Question

I already have a scrollview with an image in and I set paging in the IB to on, so I didn’t use a pageControl. That all works, and I can go between images, but how can I make it automatically scroll? Like the thing on the featured page of the App Store?

I was thinking of having two NSTimers – one to scroll 320 points in say 0.3 seconds, and a second to count 4 seconds which then fires the first one. How would I do that? Thanks!

Answer 1

Instead using of NSTimer you can use [self performSelector: withObject: afterDelay:]

- (void) viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    // start repeatable method
    [self performSelector:@selector(makeTick) withObject:nil afterDelay:4.0f];
}

- (void) makeTick {

    [self performSelector:@selector(makeTick) withObject:nil afterDelay:0.3f];

    // Calclulate new offset
    CGPoint pt = self.scrollView.contentOffset;
    pt.x += self.scrollView.frame.size.width;
    // If it's a last subview in scrollview return back
    if (!(pt.x < self.scrollView.contentSize.width)) {
        pt.x = 0;
    }
    [self.scrollView setContentOffset:pt animated:YES];
}

BUT! It’s a just simple example how to make you scroll “animated”. If you want make “infinitive” scroll behavior like in AppStore you have to use another solution.

Check this tutorial to make circular and infinitive scroll view.