UIScrollView - with paging enabled, can I “change”

问题:

What's the simplest way to have a scroll view (with pagingEnabled set to YES) have a page width set to something other than the scroll view's bounds?

Let me give an example. Suppose I have a scroll view with 10 items, each 150 pixels wide, and my scroll view is 300 pixels wide. If I start with views 1 and 2 visible and scroll horizontally to the right, I want the next "page" to show items 2 and 3. If I scroll one more page to the right, I would see items 3 and 4.

Has anyone done this? If not, what strategy would you use?

回答1:

Alexander Repty just blogged about this very topic: http://blog.proculo.de/archives/180-Paging-enabled-UIScrollView-With-Previews.html. Short answer: it's not as simple as just changing the width of the 'page', but it's not too hard.

回答2:

Mike,

use the approach from my blog that Ben linked you to. Make the UIScrollView half the size of the surrounding view (i.e. 150px) and move it to the left instead of leaving it centered.

That should give you exactly the behaviour you wanted.

Cheers, Alex

回答3:

It can surely be done with the help of scrollview delegate methods & content-offset.

Below is the detailed code for the same.

int start;

int end;

int k=0;

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView1
{

    pageControlUsed = NO;

    start = scrollView.contentOffset.x;

}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView1 willDecelerate:(BOOL)decelerate
{

    end = scrollView.contentOffset.x;

}   


- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView1{

    int diff = end-start;

        if (diff>0)
        {

         k=k+150;
         [scrollView setContentOffset:CGPointMake(k, 0) animated:YES];

        }
       else {

         k=k-150;
        [scrollView setContentOffset:CGPointMake(k, 0) animated:YES];

          }
}

回答4:

Simply override scrollViewWillEndDragging

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
    CGFloat pageWidth = 160;
    targetContentOffset->x = pageWidth * (int)(targetContentOffset->x / pageWidth);
}

回答5:

UIScrollView *album = [[UIScrollView alloc] init];
album.translatesAutoresizingMaskIntoConstraints = NO;
album.pagingEnabled = YES;
album.clipsToBounds = NO;
album.showsHorizontalScrollIndicator = NO;
album.contentInset = UIEdgeInsetsMake(0, -50, 0, -50);
[view addSubview:album];


[view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-50-[_album(220)]" options:0 metrics:metrics views:views]];

[view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[_album(300)]" options:0 metrics:metrics views:views]];

this works fine on iOS 7.1~ 8.2