https://www.jianshu.com/p/93e8459b6dae
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，並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
#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，並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
#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上並准備拖動的那一刻
- (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)並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
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