I have a UIWebView which is embedded in a UIScrollView. The webView is resized so that the scroll view manages all the scrolling (I need control over the scrolling).
In the webView I have disabled userSelection via '-webkit-user-select: none;'
Everything is working fine except one annoying detail. When I hold down my finger on the content before starting to scroll for about a second the scrollView won't scroll. My best guess is, that it has something to do with userSelection. The time is about the same it usually takes for the copy/paste/magnifying-thing to appear which usually disables scrolling as well.
I am running out of ideas on how to solve this. Every help would be greatly appreciated!
Thanks!
EDIT: Another aspect of the problem is, that the non-scrolling actually triggers JS-Eventhandler (click, mousedown, mouseup) inside my webView which leads to surprising app behavior. The user puts her finger down, waits, scrolls, nothing happens, removes her finger and this is perceived as a click, which feels wrong from a users perspective.
I would guess what is happening is that after that short duration, the scrollview is no longer interpreting the touch as being on it's view and instead passes the touch down to it's content views.
Have you tried delaying the content touches for the scrollview? This will essentially tell the scrollview to delay taking action on the touch event and instead to briefly monitor the touch and if the touch moves then it recognizes it as a swipe gesture for scrolling. If it doesn't move, it will eventually pass the touch along to it's subviews.
scrollView.delaysContentTouches = YES;
I think even then, there is a standard delay time before the scrollview will pass the touch events along the responder chain. If you hold for too long, it's going to naturally perceive it as being a press down event rather than a scroll event.
This question is not relevant anymore. As of iOS 5.0 the UIWebView is based on a real UIScrollView and also exposes that UIScrollView via a property. Use that instead.
And don't mess with UIWebViews embedded in UIScrollViews anymore. The documentation explicitly advises against that.
Relevant Documentation
Related
I'm using a UIScrollView to display a custom UIView. When the user drags a finger across the UIScrollView, there is a noticeable delay before the display begins updating. If the user keeps touching the screen, the UIScrollView becomes very responsive after a short time. Subsequent attempts to scroll result in the same initial delay, followed by high responsiveness. This delay seriously affects the usability of the view and I would like to get rid of it.
In a test project I have written to try to get to the bottom of this issue, I have only been able to partially replicate the behaviour. The first time that the user scrolls is exactly the same - however any subsequent attempts to scroll are responsive straight away.
I have tried both setting delaysContentTouches = NO and subclassing UIScrollView so that touchesShouldBegin returns NO as suggested in multiple places online, but neither has worked.
I'm using MonoTouch on iOS 4.3, but Objective-C answers are fine. I would post code to help illustrate the issue, but since I have been unable to narrow down the problem this would be well over 1000 lines. Hopefully this is enough info to get a solution.
Does anyone know what might be causing this delay, and how I can get rid of it?
Some general suggestions for improving scrolling performance.
Have your scrolling views rasterize offscreen:
myView.layer.shouldRasterize = YES;
Set that property for each sub-view on the scrollview - do not set it for the children of those sub-views or you just eat up memory that way.
If your scrolling views do not need compositing, make sure you turn that blending off:
myView.opaque = YES;
Test using the simulator by leveraging these two features that appear on the Debug menu of the iOS Simulator:
Color Off-screen Rendered
Color Blended Layers
If that doesn't address your problem, and you have implemented UIScrollViewDelegate, double-check to make sure you are not doing anything time consuming in those methods - for example, based on your description, you might be doing something in scrollViewDidScroll, scrollViewWillBeginDragging, or scrollViewWillBeginZooming and if you are, optimize that so it happens before scrolling even begins. Also, make sure you're not doing anything in touchesBegan.
I suspect what is happening is there is some kind of interaction enabled in the content of your scroll view.
The system does not know if the initial touch down is going to be a tap on one of the subviews or a drag on the scroll view, therefore is causing a delay while it waits to see if you are going to lift your finger.
What are the subviews of the UIScroll view?
As an experiment set all the subviews of the UIScrollView to have userInteractionEnabled = NO, this will not be what you want, but its just a test. Is should scroll fine after this, otherwise I am wrong.
When you're working with an atypical nested UITableViews setup - where you have an outer vertical UITableView that hosts 90° rotated UITableViews (see: Looking for a UI library to present Data horizontaly in iOS ):
is there a way to make iOS process vertical and horizontal touches at the same time?
I found that iOS is very clever in processing touches:
horizontal touches make the relevant horizontal UITableView scroll, while a vertical swipe makes the outer UITableView scroll. Perfect.
Only, I'd love to be able to move my finger diagonally and see the outer UITableView and the inner UITableView scroll at the same time.
I tried a few approaches (playing with canCancelContentTouches, delaysContentTouches, and touch messages) but I haven't found a way to make this happen.
EDIT:
Here's a XCode4 project that shows this behavior: http://marcanton.io/other/stackoverflow/nestedtableviews.zip
EDIT:
I submitted this issue to Apple Developer Technical Support, here's their reply:
Thank you for writing to Apple
Worldwide Developer Technical Support.
I am responding to your inquiry
concerning touch events in embedded
UITableViews.
Typically this is an approach that is
not recommended. The issue is that
UITableView inherits from UIScrollView
and as stated in the documentation for
UIScrollView:
"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."
http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIScrollView_Class/Reference/UIScrollView.html%23//apple_ref/occ/cl/UIScrollView
So that this time, there is not a
workaround for getting both to scroll
at the same time.
I recommend that you file an
enhancement request at
http://developer.apple.com/bugreporter/
detailing what you would like to see
us add in a future release.
Still, I think that there has to be a way to enable this functionality, although I understand that this is not recommended. In fact, Apple does not even recommend hosting UITableViews inside another UITableView, but with the exception made above, it works quite beautifully.
I'll keep this question updated with our collective findings.
EDIT: There actually is a way, detailed here: http://marcanton.io/blog/nested-orthogonal-tableviews/
This would have to be a custom mirroring of intercepted touch events. Touch events follow the responder chain model, which means that if an object in the responder chain (the top most (outermost) view) cannot handle the event or action, it resends the message to the next responder (in this case the background UITableView in the chain). This is why you are seeing the horizontal events go to the horizontal UITableView and the vertical events going to the vertical UITableView. A diagonal touch event has applicable horizontal and vertical events, so the top-most view (the outer vertical UITableView) can respond to the vertical touches and swallows the event.
If you think about it, all vertical touches likely have a little bit of horizontal events (think about when you flick your finger), so there is likely some work done in the background to determine how to interpret the touch event (either as a vertical or horizontal).
I found this tread on passing events down to the next object in the responder chain. You might want to give this a try as a partial solution to your puzzle. The rest is to figure out how to capture the horizontal touch events and pass them along to the next responder.
Interesting, I haven't played around with this kind of setup yet, but I would try to intercept touch events on the nested UITableViews and delegate any vertical movement to the outer UITableView - and vice-versa.
I want something similar to how the iPhone homescreen works. I have my scrollview inside my main view, which scrolls to the right, but when you touch on the UIButtons, they become highlighted and dragging means they don't end up getting pressed but also the scrollview doesn't end up scrolling. It doesn't do this on the homescreen. How can i make it similar to this?
A touch-down-drag is a completely different event. Apple doesn't support this directly—you'd have to code it in—start tracking the touches using the gesture responders as soon as a touch-down-inside is detected, then scroll the same amount, and stop scrolling at a touch-up-outside (or inside). This would most likely fall under the category of unusual use of interface elements, and could very well get you rejected.
I think this is a better answer to the question:
UIScrollview with UIButtons - how to recreate springboard?
I'm using a UISwitch-Component at the bottom of a view that sits within a UIScrollView.
Now the problem that appeared, is that the switch is nearly impossible to swipe because the UIScrollView seems to dominate the userinput.
Switching works very well by tapping the switch, but from my point of view, most users "switch" the UISwitch instead of tapping.
Did anyone of you face the same / or similar problems and managed to come up with a solution?
thx in advance
sam
You have a design decision to make: if your content is meant to scroll horizontally, then a user swipe over a switch is ambiguous -- does it mean they want to scroll, or toggle the switch?
The easiest solution is to modify your UI so that this ambiguity disappears. For example, if the scroll's contentSize is not wider than the bounds of the scroll view, then it can't scroll horizontally, and a horizontal swipe will always activate the switch.
If you do want to allow horizontal scrolling, then it makes sense to replace the UISwitch with a UIButton that toggles on touch, similar to a play/pause button.
On the other hand, if you don't want to modify your UI, you could always just do:
myScrollView.delaysContentTouches = NO;
This will cause your switch to "get" the touches immediately, rather than have them go to the UIScrollView first. More info here. (You can also set this boolean in Interface Builder, as pointed out by Squeegy.)
I'm about to start a new iPhone app that requires a certain functionality but I'm not sure if it's doable. I'm willing to research but first I just wanted to know if I should at least consider it or not.
I haven't seen this in an app before (which is my main concern, even though I haven't seen too many apps since I don't own an iPhone), but an example would be the iPhone shortcuts panels: you can hold on an app, and then drag it to another panel, sweeping while still dragging it. But this is the core app, is it possible to reproduce something similar within a normal app?
I only need to be sure it can be done before I start digging, I don't need code examples or anything, but if you have some exact resources that you consider helpful, that would be appreciated.
Thanks!
Yes. If you have your custom UIView subclass instance inside a UIScrollView, your view controller just needs to set the UIScrollView to delay content touches and not allow it to cancel touch events.
[scrollView setCanCancelContentTouches:NO];
[scrollView setDelaysContentTouches:YES];
When the user taps and holds in the custom view, the event goes to that custom view, which can process the touch events to drag an item around, but if the user quickly swipes, it scrolls the view.
The "panel" view that you're referring to appears to be a UIPageControl view — although, perhaps, the specific incarnation of this view that Apple uses for the iPhone's home page may be customized.
Instances of generic UIView views that you might touch-and-drag will receive touch events. By overriding methods in the view, these events can be processed and passed to the page control, in order to tell it to "sweep" between pages.
If I wanted to do what you're asking about, that's how I might approach it. It seems doable to me, in any case.
Start with this: Swip from one view to the next view
Try using a UIButton that tracks the time since the state of the button changed to "highlighted". You may need to do this in order to track the dragging and move the button around:
Observing pinch multi-touch gestures in a UITableView
Check to see if the button starts overlapping one side of the screen while being dragged. If s certain amount of time elapses since the button first started overlapping the edge and then manipulate the UIScrollView so that it switches to the next page on the corresponding side of the screen
You may need to use NSTimer to keep track of how long the button is held down, etc.
In any case there's no reason why this couldn't work.
If UIButton doesn't work then perhaps try a custom subclass of UIControl (which tracks the same touch down actions etc.). If that doesn't work then use the window event intercept thing to track everything.