TableView cell stop scrolling on cell

Question

I am trying to create feed page like Facebook, i am loading images into tableview cells using lazy loading. Sometimes a scroll lock on any random cell occurs but when i try to scroll on any other visible cell above or below, it scrolls. This issue is very sporadic. I am not able to rectify what is causing this behaviour. Please help.

Here is the code;

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    //label to show values of the menu
    static NSString *CellIdentifier = @"CellIdentifier";

    // Dequeue or create a cell of the appropriate type.
    socialFeedCustomCell *cell = (socialFeedCustomCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    if (cell == nil)
    {
        cell = [[socialFeedCustomCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] ;
        cell.accessoryType = UITableViewCellAccessoryNone;
    }

    for (UIView *tempView in cell.contentView.subviews) {
        [tempView removeFromSuperview];
    }

        [self renderInstagramData:indexPath cell:cell];

    cell.contentView.layer.opaque=YES;
    cell.layer.shouldRasterize = YES;
    cell.layer.rasterizationScale = [UIScreen mainScreen].scale;
    cell.selectionStyle=UITableViewCellSelectionStyleNone;
    cell.backgroundColor=[UIColor clearColor];
    cell.userInteractionEnabled=YES;

    return cell;
}

Thanks

The scroll lock can not be shown with the help of a screenshot, You can consider a situation where you are scrolling on a tableview and it stop's scrolling. — Superdev, Dec 18 '13 at 13:20
Regarding the code i am using custom cells and adding subviews to the tableview's contentview. — Superdev, Dec 18 '13 at 13:21
I really don't understand "Sometimes a scroll lock on any random cell occurs but when i try to scroll on any other visible cell above or below, it scrolls." What is that mean? could you describe the situation little bit more and show your code? — Dinesh Raja, Dec 18 '13 at 13:21
For scrolling on a tableview we need to swipe our finger over it, Suppose i swiped my finger over a cell(any random cell) and it doesn't scroll. You are not able to identify the cell, as next time when you reload your app that cell can let you scroll. — Superdev, Dec 18 '13 at 13:28

score 0 · Answer 1 · answered Dec 18 '13 at 14:03

0

It looks like something is blocking your main thread (the thread responsible for the UI updates). Move all the operations not related to UI updates to background queues using GCD. For example:

dispatch_queue_t jsonParsingQueue = dispatch_queue_create("jsonParsingQueue", NULL);

    // execute a task on that queue asynchronously
    dispatch_async(jsonParsingQueue, ^{
     // Parse your data here

        dispatch_async(dispatch_get_main_queue(), ^{
           // Update your UI in the main thread
           [self.tableView reloadData];
        });
    });

answered Dec 18 '13 at 14:03

Nikos M.

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i am already using this technique, but din't get any luck. The cell that is locked will let you perform tap gesture, button click etc but not scrolling. – Superdev Dec 18 '13 at 14:07
one more weird this is when i try to scroll using two fingers it will scroll. – Superdev Dec 18 '13 at 14:07
Do you have any other scrollview inside the cell? – Nikos M. Dec 18 '13 at 14:09
No, the cell only contains an imageview, some labels and buttons. – Superdev Dec 18 '13 at 14:10
i have added the code in my question above, the method "renderInstagramData" will add subviews in the cell contentview. – Superdev Dec 18 '13 at 14:18

score 0 · Answer 2 · answered Dec 19 '13 at 02:52

In tableView:cellForRowAtIndexPath:, don't remove all of the views in cell.contentView.subviews. Presumably you are re-installing those views somewhere else. This technique almost defeats the purpose of re-using table cells.

Keep the content view's subviews in place; re-use them by assigning different data to them. This should improve performance. If it doesn't, then post the code for renderInstagramData:cell:.

TableView cell stop scrolling on cell

2 Answers2