I placed a few uiimageview objects into a scrollview. How can the imageview know the scrollview is being scrolled? Since the imageview is a subview of the scrollview i can't set the scrollview delegate to the imageview.
I want to create something similar to the apps view on the iphone. Where you can hold down an app and then drag it, but if you hold and move your finger too far to the left or right the action is stopped and scrolling takes over.
"Since the imageview is a subview of the scrollview i can't set the scrollview delegate to the imageview."
And why not?
You have viewcontroller which shows the particular scrollview correct? this viewcontroller should be the delegate of the scrollview, and viewcontroller should also hold pointers (either explicitly in an array or through tag of some sort) to the uiimageviews.
Then, whenever scrollview notifies viewcontroller (through scrollviewdidscroll type of delegate method), implement your logic to update uiimageview.
To implement the exact touch sequence, you can subclass UIGestureRecognizer or write your own touch handler.. take a look at Apple's documentation on Event Handling Guide :
http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/Introduction/Introduction.html#//apple_ref/doc/uid/TP40009541
It doesn't, it just draws and draws. The scrollView makes sure you only see the part you really want to see
You might want to look at three20, they have a class that is very similar to the springboard. -- Used in facebook.app
Thanks Everyone, but I found out that UIScrollView sends the touchesCancelled message to the subview when scrolling starts.
Related
I have an atypical iOS interface. Perhaps it's not practical but I'm giving it a go. Hope someone can help!
I have a menu in the form of a UIVIew. It contains 5 small UIImageViews. A UIPinchGestureRecognizer is attached to the UIVIew. When pinched inward, the 5 UIImageViews animate from off screen to form a circle in the middle of the window. When pinched outward, they animate back offscreen. Everything works great there.
I'd like to be able to, at any point in the application, pinch the screen to reveal the menu, select one of the 'buttons' (UIImageView), and load the associated subview.
The real problem is, if the current visible view is a UIScrollView or UITableView, my app is having trouble figuring out whether the menu or other subview should handle the touch event. If I really focus and make sure two finger touch the screen at the EXACT same time, the pinch will work and pull the menu inward. But otherwise, it attempts to scroll the current visible view.
I would like all events except the pinch gesture, (and a tap gesture when the menu is visible), to pass through the menu view to the rest of the subviews.
I understand I can override the hitTest:withEvent method to determine the correct view to handle the event, but I'm unclear at this point how exactly to use it. Neither the Apple docs nor any answers I've read on stack overflow have made this method clear to me.
Any help is much appreciated.
As UITableView is a subclass of UIScrollView, it inherits all of UIScrollView's properties including its gesture recognisers.
UIScrollView declares a UIPinchGestureRecognizer and UIPanGestureRecognizer. I'm not sure of the implementation details but I imagine the UITableView disables the pinch gesture recogniser as you are not supposed to be able to zoom a tableview!
In any case, you can attach your own UIPinchGestureRecognizer to the table view:
UIPinchGestureRecognizer *yPGR = [[UIPinchGestureRecognizer alloc]
initWithTarget:probablySelf action:yourMenuShowSelectorHere];
UITableView *tv = ...
// ...
[tv addGestureRecognizer:yPGR];
Then, you can make sure that the UITableView scoll does NOT scroll until your pinch has failed:
[tv.panGestureRecognizer requireGestureRecognizerToFail:yPGR];
This way, the UITableView will not scroll until it is sure that it has not detected a pinch.
EDIT: UIScrollView only uses (or at least declares public access to) UIGestureRecognizers in iOS 5 and up.
I have a scrollview with lots of buttons in it,I have a header-imageview with close-button and a title-label in it.the problem is when I scroll the scrollview the header-image also scrolls up.I don't want this,how can I stop scrolling the header-image with the other buttons.
How can I do this?.Thanks in advance.
There are two ways to do this:
You can subclass UIScrollView and override layoutSubviews to reposition your header view.
You can assign a delegate to your UIScrollView and implement scrollViewDidScroll: in the delegate to reposition your header view.
The WWDC 2011 session video "Advanced ScrollView Techniques" explains how to do it. In the video it is called a "stationary view". Go watch it.
Preparing a parent view to which both scroll view and header image will be attached as subviews should do.
I have a transparent overlay that I'd like to put over a UIScrollview. I'm adding it as an Imageview sibling view to the scrollview so that it remains stationary while the scrollview subviews move freely underneath. The problem is that views pass their events to the superview, not the siblings. IS there a way to pass events from this overlay to the scrollview? Or can anyone think of a better way to achieve the same effect? Thanks!
This should Just Work, as long as the UIImageView has its userInteractionEnabled property set to NO: the superview sends -hitTests:withEvent: to its subviews in order, and the UIImageView should return nil, whereas the UIScrollView should return itself (because it has gesture recognizers).
If it's not working for you, the chances are that your view layout is not what you think it is. UIView has a useful method called -recursiveDescription which you should call on the superview and NSLog the result.
UIView -> UIImageView
I know I have things somewhat working ok since I can tap on my UIImageView and see an NSLog() statement in my touchesBegan method.
.
UIView -> UIScrollView -> UIImageView
I drag that same UIImageView into a UIScrollView and touchesBegan no longer gets called when I tap on my UIImageView. (I haven't changed anything else. All the same connections, methods, and code remains unchanged.)
Why does touchesBegan no longer work? And what can I do to get it working again?
Add uitapgesture to get event
Code is
UITapGestureRecognizer *ges11=[[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(Handeltap:)];
[imagename addGestureRecognizer:ges11];
Create one action name "Handeltap" U will get called there.
by default UIImageView don't handle user gestures.
set UIImageView instance's userInteractionEnabled to YES
Have a look at the documentation for UIScrollView.
Because a scroll view has no scroll bars, it must know whether a touch signals an intent to scroll versus an intent to track a subview in the content. To make this determination, it temporarily intercepts a touch-down event by starting a timer and, before the timer fires, seeing if the touching finger makes any movement. If the timer fires without a significant change in position, the scroll view sends tracking events to the touched subview of the content view. If the user then drags their finger far enough before the timer elapses, the scroll view cancels any tracking in the subview and performs the scrolling itself. Subclasses can override the touchesShouldBegin:withEvent:inContentView:, pagingEnabled, and touchesShouldCancelInContentView: methods (which are called by the scroll view) to affect how the scroll view handles scrolling gestures.
I'd also recommend reading the Scroll View Programming Guide.
I have a view hierarchy that is layed out as follows:
parentView
scrollView
contentViewA
containerView
contentViewB
contentViewC
I want contentViewB to respond to touches. Unfortunately scrollView makes this almost impossible because it tries to ingest the touches itself making touch response of contentViewB spotty.
So, instead, I want to intercept all touches in the parentView, manipulate contentViewB directly, and then pass the touches on to scrollView so it can do its thing.
Can someone please show me the correct way to pull this off?
Thanks in advance.
Cheers,
Doug
UPDATE:
I did a bit more digging and found the property canCancelContentTouches which seems to work wonders. I'm using IB so I unchecked "Cancellable Content Touches" in IB - first tab of the Scroll View Attribute Inspector. Now, when I run the app, touches appear to be arriving at contentViewB reliably.
Here's how the UIScrollView docs describe this property:
Discussion
If the value of this property is YES and a view in the content has begun tracking a finger touching it, and if the user drags the finger enough to initiate a scroll, the view receives a touchesCancelled:withEvent: message and the scroll view handles the touch as a scroll. If the value of this property is NO, the scroll view does not scroll regardless of finger movement once the content view starts tracking.
Rather opaque huh? Anyway, it seems to work.
To stop the scroll view from intercepting the touch events, set the userInteractionEnabled property like so:
scrollView.userInteractionEnabled = NO;
Another way of doing this is to add another subview to your ui so it looks like so :
parentView
scrollView
contentViewA
containerView
contentViewB
contentViewC
touchGrabber
and, in touchGrabber, detect all the touches that you want (by subclassing UIView)
This is more complicated than Phil Nash's solution but has the advantage that you can add/remove other views from your parentView without having to deal with their userInteractionEnabled value - this is useful if you have a third party library adding views for example.
However, if you definately only going to have the scrollView, Phil Nash's answer is the way forward!
Thanks,
Sam