I have a UIView which has an X origin that makes it off screen to the right. Then, I do a keyframe animation with CATransform3D:
[NSValue valueWithCATransform3D:CATransform3DMakeTranslation(-view.width, 0, 0)]
The problem is, after the animation completes, the view's frame is visually in the correct place, but it still thinks it's off screen, so I can't interact with it. Logging its frame property also shows that it's offscreen, but visually, it's not.
The fill mode for the animation is kCAFillModeForwards, so the final value of the animation sticks.
What is the solution to this problem, that is, interacting with this view after the animation and notifying the view that it is indeed visible?
You can use CAAnimation delegate method -animationDidStop:finished: to fix it when the animation done:
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
...
}
The better answer is to use UIView animation methods like animateWithDuration:animations:completion: (and variants on that method.)
Those methods let you do animations on the actual view properties, and when the animation is complete, the view is at it's actual destination location.
The center property is the easiest way to move views around. The frame property isn't valid if you've applied a transform, but the center property IS always valid for both reading and writing.
Core Animation only creates the illusion that your views move. The animation takes place on a display-only copy of the layer tree. You can query the properties of an animating layer by reading those same properties from the layer's presentationLayer. However, the view objects will not respond to the user interaction at their apparent location. The views still think they are at their original locations.
As the other poster said, you could use the animation completion delegate method to move the view to it's final location once the animation is over, but that's a lot of fussy work to do something that UIView animation does for you much more cleanly and simply.
Can you interact with the view even before you animate it?
is the view.userInteractionEnabled is set to YES??
Related
I want to animate an UIView with a given CAAnimation and interact with the view while it's animating (the view has a gesture recognizer).
If I understand correctly CAAnimation only animates the view's layer, but the view itself will remain in the original position.
How can I make the UIView move with the CAAnimation?
If you only care about visual "stickiness" you can do:
[myAnimation setRemovedOnCompletion:NO];
But this is only visual. It doesn't change the actual layer's properties.
If you want the layer's properties to be updated to new values also, you can do something like:
// You have code above that to register the property you want to animate...
[myAnimation setFromValue:[NSNumber numberWithFloat:0.0f]];
[myAnimation setToValue:[NSNumber numberWithFloat:1.0f]];
Rather than attempting to move it, you could expand your UIView to cover the area you want to receive touches in, and then animate its layer within it. Make sure to set the view opaque property to NO.
You may want to add a sublayer to view.layer rather than moving the view's own layer, for example if you want the layer to go outside the bounds of the view without affecting the layout of subviews of the view.
I'm trying out the animation stuff with the iPhone and I have a small app that has circles falling from the top of the screen to the bottom. I added the UIViewAnimationOptionAllowUserInteraction option to the animation and set userInteractionEnabled = YES on both my sub views and my main view. I am generating the subview programmatically everytime my NSTimer fires, which makes the circles.
The problem I am having is that even if I implement - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event on my main view and my subviews, the event only ever fires on the main view regardless of how hard or how many times I smash the falling circles.
How do I get that event to fire on my circles instead? Why doesn't the touch fire on the view on top?
The problem is that when you perform a "tween" animation with Core Animation (which occurs implicitly when you use the UIView animation methods), the new value is immediately applied to what's known as the model layer tree.
The animation is committed to Core Animation, and the next time the main run loop occurs, Core Animation does the necessary rendering to make it look as if an animation is occurring. In reality, though, the model values of your view (e.g., its frame or transform properties) are changed immediately.
Try tapping at the bottom of the screen where the buttons land (assuming they finish on screen). If you do this, it should respond to the interaction event as you expect.
You could manually change the frame of your circles by constantly firing a timer and applying small changes at each step. This, however, is likely not ideal.
Another option is to make use of your view's layer's presentationLayer method. This layer represents the state of the layer at any point in time, as we see it on the screen. Off the top of my head, I imagine that your main view's touch handling method can iterate through each subview and check to see if the touch point intersects the frame of the subview's layer's presentation layer. If it does, then that means someone "touched" your subview.
for (UIView *subview in self.subviews)
{
CALayer *presentationLayer = (CALayer *)[subview.layer presentationLayer];
if (CGRectContainsPoint(presentationLayer.frame, touchPoint)
{
// Found the subview the user touched
}
}
I should note that presentationLayer returns id, because the presentation layer may be CALayer or any of its subclasses. So, for example, if you're using CAShapeLayer, then -presentationLayer will return a CAShapeLayer. Still, it's fine to just cast it to a CALayer since all you care about for the purposes of this task is to check its frame property.
I have an animation I'm using to snap a rotatable UIView to a circular grid. As the view animates, I need to update another view based on the rotating views position.
How can I go about getting the position of the rotating view as it animates into position?
When animation starts you can start a function that will be polling current view position using a timer (I suppose you will need to get presentationLayer from view's layer and get position values from it).
There's no callbacks for CAAnimation other than animationDidStart and animationDidStop so it seems that's the solution (if I'm not mistaken it was also mentioned so in one of WWDC videos).
I am banging my head on the wall here due to this problem:
When I create a UIImageView this view has a certain orientation and size. Lets call this state "A".
This view responds to taps. It can be dragged around the screen.
At some point in the code I apply a CGAffineTransform to the view. Does not matter if the affine is a scale, a rotation, a translation or a combination of all. Does not matter also if the transform is absolute or relative. Not to mention the device can change its orientation and the view is autorotated to the correct orientation (that we can cay is a kind of rotation or transformation applied to the view).
The problem is: the moment I touch that object or try to animate its transparency or any other parameter, it "remembers" the state "A" and does all animations from that state, not from current state. If I simply touch the view, it returns instantly to state "A". The code is not doing it by itself. It is pretty annoying. How to I make a view assume its current state of transformations as the reset or initial state? In other words, how do I make a view forget its past transformations or states?
The only way I know is recreating the view, but this is a ridiculous way of doing this.
Is there any way to make this work as I described?
thanks
Afaik, all of the SDK animations automatically create a copy, perform the animation on the copy while hiding the original. In your code you'll have a getState line that starts this and creates the pointer to the animation object. To make it permanent at the end of your animation routine set the original objects view to the animation view.
Iirc it something like this, but I don't have my code samples in front of me:
myOriginalObject.view = myMnimationObject.view
Obviously do this before you release your animations but after you're done with the transforms.
I'm making an app where one of the objects needs to appear not to move or rotate during AutoRotation, but everything else needs to rotate and be repositioned. The way I did this is by manually rotating the object, and moving it into the same position, relative to the device, that it had prior to rotation. The problem is that it looks funny, appearing to rotate into the same position it had before.
If I suppress the animation effects during rotation, it would appear that the object never moved, and everything else just snapped into place, which is what I want. I haven't been able to find anything in the documentation that tells me how to do this though. How do I do this?
When it comes to UIViewController rotation there are two ways you can set up so you get a chance to rotate and move your own views.
In the one-step process, in your UIViewController-derived class provide an implementation of willAnimateRotationToInterfaceOrientation. It gets called and you can kick off your object rotation so while the system is rotating everything else your object is getting counter-rotated so it looks like it's staying put. You'll want to calculate how much to counter-rotate and in which direction based on current interface orientation vs. new orientation.
The other way is to get notified to do custom rotation in two steps. For example, in the first half you can shrink the object down, move it, and rotate it part way then in the second half finish the rotation as you scale back up to normal size. It's a pretty clever way to make the rotation animation look smoother to the eye.
For the two-step process, you need to define two methods. willAnimateFirstHalfOfRotationToInterfaceOrientation gets called for the first half of the rotation (i.e. up to 45 degrees for a 90 degree rotation and at 90 degrees for an upside down flip). Once past that point the second half is called via willAnimateSecondHalfOfRotationFromInterfaceOrientation.
If your object has a 1:1 aspect ratio (i.e square or round) and in the middle of the view then the one-step process will probably work fine. But if it's a non-square object and has to move position (for example if it's at position 40, 60 in portrait but moves to 20, 100 in landscape) and maybe even needs a bit of scaling to look better then you may want to try the two-step process and see if it looks smoother.
If your object is inside its own individual UIView then it's pretty easy to schedule the rotations through UIView animations. Just create a transform through CGAffineTransformMakeRotation, then inside a pair of UIView beginAnimations/commitAnimations blocks set the transform property of the view to this value. You can tweak the timing through setAnimationDuration.
EDIT: Based on the comments, I'm adding some code to show how you could attach the view to the top-level window instead of to the view controller. Your object would then reside in this view instead of the one managed by controller (which is getting rotated). You still need to over-ride the UIViewController rotate methods, but instead of rotating an object under control of the view controller you would trigger a counter-rotation in the object on the top-level.
To add a view to the top-level window:
YourAppDelegate* windowDelegate = ((YourAppDelegate*) [UIApplication sharedApplication].delegate);
[windowDelegate.window addSubview:yourView];
Keep a reference to yourView somewhere you can get to, then in the UIViewController's willAnimateRotationToInterfaceOrientation counter-rotate yourView, i.e. calculate how much to rotate the view in reverse to where you're going--if the phone is turning 90-degrees clockwise, you'll want to rotate the view back 90 degrees counter-clockwise, etc. Then use UIView animations on yourView.
If you don't want rotation animations, overload -shouldAutorotateToInterfaceOrientation: in your UIViewController and return NO. You can then observe UIDeviceOrientationDidChangeNotification to receive manual orientation change notifications.
This may work:
Listen for willRotateToInterfaceOrientation
[UIView setAnimationsEnabled:NO];
Listen for UIDeviceOrientationDidChangeNotification
[UIView setAnimationsEnabled:YES];
Untested, but I know that does work for some cases.