UIView Animate and completion block

Question

I'm trying to animate a tableview's offset down, then in the completion block would move it back up. But my code is not doing anything in the completion block:

-(void)viewDidAppear:(BOOL)animated {
    if (TRUE) {
         NSLog(@"animating table view");

        [UIView animateWithDuration:.25
                         animations:^{
                             self.tableView.contentOffset = CGPointMake(self.tableView.contentOffset.x, self.tableView.contentOffset.y - 60);
                         }
                         completion:^(BOOL finished){
                             NSLog(@"completion block");
                         }];
    }
}

"completion block" never gets outputted... any ideas?

EDIT:

Ok, so it has something to do with my UIREfreshControl:

- (void)viewDidLoad
{
    [super viewDidLoad];

    if (TRUE) {
        UIRefreshControl *refresh = [[UIRefreshControl alloc] init];
        refresh.attributedTitle = [[NSAttributedString alloc] initWithString:@"Pull to Refresh"];
        [refresh addTarget:self action:@selector(refreshTableView:) forControlEvents:UIControlEventValueChanged];

        [self setRefreshControl:refresh];
    }
}

When the refresh controll is added, it won't fire off the completion block. if i dont' add the control, it works as intended.

EDIT 2:

K, so if i scroll the table view, the completion block is then fired:

2013-02-15 13:37:06.266 [1922:14003] animating table view
2013-02-15 13:37:14.782 [1922:14003] completion block

the code as written should log "completion block" right after "animating table view", but it has a 8 second delay cause thats when i scrolled the table view myself.

how the "Pull to Refresh" looks like:

enter image description here

just tryed your code on test project, and 'completion block' is ouputed to console. You tryed this on simulator or on device. Which iOS version you used, XCode version? — jamapag, Feb 15 '13 at 19:10
Simulator, iOS 6.1, xcode 4.6. You did this in the `viewDidAppear:` method? — Padin215, Feb 15 '13 at 19:27
Works for me. Xcode 4.6. I tested in the 5.0 simulator and the 6.1 simulator and both worked correctly. — rob mayoff, Feb 15 '13 at 19:30
I can reproduce this problem. What are you trying to achieve? Maybe we can find an alternative solution. — pgb, Feb 15 '13 at 21:10
To be able to animate the tableView.contentOffset back to 0. the over all effect is table view opens, it slides down to show the "Pull to Refresh" and slide back up after 3 seconds; kind of a peek at it so users know that option is available. — Padin215, Feb 15 '13 at 21:26
See my answer below. You just need to add a delayed call and you are all set! — pgb, Feb 15 '13 at 21:29

score 14 · Answer 1 · edited Jul 08 '14 at 01:23

14

I used this and working fine. Its alternative solution.

[UIView animateWithDuration:0.5
                              delay:0.1
                            options: UIViewAnimationOptionCurveEaseOut
                         animations:^
         {
             CGRect frame = self.adBannerView.frame;

             self.adBannerView.frame = frame;
         }
                         completion:^(BOOL finished)
         {
         }];

try adding delay and options.

edited Jul 08 '14 at 01:23

Rok Jarc

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answered Feb 15 '13 at 18:23

Guru

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102

Why would that make a difference? There is a `animateWithDuration:animations:completion:` method as well – David Rönnqvist Feb 15 '13 at 18:26

pgb · Accepted Answer · 2013-02-15T22:51:26.873

I was able to reproduce this issue and found a workaround.

When using a UIScrollView, which UITableView inherits from, you can't change its contentOffset is not an animatable property. Instead, you need to use the method setContentOffset:animated:.

So, what you need to do is as follows:

Set your view controller as the UITableView delegate. I did in on viewDidAppear.
Set a flag, so you know in the delegate that the scroll happened because you triggered.
In the delegate method - (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView, bounce back the animation (you could here add a delay by using performSelector:afterDelay:.

Here's the code:

@interface MyViewController ()

@property (assign, nonatomic) BOOL shouldReturn;

@end

@implementation MyViewController

-(void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    if (TRUE) {
        NSLog(@"animating table view");
        self.shouldReturn = YES;
        self.tableView.delegate = self;
        [self.tableView setContentOffset:
                     CGPointMake(self.tableView.contentOffset.x,
                                 self.tableView.contentOffset.y - 60)
                                animated:YES];
    }
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    if (TRUE) {
        UIRefreshControl *refresh = [[UIRefreshControl alloc] init];
        refresh.attributedTitle = [[NSAttributedString alloc] initWithString:@"Pull to Refresh"];
        [refresh addTarget:self action:@selector(refreshTableView:) forControlEvents:UIControlEventValueChanged];

        [self setRefreshControl:refresh];
    }
}

- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
    if (self.shouldReturn) {
        self.shouldReturn = NO;
        [self.tableView setContentOffset:CGPointZero animated:YES];
    }
}

@end

Ok, this works! i'm not sure why you set `self.tableView.delegate = self` though. I didn't add that and it works. I added in a `[self performSelector:@selector(test) withObject:nil afterDelay:2]' and works perfect, thanks! — Padin215, Feb 15 '13 at 21:35
I set the delegate because I don't have it wired on IB. I guess you didn't meet it because your view controller was already the table delegate. — pgb, Feb 15 '13 at 22:48
I realize this is old as all, but @Log139's solution is fragile. You don't know exactly how long the animation will take. @pgb sets the delegate so he can get callbacks on `scrollViewDidEndScrollingAnimation` — Benhamine, Jul 05 '17 at 17:29

UIView Animate and completion block

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