Question

I have the following situation:

From within a view controller, I go about creating an arbitrary number of transparent UIButtons which toogle the appearance and disappearance of UIViews over the controller’s main view. Right now, when my “zoom in” and “zoom out” methods are called, there’s code for modifying the default animation of two CALayer properties (just duration really). This code then gets called every time the actions take place. But I’d like to set the animation code once inside the layer and not have it in the zoom methods. I’ll explain more after I show the basic idea:

The buttons/sensors creation code is too long to post (and not that relevant to the real question), but it’s something along the lines of this pseudo code:

- (void) createSensors:[number of sensors]
{
  for(number of sensors)
  {
    create UIVIew with some content;
    create transparent UIBUtton as sensor and place somewhere in main view;
    calculate a transform to "shrink" the UIView's layer to the size and position of the button.
    apply transform;
    set the UIVIew's layer opacity to 0;
    add UIVIew to main view 
    (but the rest of my interface is in a container view, so I can dim the screen and have this view displayed in a modal-like way.)
    do some tagging so the button's tag can later be used to retrieve this view and transform.
    }
}

Now, when a sensor is clicked, I perform a “zoom in” for the view associated with the sensor/view. I actually dim the screen to white, and animate the view’s (the layer’s really) position and scaling to the center of the screen. And on clicking a button in the view, I do the opposite to dismiss it. This is the code:

- (void)animateZoomIn:(UIButton*)sender
{  
  NSString *sourceTagKey = [NSString stringWithFormat:@"%i",sender.tag]; 
  AnimationSettings *settings = [zoomTransforms objectForKey:sourceTagKey];

  UIView *newBox = [[self.view subviews] objectAtIndex:sender.tag]; 
  activeZoomBox = newBox;

  CABasicAnimation *a = [CABasicAnimation animation];
  a.duration = .4;
  [mainCanvas.layer addAnimation:a forKey:@"opacity"];

  a = [CABasicAnimation animation];
  a.duration = 1;
  [activeZoomBox.layer addAnimation:a forKey:@"opacity"];

  a = [CABasicAnimation animation];
  a.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
  a.duration = .5;
  [activeZoomBox.layer addAnimation:a forKey:@"transform"];  

  [mainCanvas setUserInteractionEnabled:NO];

  if([settings wantsBackgroundFade])
    [mainCanvas.layer setOpacity:.2];

  [activeZoomBox.layer setOpacity:1];  
  [activeZoomBox.layer setTransform:CATransform3DIdentity];
}


- (void)animateZoomOut:(UIButton*)sender
{
  NSString *sourceTagKey = [NSString stringWithFormat:@"%i",sender.tag]; 
  AnimationSettings *settings = [zoomTransforms objectForKey:sourceTagKey];

  CABasicAnimation *a = [CABasicAnimation animation];
  a.duration = .4;
  [mainCanvas.layer addAnimation:a forKey:@"opacity"];

  a = [CABasicAnimation animation];
  a.duration = 1;
  [activeZoomBox.layer addAnimation:a forKey:@"opacity"];

  a = [CABasicAnimation animation];
  a.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
  a.duration = .5;
  [activeZoomBox.layer addAnimation:a forKey:@"transform"];


  [mainCanvas setUserInteractionEnabled:YES];

  if([settings wantsBackgroundFade])
    [mainCanvas.layer setOpacity:1];

  [activeZoomBox.layer setOpacity:0];  
  [activeZoomBox.layer setTransform:[settings transform]];
}

So, the question:

I’d like to not have this kind of code:

CABasicAnimation *a = [CABasicAnimation animation];
  a.duration = .4;
  [mainCanvas.layer addAnimation:a forKey:@"opacity"];

in the action methods. I’d rather replace the animation once and make it “permanent” for each layer created and for the mainCanvas view. For instance, I’d prefer to have this code once on the controller’s init method and forget about it:

CABasicAnimation *a = [CABasicAnimation animation];
    a.duration = .4;
    NSMutableDictionary *animations = [NSMutableDictionary dictionaryWithDictionary:[mainCanvas.layer actions]];
    [animations setObject:a forKey:@"opacity"];
    [mainCanvas.layer setActions:animations];

Then, whenever I’d call [mainCanvas setOpacity:] it would last .4 secs by default. With a delegate-less CALayer it’d work.But in this case, my layers have their views as delegates, which have precedence over the actions dictionary, and I sort of need the views as delegates..

So is there a way to still have the layers respond to the dictionary instead? And if not, what would be the best way to “permanently replace” or add animations to these layers, so that the animations are contained in the layer objects (which is why I’d prefer to not override the view’s delegate methods for the CAAction Protocol)?

Answer 1

Why not just override -actionForLayer:forKey: on the UIView to provide the action you want on the important keys (and call super for the others)? There is no way to change the precedence, so your only options are implement -actionForLayer:forKey: or go with the manual animations.