//项目源码 ：http://download.csdn.net/detail/xiaopeng5130301994/9590075
// ViewController.m
// UIScrollView循环滚动
//
// Created by xp on 16/7/29.
// Copyright © 2016年 xiaopeng. All rights reserved.
//
//项目源码 ：http://download.csdn.net/detail/xiaopeng5130301994/9590075
#import "ViewController.h"
NSInteger totalImage = 6;
@interface ViewController (){
}
@property (nonatomic,strong,readwrite)UIScrollView *scrollView;
@property (nonatomic,strong,readwrite)UIPageControl *pageControll;
@property (nonatomic,strong,readwrite)NSMutableArray *imageNameList;
@property (nonatomic,assign,readwrite)NSInteger currentIndex;
//初始化三个UIImageView
@property (nonatomic,strong,readwrite)UIImageView *leftImageView;
@property (nonatomic,strong,readwrite)UIImageView *currentImageView;
@property (nonatomic,strong,readwrite)UIImageView *rightImageView;
@property (nonatomic,strong,readwrite)NSTimer *timer;
//@property (nonatomic,strong,readwrite)NSMutableArray *
//初始化数据源
-(void)initializeDataSource;
//初始化用户界面
-(void)initializeUserInterface;
//初始化图片数据
-(void)initImages;
//当scrollViewDidScroll触发时，时刻更新UI,此函数是实现循环的关键
-(void)updateUI;
//Timer事件处理
-(void)processTimer;
@end
@implementation ViewController
- (void)viewDidLoad {
[superviewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[self initializeDataSource];
[self initializeUserInterface];
}
//初始化数据源
-(void)initializeDataSource{
_currentIndex =0;
_imageNameList = [[NSMutableArray alloc]init];
//初始化图片
for(NSInteger i=0;i<totalImage;i++){
NSString *imageName = [NSString stringWithFormat:@"%ld.png",i];
[_imageNameList addObject:imageName];
}
}
//初始化用户界面
-(void)initializeUserInterface{
[self.view setBackgroundColor:[UIColor whiteColor]];
CGFloat VIEW_WIDTH =CGRectGetWidth(self.view.bounds);
_scrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(0,20, VIEW_WIDTH, 260)];
[_scrollView setDelegate:self];
[_scrollView setBounces:NO];
[_scrollView setShowsHorizontalScrollIndicator:NO];
[_scrollView setContentSize:CGSizeMake(VIEW_WIDTH*3,260)];
[_scrollView setPagingEnabled:YES];
[_scrollView setContentOffset:CGPointMake(VIEW_WIDTH,0)];
[self.viewaddSubview:_scrollView];
//初始化三个UIImageView，并固定他们位于_scrollView中的位置
_leftImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0,0, VIEW_WIDTH, 260)];
//[_leftImageView setContentMode:UIViewContentModeScaleToFill];
_currentImageView = [[UIImageView alloc]initWithFrame:CGRectMake(VIEW_WIDTH,0, VIEW_WIDTH, 260)];
[_currentImageView setContentMode:UIViewContentModeScaleToFill];
_rightImageView = [[UIImageView alloc]initWithFrame:CGRectMake(VIEW_WIDTH*2,0, VIEW_WIDTH, 260)];
[_rightImageView setContentMode:UIViewContentModeScaleToFill];
//用UIImage的图像来初始化三个ImageView;
[selfinitImages];
[_scrollView addSubview:_leftImageView];
[_scrollView addSubview:_currentImageView];
[_scrollView addSubview:_rightImageView];
//初始化_pageControll
_pageControll = [[UIPageControl alloc]initWithFrame:CGRectMake(0,260, VIEW_WIDTH, 30)];
[_pageControll setNumberOfPages:totalImage];
[_pageControll setCurrentPage:_currentIndex];
[_pageControll setEnabled:NO];
[_pageControll setCurrentPageIndicatorTintColor:[UIColor blackColor]];
[_pageControll setPageIndicatorTintColor:[UIColor grayColor]];
[self.viewaddSubview:_pageControll];
//实例化_timer;
_timer = [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(processTimer) userInfo:nil repeats:YES];
}
-(void)initImages{
//根据当前的_currentIndex（当前需要显示的索引）来初始化三个ImageView对应的图片
[_leftImageView setImage:[UIImage imageNamed:_imageNameList[(_currentIndex-1+totalImage)%totalImage]]];
[_currentImageView setImage:[UIImage imageNamed:_imageNameList[_currentIndex]]];
[_rightImageView setImage:[UIImage imageNamed:_imageNameList[(_currentIndex+1)%totalImage]]];
}
-(void)updateUI{//核心函数
CGFloat VIEW_WIDTH =CGRectGetWidth(self.view.bounds);
CGFloat Offset_x =_scrollView.contentOffset.x;
//判断是否需要更新界面
BOOL isUpdate =NO;
if(Offset_x==2*VIEW_WIDTH){
isUpdate = YES;
_currentIndex = (_currentIndex+1)%totalImage;
}
else if(Offset_x==0){
isUpdate = YES;
_currentIndex = (_currentIndex-1+totalImage)%totalImage;
}
//仅仅前面的if和else if便能够实现完整的循环滚动
//后面这两个else if和最后的else实现的功能是：当你页面划过一半时，_pageControll的当前页就立马换到上一页或者下一页，就不需要等滑动完才看到_pageControll更新。
else if (Offset_x<=0.5*VIEW_WIDTH){
//_pageControll更新到上一页
[_pageControll setCurrentPage:(_currentIndex-1+totalImage)%totalImage];
}
else if (Offset_x>=1.5*VIEW_WIDTH){
//_pageControll更新到下一页
[_pageControll setCurrentPage:(_currentIndex+1)%totalImage];
}
//页面滑动未达到一半时，需要将_pageControll设置为当前索引页。有人可能会觉得设置为当前页是一个多余的操作，因为他们会想，页面都没划过一半，说明_pageControll就没改变过，为什么还要设置为当前页呢。原因是：当一个人将页面划过一半后，并未松手，他又划回低于一半页面时松手。这时，上面的两个else if()当中的一个将会触发，从而引起_pageControll当前页发生改变，所以我们需要做一个[_pageControll setCurrentPage:_currentIndex]来恢复当前的_pageControll显示页，这样做就能防止页面划过一半后又划回的操作。
//又介于以下两个操作执行代码均相同，并且恰好是所有剩余的情况，所以我将其合并在else中执行。
//为了理解，我也将以下else if()代码贴出并注释掉
/*
else if (Offset_x>0.5*VIEW_WIDTH&&Offset_x<VIEW_WIDTH){
[_pageControll setCurrentPage:_currentIndex];
}
else if (Offset_x>VIEW_WIDTH&&Offset_x<1.5*VIEW_WIDTH){
[_pageControll setCurrentPage:_currentIndex];
}
*/
else{
[_pageControll setCurrentPage:_currentIndex];
}
if(!isUpdate){
return;
}
[self initImages];
[_scrollView setContentOffset:CGPointMake(VIEW_WIDTH,0)];
[_pageControll setCurrentPage:_currentIndex];
}
-(void)processTimer{
[_scrollView setContentOffset:CGPointMake(2*CGRectGetWidth(self.view.bounds),0)animated:YES];
}
//实现代理方法
-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
[self updateUI];
}
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
[_timer setFireDate:[NSDate distantFuture]];
}
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
[_timer setFireDate:[NSDate dateWithTimeIntervalSinceNow:2]];
}
@end