Perhaps there's a better way to set this up so I'm open to suggestions.
But here's what I'm doing. I have a main UIView. On top of that I have a UIImageView and another UIView. When the UIImageView changes, I want to change the second UIView. So I have a class for it and the IB object's type is set to the class. In the .m of that class is a drawRect method that draws some rectangles. Also in the .m is a NSMutableArray property that is synthesized. I created an instance of that class in the controller of the main view.
The problem: despite the fact that the drawRect works fine when the app starts (as traced in the debugger,) when the UIImageView changes I call a "setNeedsDisplay" on the instance variable of the second view after updating the #synthesize'd array but the drawRect does not get called.
I think it has to do with instances. I wouldn't think threading would be an issue here. I just want to draw in a separate area of the screen based on an image also displayed.
OK, for those who see this and are having a similar issue...
It was indeed an 'instance' problem. I had created the secondary UIView in IB. I think because I had established a connection there, the code ran fine on startup.
The fix was to create the subview programmatically and add it to the main view. That way there was only the one instance. Updating the #synthesize'd array variable and the subsequent calls to drawRect (via setNeedsDisplay) went to the one instance of the secondary view, the one I had added as a subview to the main one. Problem solved.
Related
I was googling for a while and I found similar problems but when the custom View is inside a ScrollView, but that is not my case.
I have a custom view that consists of a UILabel behind a UITextField, so I can animate that label later.
The problem is that when I add a View in my ViewController and in the Identity Inspector I set the Class as my custom class, when I use the application the UITextField within my custom view does not receive the touches well and it takes time to gain focus and therefore to open the keyboard. The strange thing is that if I move that same arrangement of views to my main ViewController in Storyboard everything works fine. Why doesn't it do it when I place it using the described method?
I plans to reuse this custom view a lot, so putting logic and views in each ViewController is not an option.
Thanks in advance
Well, the problem was in the constraints of the container UIView. That means, the UIView in my main ViewController. The Height of the UIView was a little bit smaller than the space required for my custom view, so although my custom view seemed to draw correctly, it was not receiving the gestures correctly. The solution was simply increase the height to the correct value occupied by my custom View. Thanks a lot!
I am using the AFOpenFlow library to generate a coverflow-like effect, but trying to add arbitrary UIViews to an AFOpenflowView, not just images. I am doing this by creating a subclass of of AFItemView, lets call it NewAFItemView, which represents the view I want to add. I also extended AFOpenFlowView, call it NewAFOpenFlowView and overrode the method
-(AFItemView *)coverForIndex:(int)coverIndex;
In the overridden method, I allocate an NewAFItemView object and return it as the cover view for that index. The NewAFItemView views appear correctly in the open flow but scrolling is immediately disabled. Switching back to allocating AFItemViews works but using NewAFItemViews does not scroll.
I have not overridden any of the touch events.
Any ideas on what might be happening?
Cheers.
why don´t you use iCarousel?
https://github.com/nicklockwood/iCarousel
i use this, and it works perfect for uiviews =).
I have a custom UIView which is a sub-view of a UITableViewCell. When the cell is drawn, so is my custom view, correctly calling drawRect: in my UIView sub-class. When the cell is reloaded, the view is drawn correctly (drawRect: is called).
When a certain event happens (eg timer), I want to redraw the view without having to reload the whole cell. (This is not the only view in the cell.)
However, when I call setNeedsDisplay on my sub-view, nothing happens.
I'm guessing that when my view's drawRect: is called, the resulting image is cached in a backing somewhere such that when I call setNeedsDisplay that backing is redrawn to the screen, but my drawRect: call is never called again.
Why is drawRect: never called again after the cell is created?
EDIT: The cell's subviews are created from from a nib. ie: a UIViewController is loaded from the nib and its view is added to the UITableViewCell.
I made a test case from scratch with a custom view that isn't loaded from a nib (created by code) and it works as expected: setNeedsDisplay results in a drawRect: call. It must be something that's either set up in the .xib file or something that happens differently to a view when it's loaded from a nib.
I just ran into the same problem myself. For me it was an issue with my XIB - I am subclassing a UIView though - so adapt accordingly. My mistake in IB was that I attached my controls to the "file's owner" instead of attaching them to the UIView. I'm sure that in my inexperience there is something larger going on - perhaps someone with a bit more experience can elaborate.
Hope that helps!
I have some custom drawing code in drawRect which also performs some calculation of sizes.
When is the earliest I can be sure that this code has been loaded, e.g. if I want to modify it's containers size accordingly?
-[NSView viewWillDraw] is a reasonable place for last minute layout.
I have some custom drawing code in drawRect which also performs some calculation of sizes.
When is the earliest I can be sure that this code has been loaded, e.g. if I want to modify it's containers size accordingly?
An object can't exist until its class is fully loaded. If you have an instance, the class that it's an instance of is completely loaded, because you wouldn't have an instance of it if it wasn't.
As for when it's called: It's called when you need to draw. This normally happens as part of the event loop, if anything has marked the view as needing display. It is possible to directly tell an NSView to display, but, as far as I can tell, this is not possible for UIViews.
So, if you need to do something to it before it gets told to, either do it immediately after creating it or, if you're about to set the view as needing display, do it before you do that.
Just before the view is displayed or when you call
[aView setNeedsDisplay];
I just created my first customView app. This was one of my questions. my drawRect method was called once upon creating my window (or recreating). And millions of time when resizing my window.
I am trying to create a custom UIView that is stored in a nib so that I can position it using Interface Builder.
I have created a class called RippleView that extends UIView. I'd like to position this view as a subview using Interface Builder. To do so, I've dragged a new view into my existing view in Interface Builder and gave it the RippleView class identity. I then linked my RippleView outlet to the view I just created.
In the RippleView class, I've implemented initWithCoder which doesn't do anything other than call [super initWithCoder...]. In awakeFromNib I go ahead and initialize my code.
Now, for some reason, if I try to check the bounds of the RippleView in awakeFromNib, I get ridiculous values (0 width and 1081171968 height). These bounds don't change in drawRect, so I don't think it's an issue of the view not being initialized. I get similar values in my touchesMoved event handler.
I had no problems when I was programmatically creating the subview (initWithFrame). What could be causing the frame bounds to go haywire?
Solved! The issue had nothing to do with the code. The UIView bounds are floats and I was printing them as integers. It's things like this that separate the programmers from the dropouts :p
Can you post your initWithCoder: implementation? If you're not setting the value of self, or if you've misspelled initWithCoder:, you might see these sorts of problems. Have you tried setting a breakpoint in initWithCoder: to make sure it gets called?