Basically I want to give a physicsBody "health" and when it gets hit I want to decrease that health dynamically. If it gets hit hard, I want to take away a lot of health.
I know how to give the node the health and take away from that value using Node.userData, but I don't know how to detect the force of an impact.
I also know you can detect an "impact" with CGRectIntersectsRect but that doesn't return a magnitude obviously, as it is a method of the node not the physicsBody..
How can I accomplish this?
In didBeginContact: you get a SKPhysicsContact object which contains a collisionImpulse property:
The impulse that specifies how hard these two bodies struck each other
in newton-seconds.
The didBeginContact: message is received by the SKPhysicsWorld's delegate (SKPhysicsContactDelegate).
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A Tale of Two Subclasses
By Ben Stock
Prologue
I'm in the process of making a really nice looking set of controls which automatically change their appearance depending on the type of window they're used in (e.g. If you drop a button in a normal window, it looks like any other standard Aqua button. If you drop it on an NSPanel with a window mask of NSHUDWindowMask, however, it'll automatically switch its style to look good on a HUD background. So far, I've subclassed NSButton, NSTextField, NSSlider, and NSSearchField. Last night I started on NSTabView, only to be slammed down by its lack of customizability. It's a real pain in the ass, but I'm a developer, so I'm used to finding my own way. The first thing I think to do is add an instance of NSSegmentedControl in place of the private tabs used by NSTabView. So far, so good. I've got the buttons selectable, they automatically update when new NSTabViewItem's are added, and they work just like the real thing.
And the Pain Begins …
Finally, I start to style my segments, and … WTF have I gotten myself into‽ I should've just gone into acting or something. Objective-C development is slowly taking years off my life. No matter what I do, the "tracking areas" used by NSSegmentedCell don't seem to be updating when my segment widths change. So when my widths change, my artwork does, too. However, the actual tracking area doesn't update (even when I override -updateTrackingAreas. It's really hard to explain, so I decided to draw my segment rectangles behind and in front of the ones drawn by super in -drawSegment:inFrame:withView. Here's a screenshot with my art drawn on top of the underlying tracking areas:
And here's super's implementation above my segment rects:
I've tried overriding everything I can think of. Here are a few of the methods I've overridden (and un-overridden):
-cellSize (NSSegmentedCell)
-cellSizeForBounds: (NSSegmentedCell)
-sizeToFit (NSSegmentedControl)
-intrinsicContentSize (NSSegmentedControl)
-setWidth:forSegment: (NSSegmentedControl/Cell)
-startTrackingAt:inView: (NSSegmentedCell)
-continueTracking:at:inView: (NSSegmentedCell)
-stopTracking:at:inView:mouseIsUp: (NSSegmentedCell)
At this point, some of those methods in the above list are still using my overrides and some aren't. I've mixed and matched, deleted, simplified, rewrote, and refactored, and no matter what I do, the underlying rectangles don't change. I love Apple as much as the next guy, but their view of customization needs to change. I can't stand not being able to understand what's going on in the implementation of all these stupid controls. Not to mention the fact that I still can't fully wrap my head around Auto Layout (which is about the most un-"auto" thing I've ever dealt with), but that's a post for another day. Anyway, if anybody could help a brotha out, I'd be super grateful. Sorry for ranting and thanks for reading!
P.S. None of these things are finished, so please don't be too hard on a few pixel imperfections. ;-)
Want to create a loading view that matches the speed of the UIActivityIndicatorView depending on the network type.
Is it accessible via the SDK or at the very least disclosed?
How fast it spins? Short answer is no :(
Not with a simple property or something like that. You do have a few options though:
Create it yourself. The images are available when you use iOS Artwork Extractor, so you could give it the same look. Perhaps a little tedious. Maybe you could even subclass it.
Do some hackery with the current startAnimating and stopAnimating methods. Basically start and stop it for a period of time using a timer. This may not look great though as NSTimer doesn't always give you the precision you'd want in this case.
Since UIActivityIndicatorView inherits from UIView, you can access its layer property. This is a CALayer, which has instance methods like animationKeys and animationForKey. This is probably the best way to go about it, though it's not very future-proof since you're modifying the internals which can always change.
I'm trying to get to grips with using Chipmunk (not the Obj-C version) with UIKit components on iOS, and still struggling immensely.
I'm trying to establish how, in the ChipmunkColorMatch example in the documentation, the UIButton instances are actually hooked up to any of the physics calculations. I see that the UIButtons are created inside the Ball class, and some of their properties are set, (type, image, etc.), but I'm not understanding where the cpBody or cpShape or whichever it is is actually attached to that UIButton. I assume it needs to be, else none of the physics will be reflected in the UI.
I've looked in the SimpleObjectiveChipmunk tutorial on the website too, but due to the fact that it uses libraries unavailable to me (the Obj-C libraries), I can't establish how it works there, either. Again, I see a UIButton being created and positioned on-screen, but I don't see how the cpBody (or in that case, ChipmunkBody) is linked to the button in any way.
Could anyone shed some light on how this works? Effectively what I'm going to need are some UIButton instances which can be flicked around, but I've not even got as far as working out how to create forces yet, since I can't get the bodies hooked up to the buttons.
Much obliged, thanks in advance.
EDIT: Should also point out that I am not, and do not want to use cocos2d in this project at all. I've seen tutorials using that, but that's a third layer of confusion to add in. Thanks!
Assuming this source is the project you're asking about, it looks like the magic happens in Ball's sync method -- it creates a CGAffineTransform representing the translation and rotation determined by the physics engine, and applies that to the button.
In turn, that method is called by the view controller's draw: method, which is timed to occur on every frame using CADisplayLink, and updates the physics engine before telling each Ball to sync.
I've come across a problem to which the simplest solution would be to extend the length of a UIGestureRecognizer. What I mean is that I need the iOS device to still believe the user has their finger on the screen for about 0.1 seconds after they release it. I need the device to think that the finger is in the exact same position for the 0.1 seconds as it was when the user released this.
Any help as to weather this is possible would be greatly appreciated!
Thank you!!!
EDIT:
Sorry for the late reply, I've been really busy with work.
To elaborate, I'm using a set of classes made by Alan Quartermain called AQGridView. It's a class that strongly resembles UITableView; however, it displays data in a grid instead of a list. There appears to be a bug where (if I understand correctly, and I may very well not) the data of the grid is reloaded before the delegate method, that is called when a user ends a UIGestureRecognizer, finishes if the user releases their finger while dragging a cell (from one grid index to another) very quickly. This causes a graphical glitch (which can be recreated in the springboard example that comes with the class set) where the dragging cell appears to settle one cell before or after it's appropriate location, and then quickly jumps to it's proper location. I believe this is because there is a brief period, when the user releases their finger, where the grids count is -1 of what it is when the cell settles.
This is a poor explanation of the problem, but the best I could come up with. As well, I'm a relatively new developer and could be way off on the cause of the problem. That is why I believe the most appropriate fix would be to extend the gesture length by a very small amount. If anyone wants to take a look at the AQGridView classes (https://github.com/AlanQuatermain/AQGridView/) I would really appreciate it! But if possible a simpler fix would just be to simulate the touch that the user inputed right before they released their finger so that the desired animation occurs.
Inside touchesEnded delegate method, start timer for 0.1 second and perform your selector.
You can even, subclass UIGestureRecogniser and implement your own gestures, Check the first answer of this question.
See : custom iOS gesture
I have a situation where my UIPickerView is getting "starved" by a computation task; in other words, the UIPickerView is never updated -- and hence, never sends messages -- because a very heavy compute task is happening. The picker controls aspects of the computation, so the two have to play nice.
I thought of running the computation in a separate thread. Seems like that would leave the picker free to update. However, it'd be a massive undertaking to make my computation multithread-able, so I'd like to find another solution.
Is it possible for a picker (or other UI controls) to "preempt" the execution of a block of code? The computation is in a loop; the number of iterations is what makes it heavy. If the picker could even set a flag somewhere, the loop could break itself, which would work with the flow of the program.
If the loop could poll the picker, that would also work. But, I haven't found a way to do that.
Ideas?
(ps. I posted a similar question yesterday, but didn't really ask it correctly -- didn't quite know what the problem was at that time!)
I assume you mean by flag that if the picker is moved, set a flag. If so you can do this - look at the picker delegates, and when any or all of them get called, set a flag. If your computation is done by another class or classes, then create a new property on those classes "cancelled", the picker can set it, and when set the computation ends.
Before you start another computation you would clear that cancel flag, then kick off the computation.
You can also put a simple toolbar above the picker (common practice) where you have controls that could start the computation, show progress, and cancel it.
EDIT: if the issue is the picker is stuttering when the user is trying to manipulate it, then subclass UIPicker, intercept touch events, and while the picker is being touched, cancel all computations. The only complication is that if the user "spins" the picker, you'd want to wait til it settles, but you would not know how long to wait. Depending on the last touch message, you would have to use a heuristic to wait for didSelectRow: or a timeout before restarting the computation.