Is it possible to get the absolute touch coordinates from [UIPanGestureRecognizer translationInView]? I'm working on an iPad app and have been searching a lot to get the touch coordinate values from UIPanGestureRecognizer!
I've also tried offsetting using the values we get from transaltionInView but I'm not really able to comprehend the math behind it...
Any suggestions guys?
Ravi
translationInView is the delta change of a gesture. If you move your finger to the left by 20 pt, you'll get (-20.0, 0.0), it's already "absolute" in that sense.
What you probably mean is that you want the locationInView, which relative to the view handed through the argument, even if said view is not the one recognizing the events. Typically, you would hand the view of the view controller, or the view that will take care of the event, or the subview which makes more sense to your implementation.
Also, keep in mind, if you need the real absolute, you can hand nil through the arguments, and it returns it relative to the window (aka. "absolute")
And, if you need to do logic with other views, you can convert the coordinate from one view to another with the UIView instance methods: convertRect:fromView:, convertRect:toView:, convertPoint:fromView:, convertPoint:toView:. These methods also accept nil as the view argument to mean "absolute" to the window.
Here is an easier way:
gesture.locationInView(myView)
Returns the point computed as the location in a given view of the gesture represented by the receive as CGPoint.
Related
I'm currently working on an interactive view that relies heavily on the user's touch location. I have found that there are a few ways to interact with the UITapGestureRecognizer while VoiceOver is on, but when I tap my point the values given are very wrong. I've looked elsewhere, but my use case is outside of the norm so there is not a lot to tell me what is going on. Has anyone experienced this before?
I am aware that I can change accessibilityTrait to UIAccessibilityTraitAllowsDirectInteraction which will give me the correct screen point when used, but I would like to know what is causing this issue at the very least for the sake of knowledge. To interact with the UITapGestureRecognizer I either double tap or do a 3D touch by pressing on hard on the screen. The ladder method doesn't work for the tap gesture but will work for the pan gesture.
This is the only line I use to get my screen points. My map view is a UIImageView
CGPoint screenPoint = [tapGesture locationInView:map];
I'm using a map of a building and I try to tap the same corner or landmark for my testing. I know I can't hit the same exact point every time, but I do use a stylus and I can get pretty close.
Without VoiceOver on I would get the result: (35.500, 154.363)
With VoiceOver on and tapping in generally the same spot, I get : (187.500, 197.682)
The point I am using to test is on the left side of the screen and the result from VoiceOver being on is in the middle of the screen. I believe the y-axis value may have changed because of my tool bar's size, but I have no idea what is throwing off the x-axis value. If more information is needed let me know.
UPDATE: Upon further investigation, it turns out that the UITapGestureRecognizer will always return (187.500, 197.682) no matter where I touch in the map view when VoiceOver is on. That point seems to be the middle of the map view. Oddly enough though, the UIPanGestureRecognizer will give me the correct (x,y) for my view if I use the 3D touch while VoiceOver is on.
On a side note not relating to the problem at hand, it seems if I use the accessibility trait UIAccessibilityTraitAllowsDirectInteraction the method UIAccessibilityConvertFrameToScreenCoordinates returns a frame that is higher than my view. It works fine if I do not change the trait.
Your problem may deal with the reference point used when VoiceOver is on.
Verify what your point coordinates are referring to : view or screen coordinates ?
I suggest you take a look at the following elements :
accessibilityFrame
accessibilityFrameInContainerSpace
UIAccessibilityConvertFrameToScreenCoordinates
According to your project, the previous elements may be interesting to get your purposes.
I'm coding in Swift 2.0 for devices running iOS7+.
Is it possible to present a tableview in a skewed/diagonal/slanted format as indicated below?
Obviously if the answer is yes, what process would I need to go through to get the result?
Yes it's possible. Views in iOS have a transform property, of type CGAffineTransform. You can use that to make the view appear skewed. I don't know offhand how to create a transform that creates the skewing effect. I suggest doing some google searching.
The next issue you will face is interacting with taps. Changing the transform of a view does not transform the coordinate system applied to taps, so taps will still land on the non-skewed views. That will be much harder to sort out, and without doing a fair amount of research I don't have an answer for you on that one. (It would probably be possible to intercept touch events before they get to your table view and apply the inverse of your skewing transform to them so that you map the taps back to the rectangular coordinate system the table view is expecting.)
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.
I'm facing a delicated problem handling touch events. This is problably not a usual stuff to make but i think it is possible. I just don't know how...
I have a Main View (A) and Main View (B) with a lot of subviews 1,2,3,4,5,...
MainView
SubView(A)
1
2
3
SubView(B)
1
2
3
Some of these sub sub views (1,2,4) are scrollviews.
It happens that I want to change between A and B with a two finger pan.
I have tried to attach a UIPanGestureRecognizer to MainView but the scrollviews cancel the touches and it only works sometimes.
I need a consistent method to first capture the touches, detect if it is a two finger pan, and only then decide if it will pass the touches downwards (or upwards... i'm not sure) the responder chain.
I tried to create a top level view to handle that, but I cant make to have the touches being passed through that view.
I have found a lot of people with similar problems but couldn't find a solution to this problem from their solutions.
If any one could give me a light, that would be great as i'm already desperate with this.
You can create a top level view to capture the touches and the coordinates of touches then you can check if the coordinates of touch is inside of the sub views. You can do that using
BOOL CGRectContainsPoint(CGRect rect, CGPoint point)
Method. Rect is a frame of the view, and point is point of touch.
Please not that the frames and touch locations are relative to their super views, therefore you need to convert them to coordinate system of app window.
Or maybe it can be more helpful
Receiving touch events on more then one UIView simultaneously
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.