Best way to check if UITableViewCell is completely visible

Question

I have a UITableView with cells of different heights and I need to know when they are completely visible or not.

At the moment I am looping through each cell in the list of visible cells to check if it is completely visible every time the view is scrolled . Is this the best approach?

Here's my code:

- (void)scrollViewDidScroll:(UIScrollView *)aScrollView {

    CGPoint offset = aScrollView.contentOffset;
    CGRect bounds = aScrollView.bounds;    
    NSArray* cells = myTableView.visibleCells;

    for (MyCustomUITableViewCell* cell in cells) {

        if (cell.frame.origin.y > offset.y &&
            cell.frame.origin.y + cell.frame.size.height < offset.y + bounds.size.height) {

            [cell notifyCompletelyVisible];
        }
        else {

            [cell notifyNotCompletelyVisible];
        }
    }
}

Edit:

Please note that *- (NSArray )visibleCells returns visible cells which are both completely visible and partly visible.

Edit 2:

This is the revised code after combining solutions from both lnafziger and Vadim Yelagin:

- (void)scrollViewDidScroll:(UIScrollView *)aScrollView {
    NSArray* cells = myTableView.visibleCells;
    NSArray* indexPaths = myTableView.indexPathsForVisibleRows;

    NSUInteger cellCount = [cells count];

    if (cellCount == 0) return;

    // Check the visibility of the first cell
    [self checkVisibilityOfCell:[cells objectAtIndex:0] forIndexPath:[indexPaths objectAtIndex:0]];

    if (cellCount == 1) return;

    // Check the visibility of the last cell
    [self checkVisibilityOfCell:[cells lastObject] forIndexPath:[indexPaths lastObject]];

    if (cellCount == 2) return;

    // All of the rest of the cells are visible: Loop through the 2nd through n-1 cells
    for (NSUInteger i = 1; i < cellCount - 1; i++)
        [[cells objectAtIndex:i] notifyCellVisibleWithIsCompletelyVisible:YES];
}

- (void)checkVisibilityOfCell:(MultiQuestionTableViewCell *)cell forIndexPath:(NSIndexPath *)indexPath {
    CGRect cellRect = [myTableView rectForRowAtIndexPath:indexPath];
    cellRect = [myTableView convertRect:cellRect toView:myTableView.superview];
    BOOL completelyVisible = CGRectContainsRect(myTableView.frame, cellRect);

    [cell notifyCellVisibleWithIsCompletelyVisible:completelyVisible];
}

Just as a side note, you should go to all of your previous questions and accept answers of those who helped you. — Baub, Mar 22 '12 at 22:44
Thanks for telling me! I had already given them +1 but had forgotten about the set accepted answer feature. — RohinNZ, Mar 23 '12 at 01:12
Your code looks correct to me, and although it's complicated, it works. Don't fix what ain't broke, eh? — CodaFi, Mar 23 '12 at 04:43

Vadim Yelagin · Accepted Answer · 2015-09-22T09:28:23.630

131

You can get the rect of a cell with rectForRowAtIndexPath: method and compare it with tableview's bounds rect using CGRectContainsRect function.

Note that this will not instantiate the cell if it is not visible, and thus will be rather fast.

Swift

let cellRect = tableView.rectForRowAtIndexPath(indexPath)
let completelyVisible = tableView.bounds.contains(cellRect)

Obj-C

CGRect cellRect = [tableView rectForRowAtIndexPath:indexPath];
BOOL completelyVisible = CGRectContainsRect(tableView.bounds, cellRect);

Of course this will not regard the table view being clipped by a superview or obscured by another view.

edited Sep 22 '15 at 09:28

answered Mar 23 '12 at 16:45

Vadim Yelagin

2,944
2
15
20

Thank you! I've combined this code with lnafziger's solution. – RohinNZ Mar 25 '12 at 20:51
11

On the second thought it can be just `CGRectContainsRect(tableView.bounds, [tableView rectForRowAtIndexPath:indexPath])` – Vadim Yelagin Oct 01 '13 at 10:06
1

why is that my cellRect's origin.x = 0, origin.y = 0, width = 0, height = 0? although on UI they are not all 0s, I am using auto layout, any ideas? – RainCast Apr 18 '16 at 21:20
7

Swift 3: `let completelyVisible = tableView.bounds.contains(tableView.rectForRow(at: indexPath))` – cbartel Apr 27 '17 at 21:51
How can we handle similar functionality for UICollectionView? – Satyam Jun 27 '18 at 06:29

lnafziger · Answer 2 · 2013-05-29T22:33:42.927

I would change it like this:

- (void)checkVisibilityOfCell:(MyCustomUITableViewCell *)cell inScrollView:(UIScrollView *)aScrollView {
    CGRect cellRect = [aScrollView convertRect:cell.frame toView:aScrollView.superview];

    if (CGRectContainsRect(aScrollView.frame, cellRect))
        [cell notifyCompletelyVisible];
    else
        [cell notifyNotCompletelyVisible];
}

- (void)scrollViewDidScroll:(UIScrollView *)aScrollView { 
    NSArray* cells = myTableView.visibleCells;

    NSUInteger cellCount = [cells count];
    if (cellCount == 0)
        return;

    // Check the visibility of the first cell
    [self checkVisibilityOfCell:[cells firstObject] inScrollView:aScrollView];
    if (cellCount == 1)
        return;

    // Check the visibility of the last cell
    [self checkVisibilityOfCell:[cells lastObject] inScrollView:aScrollView];
    if (cellCount == 2)
        return;

    // All of the rest of the cells are visible: Loop through the 2nd through n-1 cells
    for (NSUInteger i = 1; i < cellCount - 1; i++)
        [[cells objectAtIndex:i] notifyCompletelyVisible];
}

The < and > in the if statement should be <= or >=, i'll correct this in the answer... — Aardvark, Feb 13 '13 at 18:04

score 14 · Answer 3 · answered Jun 04 '15 at 00:53

You can try something like this to see how much percentage is visible:

-(void)scrollViewDidScroll:(UIScrollView *)sender
{
    [self checkWhichVideoToEnable];
}

-(void)checkWhichVideoToEnable
{
    for(UITableViewCell *cell in [tblMessages visibleCells])
    {
        if([cell isKindOfClass:[VideoMessageCell class]])
        {
            NSIndexPath *indexPath = [tblMessages indexPathForCell:cell];
            CGRect cellRect = [tblMessages rectForRowAtIndexPath:indexPath];
            UIView *superview = tblMessages.superview;

            CGRect convertedRect=[tblMessages convertRect:cellRect toView:superview];
            CGRect intersect = CGRectIntersection(tblMessages.frame, convertedRect);
            float visibleHeight = CGRectGetHeight(intersect);

            if(visibleHeight>VIDEO_CELL_SIZE*0.6) // only if 60% of the cell is visible
            {
                // unmute the video if we can see at least half of the cell
                [((VideoMessageCell*)cell) muteVideo:!btnMuteVideos.selected];
            }
            else
            {
                // mute the other video cells that are not visible
                [((VideoMessageCell*)cell) muteVideo:YES];
            }
        }
    }
}

If the table view is able to display 2 cells with videos (on iPad for instance), both videos will play with the above code ? — Jerome, Oct 18 '16 at 21:28
@Catalin I've tried your solution but my tableview gets slowdown. Any way to improve scrolling performence ? — Rahul Vyas, Dec 06 '18 at 09:51
@RahulVyas sorry but no :( check your inner elements maybe the layout can be optimized a bit as it regards layers/sublayers — Catalin, Dec 11 '18 at 13:12

score 6 · Answer 4 · answered Apr 04 '18 at 10:19

If you also want to take the contentInset into account, and don't want to rely on a superview (the table view frame in superview could be something else than 0,0), here's my solution:

extension UITableView {

    public var boundsWithoutInset: CGRect {
        var boundsWithoutInset = bounds
        boundsWithoutInset.origin.y += contentInset.top
        boundsWithoutInset.size.height -= contentInset.top + contentInset.bottom
        return boundsWithoutInset
    }

    public func isRowCompletelyVisible(at indexPath: IndexPath) -> Bool {
        let rect = rectForRow(at: indexPath)
        return boundsWithoutInset.contains(rect)
    }
}

score 5 · Answer 5 · edited Jun 20 '20 at 09:12

5

From the docs:

visibleCells Returns the table cells that are visible in the receiver.

- (NSArray *)visibleCells

Return Value An array containing UITableViewCell objects, each representing a visible cell in the receiving table view.

Availability Available in iOS 2.0 and later.

See Also – indexPathsForVisibleRows

edited Jun 20 '20 at 09:12

Community

1
1

answered Mar 22 '12 at 22:32

CodaFi

42,165
8
102
150

4

Sorry maybe I was not clear enough. I'm only interested in the cells which are completely visible. - (NSArray *)visibleCells and indexPathsForVisibleRows both return the cells which are completely visible and partly visible. As you can see in my code I am already using - (NSArray *)visibleCells to find the ones which are completely visible. Thanks anyway though. – RohinNZ Mar 23 '12 at 01:06

score 1 · Answer 6 · answered Mar 15 '21 at 17:15

Swift 5+

we can use

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
       ...
    }

func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    ...
}


let cellRect = tableView.rectForRow(at: indexPath)
let completelyVisible = tableView.bounds.contains(cellRect)

score 0 · Answer 7 · answered Feb 25 '13 at 21:53

UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:indexPath];
CGRect frame = cell.frame;
if (CGRectContainsRect(CGRectOffset(self.collectionView.frame, self.collectionView.contentOffset.x, self.collectionView.contentOffset.y), frame))
{
    // is on screen
}

score 0 · Answer 8 · edited Oct 24 '17 at 22:36

0

- (BOOL)checkVisibilityOfCell{
    if (tableView.contentSize.height <= tableView.frame.size.height) {
        return YES;
    } else{
        return NO;
    }
}

edited Oct 24 '17 at 22:36

Fantini

1,819
18
29

answered Dec 16 '16 at 06:48

Naresh Jain

17
1

score 0 · Answer 9 · answered Oct 11 '17 at 11:02

Even if you said you want to check it every time you scrolled, you can also use

-(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
       CGRect cellRect = [tableView convertRect:cell.frame toView:tableView.superview];
       if (CGRectContainsRect(tableView.frame, cellRect)){
            //Do things in case cell is fully displayed
        }

}

score 0 · Answer 10 · answered Jan 26 '18 at 09:43

0

Maybe for this issue better used next function from UITableViewDelegate

func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath)

answered Jan 26 '18 at 09:43

Artyom

969
12
18

This will not work. From a doc `tells the delegate that the specified cell was removed from the table.` – anatoliy_v May 31 '18 at 10:39

fahlout · Answer 11 · 2018-04-18T22:20:34.200

0

The code below will let you check if a collection view cell is completely visible through the layout attributes of the collection view.

guard let cellRect = collectionView.layoutAttributesForItem(at: indexPath)?.frame else { return } let isCellCompletelyVisible = collectionView.bounds.contains(cellRect)

edited Apr 18 '18 at 22:20

answered Apr 18 '18 at 22:13

fahlout

49
3

Best way to check if UITableViewCell is completely visible

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