ios - 如何下载图像来填充我的 collectionviewcell JSON？

Question

//Parsing JSON Oké
    let parsedData : [String:AnyObject]
    do{
        parsedData = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as! [String:AnyObject]
        guard let results = parsedData["results"] as? [[String:AnyObject]] else {
            print("There is a problem related to results fetch"); return }
        for res in results {

            var dataMi : Data!
            //For the image data
            let urlOfthePic = URL(string: "https://image.tmdb.org/t/p/w92\(res["backdrop_path"]!)")
            let downLoadPicTask = URLSession.shared.dataTask(with: urlOfthePic!, completionHandler: { (data, res, err) in
                guard let data = data else {print("second"); return}
                dataMi = data
                self.mov.movImage = UIImage(data: dataMi)!
                print(dataMi)
            });downLoadPicTask.resume()
            print("2:", dataMi)
            //Error is occured because of the "nil" 
            //self.mov.movImage = UIImage(data:dataMi)!

            self.mov.movTitle = res["original_title"] as! String
            self.mov.desctiption = res["overview"] as! String
            self.movResult.append(self.mov)
            self.resultCount = results.count
        }
        DispatchQueue.main.async() {
            self.myCollectionView.reloadData()
        }
    }catch{
        print("Error is occured because of the Json Serialization")
    }
};task.resume()

Problem about the sequence of the downloading

此代码运行良好，但下载图像时存在问题，因为图像 url 取决于 json url。我想在下载其他数据(例如电影标题、电影描述等)时下载图像。

当代码运行时:

print(dataMi)

返回数据但是...

print("2:", dataMi) 

返回零。那么我该怎么做才能正确运行该部分呢？ 因为它也会导致错误，所以我无法在单元格中设置我的 ImageView

 //Error is occured because of the "nil" 
 //self.mov.movImage = UIImage(data:dataMi)!

Console Screen Shot

Answer 1

对于您的第一个问题，

let downLoadPicTask = URLSession.shared.dataTask(with: urlOfthePic!, completionHandler: { (data, res, err) in
    guard let data = data else {print("second"); return}
    dataMi = data
    self.mov.movImage = UIImage(data: dataMi)!
    print(dataMi)
});downLoadPicTask.resume()
print("2:", dataMi)

这段代码是异步运行的，所以print("2:", dataMi)将立即执行，但 print(dataMi)将在 dataTask 之后执行已完成。因此，如果您打印 dataMi立即，它将是 nil当然。之后dataTask完成，dataMi不是nil已包含数据。

对于您的第二个问题，请检查您的 urlOfthePic 是否是正确且可访问的。