Spinning UITableViewCells

Question

I have a UITableView loading its data from the Web, and while the data is loading there are few cells, to indicate the process. Each cell got an UIImageView inside which i want to be spinning constantly.

Inside the UITableViewController i got this:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:    (NSInteger)section
{
    //there are three "default" cells
    return self.datasource.count > 0 ? self.datasource.count : 3;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if(self.datasource.count)
    {
    //return a cell with loaded data
    }
    else
    {
        LoadingTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"LoadingIndicationCell"];

        return cell;
    }
}

LoadingTableViewCell has a *.xib file with a corresponding reference outlet to the UIImageView, called "circle"

- (void)awakeFromNib {
    self.circle.alpha = .3f;
    self.spinning = NO;
    [self startSpin];
}
- (void) spinWithOptions: (UIViewAnimationOptions) options {
    NSLog(@"SPINNIN'");
    // this spin completes 360 degrees every 2 seconds
    [UIView animateWithDuration: 0.5f
                          delay: 0.0f
                        options: options
                     animations: ^{
                         _circle.transform =     CGAffineTransformRotate(_circle.transform, M_PI / 2);
                     }
                     completion: ^(BOOL finished) {
                         if (finished) {
                             if (_spinning) {
                             [self spinWithOptions: UIViewAnimationOptionCurveLinear];
                         } else if (options != UIViewAnimationOptionCurveEaseOut) {
                             [self spinWithOptions: UIViewAnimationOptionCurveEaseOut];
                         }
                     }
                 }];
}

- (void) startSpin {
    if (!self.spinning) {
        self.spinning = YES;
        [self spinWithOptions: UIViewAnimationOptionCurveEaseIn];
    }
}

- (void) stopSpin {
    self.spinning = NO;
}

It seems to spin 2 times and then stops. In the console there are 6 "SPINNIN'" outputs, two for each cell, i suppose.

I'm very new to iOS-development, been tryin' to figure this out the entire evening. Btw, what will happen to these cell objects when they will get replaced by cells with loaded data? Where do i call stopSpin then?

it seems your code don't have problem. you can add more log and breakpoint at completion block to debug. also notice sometime the completion block will call with finished = NO. for example, when cell get replaced, it will remove first, this will stop animation, and completion callback's finish will be NO — SolaWing, Mar 18 '15 at 03:18
@SolaWing thank you for the hint on the "finished" flag. I've slightly edited spinWithOptions method and it works from now on. — Alexander, Mar 18 '15 at 09:31

score 0 · Accepted Answer · answered Mar 18 '15 at 09:29

Eventually i ended up with this code:

- (void) spinWithOptions: (UIViewAnimationOptions) options {
    if([self isHidden]) [self stopSpin]; //stop spinning when the cell got replaced
    // this spin completes 360 degrees every 2 seconds
    [UIView animateWithDuration: 1.0f
                      delay: 0.0f
                    options: options
                 animations: ^{
                     _circle.transform = CGAffineTransformRotate(_circle.transform, M_PI / 2);
                 }
                 completion: ^(BOOL finished) {
                        if (_spinning) {
                             [self spinWithOptions: UIViewAnimationOptionCurveLinear];
                        }
                 }];
}

@MatthiasBauch i stopped relying on "finished" flag at the completion block, thus made it infinite. But when a cell got removed from the tableview, it's isHidden method will return YES, and when it happens i stop the spinning. — Alexander, Mar 18 '15 at 09:44

Spinning UITableViewCells

1 Answers1