Determine if a cell in on screen and perform a function

Question

I want to find out if a cell is displaying onscreen in a table view.

I tried out willDisplay method but it's of no use. I even tried

if (tableView.indexPathsForVisibleRows?.contains(indexPath))! {
                    print("showing now")
}

This function works, But it doesn't print anything when the cell is on screen or as I scroll down. Ex: If I have 5 cells, As the app launches and the cell are on the display, nothing is printed. Also, when I scroll from cells 1 to 5, Nothing is displayed. On contrary, If I scroll back from cells 5 to 1, It will display it, which completely defies my purpose.

I hope you understood my query and can help me with an apt solution.

Cheers!

show your tried code willDisplay should have worked. – Tushar Sharma Aug 20 '17 at 08:11 — Tushar Sharma, Aug 20 '17 at 08:11

Tushar Sharma · Accepted Answer · 2017-08-20T08:37:38.940

1

willDisplay method of tabView should work for you.

Give DataSource and Delegate properly. Control+drag from TableView to yellow icon will display you correct options.

Add extension to ViewControllerClass and confirm table protocols-:

extension ViewController : UITableViewDelegate,UITableViewDataSource{

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }// Default is 1 if not implemented

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int{
        return 2
    }


    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell{
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell")
        cell?.textLabel?.text = indexPath.row
        return cell!
    }

    // will display prints while displaying cells

    func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        print("visible now")
    }

edited Aug 20 '17 at 08:37

answered Aug 20 '17 at 08:14

Tushar Sharma

2,839
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Well, I had called this method earlier. It didn't quite work. It somehow is working now. – Aakash Dave Aug 20 '17 at 08:30
Also, is there a way by which i can print "visible row" only if it is completely visible and not partially. – Aakash Dave Aug 20 '17 at 08:31
@AakashDave this will help you-:https://stackoverflow.com/questions/3326658/determine-if-a-tableview-cell-is-visible/3326891 – Tushar Sharma Aug 20 '17 at 08:35

krlbsk · Answer 2 · 2017-08-20T08:15:49.827

0

Remember to connect UITableView's delegate property and conform to UITableViewDelegate.

Try

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    print("cell \(indexPath.row) is about to display")
}

from UITableViewDelegate's protocol. Documentation could be found here.

edited Aug 20 '17 at 08:15

answered Aug 20 '17 at 08:09

krlbsk

1,051
1
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Determine if a cell in on screen and perform a function

2 Answers2