I have a scrollview where I added several buttons (dynamically, programmatically). Hence my view is totally covered with buttons. Also there are some labels
However, I observed that the uiscrollview is not scrolling when the drag starts on the button. All labels work fine. But I want this scroll to happen i.e. when drag event occurs in the uibutton, I want it to send this event to its superview (scrollview).
Please note, according to my search, subclassing the scrollview and overrriding the content touches event, or add touch began actions to uibuttons are not helpful.
How do one in general work with this event passing things when objects are added dynamically?
You have to subclass the UIScrollView, there's no other proper way, but you do not need to mess with the touch events. All you have to do is override this method
- (BOOL)touchesShouldCancelInContentView:(UIView *)view {
return YES;
}
And set the canCancelContentTouches property of the UIScrollView to YES.
Related
I have my standard app setup, window with lots of views. From time to time I place an NSView over the top of everything, black with some transparency, to act an a dimmer/overlay.
I need this top overlay view to absorb all clicks so that any views underneath it can't be interacted with. E.g. an NSButton under this NSView won't be clickable.
How can I do this?
I have seen -(NSView *)hitTest:(NSPoint)aPoint but I don't want to put this on every single subview with a rule to block clicks while the overlay view is present.
Override the NSView with an empty mouseDown: and the views underneath will not receive any mouse events.
In my iOS app have a UITableView which contains a custom subview in one of it's cells. This cell is an interactive view that handles touch events (touchesBegan, touchesEnded, touchesMoved) to update itself.
The problem is that when the user 'drags' up or down, the tableView catches these touches (although I don't pass the touches up the responder chain), scrolls the table and prevents the subview from working correctly. I would like to prevent the table from scrolling as long as the user is touching that particular subview.
The subview has no reference at all to the tableView.
How can I prevent the scrolling behavior of the table?
Update
Despite accepting the answer below, I ended up handling my situation differently. I handle the touch events in my custom view now, pass them up the responder chain (to the table cell), the cell handles the touch events as well, using them to enable/disable scrolling on the superview (the table).
Turning off "Cancellable Content Touches" in the UITableView solved this for me (in the UITableView attributes inspector under Scroll View / Touch). I got this from this SO question: Scrolling a UITableView inside a UIScrollView
From the UIScrollView:canCancelContentTouches doc:
If the value of this property is NO, the scroll view does not scroll
regardless of finger movement once the content view starts tracking.
The most common method I use in such cases is to delegate information up the event chain. Set delegates in manner:
subview->cell->table
The second thing you can do is to send a notification via Notificaion Center. Table would listen to any events that forbid normal scrolling. It is overshoot but it will leave your code consistent.
I have no more ideas at the moment.
I have a view controller that is basically a form with multiple UITextFields and UITextView, embedded in a UIScrollView. When an UITextField becomes first responder, the scroll view automatically move to the focused field, which is believe is the behaviour explained in the first answer in this topic :
Disable UIScrollView scrolling when UITextField becomes first responder
This does not happen when the first responder is an UITextView though, and I'm not sure why and how I should fix it.
The second problem is that when the keyboard is shown, the scroll view does not scroll if the UITextView is not in view (because it's hidden by the newly shown keyboard). I implemented the code of Apple's documentation on how to manage the keyboard :
http://developer.apple.com/library/ios/#DOCUMENTATION/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/KeyboardManagement/KeyboardManagement.html
And added another activeField variable named activeView for textViews (initialized in the beginEditing of TextView, set to nil in endEditing, and scrollToVisible according to it's frame when the keyboard is shown). The problem here is that the beginEditing in UITextView is called after the keyboardWasShown, so the activeView is not initialized and thus does not scroll. For some reason, for UITextFields the beginEditing is called before, which is the intended behaviour.
How can I scroll to an UITextView and it's the first responder, and how can I move to it when the keyboard is shown and hide it?
To scroll to show anything in a UIScrollView do
scrollRectToVisible:/*frame of object you want to show*/ animated:YES
Subscribe to UITextViewTextDidBeginEditingNotification and call the above method when you get it.
I have custom UIScrollView subclass with some content views inside. In some of them I have UITapGestureRecogniser. All works fine when scroll view is not scrolling. But when it scrolling content views does not receive tap action. What is the simplest solution to handle tap action by subview while scroll view is scrolling?
Details:
MyScrollView scrolls horizontally. It contains a lot of content views (e.g. MyContentView). Each MyContentView has width about one third of MyScrollView width. So there are about 3-4 visible MyContentView elements at a moment. The main behavior of MyScrollView is to 1)make sure that after scrolling one of MyContentView elements will be at center of screen and 2)to scroll to center of MyContentView if user taps on it. So the main answer I hope to get is how to "properly" implement handling of tap action in MyContentView while MyScrollView is decelerating.
I found some same questions and answers but none of them satisfied me. The best was to implement gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: of UITapGestureRecogniser delegate. But in this case I sometimes (when I tap, make smaaaal drag and release finger so tap is steel recognizable(lets called it quasi tap)) have both tap and scroll events and it leads to bugs for me even if scroll view is not scrolling when I begin tap. When user make quasi tap my application tries to scroll to tapped MyContentView element and than immediately handle normal scrolling. It seems even more terrible, due to some other functionality start to perform after handling tap (it must not perform when normal scrolling).
I need solution where scroll view wait enough to decide it is not tap event and only then make scroll. Otherwise if tap event had recognized scroll must not happen.
You can go with the custom delegates methods as well, using #protocol. Implement those delegate methods in view controller where your UIScrollView has been added.
like in MyContentView:
In touchesBegan method,
[self.delegate contentViewTapped:self];
Now in ContainerView class where scroll view is added, implement that method:
- (void)contentViewTapped:(MyContentView *)myContentView {
NSLog (#"ContentView no: %d", myContentView.tag); // if tag has been set while adding this view to scrollview.
}
Go through the examples for #protocol.
Hope this is what you required.
Enjoy Coding :)
This is built into UIScrollView - take a look at the delaysContentTouches and canCancelContentTouches properties. This should alleviate the problem when dragging a small bit after a tap.
This is all system built-in behaviour. I would suggest sticking with what Apple has provided for the feel of your interface (how it reacts to small drags, for instance) so that your app doesn't feel out of place on a user's phone.
EDIT:
Alternatively, you could disable scrolling of your scroll view in you gesture recognizer and re-enable it once it's ended/cancelled.
Further Edit:
I don't understand - I've created a sample project that illustrates how to intercept touches in a subview of a scroll view using gesture recognizer delegate methods. Play close attention to the "Cancellable Content Touches" and "Delays Content Touches" properties of the scroll view. They're both YES for very important reasons.
You scroll view should be delaying content touches until it has determined if the user is attempting a tap, pseudo-tap (as you put it), or a pan for the scroll view. Apple has already written the functionality you're trying to build; UIScrollView will already do what you want.
The problem is that the system doesn't want a scroll view's subviews intercepting tap events while the scroll view is scrolling. To this end, it cancels touch events if it determines that the user is actually trying to pan. Setting "Delays Content Touches" enables this behaviour. Ensure it's turned on and you should be fine.
I have a UITapGestureRecognizer on a UIViewController, which has a UIScrollView and UIWebView inside. It recognizes the tap gesture only after I scroll the UIWebView. How could I prevent this ?. Basically I want the tap gesture to be detected, when I am not scrolling the web view. I looked around and the closest I found is this:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer*)otherGestureRecognizer {
return YES;
}
but not sure how can I use this to disable the tap while scrolling. Any idea?
Another thing I want to do is to disable the UITapGestureRecognizer, when a link on the UIWebView is clicked (shouldStartLoadWebRequest is called). I checked that the tap gesture recognizer is called, before the shouldStartLoadWebRequest is called. Basically when clicking on a link on a UIWebView, it shouldn't trigger the action invoked by the UITapGestureRecongnizer. Any idea on how to do this?
So Apple's documentation strongly recommends you don't nest a UIWebView inside a scroll view:
Important: You should not embed UIWebView or UITableView objects in UIScrollView objects. If you do so, unexpected behavior can result because touch events for the two objects can be mixed up and wrongly handled.
It is possible on iOS 5 and above to get direct access to the underlying scroll view on a UIWebView (using the scrollView) property - playing around with this might help you.