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.
Related
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
Imagine in my app I have a label representing a virtual time and I want to change this label and update the time but this time is not system time and I want to be able to change it with different speeds (like every one real second is one or two minutes in this virtual time) and I also want to be able to call some functions at specific times.
I use UIKit.
How can I do this?
You will find that UIKit has UILabel. UILabel is a pretty straightforward thing to use. You can create it programmatically and position it, or use Interface Builder to create it as part of your View Controller's layout.
Either way, to update it, simply set the text property.
You can use NSTimer to update the text with a time and scale it using some sort of multiplier. Time calculations get tricky, so you may need to open a different question with more specifics about your time update.
Use the scheduledTimerWithTimeInterval:target:selector:userInfo:repeats: method to have it call a method on your object, then [NSTimer invalidate]; to cancel it.
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.
I'm doing a countdown timer using NSTimer and a circle Animation like this one: GitHub.
My first question is: What CAMediaTimingFunction is for?
My second and most important question is: I'm getting NSTimer and my animation out of sync. Typically the timer reaches 0 before the animation. What is the best approach on this situation?
One way to be sure you are in sync is not using core animation, but setting the strokeEnd manually in the timer callbacks. I would suggest using a CADisplayLink instead of the NSTimer since it is bound to the refresh rate of the display.
Use its timestamp to calculate how much time passed and set the label text and the circle's strokeEnd appropiately.
I've seen a lot of helpful tutorials that show one how to:
make an image move according to a predefined path, or
move the image, a few pixels at a time, in response to a UIButton.
What I want to do is have the image "drift" arbitrarily according to an Vxy velocity I define, then have the button(s) change the velocity. (Yes, I'd have it slow down with time if no action made).
In other languages there might have been a way to do Change Pxy position by Vxy (to ad infinitum) unless button pushed. I believe GET was the command. I can think of a way to do that in iOS I suppose but that would involve setting up a series of 1 sec CGMutablePathRef anims. Alternatively, I have seen some talk of NSTimer: would it be a good practice to introduce some sort of delay: draw, delay, draw, delay.
Request: specific classes or terms I can search in the manuals for myself.
Iirc using uiview's animateWithDuration:completion is cheaper than using core animation. frame is an animatable property. So, yeah I think I would use an NSTimer to call your method for default calculation of the end frame of your view and then call animateWithDuration:completion there.
[deleted bad idea]
I ran across a wonderful tutorial for anyone considering such a project;
http://www.youtube.com/watch?v=nH_Rj152DRM
I believe the key "noob" problem I was having was in not realizing I should declare the instance variable for my sprite/ image in the
-(void) viewDidLoad{
then work on other properties of the animation in touches/ other user events. Once I figured that out, I am now capable of doing the heavy lifting for the rest of the project myself.