In my iOS app I am observing changes to the contentOffset property of my scrollView subclass. My observer handler looks like this:
- (void)observeContentOffsetHandler:(id)aContentOffset {
NSLog(@"%@", aContentOffset);
}
I chose the parameter to the method arbitrarily as an id for simplicity.
My NSLog'ging looks like this:
-[MyScrollView observeContentOffsetHandler:] [Line 111] NSPoint: {296, 375}
-[MyScrollView observeContentOffsetHandler:] [Line 111] NSPoint: {296, 389}
-[MyScrollView observeContentOffsetHandler:] [Line 111] NSPoint: {295, 401}
-[MyScrollView observeContentOffsetHandler:] [Line 111] NSPoint: {291, 415}
I need to use the x and y values but I have no idea how to get at them. I've tried casting the id to a CGPoint, nope. I've tried changing the param to a CGPoint, nope.
UPDATE
It gets deeper. @mgold no joy. Here is how I set up observation:
self.contentOffsetObserver = [[[Observer alloc] initWithTarget:self action:@selector(observeContentOffsetHandler:)] autorelease];
[self.myScrollViewSubclass addObserver:self.contentOffsetObserver forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew context:NULL];
Observer is a handy class I use to make observation easy. Note the observer callback observeContentOffsetHandler:. When I change the signature of this method from its current:
- (void)observeContentOffsetHandler:(id)aContentOffset
to @mgold's suggestion of CGPoint:
- (void)observeContentOffsetHandler:(CGPoint)aContentOffset
It is incorrect as NSLog shows with all zeros for aContentOffset:
-[MyScrollController observeContentOffsetHandler:] [Line 74] aContentOffset 0 0
-[MyScrollController observeContentOffsetHandler:] [Line 74] aContentOffset 0 0
-[MyScrollController observeContentOffsetHandler:] [Line 74] aContentOffset 0 0
-[MyScrollController observeContentOffsetHandler:] [Line 74] aContentOffset 0 0
Not sure what my move here is.