So I am working on implementing a custom view on iOS which will animate with momentum. This is something like the "wheel of fortune" wheel, where the user can flick it, and it will spin around with momentum, and eventually slow down and snap into place.
So I would like to have something like a "tick" function to update the view every frame (pseudocode):
// Function called on each animation frame
func tickAnimation(deltaTime: TimeInterval) {
myView.rotateBy(deltaTime)
...
}
So the naiive way to do this would be to just have a timer:
let timer = Timer.scheduledTimer(withTimeInterval: 1.0/60, repeats: true) { timer in
tickAnimation(deltaTime: 1.0/60)
}
But is there a better way to do this, where I can hook directly into the iOS animation system and synchronize my updates with the screen refresh directly?
I.e. is there something similar to Window.requestAnimationFrame() which you have on web?
I found something exactly you want but there is no short answer for your question hence I drop a wheel of fortune link.
If you want something shorter than you should look for UIview.animate()
you can set time of duration, delay and animation style such as curveEaseIn, curveEaseOut etc. It could be helpful for your question.
Related
I have a problem with animation as I want the same animation with different end points, to be called upon finishing the previous animation and to be executed smoothly without slight stop.
Let me elaborate with a sample code and comments.
Func animate()
{
Start animation(completionHandler: {
If condition is true
Repeat the animation and check after it finishes
}
}
but the problem with this code is that, between finishing the first animation and starting another one, there will be a split second stop which is not smooth movement. For example, I have a view on zero point to move with animation to point A (x:100,y:100), and then it will receive point B (x:500, y:900), after it reaches point A it will stop a split second then move to point B. Since the points are Dynamic, I cannot know if there is a new point or not, and if I did i will not know the coordinates beforehand, so I need to keep the logic dynamic and keeps the animation smooth between points.
I tried many logics and results were not the thing I wanted. problems I faced toward a smooth queued animation are:
I tried UIView.animate in the following:
a. I tried setting an animation duration let's say 2 sec, then after it finishes, it calls animation again within completion hander/closure/block, but it will result in a less than second stop between the two animations.
b. I tried to start 2 animations, the second is delayed with the exact duration go the first animation, but results also brief stop between 2 animations.
2.I tried animation with keyframes, but since I don't know all animations in advance, this won't work.
Can you help please with my approach toward a smooth dynamic animation?
Your own pseudocode answers your question. Just test whatever your condition, and if you need to animate again, work out the new start and end points and animate again:
func animate(start:Int, end:Int) {
UIView.animate(withDuration: 5, animations: {
// animate here based on new start and end
}, completion: { _ in
var weShouldDoItAgain = false
// figure out if we should do it again
// if so, change weShouldDoItAgain to true
if weShouldDoItAgain {
var start = start // and now change it to new value
var end = end // and now change it to new value
self.animate(start:start, end:end)
}
})
}
Just change all the values and types to suit your use case.
I want to make a view/header collaspe/expand animation, but I also want to be able to pause or stop from expanding/collapsing while the user takes his finger off the screen.
I have a current implementation for this, but the animation is not very smooth.
I will also add some images to explain better what I want to do.
So the first image is how it should look when expanded.
The second image is how it should look if the user decides to take take his finger off the screen while he would scroll slowly so the animation/the view should stop in a state similar to that.
The third image is how it should look when it is collapsed.
If someone has any recommendation how I could achieve this I would be very grateful.
If you are targeting iOS 10+, use UIViewPropertyAnimator which encapsulates an animation and allows scrubbing and controlling the animation:
Start, pause, resume, and stop animations; see the methods of the UIViewAnimating protocol.
Add animation blocks after the original animations start using the addAnimations(_:) and addAnimations(_:delayFactor:) methods.
Scrub through a paused animation by modifying the fractionComplete property.
Change the animation’s direction using the isReversed property.
Modify the timing and duration of a partially complete animation by pausing the animation and using the continueAnimation(withTimingParameters:durationFactor:) method to finish it.
You just need to wire up touches to UIViewPropertyAnimator object encapsulating the animation.
There are many good tutorials on how to start with it, e.g. this one.
Is there a way to observe the "time progress" of UIView.animateWithDuration...family of methods from UIView /alternatively CA animations?
I am animating a view's frame and I need to be informed how it is progressing.
My line of thinking was I can either
1) tap into CAAnimation related stuff or
2) observe the animated properties (like frame) and do my own calculations each screen frame.
Approach 1) turns out to be a dead end, inspecting the internal of how CAAnimations work told me absolutely nothing...and 2) is flawed as the "model layer tree is updated immediately and tapping into the presentation tree is difficult as the presentation layer is nil when you start.
I am pretty desperate, I was thinking that hooking into CADisplayLink will give me a tick and then I simply check something that is affected by the animation but there is nothing to tap to.
Do you think going the NSTimer way that is launched in the same scope as the animation method is ok? If I know animation duration then I can generate the progress myself.
If all you want is the time value, then you can do math on the CACurrentMediaTime() minus the animation start time. I have a sample project on Github called KeyframeViewAnimations that does exactly that.
That project supports pausing and resuming and scrubbing both UIView and CAAnimation based animations. In both cases it digs into the underlying CAAnimations.
I have another project that uses the values of the animated layer's presentationLayer in order to do hit testing so you can tap on an in-flight view and start/pause the animation. That one can be found here:
iOS-CAAnimation-group-demo
My code uses an NSTimer to update the progress of the animation. It would be better to use a CADisplayLink timer, as you mentioned.
I am also looking at the new UIViewPropertyAnimator class that was added to iOS 10. That makes pausing, reversing, and scrubbing UIView animations easy without having to dig into the underlying CAAnimations. See this thread I just posted:
Is there a way to observe changes to fractionComplete in UIViewPropertyAnimator
So I'm making a simple trivia game and I have a timerView that shrinks as time passes. When the user selects an answer, it needs to stop shrinking immediately - it must be very responsive. I give the user 10 seconds per question. Originally I would animate 10 times (with a duration of 1.0f), calling the next "segment" of animation in the completion block of the previous animation. In the completion block I would check to see if the user has tapped an answer, and if so I don't continue the chain. That solution works fine except that it's not very responsive because it's on a per second basis-- user taps an answer at the start of the second segment and the bar has a noticeable continuation.
My solution to THAT problem was to instead have 1000 animation calls with a duration of 0.01f. After doing that, the responsiveness was on point - the view stops animating as soon as I tap an answer -- the issue though, is that it's not actually 10 seconds, it takes more like 20.
So question number 1: what's the smallest time interval animateWithDuration can actually process properly?
Question number 2: is there a better way to accomplish what I'm trying to do accomplish?
ill answer question two: yes there definitely is a better way, have a look at CADisplayLink
use it to shrink your view a little bit each frame, and end the display link when you need to
the most responsive way is: the user taps an answer, you response in the touch callback, remove animations. you can remove animations by CALayer's removeAllAnimations method
Another way to do it is to set the view to shrinking using a single animation with linear timing, and then set the speed of the view's layer to 0 to pause the animation. When you set the speed on the layer to 0 the animation pauses instantly.
This works because under the covers, UIView animation actually creates and installs CAAnimation objects on the view's layers. It's possible to pause and continue an in-flight UIView animation just like you can a CAAnimation.
I have a project called KeyframeViewAnimations (link) on github that allows you to pause, continue, or "scrub" UIView and CAAnimations back and forth with a slider. You could use that technique. The tricky bit will be figuring out how far along the animation is.
In my current project I've created an app that utilizes the position of the UISlider in relation to a target value displayed to the user. I've got full functionality however I'm now trying to spice it up a bit.
Is it possible to set the UISlider to move from (minimum through maximum) than (maximum through minimum) back and forth on its own when the user enters the app rather than having them drag it?
Thoughts:
Possibly use a looping sequence?
Not looking for someone to code this for me I quite enjoy that part. Just looking for guidance.
Further to the NSTimer answer, I wouldn't suggest using that, but CADisplayLink instead. Similar process, but instead of using NSTimer use CADisplayLink.
CADisplayLink synchronises with the screen refresh rate, so you can adjust the animation and slider value based on current frame, so the animation appears smooth.
http://patzearfoss.com/2011/09/02/more-cadisplaylink/
I think that in this case you would have to setup an NSTimer with a time that you wish per frame, separate out the action code within the slider into a routine that can be called by you, then within the timer action code, call your routine, and then set the slider position manually.
Look here for setting up an NSTimer
How do I use NSTimer?
The NSTimer will essentially allow you to setup any framerate you wish, AND keep it off of the MAIN thread.
UISlider has this method that allows you to programatically change the slider's value:
- (void)setValue:(float)value animated:(BOOL)animated
Be careful about using loops though, you don't want to block your main thread an make your app unresponsive.
Trumpetlick's answer provides good information on using an NSTimer, which should help you with this.