桌面视图上的iOS9浮动按钮不起作用

Question

我有一个浮动按钮，显示在tableview的顶部，允许用户快速返回到顶部。由于某些原因，它适用于除iOS9之外的所有iOS版本。当用户开始向上滚动时，会出现该按钮。当我点击它时，它只是停止滚动的tableview并且不执行按钮的动作。如果tableview没有滚动，则按钮有效。如果有人有任何建议，请告诉我。谢谢！

-(void)viewDidLoad {
   [super viewDidLoad];
   self.scrollToTopButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
   self.scrollToTopButton.alpha = 0.0f;
   self.scrollToTopButton.frame = CGRectMake(0, self.tableView.contentOffset.y, [UIScreen mainScreen].bounds.size.width, 37);
   self.scrollToTopButton.titleLabel.font = [UIFont boldSystemFontOfSize:13.0f];
   self.scrollToTopButton.titleLabel.textColor = [UIColor whiteColor];
   self.scrollToTopButton.tintColor = [UIColor whiteColor];
   [self.scrollToTopButton setTitle:@"Scroll To Top" forState:UIControlStateNormal];
   self.scrollToTopButton.backgroundColor = golfGamutGreen;
   [self.scrollToTopButton addTarget:self action:@selector(scrollToTop) forControlEvents:UIControlEventTouchDown];
   [self.tableView addSubview:self.scrollToTopButton];
   [self.tableView bringSubviewToFront:self.scrollToTopButton];
}

-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
   lastContentOffset = scrollView.contentOffset.y;
 }

 -(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    [UIButton animateWithDuration:0.8 delay:0.0     options:UIViewAnimationOptionAllowUserInteraction animations:^{
    [self.scrollToTopButton setAlpha:0.0f];
   } completion:^(BOOL finished) {
 }];
}

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

  self.scrollToTopButton.frame = CGRectMake(0, self.tableView.contentOffset.y, [UIScreen mainScreen].bounds.size.width, 37);
  [self.tableView bringSubviewToFront:self.scrollToTopButton];
  if (lastContentOffset > scrollView.contentOffset.y && scrollView.contentOffset.y > 1000 && isScrollingToTop == NO) {
      [UIButton animateWithDuration:0.8 delay:0.0 options:UIViewAnimationOptionAllowUserInteraction animations:^{
     [self.scrollToTopButton setAlpha:0.9f];
      } completion:^(BOOL finished) {
    }];
 }
 else  {
     [UIButton animateWithDuration:0.8 delay:0.0 options:UIViewAnimationOptionAllowUserInteraction animations:^{
     [self.scrollToTopButton setAlpha:0.0f];
    } completion:^(BOOL finished) {
   }];
 }
  if (scrollView.contentOffset.y == 0) {
     [UIButton animateWithDuration:0.8 delay:0.0 options:UIViewAnimationOptionAllowUserInteraction animations:^{
     [self.scrollToTopButton setAlpha:0.0f];
   } completion:^(BOOL finished) {
   }];
     isScrollingToTop = NO;
   }
 }

  - (void)scrollToTop {
   NSLog(@"Scroll To Top");
   //[self.tableView scrollRectToVisible:CGRectMake(0, 0, self.tableView.frame.size.width, self.tableView.frame.size.height) animated:YES];
     [self.tableView setContentOffset:CGPointMake(0, 0 - self.tableView.contentInset.top) animated:YES];
     isScrollingToTop = YES;
 }