問題描述

我希望 UIScrollView 在快速掃過后快速滾動，像這樣.雖然，當打開分頁時，滾動一次一頁.是否可以在不使用手勢識別器手動實現(xiàn)的情況下通過手指輕彈啟用分頁時快速滾動?

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?

推薦答案

這很簡單，但是您必須自己實現(xiàn)分頁方面(這很簡單).您不需要手勢識別器.

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

首先，調(diào)整你的UIScrollView減速率:

First, adjust your UIScrollView deceleration rate:

scrollView.decelerationRate = UIScrollViewDecelerationRateFast

假設我們有一個內(nèi)容數(shù)組——我們稱之為yourPagesArray.在您的 UIScrollViewDelegate 中，實現(xiàn)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
}

您還需要實現(xiàn)以下委托方法，以處理用戶輕輕抬起手指而不會導致任何滾動減速的情況:

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 下您可能不需要這樣做.現(xiàn)在似乎在零速度時調(diào)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)
    }
}

目標-C

設置你的減速率:

Objective-C

Setting your deceleration rate:

scrollView.decelerationRate = UIScrollViewDecelerationRateFast;

然后你的滾動視圖委托實現(xiàn):

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];
    }
}

這篇關于UIScrollView 的靈敏度/滾動速度與分頁的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！