使计时器无效并创建新实例

Question

我有一个计时器，我在闭包中运行它来帮助执行一些 ui 更新（进度条）。它适用于第一个项目，但我希望它适用于多个项目。因此，每次运行闭包时，都会运行一个新的计时器实例并运行新的 userInfo。

    // dispatch and add run loop to get it to fire
    DispatchQueue.main.async(execute: {
        timer = Timer.init(timeInterval: 0.25, target: self, selector: #selector(self.downloadTimer(_:)), userInfo: [innerCell, collectionView, indexPath], repeats: true)
        RunLoop.main.add(timer, forMode: RunLoopMode.defaultRunLoopMode)
    })

当下面的这个函数完成后，我希望重新创建计时器并将新的 userInfo 传递给选择器..

func downloadTimer(_ timer: Timer) {

    // need to pass arguments to timer as array inside userInfo
    // then create dictionary and extract

    let dict = timer.userInfo as! NSArray
    let cell = dict[0] as! InnerCollectionCell
    let collectionView = dict[1] as! UICollectionView
    let indexPath = dict[2] as! IndexPath


    // the index path isnt getting reset

    // without casting the progress bar in each cell was displaying when coming back to DownloadCollectionController
    if let downloadingCell = collectionView.cellForItem(at: indexPath) as? InnerCollectionCell {

        DispatchQueue.main.async(execute: {

            downloadingCell.progressBar.isHidden = false
            downloadingCell.contentView.bringSubview(toFront: cell.progressBar)
            downloadingCell.progressBar.setProgress(downloadProgress, animated: true)
            downloadingCell.setNeedsDisplay()


            if downloadProgress >= 1.0 {
                print("TIMER STOPPED")
                downloadingCell.progressBar.isHidden = true
                //downloadQueue.operations[0].cancel()
                timer.invalidate()
                collectionView.reloadItems(at: [indexPath])

            }
        })
    }

}

包含 timer = Timer 的闭包重新运行，但新的用户信息没有传递给计时器，它只是继续使用原始的 userInfo 运行。如果我使计时器无效，它就不能再被触发了？

我尝试在初始触发时在本地创建它：

var timer = Timer()
timer = Timer.init(timeInterval: 0.25, target: self, selector: #selector(self.downloadTimer(_:)), userInfo: [innerCell, collectionView, indexPath], repeats: true)

但它不会重新创建计时器，如果用户离开视图控制器，我希望能够停止它。

有没有更好的方法来实现这一点？我知道你不应该让计时器退役。每次都必须有一种方法来创建它的唯一实例。

---- 编辑----

这是索引路径打印的内容：

[0, 5]
[0, 5]
[0, 5]

[0, 5]
[0, 2]
[0, 5]
[0, 2]

[0, 1]
[0, 1]
[0, 1]
[0, 1]

因此它需要一段时间才能使计时器无效，并且在那个时候计时器已被重新触发，并且该函数使用旧的索引路径，直到进度 = 1

---- 编辑----

唯一发生失效的地方是进度 >= 1

            if downloadProgress >= 1.0 {
                timer.invalidate()
                downloadingCell.progressBar.isHidden = true
                downloadingCell.progressBar.progress = 0
                collectionView.reloadData()
            }

然后因为如果单元格满足某些条件，则从 cellForItemAt 触发计时器，当调用 collectionView.reloadData() 时，应重新验证计时器并发送更新的 userInfo。

这是 cellForItemAt 中的块：

for operation in downloadQueue.operations {
        if operation.name == self.multiPartArray[collectionView.tag][indexPath.item].name  {
            // edits for all queued operations
            innerCell.spinner.isHidden = false
            innerCell.spinner.startAnimating()
            innerCell.contentView.bringSubview(toFront: innerCell.spinner)
            innerCell.spinner.activityIndicatorViewStyle = .gray
            innerCell.spinner.color = UIColor.darkGray

        // hide the progress on all in queue it will be pushed to front when needed
        innerCell.progressBar.isHidden = true

        if operation.name == downloadQueue.operations[0].name {
            // edits for the active downlaod in queue

            // hide the spinner for currently downloading cell
            // innerCell.spinner.isHidden = true
            innerCell.spinner.isHidden = false
            innerCell.spinner.startAnimating()
            innerCell.contentView.bringSubview(toFront: innerCell.spinner)
            innerCell.spinner.activityIndicatorViewStyle = .gray
            innerCell.spinner.color = UIColor.blue

                DispatchQueue.main.async(execute: {
                    let timer = Timer.init(timeInterval: 0.5, target: self, selector: #selector(self.downloadTimer(_:)), userInfo: [innerCell, collectionView, indexPath, collectionView.tag], repeats: true)
                    RunLoop.main.add(timer, forMode: RunLoopMode.defaultRunLoopMode)
                })

            break
        } else {
            // edits spinner that isnt currently downloading
            innerCell.progressBar.isHidden = true
            innerCell.spinner.color = UIColor.darkGray
        }
    } else {
        // edits the spinner that isnt in queue
        innerCell.progressBar.isHidden = true
        innerCell.spinner.color = UIColor.darkGray
    }
}

我意识到这不是最优雅的解决方案，但我有嵌套的集合视图，可能没有完全正确设置，所以在这种情况下不适合解决。

还有下载定时器：

func downloadTimer(_ timer: Timer) {

    // need to pass arguments to timer as array inside userInfo
    // then create dictionary and extract
    let dict = timer.userInfo as! NSArray
    let cell = dict[0] as! InnerCollectionCell
    let collectionView = dict[1] as! UICollectionView
    let indexPath = dict[2] as! IndexPath
    let tag = dict[3] as! Int

    print(indexPath)

    // without casting the progress bar in each cell was displaying when coming back to DownloadCollectionController
    if let downloadingCell = collectionView.cellForItem(at: indexPath) as? InnerCollectionCell {

       // self.outerCollectionView.reloadItems(at: [IndexPath(item: tag, section: 0)])

        DispatchQueue.main.async(execute: {

            downloadingCell.spinner.isHidden = true
            downloadingCell.progressBar.isHidden = false
            downloadingCell.contentView.bringSubview(toFront: cell.progressBar)
            downloadingCell.progressBar.setProgress(downloadProgress, animated: true)
            downloadingCell.setNeedsDisplay()

            if downloadProgress >= 1.0 {
                timer.invalidate()
                downloadingCell.progressBar.isHidden = true
                downloadingCell.progressBar.progress = 0
                collectionView.reloadData()
            }
        })
    }
}

Answer 1

安排和使用时间的最佳方式如下：

//schedules timer at an 4 seconds interval + pass desired userInfo 
var myTimer = Timer.scheduledTimer(timeInterval: 4.0
        , target: self, selector: #selector(timerSelector), userInfo: nil, repeats: true)

//timer selector peform your actions there and  
func timerSelector(dt:Timer){  
}

//invalidate timer when needed like this
myTimer?.invalidate()

同样要重新安排计时器，只需再次调用Timer.scheduledTimer