我正在制作一个下载管理器，由于“可重用单元”的原因，我一直在努力更新单元......
我在滚动后更新单元格时遇到问题，但我找到了一个无法正常工作的解决方法，这种方式会导致应用程序在单元格变得不可见后崩溃，我不知道为什么我希望你们可以解释一下，如果您知道如何解决它，请告诉我。
我这样添加下载任务
func addDownloadTask(URL: NSURL) {
let sessionConfiguration = NSURLSessionConfiguration.defaultSessionConfiguration()
let mainQueue = NSOperationQueue.mainQueue()
let session = NSURLSession(configuration: sessionConfiguration, delegate: self, delegateQueue: mainQueue).downloadTaskWithURL(URL)
let newDownload = RCHDownloadAddictModelClass(fileURL: URL)
newDownload.downloadTask = session
downloadingArray.append(newDownload)
newDownload.downloadIndex = downloadingArray.indexOf(downloadingArray.last!)
self.tableView.reloadData()
session.resume()
}
当NSURLSessionDownloadTask开始下载时调用此方法
func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
for (index, downloadModel) in downloadingArray.enumerate() {
if downloadTask.isEqual(downloadModel.downloadTask) {
dispatch_async(dispatch_get_main_queue(), {
let indexPath = NSIndexPath(forRow: index, inSection: 0)
/* xCode stops here when the app crashes */ let cell = self.tableView.cellForRowAtIndexPath(indexPath) as! RCHDownloadAddictTableViewCell
let countOfBytesWritten: Double!
if totalBytesExpectedToWrite < 0 {
countOfBytesWritten = 0
} else {
countOfBytesWritten = Double(totalBytesWritten) / Double(totalBytesExpectedToWrite)
}
downloadModel.fileName = downloadTask.response?.suggestedFilename
downloadModel.downloadIndex = downloadingArray.indexOf(downloadModel)
downloadModel.downloadSize = Double(totalBytesExpectedToWrite)
downloadModel.downloadProgress = Float(countOfBytesWritten)
downloadModel.downloadTaskIdentifier = downloadTask.taskIdentifier
downloadModel.didFinishDownload = false
self.updateCell(cell, forRowAt: indexPath)
})
}
}
}
这就是单元格更新的方式:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("downloadCell", forIndexPath: indexPath) as! RCHDownloadAddictTableViewCell
updateCell(cell, forRowAt: indexPath)
return cell
}
func updateCell(cell: RCHDownloadAddictTableViewCell, forRowAt indexPath: NSIndexPath) {
let arrayInfo = downloadingArray[indexPath.row]
cell.cellProgressView.setProgress((arrayInfo.downloadProgress)!, animated: true)
cell.cellFileName.text = arrayInfo.fileName
cell.cellDownloadSpeed.text = String(format: "%.1fMB", (arrayInfo.downloadSize / 1000000))
cell.cellBlock = {
switch arrayInfo.downloadTask.state {
case .Running:
arrayInfo.downloadTask.suspend()
cell.cellButton.setImage(UIImage(named: "resume.png"), forState: UIControlState.Normal)
case .Suspended:
arrayInfo.downloadTask.resume()
cell.cellButton.setImage(UIImage(named: "pause.png"), forState: UIControlState.Normal)
default:
arrayInfo.downloadTask.suspend()
cell.cellButton.setImage(UIImage(named: "resume.png"), forState: UIControlState.Normal)
}
}
if (arrayInfo.didFinishDownload == true) {
cell.cellButton.hidden = true
cell.cellFinishIndicator.text = "Finished."
cell.cellProgressView.hidden = true
cell.cellFinishIndicator.hidden = false
} else {
cell.cellButton.hidden = false
cell.cellProgressView.hidden = false
cell.cellFinishIndicator.hidden = true
}
}
最佳答案
你可以在苹果文档中看到它:
public func cellForRowAtIndexPath(indexPath: NSIndexPath) -> UITableViewCell?
// returns nil if cell is not visible or index path is out of range
//cell will be nil when this row is not visible
let cell = self.tableView.cellForRowAtIndexPath(indexPath) as! RCHDownloadAddictTableViewCell
然后你调用self.updateCell(cell, forRowAt: indexPath)它会崩溃
关于ios - 为什么以这种方式更新 UITableView 单元格是错误的？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37411532/