双击 UITabBarItem 滚动到顶部 UITableView

Question

我想在他们的列表中模拟 Twitter 或 instagram 的行为：

在 UITabBarItem 中双击时，列表会滚动到顶部。有人知道我该怎么做？我的 UITabBarController 中有 4 个项目，它们都是列表，所以我想为所有人做这件事。

问题是当我在 mi 列表的推送视图中点击栏项目时，此函数在获取导航的根视图控制器之前调用并检测双击。

希望能解决我的问题

var previousController: UIViewController?

func tabBarController(tabBarController: UITabBarController, didSelectViewController viewController: UIViewController) {
    if previousController == viewController{
        if let navVC = viewController as? UINavigationController, vc = navVC.viewControllers.first as? HomeViewController {
            vc.tableBusinessList.setContentOffset(CGPointZero, animated: true)
            print("same")
        }
    }else{
        print("No same")
    }
    previousController = viewController
}

行为不正确。当我使用选项卡栏项弹出视图时，根视图位于单元格 0

Answer 1

好的，所以我认为最好的方法是检查 tableView 的 viewController 是否可见，如果不可见，则不要调用 set content offset。

所以：

var previousController: UIViewController?

func tabBarController(tabBarController: UITabBarController, didSelectViewController viewController: UIViewController) {
    if previousController == viewController {
        if let navVC = viewController as? UINavigationController, vc = navVC.viewControllers.first as? HomeViewController {

            if vc.isViewLoaded() && (vc.view.window != nil) {
                // viewController is visible
                vc.tableBusinessList.setContentOffset(CGPointZero, animated: true)
            }

            print("same")
        }
    }else{
        print("No same")
    }

    previousController = viewController

}

Answer 2

Swift 3

extension UIViewController {
    func scrollToTop() {
        func scrollToTop(view: UIView?) {
            guard let view = view else { return }

            switch view {
            case let scrollView as UIScrollView:
                if scrollView.scrollsToTop == true {
                    scrollView.setContentOffset(CGPoint(x: 0.0, y: -scrollView.contentInset.top), animated: true)
                    return
                }
            default:
                break
            }

            for subView in view.subviews {
                scrollToTop(view: subView)
            }
        }

        scrollToTop(view: self.view)
    }
}

使用方法

var previousController: UIViewController?

func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {

        //when user is in FeedViewController and scroll at last record and want to
        if previousController == viewController {
            if let navVC = viewController as? UINavigationController, let vc = navVC.viewControllers.first as? HomeViewController {

                if vc.isViewLoaded && (vc.view.window != nil) {
                    vc.scrollToTop()
                }
                print("same")
            }
        }
        else{
            print("No same")
        }

        previousController = viewController
        return true;
    }

注意：我使用@Olivier Wilkinson 并展示了如何在需要的地方使用滚动到顶部的扩展。（已针对集合视图进行测试）

Answer 3

Olivier Wilkinsons 的回答很好，但是向上滚动部分在 Swift 4 中不再起作用，所以替换

vc.tableBusinessList.setContentOffset(CGPointZero, animated: true)

和

vc.tableBusinessList.scrollRectToVisible(CGRect(x: 0, y: 0, width: 1, height: 1), animated: true)

一切就绪

双击 UITabBarItem 滚动到顶部 UITableView

Scroll to top UITableView with double tap on UITabBarItem

ios

swift

uitableview

uitabbarcontroller

uitabbaritem