计时器到期时快速删除表视图单元格

Question

I have tried hard to find a solution but I'm stuck. have a custom table view with timer in each cell. when the timer expires the cell should get deleted even if the cell is Offscreen it should get deleted and should not be displayed.

 func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = self.tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as! iDealCell
    //        cell.SponsorLogo.image = UIImage(named: "back.png")!
    cell.SponsorName.text = iDeals[indexPath.row].SponsorName;
    cell.Distance.text = iDeals[indexPath.row].Distance;
    cell.Type.text = iDeals[indexPath.row].Type;
    cell.iDealTimer.font = UIFont(name: "DBLCDTempBlack", size: 18.0)

    onHourFromNow = NSDate(timeInterval: 10, sinceDate: timeNow)
    let TimeDiffInSec = NSCalendar.currentCalendar().components(.Second, fromDate: timeNow, toDate: onHourFromNow, options: []).second
    cell.TimeDiffInSec = TimeDiffInSec
    cell.kickOffCountdown()
    cell.backgroundColor = UIColor.clearColor()
    cell.delegate = self
    return cell
}

in cell class, three functions to initialise and run the timer

func kickOffCountdown(){
    self.setCountDown()
    Timer.invalidate()
    Timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(iDealCell.setCountDown), userInfo: nil, repeats: true)                     
}

func secondsToHoursMinutesSeconds (seconds : Int) -> (String, String, String) {
    let hours = seconds / 3600
    let minutes = (seconds % 3600) / 60
    let seconds = (seconds % 3600) % 60

    let hoursString = hours < 10 ? "0\(hours)" : "\(hours)"
    let minutesString = minutes < 10 ? "0\(minutes)" : "\(minutes)"
    let secondsString = seconds < 10 ? "0\(seconds)" : "\(seconds)"
    return (hoursString, minutesString, secondsString)
}

func setCountDown() {
    if(TimeDiffInSec > 0) {
        let (h,m,s) = secondsToHoursMinutesSeconds(TimeDiffInSec)
        self.iDealTimer.text = "\(h):\(m):\(s)"
        TimeDiffInSec = TimeDiffInSec - 1
    }
    else{
        self.iDealTimer.text = "EXPIRED"
        if let delegate = self.delegate {
            delegate.DeleteiDealID(1)
        }
        Timer.invalidate()
    }
}

Any help will be greatly appreaciated

Answer 1

I think, this will be better way:

1. Inside tableView:cellForRowAtIndexPath calculate (or fetch) time and add it's value to label in cell.
2. Remove timer from cell.
3. Add timer in main class (where tableView placed) in viewDidAppear (or inside block where you fetch data), that will every second call method, that check and remove expired objects (or you can apply filter) and fire tableView.reloadData() (or delete needed rows animated).
4. In viewDidDisappear invalidate timer.

Answer 2

You can do simple thing whenever your time have been expire you can remove those values from your array of dictionary whatever you used for row count.

Simple thing here is your all table cell depends on your row count remover particular cell with by removing particular array object.

example :

if timerExpire == true {
        array.removeAtIndex(5)
        self.table.reloadData()
}

Answer 3

This is a tricky problem, because you want:

1. Table rows to be deleted even if they are offscreen at the time the timer pops.
2. New rows can be added while the old rows are "ticking".

The first point means that you do not want the timer to be kept in the cell . It is the wrong place anyway, because cells get reused and you'd have a nightmare invalidating and restarting timers.

The second point means that the row number you want to delete at the time the timer is started could be different than the row number you delete when the timer pops. You may start your timer for row 5 to be deleted in 5 seconds, but in the meantime row 4 gets deleted, making the former row 5 now row 4 . When the former row 5 's timer pops, row 4 needs to be deleted from the table.

Here is the approach I suggest:

1. Give each row in your table a unique ID. This will just be a simple count that is maintained by your UITableViewController class.

    var nextID = 0 

2. Maintain a list of active ID's that correspond to the rows that are currently in your table. Add this property to your UITableViewController :

    var activeIDs = [Int]() 

3. Add a dictionary to your table that maps a NSTimer to an ID. Add this to your UITableViewController :

    var timerIDmap: [NSTimer: Int]() 

4. When you create a new row in your table:

    let newID = nextID activeIDs.append(newID) nextID += 1 

5. In cellForRowAtIndexPath , be sure to store the ID in a property of the cell.

    cell.cellID = activeIDs[indexPath.row] 

6. When you create a timer, you need to store the timer and its corresponding cell ID in the timerIDmap . Since you'll do this in the custom cell, the cell needs to have a weak reference to the tableViewController that holds it:

    // add this property to your cell weak var myTableVC: UITableViewController? 

   and assign that property in cellForRowAtIndexPath :

    cell.myTableVC = self 

   so that when you create the timer:

    let timer = NSTimer.scheduledTimerWithTimerInterval(... myTableVC?.timerIDmap[timer] = cellID 

7. When your timer ticks, you need to decrement the time left on that timer. That means the time left should also be kept in your model. Add this dictionary to your UITableViewController :

    var timeLeft = [Int: Int]() // maps CellID to time left 

   that means that when you create the timer in the first place, you will store timeLeft in this dictionary

    myTableVC?.timeLeft[cellID] = 50 // some appropriate value 

   OK, so now in your handleCountdown routine which should be implemented in your UITableViewController :

    func handleCountdown(timer: NSTimer) { let cellID = timerIDMap[timer] // find the current row corresponding to the cellID let row = activeIDs.indexOf(cellID) // decrement time left let timeRemaining = timeLeft[cellID] - 1 timeLeft[cellID] = timeRemaining if timeRemaining == 0 { timer.invalidate timerIDmap[timer] = nil activeIDs.removeAtIndex(row) tableView.deleteRowsAtIndexPaths(NSIndexPath(row: row, section: 0), withRowAnimation: ... } else { tableView.reloadRowsAtIndexPaths(NSIndexPath(row: row, section: 0), withRowAnimation: ... } } 

8. This leaves very little work for your custom cell. It should merely take the time left on the timer and format it for display. In cellForRowAtIndexPath , tell the cell how much time is left on the timer:

    cell.timeLeft = timeLeft[activeIDs[indexPath.row]] 

9. The number of items in your table is the same as the number of items in activeIDs , so in tableView:numberOfRowsInSection return

    return activeIDs.count 

Answer 4

I have been trying these solutions but I dont think they are viable towards the goal. Just wanted to let people know. If you have found something that works or have found the same can you please let us know

Answer 5

This is the solution I have come up with. Its not a perfect solution by any means however, it does solve the problem.

In the viewcontroller:

    func handleDate(timer: Timer) {


    DispatchQueue.main.async() {

        if self.posts.count < 1 {
            print("Empty")
            timer.invalidate()

        } else {

            let calendar = Calendar.current
            let date = Date()

            let componentsCurrent = calendar.dateComponents([.year, .month, .day, .hour, .minute, .second], from: date)
            var components = DateComponents()

            components.hour = componentsCurrent.hour
            components.minute = componentsCurrent.minute
            components.second = componentsCurrent.second
            components.year = componentsCurrent.year
            components.month = componentsCurrent.month
            components.day = componentsCurrent.day
            let currentTime = calendar.date(from: components)!

            for post in self.posts {



                let cellID = post.postID
                let row = self.postsInFeed.index(of: cellID)

                let endDate = TimeInterval(post.time)



                if currentTime.timeIntervalSince1970 >= endDate {



                        self.tableView.beginUpdates()
                        timer.invalidate()

                        print(post.postID)
                        print("Deleting tableview row")

                        self.postsInFeed.removeFirst()
                        self.posts.removeFirst()

                        let store: Dictionary<String, Any> = ["caption": post.caption, "mediaURL": post.imageUrl as Any, "likes": post.likes, "user_ID": FriendSystem.system.CURRENT_USER_ID, "time": post.time]

                        let firebasePost = FriendSystem().GROUP_REF.child(self.group.groupID).child("storage").child(post.postID)
                        firebasePost.setValue(store)

                        FriendSystem().GROUP_REF.child(self.group.groupID).child("posts").child(cellID).removeValue()

                        self.tableView.deleteRows(at: [IndexPath(row: row!, section: 0)] , with: UITableViewRowAnimation.fade)
                        self.tableView.endUpdates()
                        self.tableView.reloadData()

                        }
                    }
                }
            }
    }

In the tableviewcell:

func tick(timer: Timer) {

    guard let expiresAt = endDate else {
        return
    }
    let calendar = NSCalendar(calendarIdentifier: NSCalendar.Identifier.gregorian)
    if let components = calendar?.components([.hour, .minute, .second], from: NSDate() as Date, to: expiresAt, options: []) {
        currentTime = formatDateComponents(components: components as NSDateComponents)
        self.timerLbl.text = currentTime

        if Date() >= endDate! {
            timer.invalidate()
        }

    }
}

func formatDateComponents(components: NSDateComponents) -> String {
    let hours = components.hour
    let minutes = components.minute
    let seconds = components.second

    return "\(hours):\(minutes):\(seconds)"
}