Double tap bar button item to scroll to the top - ios

Question

I want to scroll to the top when i double tap on any BarButtonItem.
I saw a lot of answers on stackOverflow but none of them worked for me.
Maybe I'm using it wrong? Where do i put the code in the AppDelegate or the TableViewControllers i want to add this functionality specifically?
anyway, I'm using Swift 2.3 and Xcode 8 and would love to get some help.
Thank you.

Answer 1

Do you know about scrollsToTop? I think it is what you need. Description from iOS SDK related to scrollsToTop property in UIScrollView:
When the user taps the status bar, the scroll view beneath the touch which is closest to the status bar will be scrolled to top, but only if its scrollsToTop property is YES, its delegate does not return NO from shouldScrollViewScrollToTop, and it is not already at the top.
// On iPhone, we execute this gesture only if there's one on-screen scroll view with scrollsToTop == YES. If more than one is found, none will be scrolled.

Answer 2

At first setup UITabBarControllerDelegate delegate. Delegate can be easily set from Storyboard or via code with UITabBarController's delegate property.
myTabBar.delegate = myNewDelegate // Have to conform to UITabBarControllerDelegate protocol
You can even subclass UITabBarController and implement UITabBarControllerDelegate for it so it can become delegate for itself.
mySubclassedTabBar.delegate = mySubclassedTabBar
When you have delegate you can try out this method.
func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool
{
guard let tabBarControllers = tabBarController.viewControllers
else
{
// TabBar have no configured controllers
return true
}
if let newIndex = tabBarControllers.indexOf(viewController) where newIndex == tabBarController.selectedIndex
{
// Index won't change so we can scroll
guard let tableViewController = viewController as? UITableViewController // Or any other condition
else
{
// We are not in UITableViewController
return true
}
tableViewController.tableView.scrollToRowAtIndexPath(NSIndexPath(forRow: 0, inSection: 0), atScrollPosition: .Top, animated: true)
}
return true
}

Answer 3

func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
if tabBarController.viewControllers!.firstIndex(of: viewController) == 0 {
if self.selectedIndex != 0 { return true }
if let navigationController = viewController as? UINavigationController{
if let streamController = navigationController.viewControllers.last as? HomeVC
{
streamController.tableView.setContentOffset(CGPoint(x: 0, y: 0), animated: true)
}
}
return true
}
return true
}