i have a quick question,
I have a view with multiple subviews.
In my view i have touches began etc..
is there a way to retrieve a subview from the touches began without having to detect the location from the touch and then have a big if else to c which subview is in that specific area.
Thanks.
My solution is instead of calculating the touch position from the super view. Sub class the child view and get the touch position form there only and convert the point with respect to the super view.
The method you want is the UIView instance method -(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event. That will return you the lowest-level subview containing point.
So you get the point of your touch, pass it to that method of your biggest container UIView, and get back a handle to the frontmost subview that got touched. Easy peasy.
Related
I'm trying to create a menu (using UIScrollView) where the user can select images (using UIImageViews).
I intend to have at least 3 images visible at anytime. When I scroll, the images will be able to snap into position.
However, if I am to use a UIScrollView which is large enough to display 3 images at anyone time, and I enable paging, the paging will move all 3 images together and snap only at the next 3 images.
And if I am to use UIScrollView that fits just 1 image, and I enable clipsToBounds (which helps me draw the images beyond the boundary of the UIScrollView). My figure gestures can only be detected within UIScrollView itself, I want my figure gestures to be detected as long as any of the images are touched.
Thanks.
You can use following method of UIScrollView to scroll it from code as much as you want.
- (void)scrollRectToVisible:(CGRect)rect animated:(BOOL)animated
you can call this from following method of UIScrowViewDelegate.
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
Thus, you can manage how much you scroll view will call.
And for getting touches, implement a separate class that display images(inherit it from UIImageView or UIView) and implement touchesBegin or touchesEnded in that. Here when you get the touch in your custom view call some method of parent view and notify it with proper arguments(you can assign tag property and pass it to scroll view to find exactly which image was tapped).
.....I am not sure weather I am solving your problem or not.....so post here if you need any further assistance.
I wrote a custom UIView class which overrides the hitTest method of UIView.
In the header of the custom UIView class, declare a UIScrollView, later you will need to assign the UIScrollView which is displaying the menu to this variable.
UIScrollView *thatScrollView;
In the implementation, remember to synthesize the variable and overwrite hitTest
#synthesize thatScrollView;
- (UIView*)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
if ([self pointInside:point withEvent:event]) {
return thatScrollView;
}
return nil;
}
Then in the UIViewController class, create an instance of the class and assign the scrollview you want to scroll:
hiddenView.underneathButton = scrollView1;
I have a UIScrollView ontop of my UIViewController recreating an effect like in the Gowalla iPhone app when you're on a spot's page. Under my scroll view I have a button that I want to be able to perform it's action even when the scroll view's frame covers it up (where it's ontop of the button, the scroll view's clear). How would I do something like this? Is it possible? (it has to be, Gowalla [somehow] did it)
As for me, I will transfer touch event to another view by override following methods.
– touchesBegan:withEvent:
– touchesMoved:withEvent:
– touchesEnded:withEvent:
– touchesCancelled:withEvent:
Like this way,
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
// pass touch event by default implement.
[super touchesBegan:touches withEvent:event];
// redirect the touch events.
[anotherView touchesBegain:touches withEvent:event];
}
hitTest:withEvent: is used to decide which view should response touch event on the view hierarchy tree. If the view doesn't want to response touch event, it will return nil in hitTest. As result the above touch event methods won't be called.
I have no idea what this "Gowalla" app might do; hopefully, your description of "a button behind the scroll view, that you can touch 'through' the scroll view" is accurate.
If your button behind the scroll view can be sized to fill the entire contentSize area of the scroll view without screwing up your interface, the easiest solution would be to just put it inside the scroll view (under all the other views) and do just that.
Otherwise, your best bet is probably to create a custom view with a clear background to be placed in the scroll view as above. The easy solution is to have the custom view (probably a UIControl) just do whatever touching the button does. If that's not possible for some reason, your best option would be to override hitTest:withEvent: on the custom view to return the underlying button. I'd be wary of overriding hitTest:withEvent: on the scroll view itself, as that might interfere with scrolling.
Try adding the button on top of the scroll view. The only problem with that is if you hit the button, you will not be able to interact with the scrollView, but it will still be visible.
I try to create something similar to the task-menu in iOS4:
(Sorry cant post images not enough Rep)
I have normal ViewController on thats view i addSubview of my menuView. I set menuViews Y to -95 so i can just move the viewControllers view 95 Down to Display the menu. But the scrollView in my menuView doesn't work if the menuViews Y is Negative.
Your scrollview doesn't receive the touch input because it is outside the bounds of the its superview (the view of the main ViewController you mentioned). The way the touch interaction system works is the AppKit framework goes down the view hierarchy testing each view and subview with the - (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event function. If a view returns YES to this function, it will start the process all over again with all of its subviews until it finds the lowest subview that still returns YES. The problem with your setup is that the superview of Scrollview is going to return NO because the touch is above it and your menuView never even gets tested. So you have two possible solutions:
Implement your ViewControllers view as a subclass of UIView (if it is not already) and overload the pointInside:withEvent: function to return YES if the touch is within it's frame OR if it is within the bounds of menuView (ViewControllers frame minus the frame of menuView).
The second solution would be to simply put menuView at the origin of its superview (0,0) and leave the ViewControllers view at (0,0) as well.
I suggest the second as it is less convoluted and more to the point.
I'm using the touchesEnded: method to do some work when I lift a finger off my UIScrollView, but my problem (and i've confirmed using NSLog) is that the touchesEnded: method seems to only get called when I tap on my scroll view and not when I touch and hold/slide my finger and then let go?
Is there another method I need to use? (btw i'm calling super as well)
I need a way to do stuff as soon as the user removes their fingers off the view
When you simply tap, the scroll view will pass touches through to its subviews. But if you start dragging, the scrollview will send a touchesCancelled message to the subview and process the touches itself. Check out the methods on UIScrollViewDelegate - there's probably something there you can use.
Alternatively, UIScrollView has a property canCancelContentTouches. If you turn that off, its subviews will always receive touches, but of course then the scroll view won't scroll.
I have a UIViewController and an associated with it UIView. The UIView has a number of subviews.
How to handle touch event inside a specified rectangle in my UIViewController subclass?
This handling should be transparent: UIView and its subviews should still receive their touch events even if they intersect with the specified rectangle.
P.S.
Overriding touchesBegan in the view
controller doesn't work. Inner views
doesn't pass events through.
Adding a custom
button to the end of UIView subviews
list also doesn't work. Inner
subviews doesn't receive touch
events.
touchesBegan/touchesMoved/touchesEnded is probably the way to go. Depending on exactly what you are trying to do, UIGestureRecognizer may also be an option.
To make sure subviews pass events up, set userInteractionEnabled to YES on the subviews.
UIView sets this to YES by default, but some subclasses (notably UILabel) override this and set it to NO.
Just because the views don't pass events through by default doesn't necessarily mean that's the way it has to be.
You could subclass the views that you are using and have them pass the events onto the view controller.
Another idea is to literally have a transparent handler on top of all of your views. That is, have a transparent UIView that sits above your views, handling touch events but also passing them through. I have no idea if this works in practice, but it sounds like it would.
Your views, and their controllers can handle a touch using touchesBegan, touchesEnded or touchesMoved. Within touchesBegan as an example you can then choose to pass the event to
the next responder in the responder chain. This way each of your views will get a chance to do something based on the touch event.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
//do something here and then pass the event on
[self.nextResponder touchesBegan:touches withEvent:event];
}