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iOS开发UI篇—无限轮播

 

转载自 http://www.cnblogs.com/wendingding/p/3890953.html

 

一、自动滚动

添加并设置一个定时器,每个2.0秒,就跳转到下一条。

  获取当前正在展示的位置。

 1     [self addNSTimer]; 2 } 3  4 -(void)addNSTimer 5 { 6 //    NSTimer timerWithTimeInterval:<#(NSTimeInterval)#> target:<#(id)#> selector:<#(SEL)#> userInfo:<#(id)#> repeats:<#(BOOL)#> 7     [NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(nextPage) userInfo:nil repeats:YES]; 8 } 9 -(void)nextPage10 {11     NSLog(@"%@",[self.collectinView indexPathsForVisibleItems]);12 //    NSIndexPath *currentIndexPath=[[self.collectinView indexPathsForVisibleItems]lastObject];13 }

  打印查看:

  技术分享

实现步骤:

(1)添加并设置定时器

(2)设置定时器的调用方法

  1)获取当前正在展示的位置

  2)计算出下一个需要展示的位置

  3)通过动画滚动到下一个位置

  注意点:需要进行判断。

实现代码:

 1 - (void)viewDidLoad 2 { 3     [super viewDidLoad]; 4     //注册cell 5 //    [self.collectinView registerClass:[YYimageCell class] forCellWithReuseIdentifier:YYCell]; 6     [self.collectinView registerNib:[UINib nibWithNibName:@"YYcell" bundle:nil] forCellWithReuseIdentifier:YYIDCell]; 7      8      9      [self.collectinView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:50] atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];10      [self addNSTimer];11 }12 13 -(void)addNSTimer14 {15 //    NSTimer timerWithTimeInterval:<#(NSTimeInterval)#> target:<#(id)#> selector:<#(SEL)#> userInfo:<#(id)#> repeats:<#(BOOL)#>16     17    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];18     //添加到runloop中19     [[NSRunLoop mainRunLoop]addTimer:timer forMode:NSRunLoopCommonModes];20 }21 -(void)nextPage22 {23 //    NSLog(@"%@",[self.collectinView indexPathsForVisibleItems]);24         //1)获取当前正在展示的位置25     NSIndexPath *currentIndexPath=[[self.collectinView indexPathsForVisibleItems]lastObject];26     27        //2)计算出下一个需要展示的位置28     NSInteger nextItem=currentIndexPath.item+1;29     NSInteger nextSection=currentIndexPath.section;30     if (nextItem==self.news.count) {31         nextItem=0;32         nextSection++;33     }34     NSIndexPath *nextIndexPath=[NSIndexPath indexPathForItem:nextItem inSection:nextSection];35     36       //3)通过动画滚动到下一个位置37      [self.collectinView scrollToItemAtIndexPath:nextIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];38 }

定时器的说明:

  当用户在处理其他事情的时候,定时器会停止工作。应该把定时器添加到runloop中,告诉系统在处理其他事情的时候分一部分空间给它。

 

二、设置页码

  在storyboard中添加一个页码控件。

实现代码:  

 1 #pragma mark-懒加载 2 -(NSArray *)news 3 { 4     if (_news==nil) { 5         _news=[YYnews objectArrayWithFilename:@"newses.plist"]; 6         self.pageControl.numberOfPages=self.news.count; 7     } 8     return _news; 9 }10 11 - (void)viewDidLoad12 {13     [super viewDidLoad];14     //注册cell15 //    [self.collectinView registerClass:[YYimageCell class] forCellWithReuseIdentifier:YYCell];16     [self.collectinView registerNib:[UINib nibWithNibName:@"YYcell" bundle:nil] forCellWithReuseIdentifier:YYIDCell];17     18     19      [self.collectinView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:50] atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];20     [self addNSTimer];21 }22 23 -(void)addNSTimer24 {25 //    NSTimer timerWithTimeInterval:<#(NSTimeInterval)#> target:<#(id)#> selector:<#(SEL)#> userInfo:<#(id)#> repeats:<#(BOOL)#>26     27    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];28     //添加到runloop中29     [[NSRunLoop mainRunLoop]addTimer:timer forMode:NSRunLoopCommonModes];30 }31 -(void)nextPage32 {33 //    NSLog(@"%@",[self.collectinView indexPathsForVisibleItems]);34         //1)获取当前正在展示的位置35     NSIndexPath *currentIndexPath=[[self.collectinView indexPathsForVisibleItems]lastObject];36     37        //2)计算出下一个需要展示的位置38     NSInteger nextItem=currentIndexPath.item+1;39     NSInteger nextSection=currentIndexPath.section;40     if (nextItem==self.news.count) {41         nextItem=0;42         nextSection++;43     }44     NSIndexPath *nextIndexPath=[NSIndexPath indexPathForItem:nextItem inSection:nextSection];45     46       //3)通过动画滚动到下一个位置47      [self.collectinView scrollToItemAtIndexPath:nextIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];48     49     //4)设置页码50     self.pageControl.currentPage=nextItem;51 }

 自动滚动,页码的实现效果:

技术分享

三、完善

说明:监听collectionView的滚动,当手动触摸collectionView,尝试拖拽的时候,把定时器停掉,当手指移开的时候,重启定时器。

完整的实现代码:

  1 //  2 //  YYViewController.m  3 //  07-无限滚动(循环利用)  4 //  5 //  Created by apple on 14-8-3.  6 //  Copyright (c) 2014年 yangyong. All rights reserved.  7 //  8   9 #import "YYViewController.h" 10 #import "MJExtension.h" 11 #import "YYnews.h" 12 #import "YYcell.h" 13  14 #define YYIDCell @"cell" 15 //注意:这里需要考虑用户的手动拖拽 16 #define YYMaxSections 100 17 @interface YYViewController ()<UICollectionViewDataSource,UICollectionViewDelegate> 18 @property (weak, nonatomic) IBOutlet UICollectionView *collectinView; 19 @property(nonatomic,strong)NSArray *news; 20 @property (weak, nonatomic) IBOutlet UIPageControl *pageControl; 21 @property(nonatomic,strong)NSTimer *timer; 22  23 @end 24  25 @implementation YYViewController 26  27 #pragma mark-懒加载 28 -(NSArray *)news 29 { 30     if (_news==nil) { 31         _news=[YYnews objectArrayWithFilename:@"newses.plist"]; 32         self.pageControl.numberOfPages=self.news.count; 33     } 34     return _news; 35 } 36  37 - (void)viewDidLoad 38 { 39     [super viewDidLoad]; 40     //注册cell 41 //    [self.collectinView registerClass:[YYimageCell class] forCellWithReuseIdentifier:YYCell]; 42     [self.collectinView registerNib:[UINib nibWithNibName:@"YYcell" bundle:nil] forCellWithReuseIdentifier:YYIDCell]; 43      44      45      [self.collectinView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:50] atScrollPosition:UICollectionViewScrollPositionLeft animated:YES]; 46     [self addNSTimer]; 47 } 48  49 //添加定时器 50 -(void)addNSTimer 51 { 52    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(nextPage) userInfo:nil repeats:YES]; 53     //添加到runloop中 54     [[NSRunLoop mainRunLoop]addTimer:timer forMode:NSRunLoopCommonModes]; 55     self.timer=timer; 56 } 57  58 //删除定时器 59 -(void)removeNSTimer 60 { 61     [self.timer invalidate]; 62     self.timer=nil; 63 } 64  65 //自动滚动 66 -(void)nextPage 67 { 68         //1获取当前正在展示的位置 69     NSIndexPath *currentIndexPath=[[self.collectinView indexPathsForVisibleItems]lastObject]; 70      71     //马上显示回最中间那组的数据 72     NSIndexPath *currentIndexPathRest=[NSIndexPath indexPathForItem:currentIndexPath.item inSection:YYMaxSections/2]; 73     [self.collectinView scrollToItemAtIndexPath:currentIndexPathRest atScrollPosition:UICollectionViewScrollPositionLeft animated:NO]; 74      75        //2计算出下一个需要展示的位置 76     NSInteger nextItem=currentIndexPathRest.item+1; 77     NSInteger nextSection=currentIndexPathRest.section; 78     if (nextItem==self.news.count) { 79         nextItem=0; 80         nextSection++; 81     } 82     NSIndexPath *nextIndexPath=[NSIndexPath indexPathForItem:nextItem inSection:nextSection]; 83      84       //3通过动画滚动到下一个位置 85      [self.collectinView scrollToItemAtIndexPath:nextIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:YES]; 86      87 //    //4)设置页码 88 //    self.pageControl.currentPage=nextItem; 89 } 90  91 #pragma mark- UICollectionViewDataSource 92 //一共多少组,默认为1组 93 -(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView 94 { 95     return YYMaxSections; 96 } 97 -(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section 98 { 99     return self.news.count;100 }101 102 -(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath103 {104     YYcell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:YYIDCell forIndexPath:indexPath];105     cell.news=self.news[indexPath.item];106     NSLog(@"%p,%d",cell,indexPath.item);107     return cell;108 }109 110 #pragma mark-UICollectionViewDelegate111 //当用户开始拖拽的时候就调用112 -(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView113 {114     [self removeNSTimer];115 }116 //当用户停止拖拽的时候调用117 -(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate118 {119     [self addNSTimer];120 }121 //设置页码122 -(void)scrollViewDidScroll:(UIScrollView *)scrollView123 {124     int page=(int)(scrollView.contentOffset.x/scrollView.frame.size.width+0.5)%self.news.count;125     self.pageControl.currentPage=page;126 }127 @end

补充说明:

  实现瀑布流最理想的做法是继承UIScrollView,不建议使用多个UITableView的方式实现(这种方式无法实现cell的循环利用,且禁止了cell的滚动时间后,整体的tableView需要随着滚动会出现空白)。

  也可以使用collectionView来实现,但使用这种方法需要自定义collectionView的布局(流水布局)

iOS开发UI篇—无限轮播