CODEWITHSUNDEEP
iosobjective-cuikit-dynamics
Curnelious
Curnelious

Reputation: 1

Using UIDynamicAnimator on a scrollview?

I am trying to implement UIDynamicAnimator effects on a scrollView with many elements. I couldn't find too much information about it anywhere ,so i just need some starting point.

So i have my scrollView, with many UIViews in it. i want to make any kind of animation to its "subViews" while scrolling.

Tried that-nothing happens . 

  //DYNAMICS ANIMATIONS
    UIDynamicAnimator *dynamic=[[UIDynamicAnimator alloc] initWithReferenceView:scroller];
    UIGravityBehavior *gravityBeahvior = [[UIGravityBehavior alloc] initWithItems:mainCellsArray];
    [dynamic addBehavior:gravityBeahvior];

When mainCellsArray holds all the "subViews" of the scroller .

EDIT: I have a strong property for the dynamic . The array holds my costume classes pointers , that each class is a UIView subclass, and they all the scroller children's.

Upvotes: 2

Views: 1065

Answers (1)

Rob
Rob

Reputation: 437622

First, make sure you define your animator as a property, not solely as a local variable (and I tend to use animator for the name of that, to avoid confusion with the @dynamic keyword):

@property (strong, nonatomic) UIDynamicAnimator *animator;

Then instantiate the animator:

self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.scrollView];

And add the gravity:

UIGravityBehavior *gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[viewToAnimate]];
[self.animator addBehavior:gravityBehavior];

If you want them to stop when they hit the bottom of the contentSize of the scroll view, you can't use the typical translatesReferenceBoundsIntoBoundary setting. You have to make a path yourself, e.g. something like:

UICollisionBehavior *collision = [[UICollisionBehavior alloc] initWithItems:@[viewToAnimate]];
CGRect contentSizeRect = {CGPointZero, self.scrollView.contentSize};
UIBezierPath *path = [UIBezierPath bezierPathWithRect:contentSizeRect];
[collision addBoundaryWithIdentifier:@"contentSize" forPath:path];
[self.animator addBehavior:collision];

Or, if you want them to fly off the scroll view, you probably want to remove them when they no longer intersect the contentSize of the scroll view:

UIGravityBehavior *gravity = [[UIGravityBehavior alloc] initWithItems:@[viewToAnimate]];
UIGravityBehavior __weak *weakGravity = gravity;
CGRect contentSizeRect = {CGPointZero, self.scrollView.contentSize};
gravity.action = ^{
    if (!CGRectIntersectsRect(contentSizeRect, viewToAnimate.frame)) {
        NSLog(@"removing view");
        [viewToAnimate removeFromSuperview];
        [self.animator removeBehavior:weakGravity];
    }
};
[self.animator addBehavior:gravity];

Upvotes: 2

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