Timer will reset and stop running during scrolling UITableView - ios

Question

timer.gif
↑↑↑↑↑↑↑↑↑ I show the problem in this GIF ↑↑↑↑↑
There is a timer and stratButton in the tableView cell, when I click the Button, the timeLabel will start running.
Now the problem is when I scroll the running timer out of the screen and scroll it back, the timer will reset and stop.
Hope someone can help me! I check many solution but they didn't work for me! I am almost cry.
my cellForRow:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "myCell", for: indexPath) as! TimerTableViewCell
cell.timer?.invalidate()
let item = myTimerList[indexPath.row]
cell.timerName.text = item.timerName
cell.secondLeftLabel.text = "\(item.timerSecond)"
return cell
}
I created a small project contained my code for you to modify : https://app.box.com/s/axluqkjg0f7zjyigdmx1lau0c9m3ka47

Answer 1

You need to preserve the state of each cell
class Service {
static let shared = Service()
var myTimerList = [TimerClass]()
}
//
here i added another 2 vars , why timerName is left despite you have to init them the same because current will hold the changing value
class TimerClass {
let timerSecond : Int
let timerName : String
var current: Int
var isPlaying = false
init(second:Int, name:String) {
timerSecond = second
timerName = name
current = second
}
}
//
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "myCell", for: indexPath) as! TimerTableViewCell
let item = Service.shared.myTimerList[indexPath.row]
cell.tag = indexPath.row // to access the array inside the cell
if item.isPlaying {
cell.play() // add play method to the cell it has same button play action
}
else {
cell.timer?.invalidate()
}
cell.timerName.text = item.timerName
cell.secondLeftLabel.text = "\(item.current)"
return cell
}
//
inside the cell when the button is clicked , change isPlaying property to true and to false when stopped like this
// here self is the cell itself
Service.shared.myTimerList[self.tag].isPlaying = true
also when the timer ticks change
Service.shared.myTimerList[self.tag].current = // value

Answer 2

You are reusing UITableViewCell. It means once cell is out of screen, it will be reused for the cell getting into the screen. Whenever it happens, it calls the delegate method - means cell.timer?.invalidate() is invoked again and again.

Answer 3

Remove cell.timer?.invalidate() from cellForRowAt method, because every time you scroll the tableView this method is called to display new cells. In your case when you have started a timer for a cell and that cell is not in the view, next time you scroll to bring that cell again to the view cell.timer?.invalidate() causes it to stop.