Change page on UIScrollView

问题:

I have a UIScrollView with 10 pages. I am able to flick between them. I also want to have 2 buttons (a back button and a next button) which when touched will go to the previous or next page. I can't seem to figure out a way to do this though. A lot of my code comes from Apple's page control sample code. Can anybody help?

Thanks

回答1:

You just tell the buttons to scroll to the page's location:

CGRect frame = scrollView.frame;
frame.origin.x = frame.size.width * pageNumberYouWantToGoTo;
frame.origin.y = 0;
[scrollView scrollRectToVisible:frame animated:YES];

回答2:

scroll.contentOffset = CGPointMake(scroll.frame.size.width*pageNo, 0);

回答3:

scrollRectToVisible was not working for me, so I had to animate the contentOffset. This code works in swift 3.

func scrollToPage(_ page: Int) {
    UIView.animate(withDuration: 0.3) { 
        self.scrollView.contentOffset.x = self.scrollView.frame.width * CGFloat(page)
    }
}

回答4:

Here is an implementation for Swift 4:

func scrollToPage(page: Int, animated: Bool) {
    var frame: CGRect = self.scrollView.frame
    frame.origin.x = frame.size.width * CGFloat(page)
    frame.origin.y = 0
    self.scrollView.scrollRectToVisible(frame, animated: animated)
}

and is easily invoked by calling:

self.scrollToPage(1, animated: true)

Edit:

A nicer way of doing this is to support both horizontal and vertical pagination. Here is a convenient extension for that:

extension UIScrollView {

    func scrollTo(horizontalPage: Int? = 0, verticalPage: Int? = 0, animated: Bool? = true) {
        var frame: CGRect = self.frame
        frame.origin.x = frame.size.width * CGFloat(horizontalPage ?? 0)
        frame.origin.y = frame.size.width * CGFloat(verticalPage ?? 0)
        self.scrollRectToVisible(frame, animated: animated ?? true)
    }

}

This creates an extension on UIScrollView where you can scroll to any page, vertical or horisontal.

self.scrollView.scrollTo(horizontalPage: 0)
self.scrollView.scrollTo(verticalPage: 2, animated: true)
self.scrollView.scrollTo(horizontalPage: 1, verticalPage: 2, animated: true)

回答5:

For Swift 3 this is an extension that I find very convenient:

extension UIScrollView {
    func scrollToPage(index: UInt8, animated: Bool, after delay: TimeInterval) {
        let offset: CGPoint = CGPoint(x: CGFloat(index) * frame.size.width, y: 0)
        DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
            self.setContentOffset(offset, animated: animated)
        })
    }
}

And you call it like this:

scrollView.scrollToPage(index: 1, animated: true, after: 0.5)

回答6:

You can do it this way :

CGRect lastVisibleRect;
CGSize contentSize = [_scrollView contentSize];
lastVisibleRect.size.height = contentSize.height; 
lastVisibleRect.origin.y = 0.0; 
lastVisibleRect.size.width = PAGE_WIDTH; 
lastVisibleRect.origin.x  = contentSize.width - PAGE_WIDTH * (_totalItems - pageIndex); // total item of scrollview and your current page index

[_scrollView scrollRectToVisible:lastVisibleRect animated:NO];

回答7:

Here is a static method in swift:

static func scrollToPage(scrollView: UIScrollView, page: Int, animated: Bool) {
    var frame: CGRect = scrollView.frame
    frame.origin.x = frame.size.width * CGFloat(page);
    frame.origin.y = 0;
    scrollView.scrollRectToVisible(frame, animated: animated)
}

回答8:

First create a UIScrollView extension like:

extension UIScrollView {

    func setCurrentPage(position: Int) {
        var frame = self.frame;
        frame.origin.x = frame.size.width * CGFloat(position)
        frame.origin.y = 0
        scrollRectToVisible(frame, animated: true)
    }

}

then just call:

self.scrollView.setCurrentPage(position: 2)  // where 2 is your desired page

回答9:

If scrollRectToVisible doesn't work try this :

let frame = scrollView.frame
    let offset:CGPoint = CGPoint(x: CGFloat(sender.currentPage) * frame.size.width, y: 0)
    self.scrollView.setContentOffset(offset, animated: true)

回答10:

Swift Solution

func changePage(pageControl: UIPageControl) {

    let page = CGFloat(pageControl.currentPage)
    var frame = self.scrollView.frame
    frame.origin.x = frame.size.width * page
    frame.origin.y = 0
    self.scrollView.scrollRectToVisible(frame, animated: true)
}

回答11:

Additional to this code that mjdth added, remember to place it in the viewWillAppear or viewDidAppear.

CGRect frame = scrollView.frame;
frame.origin.x = frame.size.width * pageNumberYouWantToGoTo;
frame.origin.y = 0;
[scrollView scrollRectToVisible:frame animated:YES];