I use SCNTransaction to move game objects. More specifically, when the player taps somewhere on the screen, the object will move towards that destination. But sometimes the player may make a wrong move, so I want to create a button which can terminate all SCNTransactions.
However, unlike SKAction, which can be terminated with a simple line - self.removeAllActions(), SCNTransaction cannot be terminated or even paused from the outside according to the Apple Developer Documentation. Even worse, I find that before the object reaches its destination, its position has already changed to the destination's position, so I cannot simply use another SCNTransaction to counteract the ongoing one after knowing the object's current position.
Can anybody give me some hints? Thanks a lot.
SCNTransaction and its animation principles follow the one of Core Animation and CATransaction. To stop an animation you will have to set the model value to the current presentation value. For instance:
node.position = node.presentation.position
But if you are familiar with SKAction and would like to implement the same logic in your SceneKit app, you might want to have a look at SCNAction. They work identically.
Related
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.
I am making a SpriteKit game I was wondering if there was a way to prevent more than one touch at a time.
in my game an object gets added at every touch and I kinda don't want that. (even though its hilarious) if there is a way how do I do it? what would I use? and could you point me in the right direction? and I know that there are ways to do it as I have seen multiple games with that feature.
would I put something into 'appdelegate.swift' to prevent that or would it have something to do with the 'touches began' function I have tried several methods but none seem to work also I have searched all over google but to no avail.
if somebody could help me with this I would appreciate it but its not really that important as it doesn't upset the balance of the game at all.
You can use multipleTouchEnabled property of a UIView:
When set to YES, the view receives all touches associated with a
multi-touch sequence and starting within the view's bounds. When set
to NO, the view receives only the first touch event in a multi-touch
sequence that start within the view's bounds. The default value of
this property is NO.
Use it like this self.view.multipleTouchEnabled = false, where self is a scene.
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
I'd simply like to know if there is a way to detect how many pixels the finger has moved during the -touchesMoved function?
EDIT:
This is what I've tried. I made two instance variables called _previousPosition and _currentPosition. In -touchesBegan, I set them both to be the current finger location in the scene. In -touchesMoved, I set _currentPosition to be the current finger location once again. Keep in mind that during -touchesMoved, when I'm updating _currentPosition, _currentPosition is being constantly updated, while _previousPosition is not. Finally, in touchesEnded, I create another variable (not global, but private) called pixelsMoved, and set that equal to _currentPosition - _previousPosition. Right after that, in -touchesEnded, I reset _previousLocation to be the current finger location. It's all very complicated, so I'm almost positive I've made some mistake somewhere. Any help would be appreciated.
I'd simply like to know if there is a way to detect how many pixels the finger has moved during the -touchesMoved function?
-touchesMoved:withEvent: provides an event, and from the event you can get individual touch objects, each of which have an associated location that you get with -[UITouch locationInView:]. You don't get information about how far the touch has moved since the last time you looked, but you can keep track of the location of each touch and do the comparison yourself.
What is the best way to implement a smooth reversing animation which tracks touches? I am referring to those animations in which, for example, if the user executes a swipe gesture some elements smoothly animate on screen, and others off, but if the user instead slowly drags a pan gesture back and forth the same objects will move forward/backward as a percent in accordance with the touch position. This is seen in many app intros and also in transitions. I have found
One tutorial which discusses the built-in facility for this but it is only between view controller transitions, not providing the full granular control I see in many apps (http://www.doubleencore.com/2013/09/ios-7-custom-transitions/)
Jazzhands, which is a kit by IFTTT, but this is a packaged solution that might not cover how the solution is best implemented at a lower level (https://github.com/IFTTT/JazzHands)
A question here for which one answer shows how you might execute an animation after a gesture ends (iOS Touch, Gestures, Animation)
What I don't grasp - and I'm comfortable using CAAnimations and gestures - is how something can be both animated and interactive.
Typically, when I create an animation, I commit the animation and it goes from start to finish. While I could interrupt the animation as touches continue, that seems like it would be stilted.
On the other hand, moving things in response to user input is easy, but that is not animated.
How is the effect achieved where something can change according to an animation, but also have that exact same animation occur tied to touches, and yet still also have it so that although the animation reaches completion it doesn't really "finish" (become irreversible) unless the user releases touch, while at any point during interaction if the user releases panning then the animation either reverts backwards to its starting position or animates to completion depending on the last touch location and velocity. These requirements are baffling.
The glimpses of this technique I see all involve keyframe animations, but what I don't understand is where the touch events intersect with an animation to create these smooth effects I see.
Any tips, examples, or tutorials are most welcome.
What I don't grasp - and I'm comfortable using CAAnimations and gestures - is how something can be both animated and interactive.
It is because, having set up an animation, you can set that animation to any "frame" you wish. Thus you can track the animation in correspondence to the movement of a gesture.
The way this works is that an animation is a feature of the render tree, belonging to a CALayer. CALayer implements the CAMediaTiming protocol. The timeOffset of a CALayer thus determines what "frame" of an animation that layer displays. If a complex animation involves many different layers, no problem; just set the timeOffset of their mutual superlayer, to control the frame of the entire animation.
That in fact is exactly how the new iOS 7 interactive custom transition feature works (to which you rightly refer in your question). For instance, in this example code:
https://github.com/mattneub/Programming-iOS-Book-Examples/blob/master/iOS7bookExamples/bk2ch06p296customAnimation2/ch19p620customAnimation1/AppDelegate.m
... I keep updating the UIPercentDrivenInteractiveTransition to tell it how far through the gesture the user is, and the animation therefore tracks the gesture. Now ask yourself: how the heck is this possible???
Well, the UIPercentDrivenInteractiveTransition, in turn, behind the scenes, keeps adjusting the layer's timeOffset to portray the animation at the corresponding frame. (You can actually add logging code to my example to see that this is true.)
Moreover, when I end the gesture at an incomplete point, the animation either hurries to its end or runs backwards to its beginning - again, this is because of the CAMediaTiming protocol, which lets you change the speed of the animation, including a negative value to run it backwards.