像Instagram一样限制UITableView滚动速度 [英] Limit UITableView scroll speed like Instagram does it

问题描述

我正试图限制我的UITableView的滚动速度，就像Instagram一样。

I'm trying to limit the scroll speed of my UITableView, exactly like Instagram does it.

如果你看看Instagram，你会注意到他们有限制滚动浏览量的速度。

If you check out Instagram, you'll notice that they have a limit on how fast you can scroll through the feed.

由于限制不影响减速度，因此未使用decelerationRate设置。它只会影响您滚动Feed的速度。因此，如果您尝试执行轻弹手势，您将达到Instagrams最大滚动速度，并且不会像普通UITableView那样快。

It's not set using "decelerationRate" since the limit doesn't affect the deceleration. It simply affects the how fast you can scroll through the feed. So if you try to do a "flick" gesture, you will hit Instagrams max scrolling speed and won't go as fast as in a normal UITableView.

任何猜测Instagram如何实现这个目标？

Any guesses on how Instagram accomplishes this?

推荐答案

TableView有一个属性 scrollView ，这个属性将返回TableView的内部scrollView。使用以下...

TableView has a property scrollView, This property will return internal scrollView of TableView. Use following...

tableview.scrollView.decelerationRate = UIScrollViewDecelerationRateFast;

另一种方式：

TableView将作出回应to scrollView委托，所以我们需要实现scrollView的委托，如：

TableView will respond to scrollView delegate, so we need to implement scrollView's delegate like:

取这些全局变量：

CGPoint lastOffset;
NSTimeInterval lastOffsetCapture;
BOOL isScrollingFast;

实施 scrollViewDidScroll 喜欢：

- (void) scrollViewDidScroll:(UIScrollView *)scrollView {    
    CGPoint currentOffset = scrollView.contentOffset;
    NSTimeInterval currentTime = [NSDate timeIntervalSinceReferenceDate];

    NSTimeInterval timeDiff = currentTime - lastOffsetCapture;
    if(timeDiff > 0.1) {
        CGFloat distance = currentOffset.y - lastOffset.y;
        //The multiply by 10, / 1000 isn't really necessary.......
        CGFloat scrollSpeedNotAbs = (distance * 10) / 1000; //in pixels per millisecond

        CGFloat scrollSpeed = fabsf(scrollSpeedNotAbs);
        if (scrollSpeed > 0.5) {
            isScrollingFast = YES;
            NSLog(@"Fast");
        } else {
            isScrollingFast = NO;
            NSLog(@"Slow");
        }        

        lastOffset = currentOffset;
        lastOffsetCapture = currentTime;
    }
}

然后实现 scrollViewDidEndDragging 像这样：

- (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];
    }
}

希望这可以帮助你......

Hope this may help you...

这篇关于像Instagram一样限制UITableView滚动速度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！