使timer无效并创建新的timer实例

Question

我有一个从闭包中运行的计时器来帮助执行一些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和新的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的闭包会重新运行，但是新的用户信息不会传递给定时器，它只是继续使用原始userInfo运行。如果我使计时器失效，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，我希望能够停止计时器。

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。必须有一种方法可以每次创建一个唯一的实例。

--编辑

以下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，使计时器无效需要一段时间，在这段时间内，计时器已经重新启动，函数使用旧的索引路径，直到progress =1

--编辑

唯一发生无效的地方是当进程>= 1时

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

然后，由于如果单元满足特定条件，则从cellForItemAt触发计时器，因此在调用collectionView.reloadData()时，应该重新验证计时器并发送更新后的userInfo。

这就是cellForItemAt中的代码块：

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，但是我有可能还没有完全正确设置的嵌套集合视图，所以在这种情况下可以解决这个问题。

和downloadTimer：

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法如下所示：

//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()

此外，要重新安排计时器，只需再次调用Timer.scheduledTimer