Strange behavior on scroll UITableView

Question

I have a single view with nested scroll and table view with this hierarchical tree:

Tree of the view

(The table is loaded with some Huckleberry Finn rows taken from this example.)

On viewWillAppear I programmatically scroll the Table View at the last row doing

-(void)viewWillAppear:(BOOL)animated
{
   [self.tableView reloadData];
   NSIndexPath *indexPath = [NSIndexPath indexPathForRow:[self.tableView numberOfRowsInSection:0]-1 inSection:0];
   [self.tableView scrollToRowAtIndexPath:indexPath
                      atScrollPosition:UITableViewScrollPositionBottom
                              animated:YES];
}

and everything works as expected, in both orientation. As you can see, the text is rightly truncated.

portrait landscape

I've uploaded on Github my project so you can see it running. Download it here.

Now, if you add this line in the cellForRowAtIndexPath method:

cell.textLabel.numberOfLines=0;

the cells automatically will resize to embed and show the entire text label:

numberOfLines=0

BUT, and this is the issue my dear friends, as you can see the table is not scrolled to the last row but 5-6 rows above. And I cannot understand why.

The same thing happens also if NumberOfLines is 2,3 and so on. Only a value of 1 can make the TableView move down to the very last row.

(FYI, I do not use [self.tableView setContentOffset:CGPointMake(0, CGFLOAT_MAX)]; in order to scroll down the table because it throws an exception)

Maybe something is wrong with iOS8 ?

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

viewDidLayoutSubviews will do the job

I guess you use some autolayout or self sizing cells? In viewWillAppear the calculation is not finished. So you scroll to the bottom, but then thereafter autolayout resizes your cells what makes them expand in height.

For Details: Refer to apple documentation UIViewController

... "Your view controller can override this method to make changes after the view lays out its subviews. The default implementation of this method does nothing."

- (void)viewDidLayoutSubviews {
    // your code here
}

edited Jun 20 '20 at 09:12

Community

1
1

answered Oct 12 '14 at 17:21

Tuan

893
1
9
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Yes it is true you are right it could be the reason since I'm using autolayout. But what can I do to be sure? Is there any other method other than `viewWillAppear` to try? – RikiRiocma Oct 12 '14 at 18:25
Maybe you can tryy viewDidAppear but i am not sure about that. There should be some event like viewDidFinishedAutolayout. I will edit my answer if i can find something like that. – Tuan Oct 12 '14 at 20:08
No, unfortunately "viewDidFinishedAutolayout" don't exists. I resolved using "viewDidLayoutSubview" as you can read below. – RikiRiocma Oct 13 '14 at 08:03
1

viewDidLayoutSubview is a good point to do that i think. i misunderstood the documentation about that method. but now i think it will do the work. Thanks for sharing. – Tuan Oct 13 '14 at 08:11

score 0 · Answer 2 · edited May 23 '17 at 12:11

I added this event with reloadSection method and now the table scroll to the end. Also, I changed "tableView" to "myTableView" since I read that is better to give a non-default name to the views (as Sapi says in his answer here).

- (void)viewDidLayoutSubviews {

    [self.myTableView reloadSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:UITableViewRowAnimationAutomatic];
    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:[self.myTableView numberOfRowsInSection:0]-1 inSection:0];
    [self.myTableView scrollToRowAtIndexPath:indexPath
                      atScrollPosition:UITableViewScrollPositionBottom
                              animated:YES];
}

IMHO this thing is very Machiavellian, however.

Strange behavior on scroll UITableView

2 Answers2

viewDidLayoutSubviews will do the job

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