如何测试滚动视图是否弹跳？

Question

如何测试滚动视图是否弹跳？反弹结束时是否有通知或某事？

Answer 1

以下是我如何检测滚动视图是否水平弹跳:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {

  if (scrollView.contentOffset.x < 0) {
    NSLog(@"bouncing left");
  }

  if (scrollView.contentOffset.x > (scrollView.contentSize.width - scrollView.frame.size.width)) {
    NSLog(@"bouncing right");
  }
}

Answer 2

我已经实现了UIScrollView的扩展,以处理垂直和水平滚动.这甚至可以在非零的contentInsets中使用,并且在内容不足以覆盖scrollView insets的情况下:

Objective-C的

@interface UIScrollView (Bouncing)

@property (nonatomic, readonly) BOOL isBouncing;
@property (nonatomic, readonly) BOOL isBouncingTop;
@property (nonatomic, readonly) BOOL isBouncingLeft;
@property (nonatomic, readonly) BOOL isBouncingBottom;
@property (nonatomic, readonly) BOOL isBouncingRight;

@end

@implementation UIScrollView (Bouncing)

- (BOOL)isBouncing
{
    return self.isBouncingTop || self.isBouncingLeft || self.isBouncingBottom || self.isBouncingRight;
}

- (BOOL)isBouncingTop
{
    return self.contentOffset.y < - self.contentInset.top;
}

- (BOOL)isBouncingLeft
{
    return self.contentOffset.x < - self.contentInset.left;
}

- (BOOL)isBouncingBottom
{
    BOOL contentFillsScrollEdges = self.contentSize.height + self.contentInset.top + self.contentInset.bottom >= CGRectGetHeight(self.bounds);
    return contentFillsScrollEdges && self.contentOffset.y > self.contentSize.height - CGRectGetHeight(self.bounds) + self.contentInset.bottom;
}

- (BOOL)isBouncingRight
{
    BOOL contentFillsScrollEdges = self.contentSize.width + self.contentInset.left + self.contentInset.right >= CGRectGetWidth(self.bounds);
    return contentFillsScrollEdges && self.contentOffset.x > self.contentSize.width - CGRectGetWidth(self.bounds) + self.contentInset.right;
}

@end

Swift 3.0+

extension UIScrollView {
  var isBouncing: Bool {
    return isBouncingTop || isBouncingLeft || isBouncingBottom || isBouncingRight
  }
  var isBouncingTop: Bool {
    return contentOffset.y < -contentInset.top
  }
  var isBouncingLeft: Bool {
    return contentOffset.x < -contentInset.left
  }
  var isBouncingBottom: Bool {
    let contentFillsScrollEdges = contentSize.height + contentInset.top + contentInset.bottom >= bounds.height
    return contentFillsScrollEdges && contentOffset.y > contentSize.height - bounds.height + contentInset.bottom
  }
  var isBouncingRight: Bool {
    let contentFillsScrollEdges = contentSize.width + contentInset.left + contentInset.right >= bounds.width
    return contentFillsScrollEdges && contentOffset.x > contentSize.width - bounds.width + contentInset.right
  }
}

对于RxSwift你可以映射scrollViewDidScroll与isBouncing与过滤distinctUntilChanged.

Answer 3

对Justin方法的一个小修正,允许contentInset:

if( scrollView.contentOffset.x < -scrollView.contentInset.left )
{
    NSLog( @"bounce left" );
}
if( scrollView.contentOffset.x > scrollView.contentSize.width - scrollView.frame.size.width + scrollView.contentInset.right )
{
    NSLog( @"bounce right" );
}

Answer 4

是的...查看UIScrollViewDelegate规范,实现包括下面两个方法的方法,并相应地设置UIScrollView的委托:

// User stops dragging the table view.

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView
    willDecelerate:(BOOL)decelerate;

// Control slows to a halt after the user drags it

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView;

您可能对scrollViewDidEndDecelerating最感兴趣.这些也可以在我最初找到它们的UITableView中工作(UITableView继承自UIScrollView).