UIScrollView did Scroll - iphone

Question

I want to show an image that stays on the page for 5 seconds but appears everytime my scrollview scrolls. So obviously i need to marry animation for the UILabel and some method of UIScrollView. Im not sure which one to use to be honest. Also i have two UIScrollViews on one UIViewController so i dont know what i should set as delegate.
The following is the animation i have at the moment
[UIView animateWithDuration:0.3 animations:^{ // animate the following:
pageCountImage.frame = CGRectMake(0, 0, 100, 50); // move to new location
}];

Answer 1

Your view controller can be the delegate of both scroll views. Agree with #Ravi that you can use the delegate param to determine which scroll view is scrolling.
Sounds like you need a few animations packaged to make sense for the UI:
// hide or show the page count image after a given delay, invoke completion when done
- (void)setPageCountImageHidden:(BOOL)hidden delay:(NSTimeInterval)delay completion:(void (^)(BOOL))completion {
BOOL currentlyHidden = self.pageCountImage.alpha == 0.0;
if (hidden == currentlyHidden) return;
[UIView animateWithDuration:0.3 delay:delay options:UIViewAnimationOptionBeginFromCurrentState animations:^{
self.pageCountImage.alpha = (hidden)? 0.0 : 1.0;
} completion:completion];
}
// move the page count image to the correct position given a scroll view content offset
- (void)positionPageControlForContentOffset:(CGFloat)xOffset {
// assume page width is a constant (the width of a page in the scroll view)
NSInteger page = xOffset / kPAGEWIDTH;
// assume max page is a constant (the max number of pages in scroll view)
// scroll positions in the "bounce" will generate page numbers out of bounds, fix that here...
page = MAX(MIN(page, kMAXPAGE), 0);
// kPAGE_INDICATOR_WIDTH the distance the page image moves between pages
// kPAGE_INDICATOR_ORIGIN the page image x position at page zero
CGFloat xPosition = kPAGE_INDICATOR_ORIGIN + page * kPAGE_INDICATOR_WIDTH;
// assume y position and size are constants
CGRect pageIndicatorFrame = CGRectMake(xPosition, kYPOS, kWIDTH, kHEIGHT);
// finally, do the animation
[UIView animateWithDuration:0.3 animations:^{
self.pageCountImage.frame = pageIndicatorFrame;
}];
}
Then in view did scroll:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if (scrollView == /* the scroller with the page control */) {
[self setPageCountImageHidden:NO delay:0.0 completion:^(BOOL finished) {
[self positionPageControlForContentOffset:scrollView.contentOffset.x];
[self setPageCountImageHidden:YES delay:5.0 completion:^(BOOL finished){}];
}];
}
// and so on...

Answer 2

You should implement <UIScrollViewDelegate>. Make use of the method - (void)scrollViewDidScroll:(UIScrollView *)scrollView and write your animation code in there. If you have multiple scroll views, you could do this:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if(scrollView == myScrollView1)
// do something
else if (scrollView == myScrollView2)
// do something else
else
// do something else
}

Answer 3

just like tableview you should configure and control your scroll actions. You can write an extension of your controller and control all scrolling actions here. As an example you can check:
extension ExampleViewController: UIScrollViewDelegate {
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
// your actions here
}
func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
// your actions here
}
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
// your actions here
}
func scrollViewDidScroll(_ scrollView: UIScrollView) {
// your actions here
}
}