automatic UIScrollView with paging - objective-c

Question

I have a UIScrollView with paging enabled. However i want this scrollview to scroll right when a certain amount of time has passed. Is there a easy way to implement this or do i need to use a timer and programmatically scroll the scrollview?
Something like this website has in its header: http://denederlandsewateren.nl/ [notice the text "De Nederlandse Wateren" changes each x seconds]

Answer 1

You need a little method to help you scroll to the exact page, this is not implemented, but it's very simple, let's assume your scrollview is called myScrollview
This assumes you're scrolling horizontally, you can switch the code to fit your needs
-(void)scrollToPage:(NSInteger)aPage{
float myPageWidth = [myScrollView frame].size.width;
[myScrollView setContentOffset:CGPointMake(aPage*myPageWidth,y) animated:YES];
}
Then you setup a timer to call this method every 5 seconds for example, like this:
[[NSTimer scheduledTimerWithTimeInterval:5
target:self
selector:#selector(scrollPages)
userInfo:Nil
repeats:YES] fire];
Next step is to create the method that will be fired by the timer and scroll to the next page, I called it -(void)scrollPages, it also requires that you have two global variables called currentPage and numberOfPages, both are of type NSInteger
-(void)scrollPages{
[self scrollToPage:currentPage%numberOfPages];
currentPage++;
}
If something doesn't make sense let me know !

Answer 2

Found this on stackoverflow
[scrollView setContentOffset:CGPointMake(x, y) animated:YES];
To do slideshows with UIScrollView, you arrange all images in the scroll view, set up a repeated timer, then -setContentOffset:animated: when the timer fires.

Answer 3

In your .h file create outlets for scrollview and paging
#property (weak, nonatomic) IBOutlet UIScrollView *sliderScrollView;
#property (weak, nonatomic) IBOutlet UIPageControl *sliderPageControll;
#property (nonatomic,strong) NSArray *sliderImagesArray;
#property (nonatomic,strong) NSString *sliderIndexString;
#property (nonatomic,strong) NSString *currentPageIndexString;
after that in your .m file
[self.sliderScrollView setPagingEnabled:YES];
[self.sliderScrollView setBounces:NO];
[self.sliderScrollView setAlwaysBounceVertical:NO];
[self.sliderScrollView setShowsHorizontalScrollIndicator:NO];
self.sliderScrollView.alwaysBounceVertical = NO;
NSArray *imagesArray = self.sliderImagesArray;
for (int i = 0; i < [imagesArray count]; i++){
CGFloat xOrigin = i * self.imageSliderScrollView.frame.size.width;
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(xOrigin, 0, self.sliderScrollView.frame.size.width, self.sliderScrollView.frame.size.height)];
imageView.userInteractionEnabled = YES;
NSString *imgStr = [serviceImgArray objectAtIndex:i];
NSString *bikeStr = [NSString stringWithFormat:#"%#", imgStr];
NSURL *imageURL = [NSURL URLWithString:[bikeStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
[imageView sd_setImageWithURL:imageURL
placeholderImage:[UIImage imageNamed:#"profilepic_bg"]];
[imageView setContentMode:UIViewContentModeScaleAspectFill];
[self.sliderScrollView addSubview:imageView];
}
// for adding autorotate scrolling
[NSTimer scheduledTimerWithTimeInterval:5 target:self selector:#selector(autoStartSlide:) userInfo:nil repeats:YES];
self.sliderPageControll.numberOfPages = imagesArray.count;
self.sliderPageControll.currentPage = 0;
self.currentPageIndexString = [NSString stringWithFormat:#"%ld",(long)0];
[self.sliderScrollView setContentSize:CGSizeMake(self.sliderScrollView.frame.size.width * [imagesArray count], self.sliderScrollView.frame.size.height)];
if ([self.sliderPageControll respondsToSelector:#selector(setPageIndicatorTintColor:)]) {
self.sliderPageControll.currentPageIndicatorTintColor = [UIColor redColor];
self.sliderPageControll.pageIndicatorTintColor = [UIColor whiteColor];
}
CGRect frame = self.sliderScrollView.frame;
frame.origin.x = frame.size.width * [[NSString stringWithFormat:#"%#",self.sliderIndexString] integerValue];
frame.origin.y = 0;
[self.sliderScrollView scrollRectToVisible:frame animated:NO];
self.sliderPageControll.currentPage = [[NSString stringWithFormat:#"%#",self.sliderIndexString] integerValue];
after that implement scrollview delegate method
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
NSInteger scrollIndex = (NSInteger)(self.sliderScrollView.contentOffset.x / self.sliderScrollView.frame.size.width);
self.sliderPageControll.currentPage = scrollIndex;
self.currentPageIndexString = [NSString stringWithFormat:#"%ld",(long)self.sliderPageControll.currentPage];
}
Here implement your autotrotate method.
- (void)autoStartSlide:(id)sender {
if(pagger.numberOfPages > pagger.currentPage+1) {
[UIView animateWithDuration:0.5 animations:^{
slider.contentOffset = CGPointMake(slider.contentOffset.x + slider.frame.size.width, 0);
} completion:^(BOOL finished) {
}];
}
else {
slider.contentOffset = CGPointMake(slider.contentOffset.x - slider.frame.size.width, 0);
[UIView animateWithDuration:0.5 animations:^{
slider.contentOffset = CGPointMake(slider.contentOffset.x + slider.frame.size.width, 0);
} completion:^(BOOL finished) {
slider.contentOffset = CGPointMake(0, 0) ;
}];
}
}

Answer 4

Here is a Swift 5 Compatible one
var currentPage = 1;
var slideTimer : Timer?
ViewDidLoad
slideTimer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(scrollPages), userInfo: nil, repeats: true)
viewDidDisappear
slideTimer?.invalidate()
Functions
#objc func scrollPages() {
scrollToPage(page: CGFloat(currentPage%slides.count));
currentPage+=1;
}
func scrollToPage(page : CGFloat) {
let pageWidth = scrollView.frame.width
scrollView .setContentOffset(CGPoint(x: pageWidth * page, y: 0.0), animated: true)
}