iOS使用UIScrollView实现无限循环轮播图效果

//// ViewController.m// 无限轮播//// Created by limin on 17/8/23.// Copyright © 2017年 none. All rights reserved.// #import "ViewController.h" @interface ViewController ()<UIScrollViewDelegate>/* 定时器 */@property(nonatomic,strong)NSTimer *rotateTimer;/* */@property(nonatomic,strong)UIPageControl *myPageControl;@end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; //初始化scroolview大小为屏幕大小 UIScrollView *rotateScrollView = [[UIScrollView alloc]initWithFrame:self.view.frame]; //设置滚动范围 rotateScrollView.contentSize = CGSizeMake(CGRectGetWidth(self.view.frame)*3, CGRectGetHeight(self.view.frame)); //设置分页效果 rotateScrollView.pagingEnabled = YES; //水平滚动条隐藏 rotateScrollView.showsHorizontalScrollIndicator = NO; //添加三个子视图，uilabel类型 for (int i=0; i<3; i++) { UILabel *subLabel = [[UILabel alloc] initWithFrame:CGRectMake(CGRectGetWidth(self.view.frame)*i, 0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame))]; subLabel.tag = 1000+i; subLabel.text = [NSString stringWithFormat:@"我是第%d个视图",i]; [subLabel setFont:[UIFont systemFontOfSize:80]]; subLabel.adjustsFontSizeToFitWidth = YES; [subLabel setBackgroundColor:[UIColor colorWithRed:arc4random()%256/255.0 green:arc4random()%256/255.0 blue:arc4random()%256/255.0 alpha:1.0]]; [rotateScrollView addSubview:subLabel];  } UILabel *tempLabel = [rotateScrollView viewWithTag:1000]; //为滚动视图的右边添加一个视图，使得它和第一个视图一模一样。 UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(CGRectGetWidth(self.view.frame)*3, 0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame))]; label.backgroundColor = tempLabel.backgroundColor; label.text = tempLabel.text; label.font = tempLabel.font; label.adjustsFontSizeToFitWidth = YES; [rotateScrollView addSubview:label]; [self.view addSubview:rotateScrollView]; rotateScrollView.tag = 1000; self.myPageControl = [[UIPageControl alloc]initWithFrame:CGRectMake(0, CGRectGetHeight(self.view.frame)-50, CGRectGetWidth(self.view.frame), 50)]; self.myPageControl.numberOfPages = 3; self.myPageControl.currentPage = 0; [self.view addSubview:self.myPageControl];  //启动定时器 self.rotateTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(changeView) userInfo:nil repeats:YES]; //为滚动视图指定代理 rotateScrollView.delegate = self;} #pragma mark -- 滚动视图的代理方法//开始拖拽的代理方法，在此方法中暂停定时器。-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{ NSLog(@"正在拖拽视图，所以需要将自动播放暂停掉"); //setFireDate：设置定时器在什么时间启动 //[NSDate distantFuture]:将来的某一时刻 [self.rotateTimer setFireDate:[NSDate distantFuture]];} //视图静止时（没有人在拖拽），开启定时器，让自动轮播- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{ //视图静止之后，过1.5秒在开启定时器 //[NSDate dateWithTimeInterval:1.5 sinceDate:[NSDate date]] 返回值为从现在时刻开始 再过1.5秒的时刻。 NSLog(@"开启定时器"); [self.rotateTimer setFireDate:[NSDate dateWithTimeInterval:1.5 sinceDate:[NSDate date]]];}  //定时器的回调方法 切换界面- (void)changeView{ //得到scrollView UIScrollView *scrollView = [self.view viewWithTag:1000]; //通过改变contentOffset来切换滚动视图的子界面 float offset_X = scrollView.contentOffset.x; //每次切换一个屏幕 offset_X += CGRectGetWidth(self.view.frame);  //说明要从最右边的多余视图开始滚动了，最右边的多余视图实际上就是第一个视图。所以偏移量需要更改为第一个视图的偏移量。 if (offset_X > CGRectGetWidth(self.view.frame)*3) { scrollView.contentOffset = CGPointMake(0, 0);  } //说明正在显示的就是最右边的多余视图，最右边的多余视图实际上就是第一个视图。所以pageControl的小白点需要在第一个视图的位置。 if (offset_X == CGRectGetWidth(self.view.frame)*3) { self.myPageControl.currentPage = 0; }else{ self.myPageControl.currentPage = offset_X/CGRectGetWidth(self.view.frame); }  //得到最终的偏移量 CGPoint resultPoint = CGPointMake(offset_X, 0); //切换视图时带动画效果 //最右边的多余视图实际上就是第一个视图，现在是要从第一个视图向第二个视图偏移，所以偏移量为一个屏幕宽度 if (offset_X >CGRectGetWidth(self.view.frame)*3) { self.myPageControl.currentPage = 1; [scrollView setContentOffset:CGPointMake(CGRectGetWidth(self.view.frame), 0) animated:YES]; }else{ [scrollView setContentOffset:resultPoint animated:YES]; } } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated.}  @end