Question

我想在他们的列表中模拟twitter或instagram的行为：

在UITabBarItem中双击时，列表将滚动到顶部。有人知道我该怎么做？我的UITabBarController中有4个项目，所有这些都是列表，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条形项时，此函数在获取导航的根视图控制器之前调用并检测双击。

我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。当我使用标签栏项目弹出视图时，根视图位于单元格0

上

Answer 1

好的，我认为最好的方法是检查带有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)
    }
}

如何使用

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并展示如何在所需位置使用扩展滚动到顶部。（经过集合视图测试）

Answer 3

Olivier Wilkinsons的答案很棒，但滚动部分在Swift 4中不再起作用，所以请替换

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

与

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

你已经完成了

滚动到顶部UITableView，双击UITabBarItem

3 个答案: