Is it possible to control when the UITableView scrolls in my own code.
I am trying to get behaviour where a vertical swipe scrolls and a horizontal swipe gets passed through to my code (of which there are many example)
BUT
I want a DIAGONAL swipe to do nothing, i.e the UITableView should not even begin scrolling.
I tried catching it in here
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
but the scrollView.contentOffset.x is always 0 so I cannot detect a horizontal movement.
I also tried subclassing UITableView and implementing
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
etc..
but the UITableView (and I guess it's parent UIScrollView) start to scroll before the touches are notified?
To re-iterate, I want the UITableView scrolling to be locked if a diagonal swipe is made, but to scroll vertically normally.
(This behaviour can be seen in Tweetie(Twitter) for the iPhone)
Thanks for any help!
If you can work with 3.2 or later, the UIGestureRecognizer suite should allow this. There are a series of calls allowing some gestures to cancel or interoperate with other gestures, and you should be able to create a custom diagonal swipe gesture that cancels other gestures but does not actually do anything itself.
Prior to 3.2 the UIScrollView gesture handling is essentially undocumented. You can detect taps but not movements through the standard touchesBegan UIResponder calls. I think that once it detects movement it commandeers the run loop and captures all events, bypassing the normal event chain.
Note that setContentOffset is always called. You can create a subclass of UIScrollView and when you detect a diagonal shift during event tracking do not pass it to super. I do not know if, or how well this would work but it is somewhere to start.
Related
I am trying to mimic the GLPaint app and I have a TDPaintingView that has methods for -(void)touchesBegan... as well touchesMoved, touchesEnded, and touchesCanceled. However, I am not seeing any of them fire.
I have a TDAppDelegate that is hooked up to a Window in IB and a TDPaintingView in IB. The initWithCoder method for my TDPaintingView definitely fires, so I know it is being initialized. Furthermore, I can see from logging the object TDPaintingView from the context of applicationDidFinishLaunching that it is definitely there. When I change the view in trivial ways in IB (making bg red for example) it is reflected on simulator.
However, my view doesn't receive touches, and it's driving me crazy!
I set a breakpoint on -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event and it never stops, regardless of where I touch on the screen.
My TDPaintingView has no subviews, and it explicitly defines methods for those touches actions.
Where am I going wrong?
I have a custom UIView, to which I have added a UITapGestureRecognizer to the view in order to detect taps (i.e. finger press and release) on the view. This works fine.
However, I now want to change the appearance of the UIView (making it a bit darker) while the finger is pressed on the view (just like the behavior of a UIButton).
How do I do this?
Change the appearance in -(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event.
In an iPad app, wherever a user is touching the screen I want to display an image, highlighting the points they are touching. The app contains a number of nested views, all of which should receive touches and behave normally.
Seems simple, but I've failed to find a good way to do it. Using the touches began: with event and related functions on the root view controller does not work because if a subview is touched the events are not fired. I've also created a 'dummy' gesture recognizer which just passes touch events to another class which draws images. That works great-ish and buttons work, but breaks UIScrollViews and I'm guessing other subviews with gesture reconizers.
Is there nowhere you can just access all touch events without affecting where those touches are headed?
thanks.
Your dummy gesture recognizer should be ok. Just watch out for setting states. possible -> began -> ...
Basically your gesture recognizer is forwarding all touches so it can be in began or possible state all the time while any touch exists.
To get rid of problems with other gesture recognizers return YES in this delegate method.
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
return YES;
}
Other option is to subclass main UIWindow in your app and override this method
- (void)sendEvent:(UIEvent *)event
Here you should have access to all events. It's quite easy to filter them.
You can apply a UITapGestureRecognizer to the entire view and set the cancelsTouchesInView property to NO. This will allow you to be notified of all taps on the view and its subviews without intercepting all of the touch events.
Additionally, you can implement the -gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: delegate method to keep this gesture recognizer from stomping on the ones used by views like UIScrollView.
you can try overriding hitTest:withEvent:
-(UIView*)hitTest:(CGPoint)point withEvent:(UIEvent *)event
This maybe what you are looking for.
I'm getting exactly the behavior I want in a UIScrollView: when I return NO for touchesShouldBegin, the scrolling behavior happens. Otherwise, the content views get the event.
However, I'd like to show something on touch down and touch up when the scrolling behavior is occurring. Unfortunately, returning NO for touchesShouldBegin blocks the touchesBegan and touchesEnded methods.
The delegate method:
-(void) scrollViewWillBeginDragging:(UIScrollView *)scrollView {
doesn't work because sometimes the user touches but doesn't drag. How can I register touchUp and touchDown events yet preserve scrolling behavior?
You cannot. While a UIScrollview is scrolling, the subview(s) (and the view itself) are not updated or redrawn. It only scrolls. It is just how the UIResponder chain works in this scenario.
I'm working in small app for iPhone which uses openGL.
The app is supposed to :
Move around the screen with a moving touch.
Zoom in/Out by tapping
I'm overwriting this functions to handle the coordinates of the touches and move around the screen with my finger, with success, working perfectly:
(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
I'm using UIGesture recognizers to double taps, pinch gestures, swipes, counter pinch with success as well, all gestures being detected perfectly.
But I'm having conflicts. Some times for example, I do a double tap and it's recognized correctly, but it's also passed to my touchedMoved function, resulting in erratic movements. Same thing happens with pinch and counter pinch gestures, most of the time they work well in zooming in and out, but some times my touchesMoved function detect the touches as well and moves the screen.
It's a bad practice to overwrite this functions and use UIGesturerecognizer at the same time ?. If not, it's there a way to work with both without conflicts ?
I tried setting setDelaysTouchesBegan and setDelaysTouchesEnded to Yes in my recognizers, but this results in my touches not being passed to none of my overwritten functions!
I was thinking in using UIGestureRecognizer to handle swipes and scrap the overwritten functions to receive touches, and use the value of the swipe to calculate how much move my screen, is it possible ?
I can't answer for why you sometimes receive spurious touchesMoved: events, but it does sound like you may want to just ditch the overwritten functions and use a UIPanGestureRecognizer to handle moving around the screen.