ios - 从另一个 View Controller 返回时 UICollectionView 重复单元格

Question

我一直在开发天气应用程序并使用 UICollectionView 来显示天气数据。

每当我打开另一个 View Controller 并返回到 UICollectionView 的 View Controller 时，我都会得到重复的单元格。

这是代码。我使用 Alamofire 发出 api 请求，将 json 结果附加到本地字符串，然后将其分配给单元格的文本标签。

    class VaanizhaiViewController: UICollectionViewController {


    // MARK: - flow layout

    let columns : CGFloat = 2.0
    let inset : CGFloat = 3.0
    let spacing : CGFloat = 3.0
    let lineSpacing : CGFloat = 3.0
    var isRandom : Bool = false

    // MARK: - Variables
    var apiKey: String = "55742b737e883a939913f2c90ee11ec0"
    var country : String = ""
    var zipCode : String = ""
    var json : JSON = JSON.null
    var cityNames: [String] = []
    var temperature: [Int] = []
    var weather: [String] = []

    // MARK: - Actions


    // MARK: - view did load
    override func viewDidLoad() {
        super.viewDidLoad()
        let layout = BouncyLayout()
        self.collectionView?.setCollectionViewLayout(layout, animated: true)
        self.collectionView?.reloadData()

    }

    override func viewDidAppear(_ animated: Bool) {
        for i in 0...zip.count-1{
            parseURL(zipCode: "\(zip[i])", country: "us")
        }

    }


    // MARK: - Functions

    func parseURL(zipCode: String, country: String){

        let url = "http://api.openweathermap.org/data/2.5/weather?zip=\(zipCode),\(country)&APPID=\(apiKey)&units=metric"
        requestWeatherData(link: url)
    }

    func requestWeatherData(link: String){
        Alamofire.request(link).responseJSON{ response in
            if let value = response.result.value{
                self.json = JSON(value)
                self.cityNames.append(self.json["name"].string!)
                let cTemp = ((self.json["main"]["temp"].double)!)
                self.temperature.append(Int(cTemp))
                let cWeather = self.json["weather"][0]["main"].string!
                self.weather.append(cWeather)
                self.collectionView?.reloadData()

            }
        }

    }




    // MARK: UICollectionViewDataSource

    override func numberOfSections(in collectionView: UICollectionView) -> Int {

        return 1
    }


    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

        return self.cityNames.count

    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "weatherCell", for: indexPath) as! WeatherViewCell

        if !self.cityNames.isEmpty {


        cell.cityLabel.text = self.cityNames[indexPath.row]
        cell.tempLabel.text = String (self.temperature[indexPath.row])
        cell.weatherLabel.text = self.weather[indexPath.row]
            cell.backgroundColor = UIColor.brown
    }

        return cell


   }
// MARK: - UICollectionViewDelegateFlowLayout

extension VaanizhaiViewController: UICollectionViewDelegateFlowLayout{
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let width = Int ((CGFloat(collectionView.frame.width) / columns) - (inset + spacing))
        return CGSize(width: width, height: width)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: CGFloat(inset), left: CGFloat(inset), bottom: CGFloat(inset), right: CGFloat(inset))
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return spacing
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return lineSpacing
    }
}

Answer 1

每次访问 View Controller 时都会调用 viewDidAppear，而 viewDidLoad 仅在创建时被调用一次。

因此，您应该将对 self.collectionView?.reloadData() 的调用切换到 viewDidAppear，将对 parseURL 的调用切换到 viewDidLoad

如果您需要更新天气数据(例如，刷新时)，那么您需要重构 requestWeatherData 以停止附加到数组，并进行替换。