See UPDATE below:
I am confused about UIView layout as subviews are moving. I have a "Surface" UIView with several "Item" subviews on it. The user is allowed to click on the items and drag them around the surface.
What I have noticed though is that whenever a Surface's Item subview moves (is dragged by the user), the Surface is marked as needing to be relayed out.
I do not want the Surface to layout the Items after the user moved them. That is pretty much the whole point, I am allowing the user to position them as they see fit. However, there are times, initial creation is a prime example, where I do need the Surface to place the items.
So I would like one of two things:
A) Suppress SetNeedsLayout() calls on the surface when one of its Item subviews changes (moves).
--OR --
B) Know why I was asked to relayout, and if it was caused by Item motion then do nothing.
I cannot imagine I am the first to have this question.... :)
###### UPDATE:
After more investigation, I discovered more about what is going on. It is not that moving the Surface's items causes a Surface relayout, as I originally thought. It was only the initiation of a drag which caused the relayout. In digging further I discovered that it wasn't even the drag that was the cause, but a call to the Surface's bringSubviewToFront.
I need to bring the Item to the front, so that when it is dragged it appears on top of the others.
I can understand why bringing a subview might trigger a relayout, but again it is not what I want to happen.
May be you should override layoutSubviews in your Surface UIView.
Related
When swiping between stories in Instagrams new feature "Stories" (you know that cube-like transition when going from one story to another) I can't manage to understand how they do it!
First of all, if you dig deeper into the functionality you find that it works exactly like the UIPageViewControllers transition:
- It bounces when swiping fast from one view to another.
- You can pause the swipe in the middle of the transition by touching the screen.
The developing team couldn't have used a solution based on the more known workarounds out there, e.g:
https://www.appcoda.com/custom-view-controller-transitions-tutorial/
Because as far as I know my two statement above is not possible to achieve with anything else than the PageViewController.
This leaves me thinking that the Instagram Developer Team gained access to a new transition style for the PageViewController, also known as Cube-scroll, or is it a workaround that I'm not aware of?
Any ideas?
I took a shot at recreating this functionality a while back. You can check the source code on GitHub: https://github.com/oyvind-hauge/OHCubeView
I'm using a scroll view (with paging enabled) and, for each subview I'm manipulating these as a function of the given view's current x-offset in the scroll view. The actual animations are done on each subview's layer using Core Animation (more specifically, transforming an identity matrix, given by CATransform3DIdentity, using the method CATransform3DRotate).
The shadow effects are also applied to the subview's layers (view.layer.opacity), with the amount of shadow determined by how much of the view is showing on screen.
My implementation solves both of your concerns (bounces when swiping, can pause swipes). I'm sure this could have also been implemented using the a UIPageViewController, but I hate working with those.
I think you are overthinking the controller's part here. The effect can easily be achieved using a CATransformLayer and three-sided cube-like view structure, where there is one view which aligns with the screen plane, and two others rotated -90 and 90 degrees on their y axis. Then, getting a pan gesture to rotate the scene. After a successful 90 degree turn (in either direction), you can either quickly reset the scene (so that keeping on rotating appears as if continues, but actually the camera shifted back to initial position) or you can have a full 360 degree rotation, and just update previous and next "pages". A single controller can handle this scene. If you prefer to have each page as a controller, it is possible, you can still use one controller for the scene, and then use the page controllers as child controllers, and setting their views as described above.
See this article for more information on CATransformLayer. Their example already creates something that is quite close to what you need.
I have been only using Xcode 5 for a little while now and I need help when it comes to auto scrolling a UIScrollView. I am using a single view application. I need the screen to scroll down at a pace that speeds up incrementally. Also I need the screen to keep progressing even when the screen is touched. If someone can explain which code goes where it would be great! Your help will be greatly appreciated. :)
Check out this library: https://github.com/danielamitay/DAAutoScroll
It stops to scroll when the user touches the screen and that's the only solution I see possible. I don't even see why you wouldn't want the user to be able to stop the scrolling..
OK, just adding this from your duplicate question.
I suspect the Piano Tiles game is actually using something like Sprite Kit.
This allows a lot more control over thing like "scrolling" speed.
Instead of using a UIScrollView you would use an SKNode as a layer with the buttons added to that parent layer.
Then using the update game loop you can incrementally increase the speed of the movement based on the time since the game started.
In essence... don't use UIScrollView, don't use UIKit, use SpriteKit.
I can see a few options:
1) suggested by Fogmeister, use Sprite Kit instead.
2) see setContentOffset
3) just use a normal view as parent, then have another child view on top with the full content (would be longer than the parent view), create a NSTimer to periodically call a method which scrolls the child view in whatever direction and speed as required.
Note that might need something on top to mask around the child view from showing the suppose-to-be-hidden sections of the child view.
Hope this helps
I know this has been probably asked before but I've seen many approaches and i don't know which is best for me, so plz don't send me a link to another post unless it addresses my problem directly.
I have a controller which has a uiview on the top (like a header) (this header is bigger than it seems because is partially hidden on top). on that view i have a uibutton which now with a touch up inside shows the entire header view and taping again returns it to its starting position (changing frame with animation). I want to also be able to drag the view but only changing position on the y axis(dragging up and down)... i was thinking of adding the dragInside/Outside event to the button but this doesn't give me the position of the finger... and also want to know when the user releases the drag so the view ends animation to any of its two possible states (showing or partially hidden). Is this a "touches began" , "touches moved" , "touches ended" thing? if it is please provide a code example. I also want to do this with another view but this is on the left side... same thing but this one moves on the X axis... any help is appreciated. or maybe it can be made with drag event if i only can save a CGpoint of last touch, maybe that's better, any other suggestions
Look at using a UIPanGestureRecognizer to detect the touch movements. Use the translationInView: of the gesture to set the view y position. The translation is the total movement since the start of the gesture so you don't need to remember and accumulate the offset position yourself.
The main thing to worry about while implementing this is bounding the y position of the view so that no matter how far the user drags the view won't go too high or low on the screen.
Use a UIPanGestureRecognizer, that's a class dedicated to handling such drag/pan gestures.
Everything is described here in Apple's documentation, including examples, so you should find your answer here.
There is also some sample code in Apple Developer Library that shows you how to use Gesture Recognizers if needed.
Imagine a view with, say, 4 subviews, next to each other but non overlapping.
Let's call them view#1 ... view#4
All 5 such views are my own UIView subclasses (yes, I've read: Event Handling as well as iOS Event Guide and this SO question and this one, not answered yet)
When the user touches one of them, UIKit "hiTests" it and delivers subsequent events to that view: view#1
Even when the finger goes outside view#1, over say view#3.
Even if this "drag" is now over view#3, view#1 still receives touchesMoved, but view#3 receives nothing.
I want view#3 to start replying to the touches. Maybe with a "touchedEntered" of my own, together with possibly a "touchesExited" on view#1.
How would I go about this?
I can see two approaches.
side step the problem and do all the touch handling in the parent
view whenever I detect a touchesMoved outside of view#1 bounds or,
transfer to the parent view telling it to "redispatch". Not very
clear how such redispatching would work, though.
For solution #2 where I am getting confused is not about the forwarding per se, but how to find the UIVIew I want to forward to. I can obviously loop through the parent subviews until I find one whose bounds/frame contain the touch, but I am wondering if I am missing something, that Apple would have already provided but I cannot relate to this problem.
Any idea?
I have done this, but I used CALayers instead of sub-UIViews. That way, there is no worries about the subviews catching/redispatching events to the parent UIView. You might not be able to do that, but it does simplify things. My solution tended to use CGRectContainsPoint() a lot.
You may want to read Event Handling again, as it comes pretty close to answering your question:
A touch object...is associated with its hit-test view for its
lifetime, even if the touch represented by the object subsequently
moves outside the view.
Given that, if you want to accomplish your goal of having different views react to the user's finger crossing over them, and if you want to do it within the touch-handling mechanism provided by UIView, you should go with your first approach: have the parent view handle the touch. The parent can use -hitTest:withEvent: or -pointInside:withEvent: as it's tracking a touch to determine if the touch is in one of the subviews, and if so can send an appropriate message.
I've got a UIView which the user drags on and off of the screen (like a drawer).
The UIView has a bunch of buttons, some always visible, others hidden until the user 'opens' the drawer.
For some reason, the UIButtons that are 'off screen' on the initial UIView presentation aren't being passed events when they're later moved onto screen.
While the others receive all the events all the time.
Seems buggy to me, I would have thought the SDK would handle all this itself?
I've got a very simple example which you can take a look at: http://cl.ly/2r1c0k2p361B3B1A461L
Thanks in advance.
After a bit more research, it had to do with the views clipping boundaries.
The buttons were being drawn, but were essentially out of the views frame, so no events were registered.
More details on this question: Programmatically Created UIButtons Below Screen Not Working?