UiScrollview scrollviewDidScroll 检测用户触摸

Posted 2023-03-14

【中文标题】UiScrollview scrollviewDidScroll 检测用户触摸

【英文标题】：UiScrollview scrollviewDidScroll detect user touch

【发布时间】：2014-07-05 09:31:50

【问题描述】：

我在我的应用程序中使用UIScrollView，并使用scrollviewDidScroll 方法来移动不在滚动视图内的其他一些视图。这种行为应该只在用户实际用手指移动滚动视图时发生，而不是在触摸事件结束时发生。

目前我正在使用滚动视图的dragging 属性来获取此行为，但它有一个问题：当用户在滚动视图上滑动并在停止减速之前再次触摸它时，dragging 属性不正确尽管用户正在用手指拖动滚动视图。

【问题讨论】：

查看您的 tableView 的 UIGestureRecognizerState，例如 yourTableView.panGestureRecognizer.state。它将揭示用户触摸的确切状态。在scrollViewDidScroll 中进行操作。

完成。附示例代码

【参考方案1】：

UIScrollView 有一个panGestureRecogniser 属性，用于跟踪滚动视图中的平移手势。您可以在scrollViewDidScroll 中跟踪平移手势的state，以准确了解平移处于什么状态。

Swift 4.0

func scrollViewDidScroll(_ scrollView: UIScrollView) 
    if scrollView.isEqual(yourScrollView) 
        switch scrollView.panGestureRecognizer.state 
            case .began:
                // User began dragging
                print("began")
            case .changed:
                // User is currently dragging the scroll view
                print("changed")
            case .possible:
                // The scroll view scrolling but the user is no longer touching the scrollview (table is decelerating)
                print("possible")
            default:
                break
        
    

Objective-C

- (void)scrollViewDidScroll:(UIScrollView *)scrollView 

    if ([scrollView isEqual:yourScrollView]) 

        switch (scrollView.panGestureRecognizer.state) 

            case UIGestureRecognizerStateBegan:

                // User began dragging
                break;

            case UIGestureRecognizerStateChanged:

                // User is currently dragging the scroll view
                break;

            case UIGestureRecognizerStatePossible:

                // The scroll view scrolling but the user is no longer touching the scrollview (table is decelerating)
                break;

            default:
                break;
        
    

【参考方案2】：

IMO 更好的答案是使用UIScrollViewDelegate，有以下通知：

// called on start of dragging (may require some time and or distance to move)
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView;
// called on finger up if the user dragged. velocity is in points/millisecond. targetContentOffset may be changed to adjust where the scroll view comes to rest
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset NS_AVAILABLE_ios(5_0);
// called on finger up if the user dragged. decelerate is true if it will continue moving afterwards
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate;

【讨论】：

您还需要收听scrollViewDidScrollToTop。

@kelin 这与用户触摸有什么关系？

当用户双击状态栏时调用此事件。这导致表格视图滚动到顶部。在UIScrollViewDelegate 文档中阅读更多信息。

这与问题有什么关系？

【参考方案3】：

var lastVelocityYSign = 0

func scrollViewDidScroll(_ scrollView: UIScrollView) 
    let currentVelocityY =  scrollView.panGestureRecognizer.velocity(in: scrollView.superview).y
    let currentVelocityYSign = Int(currentVelocityY).signum()
    if currentVelocityYSign != lastVelocityYSign &&
        currentVelocityYSign != 0 
        lastVelocityYSign = currentVelocityYSign
    
    if lastVelocityYSign < 0 
        print("SCROLLING DOWN")
     else if lastVelocityYSign > 0 
        print("SCOLLING UP")
    

Mos6y 的回答 https://medium.com/@Mos6yCanSwift/swift-ios-determine-scroll-direction-d48a2327a004