Setting UIScrollView's Position from another ViewController

Question

I am trying to set the position of a UIScrollView by using contentOffset as such:

- (void) navigateToTableViewPosition:(CGPoint)contentOffset {
    NSLog(@"Position set method gets called...");
    NSLog(@"%@", NSStringFromCGPoint(contentOffset));
    [mainScrollView setContentOffset:contentOffset animated:YES];
}

I call this method from another view controller before I dismiss it, and everything checks out. I pass the argument correctly, and the method gets called (checked it with NSLog), but the scroll view does not move...

What is funny is that when I call this method from the view controller, in which it is located, it works fine. Only when I call it from another view controller, it stops working.

Just for future reference, here is the calling method:

MainViewController *mainView = [[MainViewController alloc] init];
[mainView navigateToTableViewPosition:contentOffset];

Content offset is a CGPoint I set beforehand. It doesn't matter here; besides, it gets passed correctly anyways.

score 2 · Accepted Answer · edited Dec 26 '12 at 11:45

Try this, You have to send notification from other viewcontroller when you want to change ..

    [[NSNotificationCenter defaultCenter] postNotificationName:@"changepostion"        object:NSStringFromCGPoint(CGPointMake(contentOffset.x, contentOffset.y))];

in mainviewcontroller

  -(void)viewDidLoad

  {
     [[NSNotificationCenter defaultCenter] removeObserver:self];
         [[NSNotificationCenter defaultCenter] addObserver:self    selector:@selector(navigateToTableViewPosition:) name:@"changepostion" object:nil];

  }

- (void) navigateToTableViewPosition:(NSNotification *)notification
  {
        contentOffset =CGPointFromString([notification object]);

   NSLog(@"Position set method gets called...");
   NSLog(@"%@", NSStringFromCGPoint(contentOffset));
    [mainScrollView setContentOffset:contentOffset animated:YES];
 }

score 1 · Answer 2 · answered Dec 26 '12 at 10:50

1

You can't set the properties of a view which is not visible. If you are using iOS5+ you can implement the offset setting in the completion in the view dismiss completion block.

answered Dec 26 '12 at 10:50

dasdom

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score 0 · Answer 3 · edited Dec 26 '12 at 11:48

0

Use delegate for backward messaging in view controllers.

Refer Basic Delegate Example link for more reference.

Your are making new instance of viewcontroller which will call method but will have no effect.

edited Dec 26 '12 at 11:48

lxt

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answered Dec 26 '12 at 10:57

Paresh Navadiya

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That seems to be the answer, but I cannot figure out how to set the delegate. A couple months ago I did something similar, and I remember it was very simple. I set a UIView's delegate to another view controller and then just called methods like [delegate method:argument]; But I don't remember how I did it, and I do not know how to apply it in this situation. – Gergely Kovacs Dec 26 '12 at 11:33

Setting UIScrollView's Position from another ViewController

3 Answers3