Ios iPhone-知道UIScrollView是到达顶部还是底部
有没有办法知道Ios iPhone-知道UIScrollView是到达顶部还是底部,ios,objective-c,iphone,uiscrollview,uiscrollviewdelegate,Ios,Objective C,Iphone,Uiscrollview,Uiscrollviewdelegate,有没有办法知道UIScrollView是否已到达内部的顶部或底部 - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate ? 谢谢。在类中实现UIScrollViewDelegate,然后添加以下内容: -(void)scrollViewDidScroll: (UIScrollView*)scrollView { floa
UIScrollView
是否已到达内部的顶部或底部
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView
willDecelerate:(BOOL)decelerate
?
谢谢。在类中实现
UIScrollViewDelegate
,然后添加以下内容:
-(void)scrollViewDidScroll: (UIScrollView*)scrollView
{
float scrollViewHeight = scrollView.frame.size.height;
float scrollContentSizeHeight = scrollView.contentSize.height;
float scrollOffset = scrollView.contentOffset.y;
if (scrollOffset == 0)
{
// then we are at the top
}
else if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
{
// then we are at the end
}
}
希望这就是你想要的!否则,可以通过向上述代码添加更多条件来进行修补,并记录scrollOffset的值。当您试图确定scrollView是在顶部还是在底部时,
内容插入也涉及其中。您可能还对scrollView位于顶部上方和底部下方的情况感兴趣。
下面是我用来查找顶部和底部位置的代码:
斯威夫特:
extension UIScrollView {
var isAtTop: Bool {
return contentOffset.y <= verticalOffsetForTop
}
var isAtBottom: Bool {
return contentOffset.y >= verticalOffsetForBottom
}
var verticalOffsetForTop: CGFloat {
let topInset = contentInset.top
return -topInset
}
var verticalOffsetForBottom: CGFloat {
let scrollViewHeight = bounds.height
let scrollContentSizeHeight = contentSize.height
let bottomInset = contentInset.bottom
let scrollViewBottomOffset = scrollContentSizeHeight + bottomInset - scrollViewHeight
return scrollViewBottomOffset
}
}
扩展UIScrollView{
var isAtTop:Bool{
return contentOffset.y=verticalOffsetForBottom
}
var verticalOffsetForTop:CGFloat{
让topInset=contentInset.top
返回-顶部插图
}
var verticalOffsetForBottom:CGFloat{
让scrollViewHeight=bounds.height
让scrollContentSizeHeight=contentSize.height
让bottomInset=contentInset.bottom
让scrollViewBottomOffset=scrollContentSizeHeight+bottomInset-scrollViewHeight
返回滚动视图底部偏移量
}
}
目标C:
@implementation UIScrollView (Additions)
- (BOOL)isAtTop {
return (self.contentOffset.y <= [self verticalOffsetForTop]);
}
- (BOOL)isAtBottom {
return (self.contentOffset.y >= [self verticalOffsetForBottom]);
}
- (CGFloat)verticalOffsetForTop {
CGFloat topInset = self.contentInset.top;
return -topInset;
}
- (CGFloat)verticalOffsetForBottom {
CGFloat scrollViewHeight = self.bounds.size.height;
CGFloat scrollContentSizeHeight = self.contentSize.height;
CGFloat bottomInset = self.contentInset.bottom;
CGFloat scrollViewBottomOffset = scrollContentSizeHeight + bottomInset - scrollViewHeight;
return scrollViewBottomOffset;
}
@end
@实现UIScrollView(添加)
-(BOOL)isAtTop{
return(self.contentOffset.y=[self verticalOffsetForBottom]);
}
-(CGFloat)垂直偏移量{
CGFloat topInset=self.contentInset.top;
返回-顶部插图;
}
-(CGFloat)底部垂直偏移{
CGFloat scrollViewHeight=self.bounds.size.height;
CGFloat scrollContentSizeHight=self.contentSize.height;
CGFloat bottomInset=self.contentInset.bottom;
CGFloat scrollViewBottomOffset=scrollContentSizeHeight+bottomInset-scrollViewHeight;
返回滚动视图底部偏移量;
}
@结束
我准确地知道了怎么做:
CGFloat maxPosition = scrollView.contentInset.top + scrollView.contentSize.height + scrollView.contentInset.bottom - scrollView.bounds.size.height;
CGFloat currentPosition = scrollView.contentOffset.y + self.topLayoutGuide.length;
if (currentPosition == maxPosition) {
// you're at the bottom!
}
如果您需要swift格式的代码:
override func scrollViewDidScroll(scrollView: UIScrollView) {
if (scrollView.contentOffset.y >= (scrollView.contentSize.height - scrollView.frame.size.height)) {
//reach bottom
}
if (scrollView.contentOffset.y <= 0){
//reach top
}
if (scrollView.contentOffset.y > 0 && scrollView.contentOffset.y < (scrollView.contentSize.height - scrollView.frame.size.height)){
//not top and not bottom
}
}
覆盖函数scrollViewDidScroll(scrollView:UIScrollView){
if(scrollView.contentOffset.y>=(scrollView.contentSize.height-scrollView.frame.size.height)){
//触底
}
if(scrollView.contentOffset.y0&&scrollView.contentOffset.y<(scrollView.contentSize.height-scrollView.frame.size.height)){
//不上不下
}
}
简单明了的扩展:
import UIKit
extension UIScrollView {
var scrolledToTop: Bool {
let topEdge = 0 - contentInset.top
return contentOffset.y <= topEdge
}
var scrolledToBottom: Bool {
let bottomEdge = contentSize.height + contentInset.bottom - bounds.height
return contentOffset.y >= bottomEdge
}
}
导入UIKit
扩展UIScrollView{
var scrolledToTop:Bool{
设topEdge=0-contentInset.top
return contentOffset.y=bottomEdge
}
}
在GitHub上:
这样做(对于Swift 3):
如果您使用的是
navigationController
,您可能需要执行类似的操作:scrollOffset=scrollContentSizeHeight
问题在于反弹…一旦到达顶部或底部,所有内容都会被调用两次。除了关闭表或集合视图反弹之外,还有什么解决方案吗?@denikov你找到解决方案了吗?scrollOffset可能是个好答案,实现scrollviewdidscroll对性能有害。如果不使用scrollviewdidscroll,我该如何称呼它?由于浮点数学的变化莫测,我得到了一个“verticalOffsetForBottom”为1879.05xxx,而我的contentOffset.y在Swift 3中位于底部时为1879。因此我将return scrollViewBottomOffset
更改为return scrollViewBottomOffset.rounded()
从iOS 11开始safeAreaInsets
也包括在内。scrollView.contentOffset.y+scrollView.bounds.height-scrollView.safeAreaInsets.bottom
欢迎使用SO!在答案中发布代码时,解释代码如何解决OP问题很有帮助:)
class MyClass: UIScrollViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if (scrollView.contentOffset.y >= (scrollView.contentSize.height - scrollView.frame.size.height)) {
//scrolled to top, do smth
}
}
}