We created a UIView in a ViewController as a grouping mechanism. Now it turns out for some reason that it does not work as the subviews within it are not drawn (and this is without setting any of the other settings hidden etc.).
I've looked through the documentation and stack but I can't find anything about it. Am I missing something basic in the draw cycle?
See the image below:
The stuff in blue does not display at all and is a subview of View. I moved the yellow out of its subview and normally within the ViewController and that does display now.
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I have a UIToolbar in IB with a custom UIBarButtonItem that is set to an image. The image height is larger than the UIToolbar height. The image does not load for some reason. Attached is a screenshot.
You should avoid using subviews that are larger than the parent view - even if it does work and draws the view outside of the bounds, you cannot always count on it because the clipping is skipped for performance reasons and depending on the drawing order the overlapping part of the subview might be covered later. Second problem is that only the part within the frame of the superview is able to handle the touch events.
As to why you don't see your image, it's probably a different problem, I doubt it has something to do with it going outside the frame. Post your code to get more feedback ;)
I'm trying to speed up my UIScrollView and one method I know of is to set everything to be opaque. I think I have done so, to my UIScrollView, its contentView, the contentView's tiledLayer (I have a CATiledLayer as the actual useful bit that the users see), and on the UIView that all of this sits in. But despite all of that when I look it through the Core Animation instrument with 'Color Blended Layers' turned on the scrollview's contents are shaded red showing they are transparent. The only green bits are outside the bounds of the contentview (which I can only see when it pans out to the side and then bounces back).
Is there something built in to ScrollViews, or CATiledLayers that could be ignoring 'setOpaque:' or have I messed up my view hierarchy and left something not-opaque?
To answer the question "Have I messed up my view hierarchy and left something not-opaque?", from https://developer.apple.com/library/ios/technotes/tn2239/_index.html:
UIView implements a useful description method. In addition, it implements a recursiveDescription method that you can call to get a summary of an entire view hierarchy.
So, call -recursiveDescription on the topmost view, and check each subview for opaque = NO;.
I have a UIView which contains a zoomable UIImageView and also another semitransparent UIView on top of that.
What I am trying to achieve is to be able to zoom the UIImageView while keeping the semitransparent view static and not zoomed.
If I add the semitransparent UIView on top of the UIImageView (which is added to the UIScrollView), everything zooms. However, if I add both as subviews to the base UIView, the touches only get tracked is the semitransparent UIView since its the last one added.
I do need control to reside first at the semitransparent UIView for the touches since I may want to resize the semitransparent view. However, I'd like to pass control of the touches to the UIScrollView if two fingers are used. Is there anyway for me to achieve this? The nextresponder doesn't seem to work. I also tried to use hittest in addition to subclassing UIWindow, but the base UIView needs to push/pop navigation controlling ability so I don't think I can subclass UIWindow to push onto the navigation stack.
Any help would be appreciated.
Thanks,
Winston
Hm.. you can try this hierarchy (possibly subclasses):
UIView (container)
> UIView (semitransparent overlay)
> UIScrollview
- UIView (zoomable content)
Like this, the overlay does not scale.
The tricky thing then is the user interaction on multiple layers. Its easy if there are areas in your overlay that should not detect user touches, for that you just set the UIView property 'userInteractionEnabled' to 'NO' for the view parts where touches should be 'forwarded' to the underlaying layers.
But if I get you right, you need something more complicated. You probably could set up some kind of master-touch-controller in the container UIView, that finds out what is happening and then calls certain methods of its subviews / forwards the events.
I don't know all the exact methods you need to override/implement in the container, but check out the tapZoom demo from the ScrollView Suite sample code. It's a pretty nice example there.
Just out of curiosity, may I ask what this interaction model is used for?
I am currently working on an application for a client, and they have made an odd request. The request involves putting a custom image as the indicator for the scrollview. I am not even sure if this is possible but if it is can you please let me know how one would go about doing that.
Thanks
UIScrollView streches a small, semi-transparent circle image to generate its scrollbars. You can find this image as the first subview of a UIScrollView:
UIImageView *circle = [scrollView.subviews objectAtIndex:0];
However, as I said this image is stretched, and as far as I can tell, only the alpha values are considered when drawing the scroll bars.
So for example if you're only interested in changing the top/bottom ends of the scroll bar, you can try to change this image. However, I doubt you'll be able to do anything interesting.
A possible solution that comes to mind, and this is only a theory, is to add a custom, transparent UIView on top of a UIScrollView. Then you can hide the default scroll bar (by using showsHorizontalScrollIndicator and showsVerticalScrollIndicator), pass the necessary touch events to the UIScrollView to scroll the content, and draw the scrollbars in your custom view.
I've created a NIB file with some button controls on it, and as a background it has an ImageView which contains a PNG file loaded from my project.
What I want to do is to draw on top of the ImageView - imagine that my UI is a clockface and I want to draw the hands of the clock on top of the background image.
Is it the correct approach to try to subclass the UIImageView and use its DrawRect as when I use the DrawRect of the default view I don't see anything on the screen?
I'm a little lost as I'm finding this particular bit of the documentation hard to follow.
Thanks.
Create a new custom UIView (e.g. named HandsView) that sits on top of your background view (by adding it as a subview of the UIImageView). In the custom view, you can use the drawRect method. Make sure, you clear the context to transparent, so that the background image can be seen below the HandsView.
If you just want to draw turning hands, you can also try to use two fixed UIImageViews with the images of the hands and use the transform property to apply a rotation.