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)nextPage 10 { 11 NSLog(@"%@",[self.collectinView indexPathsForVisibleItems]); 12 // NSIndexPath *currentIndexPath=[[self.collectinView indexPathsForVisibleItems]lastObject]; 13 }
打印查看:
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)addNSTimer 14 { 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)nextPage 22 { 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)viewDidLoad 12 { 13 [super viewDidLoad]; 14 //注册cell 15 // [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)addNSTimer 24 { 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)nextPage 32 { 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:
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 *)indexPath 103 { 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-UICollectionViewDelegate 111 //当用户开始拖拽的时候就调用 112 -(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView 113 { 114 [self removeNSTimer]; 115 } 116 //当用户停止拖拽的时候调用 117 -(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate 118 { 119 [self addNSTimer]; 120 } 121 //设置页码 122 -(void)scrollViewDidScroll:(UIScrollView *)scrollView 123 { 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)