实用小技巧（一）：UIScrollView中上下左右滚动方向的判断

https://www.jianshu.com/p/93e8459b6dae

2017.06.01 01:13* 字数 674 阅读 1201评论 0

2017.06.01 01:13* 字数 674 阅读 1201评论 0喜欢 1

版本记录

版本号

时间

V1.0

2017.05.31

前言

ios中又很多实用的小技巧，实现不难很实用，以后我会慢慢的给大家总结。这一篇主要讲述滚动方向的判断。

  滚动视图是app很常用的视图形式，而其中scrollView及其子类UITableView和UICollectionView用的很多，在用的时候有一个需求就是：需要判断当前的滚动方向

  • 向上滚动
  • 向下滚动
  • 向左滚动
  • 向右滚动
  • 下面就以两个例子对滚动方向进行判断，下面我们开始。

详情

一、左右滚动方向的判断

下面我们就以UIScrollView为例子，说明左右滚动是如何判断的，还是先看一下代码组成。

pastedGraphic.png

代码组成

思路引导

下面我们看，当我们向左滚动时可见，x为正值且越来越大，如下：

2017-06-01 00:15:47.962 scrollDirectionJudge[2981:77203] x==0.333333,y==-64.000000

2017-06-01 00:15:48.026 scrollDirectionJudge[2981:77203] x==1.000000,y==-64.000000

2017-06-01 00:15:48.057 scrollDirectionJudge[2981:77203] x==1.333333,y==-64.000000

2017-06-01 00:15:48.089 scrollDirectionJudge[2981:77203] x==1.666667,y==-64.000000

2017-06-01 00:15:48.122 scrollDirectionJudge[2981:77203] x==2.000000,y==-64.000000

2017-06-01 00:15:48.145 scrollDirectionJudge[2981:77203] x==4.000000,y==-64.000000

2017-06-01 00:15:48.170 scrollDirectionJudge[2981:77203] x==7.666667,y==-64.000000

2017-06-01 00:15:48.194 scrollDirectionJudge[2981:77203] x==11.000000,y==-64.000000

2017-06-01 00:15:48.218 scrollDirectionJudge[2981:77203] x==12.666667,y==-64.000000

2017-06-01 00:15:48.235 scrollDirectionJudge[2981:77203] x==13.000000,y==-64.000000

2017-06-01 00:15:48.956 scrollDirectionJudge[2981:77203] x==13.666667,y==-64.000000

2017-06-01 00:15:49.036 scrollDirectionJudge[2981:77203] x==14.000000,y==-64.000000

反过来，如果我们向右滑动，可见

2017-06-01 00:17:27.177 scrollDirectionJudge[2981:77203] x==412.000000,y==-64.000000

2017-06-01 00:17:27.200 scrollDirectionJudge[2981:77203] x==407.666667,y==-64.000000

2017-06-01 00:17:27.216 scrollDirectionJudge[2981:77203] x==405.333333,y==-64.000000

2017-06-01 00:17:27.240 scrollDirectionJudge[2981:77203] x==402.333333,y==-64.000000

2017-06-01 00:17:27.265 scrollDirectionJudge[2981:77203] x==401.333333,y==-64.000000

2017-06-01 00:17:27.288 scrollDirectionJudge[2981:77203] x==401.000000,y==-64.000000

2017-06-01 00:17:27.353 scrollDirectionJudge[2981:77203] x==400.666667,y==-64.000000

2017-06-01 00:17:27.377 scrollDirectionJudge[2981:77203] x==399.666667,y==-64.000000

2017-06-01 00:17:27.400 scrollDirectionJudge[2981:77203] x==397.666667,y==-64.000000

2017-06-01 00:17:27.416 scrollDirectionJudge[2981:77203] x==395.666667,y==-64.000000

2017-06-01 00:17:27.432 scrollDirectionJudge[2981:77203] x==393.333333,y==-64.000000

2017-06-01 00:17:27.448 scrollDirectionJudge[2981:77203] x==391.666667,y==-64.000000

2017-06-01 00:17:27.473 scrollDirectionJudge[2981:77203] x==390.333333,y==-64.000000

那么，我们可见，可以有这个思路，如果我们记录当前的x偏移值，并且用下一时刻临近的x偏移值与之相比较，取差值，如果下一时刻的x偏移值 - 当前x偏移值为正值，则是向左边滑动，反之则为向右滑动。

看输出结果，先看向左滑动

2017-06-01 00:24:38.629 scrollDirectionJudge[3185:84739] x==4.666667,y==-64.000000

2017-06-01 00:24:38.629 scrollDirectionJudge[3185:84739] 正在向左滑动

2017-06-01 00:24:38.652 scrollDirectionJudge[3185:84739] x==10.666667,y==-64.000000

2017-06-01 00:24:38.652 scrollDirectionJudge[3185:84739] 正在向左滑动

2017-06-01 00:24:38.676 scrollDirectionJudge[3185:84739] x==15.666667,y==-64.000000

2017-06-01 00:24:38.677 scrollDirectionJudge[3185:84739] 正在向左滑动

2017-06-01 00:24:38.700 scrollDirectionJudge[3185:84739] x==20.000000,y==-64.000000

2017-06-01 00:24:38.700 scrollDirectionJudge[3185:84739] 正在向左滑动

2017-06-01 00:24:38.726 scrollDirectionJudge[3185:84739] x==22.666667,y==-64.000000

2017-06-01 00:24:38.727 scrollDirectionJudge[3185:84739] 正在向左滑动

2017-06-01 00:24:38.747 scrollDirectionJudge[3185:84739] x==24.333333,y==-64.000000

2017-06-01 00:24:38.748 scrollDirectionJudge[3185:84739] 正在向左滑动

2017-06-01 00:24:38.764 scrollDirectionJudge[3185:84739] x==25.000000,y==-64.000000

2017-06-01 00:24:38.765 scrollDirectionJudge[3185:84739] 正在向左滑动

2017-06-01 00:24:38.792 scrollDirectionJudge[3185:84739] x==25.666667,y==-64.000000

2017-06-01 00:24:38.792 scrollDirectionJudge[3185:84739] 正在向左滑动

在看向右滑动

2017-06-01 00:25:58.949 scrollDirectionJudge[3185:84739] x==27.333333,y==-64.000000

2017-06-01 00:25:58.950 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:58.970 scrollDirectionJudge[3185:84739] x==24.333333,y==-64.000000

2017-06-01 00:25:58.970 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:58.986 scrollDirectionJudge[3185:84739] x==22.666667,y==-64.000000

2017-06-01 00:25:58.986 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.002 scrollDirectionJudge[3185:84739] x==21.333333,y==-64.000000

2017-06-01 00:25:59.003 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.018 scrollDirectionJudge[3185:84739] x==20.000000,y==-64.000000

2017-06-01 00:25:59.019 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.034 scrollDirectionJudge[3185:84739] x==19.333333,y==-64.000000

2017-06-01 00:25:59.035 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.054 scrollDirectionJudge[3185:84739] x==18.666667,y==-64.000000

2017-06-01 00:25:59.054 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.074 scrollDirectionJudge[3185:84739] x==16.000000,y==-64.000000

2017-06-01 00:25:59.074 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.090 scrollDirectionJudge[3185:84739] x==14.000000,y==-64.000000

2017-06-01 00:25:59.091 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.115 scrollDirectionJudge[3185:84739] x==11.666667,y==-64.000000

2017-06-01 00:25:59.115 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.138 scrollDirectionJudge[3185:84739] x==10.666667,y==-64.000000

2017-06-01 00:25:59.139 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.195 scrollDirectionJudge[3185:84739] x==10.000000,y==-64.000000

2017-06-01 00:25:59.196 scrollDirectionJudge[3185:84739] 正在向右滑动

2017-06-01 00:25:59.251 scrollDirectionJudge[3185:84739] x==9.666667,y==-64.000000

2017-06-01 00:25:59.251 scrollDirectionJudge[3185:84739] 正在向右滑动

代码实现

下面我们就直接看代码的实现。

JJHorizontalDirectionVC.m

#import "JJHorizontalDirectionVC.h"

@interface JJHorizontalDirectionVC () <UIScrollViewDelegate>

    

@property (nonatomic, strong) UIScrollView *textScrollView;

@property (nonatomic, assign) CGFloat lastOffSetX;

@end

@implementation JJHorizontalDirectionVC

#pragma mark - Override Base Function

- (void)viewDidLoad

{

    [super viewDidLoad];

    

    [self setupUI];

}

#pragma mark - Object Private Function

    

- (void)setupUI

{

    UIScrollView *textScrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];

    textScrollView.backgroundColor = [UIColor greenColor];

    textScrollView.contentSize = CGSizeMake(self.view.bounds.size.width * 2, 0);

    textScrollView.delegate = self;

    [self.view addSubview:textScrollView];

    self.textScrollView = textScrollView;

}

    

#pragma mark - UIScrollViewDelegate

    

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

    NSLog(@"x==%f,y==%f",scrollView.contentOffset.x,scrollView.contentOffset.y);

    

    if (scrollView.contentOffset.x - self.lastOffSetX > 0) {

        NSLog(@"正在向左滑动");

    }

    else {

        NSLog(@"正在向右滑动");

    }

}

    

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

{

    self.lastOffSetX = scrollView.contentOffset.x;

}

@end

二、上下滚动方向的判断

下面我们就以UIScrollView为例子，说明上下滚动是如何判断的，还是先看一下代码组成。

pastedGraphic_1.png

代码组织

思路引导

  前面有了左右方向的判断，相信大家掌握了，那么上下方向的判断也是这个思路。

先看向上滚动的输出

2017-06-01 00:48:03.131 scrollDirectionJudge[3579:100464] x==0.000000,y==0.666667

2017-06-01 00:48:03.148 scrollDirectionJudge[3579:100464] x==0.000000,y==2.000000

2017-06-01 00:48:03.171 scrollDirectionJudge[3579:100464] x==0.000000,y==3.666667

2017-06-01 00:48:03.187 scrollDirectionJudge[3579:100464] x==0.000000,y==5.000000

2017-06-01 00:48:03.203 scrollDirectionJudge[3579:100464] x==0.000000,y==6.000000

2017-06-01 00:48:03.229 scrollDirectionJudge[3579:100464] x==0.000000,y==6.666667

2017-06-01 00:48:03.246 scrollDirectionJudge[3579:100464] x==0.000000,y==7.000000

2017-06-01 00:48:03.733 scrollDirectionJudge[3579:100464] x==0.000000,y==7.333333

2017-06-01 00:48:03.757 scrollDirectionJudge[3579:100464] x==0.000000,y==8.000000

2017-06-01 00:48:03.773 scrollDirectionJudge[3579:100464] x==0.000000,y==8.333333

2017-06-01 00:48:03.797 scrollDirectionJudge[3579:100464] x==0.000000,y==9.333333

2017-06-01 00:48:03.832 scrollDirectionJudge[3579:100464] x==0.000000,y==10.333333

2017-06-01 00:48:03.863 scrollDirectionJudge[3579:100464] x==0.000000,y==11.000000

2017-06-01 00:48:03.981 scrollDirectionJudge[3579:100464] x==0.000000,y==11.333333

2017-06-01 00:48:04.005 scrollDirectionJudge[3579:100464] x==0.000000,y==12.666667

2017-06-01 00:48:04.029 scrollDirectionJudge[3579:100464] x==0.000000,y==14.333333

2017-06-01 00:48:04.047 scrollDirectionJudge[3579:100464] x==0.000000,y==15.000000

2017-06-01 00:48:04.064 scrollDirectionJudge[3579:100464] x==0.000000,y==15.333333

2017-06-01 00:48:04.214 scrollDirectionJudge[3579:100464] x==0.000000,y==16.000000

2017-06-01 00:48:04.237 scrollDirectionJudge[3579:100464] x==0.000000,y==17.000000

2017-06-01 00:48:04.262 scrollDirectionJudge[3579:100464] x==0.000000,y==19.333333

2017-06-01 00:48:04.286 scrollDirectionJudge[3579:100464] x==0.000000,y==21.666667

2017-06-01 00:48:04.311 scrollDirectionJudge[3579:100464] x==0.000000,y==22.666667

2017-06-01 00:48:04.494 scrollDirectionJudge[3579:100464] x==0.000000,y==23.666667

2017-06-01 00:48:04.518 scrollDirectionJudge[3579:100464] x==0.000000,y==24.666667

我们在看一下向下滚动

2017-06-01 00:49:12.548 scrollDirectionJudge[3579:100464] x==0.000000,y==735.333333

2017-06-01 00:49:12.571 scrollDirectionJudge[3579:100464] x==0.000000,y==733.333333

2017-06-01 00:49:12.587 scrollDirectionJudge[3579:100464] x==0.000000,y==732.666667

2017-06-01 00:49:12.614 scrollDirectionJudge[3579:100464] x==0.000000,y==732.000000

2017-06-01 00:49:12.660 scrollDirectionJudge[3579:100464] x==0.000000,y==731.666667

2017-06-01 00:49:12.796 scrollDirectionJudge[3579:100464] x==0.000000,y==731.333333

2017-06-01 00:49:12.813 scrollDirectionJudge[3579:100464] x==0.000000,y==730.666667

2017-06-01 00:49:12.831 scrollDirectionJudge[3579:100464] x==0.000000,y==730.000000

2017-06-01 00:49:13.101 scrollDirectionJudge[3579:100464] x==0.000000,y==729.666667

2017-06-01 00:49:13.125 scrollDirectionJudge[3579:100464] x==0.000000,y==729.000000

2017-06-01 00:49:13.149 scrollDirectionJudge[3579:100464] x==0.000000,y==725.666667

2017-06-01 00:49:13.167 scrollDirectionJudge[3579:100464] x==0.000000,y==721.333333

2017-06-01 00:49:13.183 scrollDirectionJudge[3579:100464] x==0.000000,y==717.000000

2017-06-01 00:49:13.204 scrollDirectionJudge[3579:100464] x==0.000000,y==711.000000

2017-06-01 00:49:13.221 scrollDirectionJudge[3579:100464] x==0.000000,y==709.000000

2017-06-01 00:49:13.237 scrollDirectionJudge[3579:100464] x==0.000000,y==707.333333

2017-06-01 00:49:13.265 scrollDirectionJudge[3579:100464] x==0.000000,y==706.333333

那么，我们可见，可以有这个思路，如果我们记录当前的y偏移值，并且用下一时刻临近的y偏移值与之相比较，取差值，如果下一时刻的y偏移值 - 当前y偏移值为正值，则是向上边滑动，反之则为向下边滑动。

下面看最后的输出结果，先看向上滑动。

2017-06-01 00:55:03.163 scrollDirectionJudge[3709:105104] x==0.000000,y==139.666667

2017-06-01 00:55:03.163 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.184 scrollDirectionJudge[3709:105104] x==0.000000,y==143.000000

2017-06-01 00:55:03.184 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.213 scrollDirectionJudge[3709:105104] x==0.000000,y==146.666667

2017-06-01 00:55:03.213 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.232 scrollDirectionJudge[3709:105104] x==0.000000,y==149.666667

2017-06-01 00:55:03.232 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.248 scrollDirectionJudge[3709:105104] x==0.000000,y==151.666667

2017-06-01 00:55:03.248 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.264 scrollDirectionJudge[3709:105104] x==0.000000,y==153.666667

2017-06-01 00:55:03.265 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.297 scrollDirectionJudge[3709:105104] x==0.000000,y==155.333333

2017-06-01 00:55:03.297 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.332 scrollDirectionJudge[3709:105104] x==0.000000,y==156.666667

2017-06-01 00:55:03.332 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.401 scrollDirectionJudge[3709:105104] x==0.000000,y==157.000000

2017-06-01 00:55:03.401 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.457 scrollDirectionJudge[3709:105104] x==0.000000,y==157.333333

2017-06-01 00:55:03.457 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.481 scrollDirectionJudge[3709:105104] x==0.000000,y==158.000000

2017-06-01 00:55:03.481 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.504 scrollDirectionJudge[3709:105104] x==0.000000,y==158.333333

2017-06-01 00:55:03.505 scrollDirectionJudge[3709:105104] 正在向上滑动

2017-06-01 00:55:03.561 scrollDirectionJudge[3709:105104] x==0.000000,y==159.000000

2017-06-01 00:55:03.561 scrollDirectionJudge[3709:105104] 正在向上滑动

在看一下向下滑动

2017-06-01 00:55:30.613 scrollDirectionJudge[3709:105104] x==0.000000,y==734.000000

2017-06-01 00:55:30.614 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.636 scrollDirectionJudge[3709:105104] x==0.000000,y==730.666667

2017-06-01 00:55:30.637 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.653 scrollDirectionJudge[3709:105104] x==0.000000,y==728.666667

2017-06-01 00:55:30.653 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.680 scrollDirectionJudge[3709:105104] x==0.000000,y==723.666667

2017-06-01 00:55:30.680 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.701 scrollDirectionJudge[3709:105104] x==0.000000,y==717.666667

2017-06-01 00:55:30.702 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.731 scrollDirectionJudge[3709:105104] x==0.000000,y==711.000000

2017-06-01 00:55:30.732 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.749 scrollDirectionJudge[3709:105104] x==0.000000,y==705.333333

2017-06-01 00:55:30.749 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.766 scrollDirectionJudge[3709:105104] x==0.000000,y==701.666667

2017-06-01 00:55:30.767 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.790 scrollDirectionJudge[3709:105104] x==0.000000,y==698.666667

2017-06-01 00:55:30.790 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.813 scrollDirectionJudge[3709:105104] x==0.000000,y==697.000000

2017-06-01 00:55:30.813 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.830 scrollDirectionJudge[3709:105104] x==0.000000,y==696.333333

2017-06-01 00:55:30.830 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.926 scrollDirectionJudge[3709:105104] x==0.000000,y==695.666667

2017-06-01 00:55:30.927 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.950 scrollDirectionJudge[3709:105104] x==0.000000,y==694.666667

2017-06-01 00:55:30.951 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.973 scrollDirectionJudge[3709:105104] x==0.000000,y==692.333333

2017-06-01 00:55:30.974 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:30.997 scrollDirectionJudge[3709:105104] x==0.000000,y==690.000000

2017-06-01 00:55:30.998 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.014 scrollDirectionJudge[3709:105104] x==0.000000,y==688.666667

2017-06-01 00:55:31.015 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.030 scrollDirectionJudge[3709:105104] x==0.000000,y==687.000000

2017-06-01 00:55:31.031 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.053 scrollDirectionJudge[3709:105104] x==0.000000,y==684.666667

2017-06-01 00:55:31.054 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.069 scrollDirectionJudge[3709:105104] x==0.000000,y==683.666667

2017-06-01 00:55:31.070 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.097 scrollDirectionJudge[3709:105104] x==0.000000,y==682.666667

2017-06-01 00:55:31.097 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.190 scrollDirectionJudge[3709:105104] x==0.000000,y==681.666667

2017-06-01 00:55:31.191 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.287 scrollDirectionJudge[3709:105104] x==0.000000,y==681.333333

2017-06-01 00:55:31.287 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.318 scrollDirectionJudge[3709:105104] x==0.000000,y==681.000000

2017-06-01 00:55:31.319 scrollDirectionJudge[3709:105104] 正在向下滑动

2017-06-01 00:55:31.361 scrollDirectionJudge[3709:105104] x==0.000000,y==680.333333

2017-06-01 00:55:31.361 scrollDirectionJudge[3709:105104] 正在向下滑动

代码实现

看代码实现

JJVerticalDirectionVC.m

#import "JJVerticalDirectionVC.h"

@interface JJVerticalDirectionVC () <UIScrollViewDelegate>

    

@property (nonatomic, strong) UIScrollView *textScrollView;

@property (nonatomic, assign) CGFloat lastOffSetY;

@end

@implementation JJVerticalDirectionVC

    

#pragma mark - Override Base Function

- (void)viewDidLoad

{

    [super viewDidLoad];

    

    [self setupUI];

}

    

#pragma mark - Object Private Function

    

- (void)setupUI

{

    UIScrollView *textScrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];

    textScrollView.backgroundColor = [UIColor magentaColor];

    textScrollView.contentSize = CGSizeMake(0, self.view.bounds.size.height * 2);

    textScrollView.delegate = self;

    [self.view addSubview:textScrollView];

    self.textScrollView = textScrollView;

    

}

    

#pragma mark - UIScrollViewDelegate

    

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

    NSLog(@"x==%f,y==%f",scrollView.contentOffset.x,scrollView.contentOffset.y);

    

    if (scrollView.contentOffset.y - self.lastOffSetY > 0) {

        NSLog(@"正在向上滑动");

    }

    else {

        NSLog(@"正在向下滑动");

    }

}

    

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

{

    self.lastOffSetY = scrollView.contentOffset.y;

}

@end

后记

  判断视图的滚动方向是我们经常有的需求，这篇就先介绍到这，后面还会介绍其他的实用小技巧，希望对大家有所帮助，谢谢大家。

UIScrollView如何判断是向右滚动还是向左滚动

https://blog.csdn.net/www9500net_/article/details/52622815

在做类似网易新闻和今日头条的那个效果时候

当我滚动下标为0的时候,也就是第一个标题的时候,往右继续滑动,会重复请求第一个标题的数据

同理当我滚动到最后一个标题的时候,会重复请求最后一个标题的数据

特此记录下解决方法:

1:首先设置pageEnable=YES；

然后通过Delegate实现相关方法。

2:

#pragma mark - 将要开始拖拽，手指已经放在view上并准备拖动的那一刻

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{    //拖动前的起始坐标

    startContentOffsetX = scrollView.contentOffset.x;

}

3:

#pragma mark -   将要停止前的坐标

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset{  

    willEndContentOffsetX = scrollView.contentOffset.x;

}

4:

#pragma mark - 减速停止(必须得有快速拖动的动作，scrollView滚动完毕(速度减为0)并且手已经松开的时候调用)

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{

    endContentOffsetX = scrollView.contentOffset.x;

    if (endContentOffsetX < willEndContentOffsetX && willEndContentOffsetX < startContentOffsetX) { //画面从右往左移动，前一页

    } else if (endContentOffsetX > willEndContentOffsetX && willEndContentOffsetX > startContentOffsetX) {//画面从左往右移动，后一页

    }

}

--------------------- 

作者：正能量_ 

来源：CSDN 

原文：https://blog.csdn.net/www9500net_/article/details/52622815 

版权声明：本文为博主原创文章，转载请附上博文链接！

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原文地址：https://www.cnblogs.com/sundaysgarden/p/10556452.html