IOS - Centering UIScrollView inside UIView container programmatically with Autolayout issue

问题

I'm trying to replicate the safari pages scrollview, which has its frame that is slightly narrower than iPhone screen. So According to few suggestions I'm placing a the scrollview (450x280 points) inside a "clipView" (450x320 points).

//viewController methods
-(void)viewDidAppear:(BOOL)animated{

CGRect pagingScrollViewFrame = self.clipview.frame;
pagingScrollViewFrame.size.width = 280;

NSLog(@"clipview h:%f e w:%f",self.clipview.frame.size.height,self.clipview.frame.size.width);
NSLog(@"scrollview h:%f e w:%f",pagingScrollViewFrame.size.height,pagingScrollViewFrame.size.width);
NSLog(@"center clipview :%@",NSStringFromCGPoint(self.clipview.center));

pagingScrollView = [[UIScrollView alloc] initWithFrame:pagingScrollViewFrame];
NSLog(@"center scrollview:%@",NSStringFromCGPoint(pagingScrollView.center));
pagingScrollView.contentSize = CGSizeMake(pagingScrollViewFrame.size.width *3, pagingScrollViewFrame.size.height);

pagingScrollView.clipsToBounds = NO;
pagingScrollView.center = self.clipview.center;

    [clipview addSubview:pagingScrollView];
}

As you can see I have my scrollView's center That is shifted 20points down ({140, 232}). My view Container has its center at {160, 232}.

Where am I wrong?There is anything like content offset property I should play with? is this issue related to Autolayout ?

回答1:

The issue is in this line:

pagingScrollView.center = self.clipview.center;

Should be:

pagingScrollView.center = CGPointMake(CGRectGetMidX(self.clipview.bounds), CGRectGetMidY(self.clipview.bounds));

It is common mistake to assign center of superview to its subview. They are in different coordinate systems.

来源：https://stackoverflow.com/questions/15636186/ios-centering-uiscrollview-inside-uiview-container-programmatically-with-autol