思路：三张图片无限循环，实时更新位置即可，代码如下：
#import <UIKit/UIKit.h>
typedef enum : NSUInteger {
// 不 自 动 循 环(即不开启定时器)
ZJLoopScrollDirectionNone,
// 从 右 往 左
ZJLoopScrollDirectionRightToLeft,
// 从 左 往 右
ZJLoopScrollDirectionLeftToRight,
} ZJLoopScrollDirection;
@class ZJLoopScrollView;
@protocol ZJLoopScrollViewDelegate <NSObject>
-(void)scrollView:(ZJLoopScrollView*)scrollView didSelectSubviewAtIndex:(NSInteger)index;
@end
/** 图片无限循环*/
@interface ZJLoopScrollView : UIView
@property(nonatomic,weak) id<ZJLoopScrollViewDelegate> delegate;
/** 展示图片
* @param imageStrs 可以是本地图片名称也可是网络图片地址
* @param direction 循环方向*/
- (void)showImagesWithImageStrs:(NSArray<NSString*>*)imageStrs scrollDirection:(ZJLoopScrollDirection)direction;
- (void)showDefaultCurrentIndex:(NSInteger)currentIndex;
- (void)didSelectSubviewAtIndex:(void(^)(NSInteger index))block;
@end
#import "ZJLoopScrollView.h"
@interface ZJLoopScrollView ()<UIScrollViewDelegate>
@property(nonatomic,strong) NSMutableArray <NSString*>* imageStrs;
@property(nonatomic,assign) NSInteger currentIndex;
@property(nonatomic,weak) UIScrollView * scrollview;
@property(nonatomic,weak) UIImageView * leftImgView;
@property(nonatomic,weak) UIImageView * centerImgView;
@property(nonatomic,weak) UIImageView * rightImgView;
@property(nonatomic,strong) dispatch_source_t timer;;
@property(nonatomic,assign) ZJLoopScrollDirection direction;
@property(nonatomic,copy) void(^didSelectSubviewAtIndexBlock)(NSInteger index);
@end
@implementation ZJLoopScrollView
- (instancetype)initWithFrame:(CGRect)frame{
self = [super initWithFrame:frame];
if (self) {
[self setSubViews];
}
return self;
}
-(void)setSubViews{
CGRect subframe = CGRectMake(0, 0, CGRectGetWidth([self frame]), CGRectGetHeight([self frame]));
UIScrollView * scroll = [[UIScrollView alloc] initWithFrame:subframe];
[scroll setBounces:true];
[scroll setPagingEnabled:true];
[scroll setShowsVerticalScrollIndicator:false];
[scroll setShowsHorizontalScrollIndicator:false];
[self addSubview:scroll];
[self setScrollview:scroll];
for(int i=0;i<3;i++){
CGRect subframe = CGRectMake(CGRectGetWidth([scroll frame])*i, 0, CGRectGetWidth([scroll frame]), CGRectGetHeight([scroll frame]));
UIImageView * subview01 = [[UIImageView alloc] initWithFrame:subframe];
[subview01 setContentMode:UIViewContentModeScaleAspectFit];
//[subview01 setBackgroundColor:[UIColor redColor]];
[scroll addSubview:subview01];
if(i==0){[self setLeftImgView:subview01];}
if(i==1){[self setCenterImgView:subview01];}
if(i==2){[self setRightImgView:subview01];}
}
UITapGestureRecognizer * tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapClick)];
[self addGestureRecognizer:tap];
}
-(void)tapClick{
if([self delegate] && [[self delegate] respondsToSelector:@selector(scrollView:didSelectSubviewAtIndex:)]){
[[self delegate] scrollView:self didSelectSubviewAtIndex:[self currentIndex]];
}
if([self didSelectSubviewAtIndexBlock]){
self.didSelectSubviewAtIndexBlock([self currentIndex]);
}
}
-(void)refreshScrollImagesLayoutWithImageStrs:(NSArray*)imageStrs{
[self setImageStrs:[NSMutableArray arrayWithArray:imageStrs]];
[self setCurrentIndex:0];
if([imageStrs count]==0){
[[self scrollview] setDelegate:nil];
}else if([imageStrs count] ==1){
[[self scrollview] setDelegate:nil];
}else{
[[self scrollview] setDelegate:self];
[[self scrollview] setContentSize:CGSizeMake(CGRectGetWidth([self frame])*3, 0)];
[[self scrollview] setContentOffset:CGPointMake(CGRectGetWidth([self frame]), 0)];
}
}
/*************************************************************/
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
[self refrshScrollImageViewAndCurrentIndex];
}
-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView{
[self refrshScrollImageViewAndCurrentIndex];
}
//开始拖动的时候调用
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
[self cancelTimer];
}
//结束拖动时调用
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
[self openTimer];
}
-(void)refrshScrollImageViewAndCurrentIndex{
// 计算索引
CGFloat offetIndex = [[self scrollview] contentOffset].x/CGRectGetWidth([[self scrollview] frame]);
if(offetIndex == 1){return;}
if(offetIndex>1){// 右往左滑+1
[self setCurrentIndex:[self currentIndex]+1];
if([self currentIndex]>=[[self imageStrs] count]){
// 确保索引范围
[self setCurrentIndex:0];
}
}else if(offetIndex<1){// 左往右滑-1
[self setCurrentIndex:[self currentIndex]-1];
if([self currentIndex] <= -1){
// 确保索引范围
[self setCurrentIndex:[[self imageStrs] count]-1];
}
}
// 更新UIImage
[self handleLeftImageViewWithIndex:[self currentIndex]-1];
[self handleCenterImageViewWithIndex:[self currentIndex]];
[self handleRightImageViewWithIndex:[self currentIndex]+1];
// 保证中心位置
[[self scrollview] setContentOffset:CGPointMake(CGRectGetWidth([[self scrollview] frame]), 0)];
}
-(void)handleLeftImageViewWithIndex:(NSInteger)index{
if(index<= -1){
[self imageView:[self leftImgView] imageString:[[self imageStrs] lastObject]];
}else if(index<=[[self imageStrs] count]-1){
[self imageView:[self leftImgView] imageString:[[self imageStrs] objectAtIndex:index]];
}
}
-(void)handleCenterImageViewWithIndex:(NSInteger)index{
if(index<[[self imageStrs] count]){
[self imageView:[self centerImgView] imageString:[[self imageStrs] objectAtIndex:index]];
}
}
-(void)handleRightImageViewWithIndex:(NSInteger)index{
if(index>=[[self imageStrs] count]){
[self imageView:[self rightImgView] imageString:[[self imageStrs] firstObject]];
}else if(index>=0){
[self imageView:[self rightImgView] imageString:[[self imageStrs] objectAtIndex:index]];
}
}
-(void)imageView:(UIImageView*)imgView imageString:(NSString*)string{
if([UIImage imageNamed:string]){ // 本地图片名称
[imgView setImage:[UIImage imageNamed:string]];
}else if([UIImage imageWithContentsOfFile:string]){// 本地图片路径
[imgView setImage:[UIImage imageWithContentsOfFile:string]];
}else{ // 网络图片
}
}
-(void)openTimer{
if(self.timer != nil){return;}
NSTimeInterval time = 1;
// 获得队列
dispatch_queue_t queue = dispatch_get_main_queue();
// 创建一个定时器(dispatch_source_t本质还是个OC对象)
self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
// 何时开始执行第一个任务
dispatch_time_t start = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(time * NSEC_PER_SEC));
uint64_t interval = (uint64_t)(time * NSEC_PER_SEC);
dispatch_source_set_timer(self.timer, start, interval, 0);
// 设置回调
__weak typeof(self) weakSelf = self;
dispatch_source_set_event_handler(self.timer, ^{
if([weakSelf direction] == ZJLoopScrollDirectionLeftToRight){
CGPoint offset = [[weakSelf scrollview] contentOffset];
offset.x -= CGRectGetWidth([[weakSelf scrollview] frame]);
[[weakSelf scrollview] setContentOffset:offset animated:true];
}else if([weakSelf direction] == ZJLoopScrollDirectionRightToLeft){
CGPoint offset = [[weakSelf scrollview] contentOffset];
offset.x += CGRectGetWidth([[weakSelf scrollview] frame]);
[[weakSelf scrollview] setContentOffset:offset animated:true];
}else{
[weakSelf cancelTimer];
}
});
// 启动定时器
dispatch_resume(self.timer);
}
/** 销毁定时器*/
-(void)cancelTimer{
if(self.timer){
dispatch_cancel(self.timer);
self.timer = nil;
}
}
-(void)dealloc{
[self cancelTimer];
}
#pragma mark * * * * * * * * * * * * * * * * * * * * * * * * * * *
- (void)showImagesWithImageStrs:(NSArray<NSString*>*)imageStrs scrollDirection:(ZJLoopScrollDirection)direction{
[self refreshScrollImagesLayoutWithImageStrs:imageStrs];
[self showDefaultCurrentIndex:0];
if(direction != ZJLoopScrollDirectionNone){
[self setDirection:direction];
[self openTimer];
}else{
[self cancelTimer];
}
}
- (void)showDefaultCurrentIndex:(NSInteger)currentIndex{
[self setCurrentIndex:currentIndex];
// 更新UIImage
[self handleLeftImageViewWithIndex:[self currentIndex]-1];
[self handleCenterImageViewWithIndex:[self currentIndex]];
[self handleRightImageViewWithIndex:[self currentIndex]+1];
}
- (void)didSelectSubviewAtIndex:(void(^)(NSInteger index))block{
[self didSelectSubviewAtIndex:block];
}
@end