iOS使用UIScrollView实现无限循环轮播图

//
//  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