"] as? String
let alcoholicType = drink["strAlcoholic"] as? String
let glassType = drink["strGlass"] as? String
let drinkInstructions = drink["strInstructions"] as? String
let drinkThumbnailUrl = drink["strDrinkThumb"] as? String
let cocktailDrink = CocktailModel(drinkName: drinkName, catagory: catagory, drinkTypeIBA: drinkTypeIBA, alcoholicType: alcoholicType, glassType: glassType, drinkInstructions: drinkInstructions, drinkThumbnailUrl: drinkThumbnailUrl)
self.totalDrinksArray.append(cocktailDrink)
}
}
} catch let error as NSError {
print("Error: \(error.localizedDescription)")
}
}
DispatchQueue.main.async {
self.drinkTableView.reloadData()
}
}
//MARK: Image Downloader
func updateImage (imageUrl: String, onSucceed: @escaping () -> Void, onFailure: @escaping (_ error:NSError)-> Void){
//named imageData because this is the data to be used to get image, can be named anything
networkManager.downloadImage(imageUrl: imageUrl, onSucceed: { (imageData) in
if let image = UIImage(data: imageData) {
self.drinkImage = image
}
onSucceed()//must call completion handler
}) { (error) in
onFailure(error)
}
}
}
//MARK: Tableview Delegates
extension DrinkViewController: UITableViewDelegate, UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
//return numberOfRows
return drinksPerPage
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = drinkTableView.dequeueReusableCell(withIdentifier: DRINK_CELL_REUSE_IDENTIFIER) as! DrinkCell
//get image from separate url
if let image = totalDrinksArray[indexPath.row].drinkThumbnailUrl{//index out of range error here
updateImage(imageUrl: image, onSucceed: {
if let currentImage = self.drinkImage{
DispatchQueue.main.async {
cell.drinkImage.image = currentImage
}
}
}, onFailure: { (error) in
print(error)
})
}
cell.drinkLabel.text = totalDrinksArray[indexPath.row].drinkName
return cell
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if let image = totalDrinksArray[indexPath.row].drinkThumbnailUrl{
updateImage(imageUrl: image, onSucceed: {
}, onFailure: { (error) in
print(error)
})
}
performSegue(withIdentifier: DRINK_SEGUE, sender: indexPath.row)
}
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
let lastElement = drinksPerPage
if indexPath.row == lastElement {
self.drinkTableView.reloadData()
}
}
}
我看到这篇文章:tableview-loading-more-cell-when-scroll-to-bottom并实现了willDisplay函数但是收到"index out of range"错误 .
1 回答
如果你一次性获得所有结果,你能告诉我为什么你这样做,那么你不必限制你的显示,因为它是由tableview自动管理的 . 在tableview中,所有单元格都被重用,因此不存在内存问题 . UITableViewCell将在显示时创建 .
因此无需限制细胞计数 .
I dont now what you are doing in your code but:
您的应用可能会崩溃,因为您可能只从服务器获得一个项目 .
If you seriously want to load more then you can try this code:
声明 numberOfItem 应该等于 drinksPerPage