[英]Swift UItableview with AlamofireImage crash when scrolling fast
我正在使用AlamofireImage以異步方式加載圖像。 它運行得很好,除非我快速滾動時應用崩潰。
我認為這是因為在很短的時間內發送了超過10個請求時,應用崩潰了(當我快速滾動時)。 我還看到內存使用量突然激增。
當我緩慢滾動並可能在短時間內發送4個請求時,它不會崩潰。
有沒有人暗示如何預防這種情況? 如何取消滾動用戶的不可見單元格的請求?
這是代碼:
// Dequeue your cell and other code goes here.
// with as! the cell is set to the custom cell class: DemoCell
// afterwards all data can be loaded from the JSON response into the cells
override func tableView(tableView: UITableView, cellForRowAtIndexPath
indexPath: NSIndexPath) -> UITableViewCell {
let cell =
tableView.dequeueReusableCellWithIdentifier("FoldingCell",
forIndexPath: indexPath) as! DemoCell
cell.delegate = self
//tag the cell with the indexpath row number to make sure the loaded asynch image corresponds to the right cell
cell.tag = indexPath.row
//clear cell of eventually reused images
cell.schoolCoverImage.image = UIImage()
cell.schoolBiggerImage.image = UIImage()
//TODO: set all custom cell properties here (retrieve JSON and set in cell), use indexPath.row as arraypointer
let resultList = self.items["result"] as! [[String: AnyObject]]
let itemForThisRow = resultList[indexPath.row]
cell.schoolNameClosedCell.text = itemForThisRow["name"] as! String
cell.schoolNameOpenedCell.text = itemForThisRow["name"] as! String
self.schoolIdHelperField = itemForThisRow["name"] as! String
cell.schoolIntroText.text = itemForThisRow["name"] as! String
// set the button's tag like below.
cell.innerCellButton.tag = indexPath.row
//call method when button inside cell is tapped
cell.innerCellButton.addTarget(self, action: #selector(MainTableViewController.cellButtonTapped(_:)), forControlEvents: .TouchUpInside)
cell.schoolIntroText.text = "We from xx University..."
//handle the image from a separate API call
let schoolIdNumber = itemForThisRow["sco_id"] as! NSInteger
let schoolIdString = String(schoolIdNumber)
//TOCHeck: maybe Id is not correct and should be replaced by indexCount
let imageNameString = itemForThisRow["image"] as! String
//only load the image of the cell which is visible in the screen
// print("current cells visible?")
// print(tableView.visibleCells)
// print("currentCell")
// print(cell.tag)
// if(tableView.visibleCells.contains(cell)) {
let urlRequest = NSURLRequest(URL: NSURL(string: "https://ol-web- test.herokuapp.com/olweb/api/v1/schools/"+schoolIdString+"/image/"+imageNameString)!)
print(urlRequest)
//does cell number/tag match current indexpath row?
if(cell.tag == indexPath.row) {
//use cache in case image has been saved to cache already, otherwise get image from networking
if(self.photoCache.imageForRequest(urlRequest) != nil) {
cell.schoolCoverImage.image = photoCache.imageForRequest(urlRequest)
cell.schoolBiggerImage.image = photoCache.imageForRequest(urlRequest)
print("image from cache loaded")
}
else
{
self.imageDownloader.downloadImage(URLRequest: urlRequest) { response in
print(response.request)
print(response.response)
debugPrint(response.result)
if let image = response.result.value {
print("here comes the printed image:: ")
print(image)
print(schoolIdString)
//set image to the cell
cell.schoolCoverImage.image = image
cell.schoolBiggerImage.image = image
self.photoCache.addImage(image, forRequest: urlRequest)
print("image from network loaded and added to cache")
print(self.photoCache.memoryCapacity.description)
print(self.photoCache.memoryUsage.description)
}
}
}
}
return cell
}
編輯:日志錯誤是一個NullPointer
30/image/Beet_Language_Bournemouth_1.jpeg }
fatal error: unexpectedly found nil while unwrapping an Optional va lue
代碼行:
let urlRequest = NSURLRequest(URL: NSURL(string: "https://ol-web- test.herokuapp.com/olweb/api/v1/schools/"+schoolIdString+"/image/"+imageNameString)!)
我在這里從上一個查詢加載params schoolIdString和imageNameString。
謝謝答案。 它是來自數據庫的損壞數據,導致URL損壞
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