Sensitivity/Scroll speed of UIScrollView with paging(UIScrollView 的灵敏度/滚动速度与分页)

问题描述

我希望 UIScrollView 在快速扫过后快速滚动，像这样.虽然，当打开分页时，滚动一次一页.是否可以在不使用手势识别器手动实现的情况下通过手指轻弹启用分页时快速滚动?

I want UIScrollView to scroll fast after fast sweep, like this. Although, when paging is turned on, the scroll works one page at a time. Is it possible to scroll fast, when paging is enabled with a flick of a finger without manually implementation using gesture recognizers?

推荐答案

这很简单，但是您必须自己实现分页方面(这很简单).您不需要手势识别器.

This is fairly straightforward, however you must implement the paging aspect yourself (which is fairly simple). You don't need gesture recognizers.

首先，调整你的UIScrollView减速率:

First, adjust your UIScrollView deceleration rate:

scrollView.decelerationRate = UIScrollViewDecelerationRateFast

假设我们有一个内容数组——我们称之为yourPagesArray.在您的 UIScrollViewDelegate 中，实现以下方法:

Assume we have an array of content — let's call it yourPagesArray. In your UIScrollViewDelegate, implement the following method:

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>)
{
    //This is the index of the "page" that we will be landing at
    let nearestIndex = Int(CGFloat(targetContentOffset.pointee.x) / scrollView.bounds.size.width + 0.5)

    //Just to make sure we don't scroll past your content
    let clampedIndex = max( min( nearestIndex, yourPagesArray.count - 1 ), 0 )

    //This is the actual x position in the scroll view
    var xOffset = CGFloat(clampedIndex) * scrollView.bounds.size.width

    //I've found that scroll views will "stick" unless this is done
    xOffset = xOffset == 0.0 ? 1.0 : xOffset

    //Tell the scroll view to land on our page
    targetContentOffset.pointee.x = xOffset
}

您还需要实现以下委托方法，以处理用户轻轻抬起手指而不会导致任何滚动减速的情况:

You will also need to implement the following delegate method, to handle the case where the user lifts their finger gently without causing any scroll deceleration:

(更新:在最新的 iOS SDK 下您可能不需要这样做.现在似乎在零速度时调用了上述委托方法.)

(Update: you may not need to do this under the latest iOS SDK. It seems like the above delegate method is now called when there is zero velocity.)

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool)
{
    if !decelerate
    {
        let currentIndex = floor(scrollView.contentOffset.x / scrollView.bounds.size.width)

        let offset = CGPoint(x: scrollView.bounds.size.width * currentIndex, y: 0)

        scrollView.setContentOffset(offset, animated: true)
    }
}

目标-C

设置你的减速率:

Objective-C

Setting your deceleration rate:

scrollView.decelerationRate = UIScrollViewDecelerationRateFast;

然后你的滚动视图委托实现:

Then your scroll view delegate implementation:

- (void) scrollViewWillEndDragging:(UIScrollView *)scroll withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
    //This is the index of the "page" that we will be landing at
    NSUInteger nearestIndex = (NSUInteger)(targetContentOffset->x / scrollView.bounds.size.width + 0.5f);   

    //Just to make sure we don't scroll past your content
    nearestIndex = MAX( MIN( nearestIndex, yourPagesArray.count - 1 ), 0 );

    //This is the actual x position in the scroll view
    CGFloat xOffset = nearestIndex * scrollView.bounds.size.width;

    //I've found that scroll views will "stick" unless this is done
    xOffset = xOffset==0?1:xOffset;

    //Tell the scroll view to land on our page
    *targetContentOffset = CGPointMake(xOffset, targetContentOffset->y);
}

- (void) scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    if( !decelerate )
    {
        NSUInteger currentIndex = (NSUInteger)(scrollView.contentOffset.x / scrollView.bounds.size.width);

        [scrollView setContentOffset:CGPointMake(scrollView.bounds.size.width * currentIndex, 0) animated:YES];
    }
}

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