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
Related
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. ;-)
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'm new on iOS programming. My situation is that I try inserting a row into tableview, I've try the function insertRowsAtIndexPath:withRowAnimation but it's animation is so fast.
How can I make it slower?
I've got some answers that iOS does NOT allow to adjust its speed, so it's necessary to do my own animation within a block when calls insertRowsAtIndexPath:withRowAnimation likes
insertRowsAtIndexPath:withRowAnimation:^{.....}
But what exactly must I do in the block? Could anybody show me, I just want to make the animation slower!
There is not method insertRowsAtIndexPath:withRowAnimation:^{.....} thus you have to either accept the fact the the animation is going to fast or write you own animation code.
Which for UITableView will be vary hard to do.
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.
UPDATE: With the blush of shame I discovered that the order had nothing to do with the speed of tapping. I was calling the visual code before the super touchesEnded:withEvent call, which was why if you tapped really fast, the display never got a chance to draw the highlighted state before being dismissed again. Because the code that was actually causing the main thread to block just a few milliseconds, the highlighted state would stay visible until the main thread unblocked again, where as if you tapped really fast, it looked like nothing happened at all. Moving the super call up to the top of the overridden method fixed it all. Sorry, if any moderator sees this post it can be deleted. shame
This problem must have been asked a 1000 times at SO, yet I can't find the explanation to match my specific issue.
I have a UIButton subclass with a custom design. Of course the design is custom enough that I can't just use the regular setSomething:forControlState: methods. I need a different backgroundcolor on touch, for one, and some icons that need to flash.
To implement these view changes, I (counter-intuitively) put the display code in (A) touchesBegan:withEvent and (Z) touchesEnded:withEvent:, before calling their respective super methods. Feels weird, but it works as intended, or so it seemed at first.
After implementing addTarget:action:forControlEvents was used to bind the UIControlEventTouchUpInside to the method (X) itemTapped:, I would expect these methods to always fire in the order (A)(X)(Z). However, if you tap the screen real fast (or the mouse in simulator), they fire in the order (A)(Z)(X). Where (A) and (Z) follow each other in such rapid succession, that the whole visual feedback for tapping is invisible. This is unwanted behavior. This also can't be the way to go, for so many apps need similar behavior, right?
So my question to you is: What am I doing wrong? One thing I'm guessing is that the visual appearance of the buttons shouldn't be manipulated in the touchesBegan:withEvent and touchesEnded:withEvent, but then where? Or am I missing some other well known fact?
Thanks for the nudge,
Eric-Paul.
I don't know why the order is different, but here's 2 suggestions to help deal with it.
What visual changes are you making to the button? If it's things like changing title/image/background image, you can do all this by modifying the highlighted state of the button. You can set a few properties like title and background image per-state. When the user's finger is down on the button, the highlighted state is turned on, so any changes you make to this state will be visible at this time. Do note that if you're making use of the selected state on the button, then you'll need to also set up the visual appearance for UIControlStateHighlighted|UIControlStateSelected, otherwise it will default back to inheriting from Normal when both highlighted & selected are on.
The other suggestion is to ditch touchesBegan:withEvent: and touchesEnded:withEvent: and switch over to using the methods inherited from UIControl, namely beginTrackingWithTouch:withEvent: and endTrackingWithTouch:withEvent:. You may also want to implement continueTrackingWithTouch:withEvent: and use the touchInside property to turn off your visual tweaks if the touch leaves the control.