How can I add a drag event to a subview of a UIScrollView? The structure is the following:
-UIView
-UIScrollView
-UIView
-UIView
...
I tried to start with the following:
-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *aTouch = [touches anyObject];
CGPoint location = [aTouch locationInView:self.superview.superview];
[UIView beginAnimations:#"Dragging A DraggableView" context:nil];
self.frame = CGRectMake(location.x, location.y,
self.frame.size.width, self.frame.size.height);
[UIView commitAnimations];
}
But nothing happens! Help would be very much appreciated.
Thanks
Just incase anyone finds this question like I did, I solved this problem by adding a gesture recognizer to the subviews in the scrollview. The gesture recognizer will handle the touch event itself.
Bruno, one possibility is to use the gesture recognizers, as Scott mentions.
Another possibility is to use the touchesMoved: method you mention. Using the touchesMoved: method requires you to implement another three methods, touchesBegan:, touchesEnded:, touchesCancelled:. They cover the phases of the finger touching the screen:
First contact (touchesBegan) allows you to set up variables as needed.
Continuous move (touchesMoved) allows you to track the move and move your content continuously.
And finally removing the finger (touchesEnded) where you can finalize any changes you want to keep.
touchesCancelled is required for clean-up if the gesture is interrupted (by phone call, or some other controller grabbing the touch event).
You need all four methods on the same class, otherwise a superclass implementing the method will grab the touch processing and your code won't run as expected.
Regards, nobi
Related
I have a question that I've searched but can't find a definative answer to. Here is my layout:
UIView - ViewController
|_UIScrollView - added programatically
| |_UIView to hold a backgound/perimeter - added programmatically
|_UIView 1 - added programmatically
|_UIView 2 - added programmatically
and so on
My question is how come the ViewController calls "touchesMoved" only once when I move say UIView 2 on touch?
Now UIView has it's own touchesMoved method, but I need the controller's touchesMoved to get called as I need it to talk to the ScrollView to update its position. Such as when that UIView 2 is near the corner, so that the ScrollView moves a little to fully show UIView 2.
If there is no way around this is there a way to update ScrollView from UIView 2 to scroll when its near a corner?
Edit:
I think I may have found a work around. Not sure if this will be accepted by Apple but:
I just made a call to a instance variable that is = to self.superview which then allows me to talk back to my ScrollView within UIView's touchesMoved
in that i can call the method [ScrollView setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated] so my ScrollView gets updated as the subview(UIView2) moves close to the edge of the UIWindow.
Thank you for the suggestions.
The behavior you describe is the result of the UIScrollView hijacking the touch moved event. In other words, as soon as the UIScrollView detect that a touch moved event falls within its frame, it takes control of it. I experienced the same behavior while trying so create a special swipe handler, and it failed each time a UIScrollView was also interested by the swipe.
In my case, I solved the issue by intercepting the event in sendEvent: overridden in my custom UIWindow, but I don't know if you want to do the same. In any case, this is what worked for me:
- (void)sendEvent:(UIEvent*)event {
NSSet* allTouches = [event allTouches];
UITouch* touch = [allTouches anyObject];
UIView* touchView = [touch view];
//-- UIScrollViews will make touchView be nil after a few UITouchPhaseMoved events;
//-- by storing the initialView getting the touch, we can overcome this problem
if (!touchView && _initialView && touch.phase != UITouchPhaseBegan)
touchView = _initialView;
//-- do your own management of the event
//-- let the event propagate if you want also the default event management
[super sendEvent:event];
}
An alternative approach that you might investigate is attaching a gesture recognizer to your views -- they have a pretty high priority, so maybe the UIScrollView will not mess with them and it might work better for you.
If there is no way around this is there a way to update ScrollView from UIView 2 to scroll when its near a corner?
Have you tried to make the UIScrollView scroll by calling:
- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated
I have a MainView with MainViewController. Now I want to add a specific area where I want to register touches (painting in a specific area). How could I do this?
I thought about adding a sub-view with its own sub-viewcontroller, but this guy tells this is not a good approach.
The post you linked to is partially out of date because it was written before Apple introduced support for View Controller Containment in iOS 5.
That said, it's your choice whether:
the subview is managed by its own view controller or
you use the MainViewController directly to respond to touches in the subview or
you create a UIView subclass that interprets touches on itself without the help of a view controller.
Add a custom view as a property, called touchArea
-(void) touchesBegan/Moved/Ended (NSSet *)touches withEvent:(UIEvent *)event {
CGPoint location = [[touches anyObject] locationInView:self.view];
if (CGRectContainsPoint(touchArea.frame, location))
//code
}
}
Quick question: how do i detect if a tap gesture recognizer is within a subview of the view it is added to? Eg. if i click on an object such as a square that has been added as a subview to a background which a tap gesture recognizer has been added to, how do I detect that it has been tapped?
You can grab the point of the tap off the gesture recognizer when your handler method is called respective to any view you wish using -locationInView:. Then, use the following method on UIView: - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event to get a reference to the actual sub view that was tapped remembering that the point you pass in is in the same coordinate space as the view.
Some code to get you started:
CGPoint point = [tapGestureRecognizer locationInView:parentView];
UIView *tappedView = [parentView hitTest:point withEvent:nil];
For hit testing to work the view needs to have the userInteractionEnabled property set to YES. Many views, such as UILabels have this set to NO by default. So prior to the above:
self.subviewOfInterest.userInteractionEnabled = YES;
maybe you should set as:
subviews.userInteractionEnabled = YES;
good luck!
you can use the requireGestureRecognizerToFail: to recognize the tap on subview please refer this code
I am trying to determine a Single Tab on a View inside of a UIScrollView. The Problem is that The UIScrollview catches all the gestures.
What I tried so far:
I override the following method in my UIScrollView:
-(BOOL)touchesShouldBegin:(NSSet *)touches withEvent:(UIEvent *)event inContentView:(UIView *)view
{
UITouch *touch = [touches anyObject];
if([touch tapCount]== 2) return YES;
return NO;
}
This works fine, I can now reach the UITapGestureRecognize on my UIView, unfortunately I can only detect double-taps because the [touch tapCount] == 1 is always beeing called (dragging or zooming in the UIScrollView). But actually the UIScrollview does not need the "Single-Tap-Function"
Is there a way to decide between a drag (Scroll or zoom) and a single Tap inside this method? I cant find it..
-(BOOL)touchesShouldBegin:(NSSet *)touches withEvent:(UIEvent *)event inContentView:(UIView *)view
Thanks in advance
Fabi
It sounds like you only want the tap recognizer to succeed if the touch doesn't scroll the scroll view. This is pretty easy because the scroll view uses a pan gesture recognizer for scrolling. On iOS 5, you can just do this:
[self.tapRecognizer requireGestureRecognizerToFail:self.scrollView.panGestureRecognizer];
If you want to support older versions of iOS, you have to do this:
for (UIGestureRecognizer *recognizer in self.scrollView.gestureRecognizers) {
if ([recognizer isKindOfClass:[UIPanGestureRecognizer class]])
[self.tapRecognizer requireGestureRecognizerToFail:recognizer];
touchesShouldBegin: is a delegate method on UIView. It is not part of a UIGestureRecognizer.
You'll need to create a UITapGestureRecognizer, set the number of taps you want to trigger the recognizer and add it to your view.
Here is the documentation for UITapGestureRecognizer
I'm assuming you meant "single tap"--your scrollView belongs to the UIView tied to your controller. Assign the tap gesture recognizer to the that UIView. It gets first picks on all gestures and then passes down the ones it isn't interested in.
I have a bunch of UIViews stacked one upon the other(not nested). I want them all to react to touch, but it seems that the topmost view obscures the views beneath it, preventing them from receiving touch events.
At first i thought i’d catch all touch events with the topmost view, and then manually call
hitTest, or pointInside methods on all the underlying views, but i found out that both methods are somehow private(could it be?) and cannot be accessed.
Any ideas how to pull it off?
You can check if the touch is for your topmost view. If it doesn't you can call the same method of your superview. Something like [self.superview sameMethod:sameParameter].
Your topmost view has a method
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
Inside that method you are doing your logic right?
Inside the method can't you check if the touch received is at your topmost view with
UITouch *touch = [touches anyObject];
[touch locationInView:self];
And if it doesn't you pass it to the superView's same method using
[self.superview touchesEnded:touches withEvent:event];
Touches are sent to a single view. That view can then optionally pass them up the responder chain. If you want to handle touches to a collection of views you should have them forward those events up to the next responder and have a common parent of all of them (or their view controller since the controller is also part of the responder chain) handle those touches.
https://developer.apple.com/library/mac/documentation/General/Devpedia-CocoaApp-MOSX/Responder.html