I'm trying to create a UIView which shows a semitransparent circle with an opaque border inside its bounds. I want to be able to change the bounds in two ways - inside a -[UIView animateWithDuration:animations:] block and in a pinch gesture recogniser action which fires several times a second. I've tried three approaches based on answers elsewhere on SO, and none are suitable.
Setting the corner radius of the view's layer in layoutSubviews gives smooth translations, but the view doesn't stay circular during animations; it seems that cornerRadius isn't animatable.
Drawing the circle in drawRect: gives a consistently circular view, but if the circle gets too big then resizing in the pinch gesture gets choppy because the device is spending too much time redrawing the circle.
Adding a CAShapeLayer and setting its path property in layoutSublayersOfLayer, which doesn't animate inside UIView animations since path isn't implicitly animatable.
Is there a way for me to create a view which is consistently circular and smoothly resizable? Is there some other type of layer I could use to take advantage of the hardware acceleration?
UPDATE
A commenter has asked me to expand on what I mean when I say that I want to change the bounds inside a -[UIView animateWithDuration:animations:] block. In my code, I have a view which contains my circle view. The circle view (the version that uses cornerRadius) overrides -[setBounds:] in order to set the corner radius:
-(void)setBounds:(CGRect)bounds
{
self.layer.cornerRadius = fminf(bounds.size.width, bounds.size.height) / 2.0;
[super setBounds:bounds];
}
The bounds of the circle view are set in -[layoutSubviews]:
-(void)layoutSubviews
{
// some other layout is performed and circleRadius and circleCenter are
// calculated based on the properties and current size of the view.
self.circleView.bounds = CGRectMake(0, 0, circleRadius*2, circleRadius*2);
self.circleView.center = circleCenter;
}
The view is sometimes resized in animations, like so:
[UIView animateWithDuration:0.33 animations:^(void) {
myView.frame = CGRectMake(x, y, w, h);
[myView setNeedsLayout];
[myView layoutIfNeeded];
}];
but during these animations, if I draw the circle view using a layer with a cornerRadius, it goes funny shapes. I can't pass the animation duration in to layoutSubviews so I need to add the right animation within -[setBounds].
As the section on Animations in the "View Programming Guide for iOS" says
Both UIKit and Core Animation provide support for animations, but the level of support provided by each technology varies. In UIKit, animations are performed using UIView objects
The full list of properties that you can animate using either the older
[UIView beginAnimations:context:];
[UIView setAnimationDuration:];
// Change properties here...
[UIView commitAnimations];
or the newer
[UIView animateWithDuration:animations:];
(that you are using) are:
frame
bounds
center
transform (CGAffineTransform, not the CATransform3D)
alpha
backgroundColor
contentStretch
What confuses people is that you can also animate the same properties on the layer inside the UIView animation block, i.e. the frame, bounds, position, opacity, backgroundColor.
The same section goes on to say:
In places where you want to perform more sophisticated animations, or animations not supported by the UIView class, you can use Core Animation and the view’s underlying layer to create the animation. Because view and layer objects are intricately linked together, changes to a view’s layer affect the view itself.
A few lines down you can read the list of Core Animation animatable properties where you see this one:
The layer’s border (including whether the layer’s corners are rounded)
There are at least two good options for achieving the effect that you are after:
Animating the corner radius
Using a CAShapeLayer and animating the path
Both of these require that you do the animations with Core Animation. You can create a CAAnimationGroup and add an array of animations to it if you need multiple animations to run as one.
Update:
Fixing things with as few code changes as possible would be done by doing the corner radius animation on the layer at the "same time" as the other animations. I put quotations marks around same time since it is not guaranteed that animations that are not in the same group will finish at exactly the same time. Depending on what other animations you are doing it might be better to use only basic animations and animations groups. If you are applying changes to many different views in the same view animation block then maybe you could look into CATransactions.
The below code animates the frame and corner radius much like you describe.
UIView *circle = [[UIView alloc] initWithFrame:CGRectMake(30, 30, 100, 100)];
[[circle layer] setCornerRadius:50];
[[circle layer] setBorderColor:[[UIColor orangeColor] CGColor]];
[[circle layer] setBorderWidth:2.0];
[[circle layer] setBackgroundColor:[[[UIColor orangeColor] colorWithAlphaComponent:0.5] CGColor]];
[[self view] addSubview:circle];
CGFloat animationDuration = 4.0; // Your duration
CGFloat animationDelay = 3.0; // Your delay (if any)
CABasicAnimation *cornerRadiusAnimation = [CABasicAnimation animationWithKeyPath:#"cornerRadius"];
[cornerRadiusAnimation setFromValue:[NSNumber numberWithFloat:50.0]]; // The current value
[cornerRadiusAnimation setToValue:[NSNumber numberWithFloat:10.0]]; // The new value
[cornerRadiusAnimation setDuration:animationDuration];
[cornerRadiusAnimation setBeginTime:CACurrentMediaTime() + animationDelay];
// If your UIView animation uses a timing funcition then your basic animation needs the same one
[cornerRadiusAnimation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];
// This will keep make the animation look as the "from" and "to" values before and after the animation
[cornerRadiusAnimation setFillMode:kCAFillModeBoth];
[[circle layer] addAnimation:cornerRadiusAnimation forKey:#"keepAsCircle"];
[[circle layer] setCornerRadius:10.0]; // Core Animation doesn't change the real value so we have to.
[UIView animateWithDuration:animationDuration
delay:animationDelay
options:UIViewAnimationOptionCurveEaseInOut
animations:^{
[[circle layer] setFrame:CGRectMake(50, 50, 20, 20)]; // Arbitrary frame ...
// You other UIView animations in here...
} completion:^(BOOL finished) {
// Maybe you have your completion in here...
}];
With many thanks to David, this is the solution I found. In the end what turned out to be the key to it was using the view's -[actionForLayer:forKey:] method, since that's used inside UIView blocks instead of whatever the layer's -[actionForKey] returns.
#implementation SGBRoundView
-(CGFloat)radiusForBounds:(CGRect)bounds
{
return fminf(bounds.size.width, bounds.size.height) / 2;
}
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
self.backgroundColor = [UIColor clearColor];
self.opaque = NO;
self.layer.backgroundColor = [[UIColor purpleColor] CGColor];
self.layer.borderColor = [[UIColor greenColor] CGColor];
self.layer.borderWidth = 3;
self.layer.cornerRadius = [self radiusForBounds:self.bounds];
}
return self;
}
-(void)setBounds:(CGRect)bounds
{
self.layer.cornerRadius = [self radiusForBounds:bounds];
[super setBounds:bounds];
}
-(id<CAAction>)actionForLayer:(CALayer *)layer forKey:(NSString *)event
{
id<CAAction> action = [super actionForLayer:layer forKey:event];
if ([event isEqualToString:#"cornerRadius"])
{
CABasicAnimation *boundsAction = (CABasicAnimation *)[self actionForLayer:layer forKey:#"bounds"];
if ([boundsAction isKindOfClass:[CABasicAnimation class]] && [boundsAction.fromValue isKindOfClass:[NSValue class]])
{
CABasicAnimation *cornerRadiusAction = [CABasicAnimation animationWithKeyPath:#"cornerRadius"];
cornerRadiusAction.delegate = boundsAction.delegate;
cornerRadiusAction.duration = boundsAction.duration;
cornerRadiusAction.fillMode = boundsAction.fillMode;
cornerRadiusAction.timingFunction = boundsAction.timingFunction;
CGRect fromBounds = [(NSValue *)boundsAction.fromValue CGRectValue];
CGFloat fromRadius = [self radiusForBounds:fromBounds];
cornerRadiusAction.fromValue = [NSNumber numberWithFloat:fromRadius];
return cornerRadiusAction;
}
}
return action;
}
#end
By using the action that the view provides for the bounds, I was able to get the right duration, fill mode and timing function, and most importantly delegate - without that, the completion block of UIView animations didn't run.
The radius animation follows that of the bounds in almost all circumstances - there are a few edge cases that I'm trying to iron out, but it's basically there. It's also worth mentioning that the pinch gestures are still sometimes jerky - I guess even the accelerated drawing is still costly.
Starting in iOS 11, UIKit animates cornerRadius if you change it inside an animation block.
The path property of a CAShapeLayer isn't implicitly animatable, but it is animatable. It should be pretty easy to create a CABasicAnimation that changes the size of the circle path. Just makes sure that the path has the same number of control points (e.g. changing the radius of a full-circle arc.) If you change the number of control points, things get really strange. "Results are undefined", according to the documentaiton.
Related
In Core Animation Programming guide, there is one paragraph about How to Animate Layer-Backed Views, it says:
If you want to use Core Animation classes to initiate animations, you must issue all of your Core Animation calls from inside a view-based animation block. The UIView class disables layer animations by default but reenables them inside animation blocks. So any changes you make outside of an animation block are not animated.
There are also an example:
[UIView animateWithDuration:1.0 animations:^{
// Change the opacity implicitly.
myView.layer.opacity = 0.0;
// Change the position explicitly.
CABasicAnimation* theAnim = [CABasicAnimation animationWithKeyPath:#"position"];
theAnim.fromValue = [NSValue valueWithCGPoint:myView.layer.position];
theAnim.toValue = [NSValue valueWithCGPoint:myNewPosition];
theAnim.duration = 3.0;
[myView.layer addAnimation:theAnim forKey:#"AnimateFrame"];
}];
In my opinion, it tells that if I don't issue Core Animation calls from inside a view-based animation block, there will no animation.
But it seems that if I add the core animation calls directly without view-based animation block, it works the same.
Have I missed something ?
tl;dr: The documentation only refers to implicit animations. Explicit animations work fine outside of animation blocks.
My paraphrasing of the documentation
The simplified version of that quote from the docs is something like (me paraphrasing it):
UIView have disabled implicit animations except for within animation blocks. If you want to do implicit layer animations you must do them inside an animation block.
What is implicit animations and how do they work?
Implicit animations is what happens when an animatable property of a standalone layer changes. For example, if you create a layer and change it's position it's going to animate to the new position. Many, many layer properties have this behaviour by default.
It happens something like this:
a transaction is started by the system (without us doing anything)
the value of a property is changed
the layer looks for the action for that property
at some point the transaction is committed (without us doing anything)
the action that was found is applied
Notice that there is no mention of animation above, instead there is the word "action". An action in this context refers to an object which implements the CAAction protocol. It's most likely going to be some CAAnimation subclass (like CABasicAnimation, CAKeyframeAnimation or CATransition) but is built to work with anything that conforms to that protocol.
How does it know what "action" to take?
Finding the action for that property happens by calling actionForKey: on the layer. The default implementation of this looks for an action in this order:
This search happens in this order (ref: actionForKey: documentation)
If the layer has a delegate and that delegate implements the Accessing the Layer’s Filters method, the layer calls that method. The delegate must do one of the following:
Return the action object for the given key.
Return nil if it does not handle the action.
Return the NSNull object if it does not handle the action and the search should be terminated.
The layer looks in the layer’s actions dictionary.
The layer looks in the style dictionary for an actions dictionary that contains the key.
The layer calls its defaultActionForKey: method to look for any class-defined actions.
The layer looks for any implicit actions defined by Core Animation.
What is UIView doing?
In the case of layers that are backing views, the view can enable or disable the actions by implementing the delegate method actionForLayer:forKey. For normal cases (outside an animation block) the view disables the implicit animations by returning [NSNull null] which means:
it does not handle the action and the search should be terminated.
However, inside the animation block, the view returns a real action. This can easily be verified by manually invoking actionForLayer:forKey: inside and outside the animation block. It could also have returned nil which would cause the layer to keep looking for an action, eventually ending up with the implicit actions (if any) if it wouldn't find anything before that.
When an action is found and the transaction is committed the action is added to the layer using the regular addAnimation:forKey: mechanism. This can easily be verified by creating a custom layer subclass and logging inside -actionForKey: and -addAnimation:forKey: and then a custom view subclass where you override +layerClass and return the custom layer class. You will see that the stand alone layer instance logs both methods for a regular property change but the backing layer does not add the animation, except when within a animation block.
Why this long explanation of implicit animations?
Now, why did I give this very long explanation of how implicit animations work? Well, it's to show that they use the same methods that you use yourself with explicit animations. Knowing how they work, we can understand what it means when the documentation say: "The UIView class disables layer animations by default but reenables them inside animation blocks".
The reason why explicit animations aren't disabled by what UIView does, is that you are doing all the work yourself: changing the property value, then calling addAnimation:forKey:.
The results in code:
Outside of animation block:
myView.backgroundColor = [UIColor redColor]; // will not animate :(
myLayer.backGroundColor = [[UIColor redColor] CGColor]; // animates :)
myView.layer.backGroundColor = [[UIColor redColor] CGColor]; // will not animate :(
[myView.layer addAnimation:myAnimation forKey:#"myKey"]; // animates :)
Inside of animation block:
myView.backgroundColor = [UIColor redColor]; // animates :)
myLayer.backGroundColor = [[UIColor redColor] CGColor]; // animates :)
myView.layer.backGroundColor = [[UIColor redColor] CGColor]; // animates :)
[myView.layer addAnimation:myAnimation forKey:#"myKey"]; // animates :)
You can see above that explicit animations and implicit animations on standalone layers animate both outside and inside of animation blocks but implicit animations of layer-backed views does only animate inside the animation block.
I will explain it with a simple demonstration (example).
Add below code in your view controller.(don't forget to import QuartzCore)
#implementation ViewController{
UIView *view;
CALayer *layer;
}
- (void)viewDidLoad
{
[super viewDidLoad];
view =[[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
[self.view addSubview:view];
view.backgroundColor =[UIColor greenColor];
layer = [CALayer layer];
layer.frame =CGRectMake(0, 0, 50, 50);
layer.backgroundColor =[UIColor redColor].CGColor;
[view.layer addSublayer:layer];
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
layer.frame =CGRectMake(70, 70, 50, 50);
}
See that in toucesBegan method there is no UIVIew animate block.
When you run the application and click on the screen, the opacity of the layer animates.This is because by default these are animatable.By default all the properties of a layer are animatable.
Consider now the case of layer backed views.
Change the code to below
- (void)viewDidLoad
{
[super viewDidLoad];
view =[[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
[self.view addSubview:view];
view.backgroundColor =[UIColor greenColor];
// layer = [CALayer layer];
// layer.frame =CGRectMake(0, 0, 50, 50);
// layer.backgroundColor =[UIColor redColor].CGColor;
// [view.layer addSublayer:layer];
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
view.layer.opacity =0.0;
// layer.frame =CGRectMake(70, 70, 50, 50);
}
You might think that this will also animate its view.But it wont happen.Because layer backed views by default are not animatable.
To make those animations happen, you have to explicitly embed the code in UIView animate block.As shown below,
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
[UIView animateWithDuration:2.0 animations:^{
view.layer.opacity =0.0;
}];
// layer.frame =CGRectMake(70, 70, 50, 50);
}
That explains that,
The UIView class (which obviously was layer backed) disables layer animations by default but reenables them inside animation blocks.So any changes you make outside of an animation block are not animated.
Well, I've never used explicit Core Animation inside a view animation block. The documentation it seems to be not clear at all.
Probably the meaning is something like that, it's just a guess:
If you want to animate properties of the view that are linked to the
backed layer you should wrap them into a view animation block. In the
view's layer if you try to change the layer opacity this is not
animated, but if wrap into a view animation block it is.
In your snippet you are directly creating a basic animation thus explicitly creating an animation. Probably the doc just want to point out the differences between views and layers. In the latter animations on most properties are implicit.
You can see the difference if you write something like that:
[UIView animateWithDuration:1.0 animations:^{
// Change the opacity implicitly.
myView.layer.opacity = 0.0;
}];
This will be animated.
myView.layer.opacity = 0.0;
This will not be animated.
// Change the position explicitly.
CABasicAnimation* theAnim = [CABasicAnimation animationWithKeyPath:#"position"];
theAnim.fromValue = [NSValue valueWithCGPoint:myView.layer.position];
theAnim.toValue = [NSValue valueWithCGPoint:myNewPosition];
theAnim.duration = 3.0;
[myView.layer addAnimation:theAnim forKey:#"AnimateFrame"];
This will be animated.
I'm working on a document viewer. The document is displayed inside a UIScrollView so that it can be scrolled and zoomed. I need to draw a border around the document in order to separate it visually from the background of the UIScrollView. The border must not be zoomed together with the document -- it should maintain a constant thickness regardless of the zoom scale.
My current setup consists of a UIScrollView with two UIView children -- one for the document, and one for the border. I've overriden viewForZoomingInScrollView: to return the document view. I've also overridden layoutSubviews to center the document view (in case it's smaller than the UIScrollView) and then resize and position the border view behind it so that it looks like a frame. This works OK when the user is scrolling and zooming manually. But when I use zoomToRect:animated: to zoom programatically, layoutSubviews is called before the animation starts and my border view gets resized immediately with the document view catching up a bit later.
Clarification: The border needs to be tightly fitting around the document view and not around the UIScrollView itself.
Sample Code :
yourScrollView.layer.cornerRadius=8.0f;
yourScrollView.layer.masksToBounds=YES;
yourScrollView.layer.borderColor=[[UIColor redColor]CGColor];
yourScrollView.layer.borderWidth= 1.0f;
Don't Forget : #Import <QuartzCore/QuartzCore.h>
First you need to Import QuartzCore framework to your App.
then import that .h file on which class where you want to set the border.
like this.
#import <QuartzCore/QuartzCore.h>
Setup for Border.
ScrollView.layer.cornerRadius=5.0f;
ScrollView.layer.masksToBounds=YES;
ScrollView.layer.borderColor=[[UIColor redColor]CGColor];
ScrollView.layer.borderWidth= 4.0f;
check this one really helpful to you.
Finally, I was able to fix the problem with animated zooming. My setup is the same as described in the question. I just added some code to my layoutSubview implementation in order to detect any running UIScrollView animation and match it with a similar animation for resizing the border.
Here is the code:
- (void)layoutSubviews
{
[super layoutSubviews];
// _pageView displays the document
// _borderView represents the border around it
. . .
// _pageView is now centered -- we have to move/resize _borderView
// layers backing a view are not implicitly animated
// the following two lines work just fine if we don't need animation
_borderView.layer.bounds = CGRectMake(0.0, 0.0, frameToCenter.size.width + 2.0 * 15.0, frameToCenter.size.height + 2.0 * 15.0);
_borderView.layer.position = _pageView.center;
if (_pageView.layer.animationKeys.count > 0)
{
// UIScrollView is animating its content (_pageView)
// so we need to setup a matching animation for _borderView
[CATransaction begin];
CAAnimation *animation = [_pageView.layer animationForKey:[_pageView.layer.animationKeys lastObject]];
CFTimeInterval beginTime = animation.beginTime;
CFTimeInterval duration = animation.duration;
if (beginTime != 0.0) // 0.0 means the animation starts now
{
CFTimeInterval currentTime = [_pageView.layer convertTime:CACurrentMediaTime() fromLayer:nil];
duration = MAX(beginTime + duration - currentTime, 0.0);
}
[CATransaction setAnimationDuration:duration];
[CATransaction setAnimationTimingFunction:animation.timingFunction];
// calculate the initial state for _borderView animation from _pageView presentation layer
CGPoint presentationPos = [_pageView.layer.presentationLayer position];
CGRect presentationBounds = [_pageView.layer.presentationLayer frame];
presentationBounds.origin = CGPointZero;
presentationBounds.size.width += 2.0 * 15.0;
presentationBounds.size.height += 2.0 * 15.0;
CABasicAnimation *boundsAnim = [CABasicAnimation animationWithKeyPath:#"bounds"];
boundsAnim.fromValue = [NSValue valueWithCGRect:presentationBounds];
boundsAnim.toValue = [NSValue valueWithCGRect:_borderView.layer.bounds];
[_borderView.layer addAnimation:boundsAnim forKey:#"bounds"];
CABasicAnimation *posAnim = [CABasicAnimation animationWithKeyPath:#"position"];
posAnim.fromValue = [NSValue valueWithCGPoint:presentationPos];
posAnim.toValue = [NSValue valueWithCGPoint:_borderView.layer.position];
[_borderView.layer addAnimation:posAnim forKey:#"position"];
[CATransaction commit];
}
}
It looks hacky but it works. I wish I didn't have to reverse engineer UIScrollView in order to make a simple border look good during animation...
Import QuartzCore framework:
#import <QuartzCore/QuartzCore.h>
Now Add color to its view:
[scrollViewObj.layer setBorderColor:[[UIColor redColor] CGColor]];
[scrollViewObj.layer setBorderWidth:2.0f];
I'm trying to animate a custom UIView's bounds while also keeping its layer the same size as its parent view. To do that, I'm trying to animate the layers bounds alongside its parent view. I need the layer to call drawLayer:withContext AS its animating so my custom drawing will change size correctly along with the bounds.
drawLayer is called correctly and draws correctly before I start the animation. But I can't get the layer to call its drawLayer method on EACH step of the bounds animation. Instead, it just calls it ONCE, jumping immediately to the "end bounds" at the final frame of the animation.
// self.bg is a property pointing to my custom UIView
self.bg.layer.needsDisplayOnBoundsChange = YES;
self.bg.layer.mask.needsDisplayOnBoundsChange = YES;
[UIView animateWithDuration:2 delay:0 options:UIViewAnimationOptionCurveEaseOut|UIViewAnimationOptionAutoreverse|UIViewAnimationOptionRepeat animations:^{
[CATransaction begin];
self.bg.layer.bounds = bounds;
self.bg.layer.mask.bounds = bounds;
[CATransaction commit];
self.bg.bounds = bounds;
} completion:nil];
Why doesn't the bounds report a change AS its animating (not just the final frame)? What am I doing wrong?
This might or might not help...
Many people are unaware that Core Animation has a supercool feature that allows you to define your own layer properties in such a way that they can be animated. An example I use is to give a CALayer subclass a thickness property. When I animate it with Core Animation...
CABasicAnimation* ba = [CABasicAnimation animationWithKeyPath:#"thickness"];
ba.toValue = #10.0f;
ba.autoreverses = YES;
[lay addAnimation:ba forKey:nil];
...the effect is that drawInContext: or drawLayer:... is called repeatedly throughout the animation, allowing me to change repeatedly the way the layer is drawn in accordance with its current thickness property value at each moment (an intermediate value in the course of the animation).
It seems to me that that might be the sort of thing you're after. If so, you can find a working downloadable example here:
https://github.com/mattneub/Programming-iOS-Book-Examples/tree/master/ch17p498customAnimatableProperty
Discussion (from my book) here:
http://www.apeth.com/iOSBook/ch17.html#_making_a_property_animatable
This is because the layer you are drawing to is not the same layer as the one displayed on the screen.
When you animate a layer property it will immediately be set to its final value in the model layer, (as you have noticed), and the actual animation is done in the presentation layer.
You can access the presentation layer and see the actual values of the animated properties:
CALayer *presentationLayer = (CALayer *)[self.bg.layer presentationLayer];
...
Since you haven't provided your drawLayer:withContext method, it's unclear what you want to draw during the animation, but if you want to animate custom properties, here is a good tutorial for doing that.
Firstly, the layer of a layer backed (or hosting) view is always resized to fit the bounds of its parent view. If you set the view to be the layers delegate then the view will receive drawLayer:inContext: at each frame. Of course you must ensure that If your layer has needsDisplayOnBoundsChange == YES.
Here is an example (on the Mac) of resizing a window, which then changes the path of the underlying layer.
// My Nib contains one view and one button.
// The view has a MPView class and the button action is resizeWindow:
#interface MPView() {
CAShapeLayer *_hostLayer;
CALayer *_outerLayer;
CAShapeLayer *_innerLayer;
}
#end
#implementation MPView
- (void)awakeFromNib
{
[CATransaction begin];
[CATransaction setDisableActions:YES];
_hostLayer = [CAShapeLayer layer];
_hostLayer.backgroundColor = [NSColor blackColor].CGColor;
_hostLayer.borderColor = [NSColor redColor].CGColor;
_hostLayer.borderWidth = 2;
_hostLayer.needsDisplayOnBoundsChange = YES;
_hostLayer.delegate = self;
_hostLayer.lineWidth = 4;
_hostLayer.strokeColor = [NSColor greenColor].CGColor;
_hostLayer.needsDisplayOnBoundsChange = YES;
self.layer = _hostLayer;
self.wantsLayer = YES;
[CATransaction commit];
[self.window setFrame:CGRectMake(100, 100, 200, 200) display:YES animate:NO];
}
- (void) drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx
{
if (layer == _hostLayer) {
CGSize size = layer.bounds.size;
CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, 0, 0);
CGPathAddLineToPoint(path, NULL, size.width, size.height);
_hostLayer.path = path;
CGPathRelease(path);
}
}
- (IBAction)resizeWindow:(id)sender
{
[self.window setFrame:CGRectMake(100, 100, 1200, 800) display:YES animate:YES];
}
#end
I've got a problem with adding shadow to my UIView which is created in iOS 6 application with Autolayout.
Let's assume I have a method that adds a shadow on the bottom of UIView (this is actually a Category of UIView, so it's reusable):
- (void) addShadowOnBottom {
self.layer.shadowOffset = CGSizeMake(0, 2);
self.layer.shadowOpacity = 0.7;
self.layer.shadowColor = [[UIColor blackColor] CGColor];
self.layer.shadowPath = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;
}
When I call this method in viewDidLoad of some UIViewController, shadow is not added, probably due to all constraints, that have to be calculated.
When I call this method in viewWillAppear the same situation.
When I call this method in viewDidAppear it works, but when new view shows up there is a short moment when there is no shadow and it appears after a while.
If I resign from setting the shadowPath and remove line self.layer.shadowPath everything works, but view transitions are not smooth.
So my question is what is the right way to add a shadow to view in iOS 6 with Autolayout turned on ?
Another thing you can add to the layer when working with AutoLayout and you need a shadow on a UIView where the frame is not yet known is this :
self.layer.rasterizationScale = [[UIScreen mainScreen] scale]; // to define retina or not
self.layer.shouldRasterize = YES;
Then remove the shadowPath property because the auto layout constraints are not yet processed, so it's irrelevant. Also at the time of execution you will not know the bounds or the frame of the view.
This improves performance a lot!
i removed self.layer.shadowPath = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;
from your code and it is working for me in viewDidLoad, please confirm.
Increasing shdowOffset will make you see the shadow more clear.
Having the exact same issue...
Although I am unable to get the CALayer shadow on a view to animate nicely, at least the shadow does re-align properly after animation.
My solution (which works fine in my application) is the set the shadowOpacity to 0, then reset it to the desired value AFTER the animation has completed. From a user's perspective, you cannot even tell the shadow is gone because the animations are typically too fast to perceive the difference.
Here is an example of some code in my application, in which I am changing the constant value of a constraint, which is 'trailing edge to superview' NSLayoutContraint:
- (void) expandRightEdge
{
[self.mainNavRightEdge setConstant:newEdgeConstant];
[self updateCenterContainerShadow];
[UIView animateWithDuration:ANIMATION_DURATION delay:0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
[[NSNotificationCenter defaultCenter] postNotificationName:#"PanelLayoutChanged" object:nil];
[self.view layoutIfNeeded];
} completion:^(BOOL finished) {
nil;
}];
}
- (void) updateCenterContainerShadow
{
self.centerContainer.layer.masksToBounds = NO;
self.centerContainer.layer.shadowOpacity = 0.8f;
self.centerContainer.layer.shadowRadius = 5.0f;
self.centerContainer.layer.shadowOffset = CGSizeMake(0, 0);
self.centerContainer.layer.shadowColor = [UIColor blackColor].CGColor;
CGPathRef shadowPath = [UIBezierPath bezierPathWithRect:self.centerContainer.layer.bounds].CGPath;
[self.centerContainer.layer setShadowPath:shadowPath];
// Schedule a time to fade the shadow back in until we can figure out the CALayer + Auto-Layout issue
[self performSelector:#selector(fadeInShadow) withObject:nil afterDelay:ANIMATION_DURATION+.05];
}
- (void) fadeInShadow
{
[self.centerContainer.layer setShadowOpacity:0.8f];
}
Two things:
I could have put the fadeInShadow in the completion block, but due to the way some of my other code is factored, this works better for me.
I realize I am not performing a fade in with "fadeInShadow", but given how quickly it renderes after the completion of the animation, I found it is not necessary.
Hope that helps!
I actually stuck on a problem with animating a UILabel in my iOS Application.
After 2 days of searching the web for code snippets, still no result.
Every sample I found was about how to animate UIImage, adding it as a subview to UIView by layer. Is there any good example about animating a UILabel?
I found a nice solution for a blinking animation by setting the alpha property, like this:
My function:
- (void)blinkAnimation:(NSString *)animationID finished:(BOOL)finished target:(UIView *)target
{
NSString *selectedSpeed = [[NSUserDefaults standardUserDefaults] stringForKey:#"EffectSpeed"];
float speedFloat = (1.00 - [selectedSpeed floatValue]);
[UIView beginAnimations:animationID context:target];
[UIView setAnimationDuration:speedFloat];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:#selector(blinkAnimation:finished:target:)];
if([target alpha] == 1.0f)
[target setAlpha:0.0f];
else
[target setAlpha:1.0f];
[UIView commitAnimations];
}
Call my function on the UILabel:
[self blinkAnimation:#"blinkAnimation" finished:YES target:labelView];
But how about a Pulse, or scaling animation?
Unfortunately font size is not an animatable property of NSView. In order to scale a UILabel, you'll need to use more advanced Core Animation techniques, using CAKeyframeAnimation:
Import the QuartzCore.framework into your project, and #import <QuartzCore/QuartzCore.h> in your code.
Create a new CAKeyframeAnimation object that you can add your key frames to.
Create a CATransform3D value defining the scaling operation (don't get confused by the 3D part--you use this object to do any transformations on a layer).
Make the transformation one of the keyframes in the animation by adding it to the CAKeyframeAnimation object using its setValues method.
Set a duration for the animation by calling its setDuration method
Finally, add the animation to the label's layer using [[yourLabelObject layer] addAnimation:yourCAKeyframeAnimationObject forKey:#"anyArbitraryString"]
The final code could look something like this:
// Create the keyframe animation object
CAKeyframeAnimation *scaleAnimation =
[CAKeyframeAnimation animationWithKeyPath:#"transform"];
// Set the animation's delegate to self so that we can add callbacks if we want
scaleAnimation.delegate = self;
// Create the transform; we'll scale x and y by 1.5, leaving z alone
// since this is a 2D animation.
CATransform3D transform = CATransform3DMakeScale(1.5, 1.5, 1); // Scale in x and y
// Add the keyframes. Note we have to start and end with CATransformIdentity,
// so that the label starts from and returns to its non-transformed state.
[scaleAnimation setValues:[NSArray arrayWithObjects:
[NSValue valueWithCATransform3D:CATransform3DIdentity],
[NSValue valueWithCATransform3D:transform],
[NSValue valueWithCATransform3D:CATransform3DIdentity],
nil]];
// set the duration of the animation
[scaleAnimation setDuration: .5];
// animate your label layer = rock and roll!
[[self.label layer] addAnimation:scaleAnimation forKey:#"scaleText"];
I'll leave the repeating "pulse" animation as an exercise for you: hint, it involves the animationDidStop method!
One other note--the full list of CALayer animatable properties (of which "transform" is one) can be found here. Happy tweening!