ios - 在平移 View 中实时检测 scrollView 位置

Question

我在初始启动时有一个平移的 UIViewController，它加载了两个单独的 XIB View ，用户可以滑动它们来遍历它们。我想在用户在总宽度(两个 View 的平移宽度)上滑动 2/3 时触发代码，但我的检测不是实时的。

到目前为止，这是我的代码...

let vc0 = ViewController0(nibName: "ViewController0", bundle: nil)
let vc1 = ViewController1(nibName: "ViewController1", bundle: nil)

class ViewController: UIViewController {

    @IBOutlet weak var scrollView: UIScrollView!

    override func viewDidLoad() {
        super.viewDidLoad()

        self.addChildViewController(vc0)
        self.scrollView.addSubview(vc0.view)
        vc0.didMoveToParentViewController(self)

        var frame1 = vc1.view.frame
        frame1.origin.x = self.view.frame.size.width
        vc1.view.frame = frame1


        self.addChildViewController(vc1)
        self.scrollView.addSubview(vc1.view)
        vc1.didMoveToParentViewController(self)

        self.scrollView.contentSize = CGSizeMake(self.view.frame.size.width * 2, self.view.frame.size.height - 66)

        // This doesn't work
        scrollView.delegate = self


        // If the user user swipes 2/3 in (or it can be any other offset that's practical)
        if (scrollView.contentOffset.x > (self.view.frame.size.width*2)*(2/3)) {
             // Code I'd like to execute
             // ...
        }
 }

Swift 如何做到这一点？

Answer 1

你应该设置 ScrollView 的代理

scrollView.delegate = self

并声明你的类实现了UIScrollViewDelegate:

class ViewController: UIViewController, UIScrollViewDelegate

然后实现 scrollViewDidScroll 每次你的 scrollview 的滚动改变时调用它。

func scrollViewDidScroll(scrollView: UIScrollView) {
   // If the user user swipes 2/3 in (or it can be any other offset that's practical)
   if (scrollView.contentOffset.x > (self.view.frame.size.width*2)/(2/3)) {
     // Code I'd like to execute
     // ...
   }
}