實用小技巧（一）：UIScrollView中上下左右滾動方向的判斷

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

2017.06.01 01:13*?字數 674?閱讀 1201評論 0喜歡 1

2017.06.01 01:13* 字數 674 閱讀 1201評論 0喜歡 1

版本記錄

版本號	時間
V1.0	2017.05.31

前言

ios中又很多實用的小技巧，實現不難很實用，以后我會慢慢的給大家總結。這一篇主要講述滾動方向的判斷。

??滾動視圖是app很常用的視圖形式，而其中scrollView及其子類UITableView和UICollectionView用的很多，在用的時候有一個需求就是：需要判斷當前的滾動方向

• 向上滾動
• 向下滾動
• 向左滾動
• 向右滾動
• 下面就以兩個例子對滾動方向進行判斷，下面我們開始。

詳情

一、左右滾動方向的判斷

下面我們就以UIScrollView為例子，說明左右滾動是如何判斷的，還是先看一下代碼組成。

?

代碼組成

思路引導

下面我們看，當我們向左滾動時可見，x為正值且越來越大，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

反過來，如果我們向右滑動，可見

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，我們可見，可以有這個思路，如果我們記錄當前的x偏移值，并且用下一時刻臨近的x偏移值與之相比較，取差值，如果下一時刻的x偏移值 - 當前x偏移值為正值，則是向左邊滑動，反之則為向右滑動。

看輸出結果，先看向左滑動

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] 正在向左滑動

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] 正在向左滑動

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] 正在向左滑動

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] 正在向左滑動

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] 正在向左滑動

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] 正在向左滑動

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] 正在向左滑動

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] 正在向左滑動

在看向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

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] 正在向右滑動

?

代碼實現

下面我們就直接看代碼的實現。

JJHorizontalDirectionVC.m

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#import "JJHorizontalDirectionVC.h"

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@interface JJHorizontalDirectionVC () <UIScrollViewDelegate>

?? ?

@property (nonatomic, strong) UIScrollView *textScrollView;

@property (nonatomic, assign) CGFloat lastOffSetX;

?

@end

?

@implementation JJHorizontalDirectionVC

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#pragma mark - Override Base Function

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- (void)viewDidLoad

{

? ? [super viewDidLoad];

?? ?

? ? [self setupUI];

}

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#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(@"正在向左滑動");

? ? }

? ? else {

? ? ? ? NSLog(@"正在向右滑動");

? ? }

}

?? ?

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

{

? ? self.lastOffSetX = scrollView.contentOffset.x;

}

?

@end

?

?

二、上下滾動方向的判斷

下面我們就以UIScrollView為例子，說明上下滾動是如何判斷的，還是先看一下代碼組成。

?

代碼組織

思路引導

??前面有了左右方向的判斷，相信大家掌握了，那么上下方向的判斷也是這個思路。

先看向上滾動的輸出

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

?

我們在看一下向下滾動

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，我們可見，可以有這個思路，如果我們記錄當前的y偏移值，并且用下一時刻臨近的y偏移值與之相比較，取差值，如果下一時刻的y偏移值 - 當前y偏移值為正值，則是向上邊滑動，反之則為向下邊滑動。

下面看最后的輸出結果，先看向上滑動。

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

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] 正在向上滑動

?

在看一下向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

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] 正在向下滑動

代碼實現

看代碼實現

JJVerticalDirectionVC.m

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#import "JJVerticalDirectionVC.h"

?

@interface JJVerticalDirectionVC () <UIScrollViewDelegate>

?? ?

@property (nonatomic, strong) UIScrollView *textScrollView;

@property (nonatomic, assign) CGFloat lastOffSetY;

?

@end

?

@implementation JJVerticalDirectionVC

?? ?

#pragma mark - Override Base Function

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- (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(@"正在向上滑動");

? ? }

? ? else {

? ? ? ? NSLog(@"正在向下滑動");

? ? }

}

?? ?

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

{

? ? self.lastOffSetY = scrollView.contentOffset.y;

}

?

@end

后記

??判斷視圖的滾動方向是我們經常有的需求，這篇就先介紹到這，后面還會介紹其他的實用小技巧，希望對大家有所幫助，謝謝大家。

?

?

UIScrollView如何判斷是向右滾動還是向左滾動

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

在做類似網易新聞和今日頭條的那個效果時候

?

當我滾動下標為0的時候,也就是第一個標題的時候,往右繼續滑動,會重復請求第一個標題的數據

?

同理當我滾動到最后一個標題的時候,會重復請求最后一個標題的數據

?

特此記錄下解決方法:

?

1:首先設置pageEnable=YES；

?

然后通過Delegate實現相關方法。

?

2:

?

#pragma mark -?將要開始拖拽，手指已經放在view上并準備拖動的那一刻

?

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{? ? //拖動前的起始坐標

?

? ? startContentOffsetX = scrollView.contentOffset.x;

?

}

?

3:

?

#pragma mark - ??將要停止前的坐標

?

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

?

? ? willEndContentOffsetX = scrollView.contentOffset.x;

?

}

?

4:

?

#pragma mark -?減速停止(必須得有快速拖動的動作，scrollView滾動完畢(速度減為0)并且手已經松開的時候調用)

?

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

?

? ? endContentOffsetX = scrollView.contentOffset.x;

?

? ? if (endContentOffsetX < willEndContentOffsetX && willEndContentOffsetX < startContentOffsetX) {?//畫面從右往左移動，前一頁

?

? ? } else if (endContentOffsetX > willEndContentOffsetX && willEndContentOffsetX > startContentOffsetX) {//畫面從左往右移動，后一頁

?

? ? }

?

}

---------------------?

作者：正能量_?

來源：CSDN?

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

版權聲明：本文為博主原創文章，轉載請附上博文鏈接！

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