iOS筆記之ScrollView

標籤：

ScrollView三個基本的要理解的屬性；

contentSize

The size of the content view.所以很好理解，contentSize也就是scrollView可滾動的地區.

contentOffset

The point at which the origin of the content view is offset from the origin of the scroll view.

這裡標註的是point，是當前顯示的地區的origin相對於整個scrollView的origin的位置.

contentInset

The distance that the content view is inset from the enclosing scroll view.

這裡說得是distance，四個值分別是上下左右, 預設值是 UIEdgeInsetsZero，也就是四個值都為0.

  _|←_cW_→_|_↓_   |       | ---------------   |content| ↑ ↑ |content| contentInset.topcH |content| ↓ |content| contentInset.bottom   |content| ↓---------------  _|_______|___              ↑(cH = contentSize.height; cW = contentSize.width)

  

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView; //返回要縮放的圖片(必須在代理類裡實現)

 

圖片縮放保持置中，實現代碼：

（在viewWillLayoutSubviews也要調用）

    func recenterImage() {        let scrollViewSize = scrollView.bounds.size        let imageSize = imageView.frame.size                let horizontalSpace = imageSize.width < scrollViewSize.width ? (scrollViewSize.width - imageSize.width) / 2 : 0        let verticalSpace = imageSize.height < scrollViewSize.height ? (scrollViewSize.height - imageSize.height) / 2 : 0                scrollView.contentInset = UIEdgeInsets(top: verticalSpace,            left: horizontalSpace,            bottom: verticalSpace,            right: horizontalSpace)    }

 

iOS筆記之ScrollView