I would like to animate a radial gradient to shrink and grow the inner radius, as if it were pulsing.
Right now I'm rendering the gradient with CGGradient, but I'm not sure how to animate it. I've seen this topic
Can you animate gradients using Quartz in an iPhone?
Which explains how animate a linear gradient with CAGradientLayer, but it doesn't seem like this will draw a radial gradient.
Is there an easy way to animate a CGGradient, or some way to create a radial gradient CAGradientLayer?
Any thoughts are appreciated.
If only Core Image was on the phone, this would be trivial. An animatable filter is what you need. ;-)
The CAGradientLayer does allow for animating its properties, however, it currently only supports linear gradients.
The only thing I can think of if you're wanting to animate using Core Animation is to animate the transform of the view into which you're drawing your gradient.
You can animate any view's transform pretty simply. Just draw your gradient in the view as you're probably already doing and then animate the transform using scaling. Using explicit animation, it would be something like:
CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:#"transform"];
[anim setFromValue:[NSValue valueWithCATransform3D:CATransform3DIdentity]];
// Scale x and y up
[anim setToValue:[NSValue valueWithCATransform3D:
CATransform3DMakeScale (1.0f, 1.0f,0.0f)]];
[anim setAutoreverses:YES];
[anim setRepeatCount:HUGE_VALF];
[[gradientView layer] addAnimation:anim];
Unfortunately this would look like expanding and contracting more than pulsing, I think (though I haven't tried it).
I think if you want a true pulsing with your gradient at this point, you probably have to do the animation manually using your own timer. Just re-draw periodically changing your inner radius value as you go. Ugh. I'm not absolutely sure that's the only way, but I have yet to see a compelling pulse animation on the phone with a gradient as you're wanting.
There is one other idea I would like to try at some point. Core Animation now allows animating arbitrary properties/values. You could theoretically set up an animation using some arbitrary keypath that you name (say innerRadius, for example) and override the -drawLayerInContext delegate method. Then you could grab the current value from the presentationLayer while it's in mid-flight and re-draw your gradient there instead. This is just theoretical as I haven't tried it, but it seems like it might be worth looking into.
Best regards.
Related
hi all upto now i know making rectangle with the CGrectmake and this rect(frame) i am using as imageview frame like UIImageView *someImage=[[uiimageview alloc]initwithframe:someRect]; now i can add an image with the frame of someRect. my problem here is when the coordinates like
(rectangleFirstx-coordinate,tectangleFirstY-cordinate)=(10,10)
(rectangleLastx-cordinate,rectangleLasty-cordinate)=(17,7) this, how can i give frame to the uiimageview....This is like a inclined rectangle..can any one suggest me how to apply frame through the ios library for these type of coordinates..Thanks in advance..
Your example isn't very clear because a rectangle with opposite corners at (10,10) and (10,7) can be in any one of a myriad of different orientations, including one perfectly aligned along the x and y axis.
What you can certainly do is create a UIImageView of the desired size and location and then rotate it by using one of many techniques, including animation methods.
[UIImageView animateWithDuration:0.1 animations:^
{
your_UIImageView_here.transform = CGAffineTransformMakeRotation((M_PI/180.0) * degrees);
}];
You can hide the UIImageView until the rotation is done and then show it.
If your question is about how to use the coordinates you provided to arrive at an angle I'd suggest that more data is needed because it is impossible to pick one of the billions of possible rectangles with corners at those two points without more information. Once you have more data then it is pretty basic trigonometry to figure out the angle to feed into the rotation.
For an animation effect perfectly suited to an animation group approach as shown in Brad Larson's answer here, I need the animation to proceed according to inputs. Specifically touch and position of detected touches. It is easy to handle touchesMoved: and to set the position of the elements for every touch but it just isn't smooth like the core animation approach.
Imagine a marble in a grooved track. I want to push the marble along to any position at any speed in one direction or the other. The animation has to do something like that, moving a visual element along a path in response to touches. CAKeyframeAnimation has the path bit exactly but seems to always want to base the transition from frame to frame on time elapsed, not on any other factor, and in one direction.
31 January update - Thanks all for the responses so far however none is really solving the problem. I have a circular menu that is dragged to select an option. All of it needs to move together and I have worked around it by using an view that has a rotational transform applied and the inverse rotational transform applied to its subviews so the icons all rotate with appropriate ferris wheel orientation. It really looks better when the icons are animated along a slightly ovoid path though... the marble description is an attempt to make clear what I'm trying to do. Better perhaps to imagine magnets oriented to repel all travelling in a groove - move one and its neighbours move too but not necessarily in the direction that the dragged magnet moves as the path curves.
Right now the problem is one of following a simple path created with one circle but I'd really like to know how to animate objects along an arbitrary path, position controlled purely by touch with no calculations involving velocity or direction.
You may be able to use the hierarchical nature of timelines in layer trees to achieve what you’re looking for. Objects implementing CAMediaTiming, which include both CAAnimation and CALayer, inherit a timespace from their parent, which they can modify (via scaling, shifting and repeating) and propagate to their children. By setting the speed property of a layer to 0.0 and adjusting the timeOffset property manually, you can decouple that layer (and all of its sublayers) from the usual notion of time.
What you’d do in your case is define the animations for all your menu items to animate their position along your desired CGPath from time t0 to t1, with the appropriate timeOffset on each animation to keep your items appropriately spaced. Note that a beginTime of 0.0 on an animation is usually interpreted as starting from the time the animation was added to its layer, so if you want t0 to be 0.0, you'll probably have to set it to a tiny epsilon > 0.0.
CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:#"position"];
animation.beginTime = 1e-100;
animation.duration = 1.0;
animation.fillMode = kCAFillModeBoth;
animation.removedOnCompletion = NO;
animation.path = path;
animation.calculationMode = kCAAnimationPaced;
animation.timeOffset = timeOffset;
You’d then set the speed property to 0.0 on a parent layer (containing only these menu items) and update its timeOffset to values between t0 and t1 in response to your touch events.
This approach has two potential caveats. Because you’ve taken over the nature of time on this layer subtree, you probably won’t be able to animate other properties at the same time. Additionally, if you want coasting behavior for a fast flick, you’ll probably need to animate time forward on your own.
If you are targeting iOS 4.0 or greater then you can use the new block based class methods to start animatable changes to view objects. So from your touch event you can initiate an animatable change to properties on the view:
[UIView animateWithDuration:1.0 animations:^{
yourView.alpha = 0.0; // fade out yourView over 1 second
}];
N.B. This could just as easily be a change to another property on the view, like its location. You can animate the following properties on the view this way:
#property frame
#property bounds
#property center
#property transform
#property alpha
#property backgroundColor
#property contentStretch
If you are targetting earlier versions of iOS you will need to use UIView beginAnimations and commitAnimations methods to create an animation block:
[UIView beginAnimations:nil context:context];
[UIView setAnimationDuration:1.0];
yourView.alpha = 0.0;
[UIView commitAnimations];
This stuff works really well and once you start using it, you will have to be careful you don't get addicted. ;)
Update for comment:
You can bind the position of the marble to the location of the touch event. Once you get the touchesEnded event you can then animate the location of the marble using an animation block.
velocity = distance/time. You can try by giving delay according to touches moved and time. You can calculate time between touchesBegan and touchesEnded methods.
I'm not entirely certain I understand exactly what you want to do but... Why not just draw the marble wherever the user's finger is? No animation required.
If you want to keep the marble moving after the user lets go, you need to maintain a concept of momentum and use that to animate the marble slowing down. You could use either CoreAnimation for that or a timer.
I would make a velocity calculation in touches moved, and add it to a local variable that a block can mutate via a timer.
in other words, in touches moved make a velocity calculation bearing in mind the direction of a previous velocity. In touches ended, fire a block that translates the 'marble' decaying the velocity as you disire. If the user moves the marble again, modify the local variable, this will in turn speed up the animation of the marble or slow it down/change direction depending on on the direction of the touch.
In an application showing chunks of text, I'm having the font size increase when the device is turned to a landscape orientation. I don't like how it does the whole animation and then suddenly jumps to the new size, so I'd like to animate the size change over the course of the rotation.
I read somewhere that throwing this change in a UIView animation block doesn't work because the font property is not animatable, so what are my options for doing this?
For my specific implementation I'm not simply scaling the UILabel/UITextView as-is; The bounds of the box is increasing more (proportionally) than the font-size, so there will be re-flow in the text. That's fine by me.
Edit: I would be fine with simply scaling the UITextView.
Also, I was considering "animating" it manually: I have a method that lays out my views and adjusts for font size. If I knew when the rotation was about to start, and the duration of the animation, I could time it so it renders an intermediate font size or two in the middle of the animation. Any help with getting those would be appreciated.
One option is to fade the old text out, change the font size, and fade it back in. The font property may not be animatable, but alpha is. Since alpha is a property of UIView, you can treat all your text-bearing views the same way: UILabel, UITextView, etc. It looks good, too.
If I knew when the rotation was about
to start, and the duration of the
animation...
Funny you should mention that. Just before the animation starts, your view controller will receive a willAnimateRotationToInterfaceOrientation:duration: message that gives you the exact information you need.
A way to proceed could be to:
Create a CAKeyframeAnimation
Define the scaling and rotation you want to achieve during that animation using a set of CATransform3D objects
Add these transforms to your keyframed animation
Send the addAnimation message to your label layer object: [[label layer] addAnimation];
Here would be a code sample assuming yourLabel is the UILabel you want to scale and rotate:
CAKeyframeAnimation *scale = [CAKeyframeAnimation animationWithKeyPath:#"transform"];
CATransform3D scaleUp = CATransform3DMakeScale(1.5, 1.5, 1); // Scale in x and y
CATransform3D rotationScaled = CATransform3DRotate (scaleUp, 90, 0, 0, 1); // Rotate the scaled font
[scale setValues:[NSArray arrayWithObjects:
[NSValue valueWithCATransform3D:CATransform3DIdentity],
[NSValue valueWithCATransform3D:rotationScaled],
nil]];
// set the duration
[scale setDuration: 1.0];
// animate your label layer
[[yourLabel layer] addAnimation:scale forKey:#"scaleText"];
This is typically how a text bouncing around would be animated for instance.
You could start this when the device starts rotating and retrieve the animation when it's done rotating so you can update your label with the proper scale/position.
You will need tuning to find the proper timing and rotation.
Change the font size when didAnimateFirstHalfOfRotationToInterfaceOrientation: is called.
That way the user won't see the change once the rotation completed. It would be pretty hard to see the font size change then, as the rotation is happening!
I have 5 buttons on a UIView that I would like to plot evenly along a circular path, and have them rotate continuously along that path. To be clear, I don't want to rotate the buttons themselves, I just want them to move along the circular path.
What is the best way to manage this?
Create a UIBezierPath or CGPath for each button, adjusting the starting angle and ending angle to account for the initial starting points of each. Then for each button/path create a CAKeyframeAnimation, give it the path, set it to autorepeat and add it to the appropriate button's layer.
The UIBezierPath method +bezierPathWithArcCenter:radius:startAngle:endAngle:clockwise: will help you create the circular paths. You'll need to calculate the correct angles, but that's just a small bit of math.
There's no reason to animate each button individually along a path. You said that you have 5 buttons on a UIView. Just rotate this view you've added them to and all other buttons will rotate providing the same effect as what you're asking for with a path.
The trick is you will need an explicit animation rather than the UIView animation shortcuts:
CABasicAnimation* rotationAnimation =
[CABasicAnimation animationWithKeyPath:#"transform.rotation.z"];
[rotationAnimation setToValue:[NSNumber numberWithFloat:DegreesToRadians(360)]];
// Make a full rotation in five seconds
[rotationAnimation setDuration:5.0];
// Repeat forever.
[rotationAnimation setRepeatCount:HUGE_VALF];
// Make the animation timing linear
[rotationAnimation setTimingFunction:
[CAMediaTimingFunction
functionWithName:kCAMediaTimingFunctionLinear]];
[[rotationView layer] addAnimation:rotationAnimation forKey:nil];
The variable rotationView is the view that contains all of the buttons. At this point all you really need to do is calculate where your buttons should be positioned initially. Everything else is handled for you.
Horizontal gradient is working fine. Is there any way to get a vertical color gradient from horizontal gradient?
I have seen a related question regarding this where they did this by rotating the frames.
Is there any simpler way to achieve a vertical gradient?
The default startPoint and endPoint would have the gradient display your colors from top to bottom (which in my mind is a vertical gradient). If you want the gradient to display from left to right (again in my mind this is a horizontal gradient), use this code on your CAGradientLayer:
[gradientLayer setStartPoint:CGPointMake(0.0, 0.5)];
[gradientLayer setEndPoint:CGPointMake(1.0, 0.5)];
A 3D transform is unnecessary.
How about rotating it 90º?
edit judging from your comment, it seems that you're doing this via CAGradientLayer. CAGradientLayer is a subclass of CALayer, which has a transform property. This transform property takes a CATransform3D, which is a struct that represents some sort of linear transformation to be applied to the layer (such as scaling, translation, or rotation).
So really you just need to make a rotational CATransform3D and set it as the transform property of your CAGradientLayer.
You could probably also make this work by fiddling with the startPoint and endPoint (which would actually probably be simpler).