iOS— UIScrollView和 UIPageControl之间的那些事

本代码主要实现在固定的位置滑动图片可以切换。

目录图如下：

ViewController.h

#import <UIKit/UIKit.h>
// 通过宏定义定义宽和高
#define WIDTH self.view.frame.size.width
#define HEIGHT self.view.frame.size.height

@interface ViewController : UIViewController<UIScrollViewDelegate>

@property(strong,nonatomic) UIScrollView *myScrollView;
@property(strong,nonatomic) UIPageControl *myPageControl;
// 储存图片的集合
@property(strong,nonatomic)NSMutableArray *imageArray;

// 储存照片
@property(strong,nonatomic)UIImageView *firstimage;
@property(strong,nonatomic) UIImageView *secondimage;
@property(strong,nonatomic) UIImageView *thirimage;
// 当前页码
@property(assign,nonatomic)int currentPage;

@end

ViewController.m

 #import "ViewController.h"

 @interface ViewController ()

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];
     self.myScrollView=[[UIScrollView alloc] initWithFrame:CGRectMake(, , WIDTH, HEIGHT)];
     self.myScrollView.backgroundColor=[UIColor colorWithRed:0.315 green:0.843 blue:0.892 alpha:1.000];
     self.myScrollView.contentSize=CGSizeMake(*WIDTH, HEIGHT);
     // 设置分页
     self.myScrollView.pagingEnabled=YES;
     //  隐藏滚动条
     self.myScrollView.showsHorizontalScrollIndicator=NO;
     // 锁定滚动方向
     self.myScrollView.directionalLockEnabled=YES;
     // 引用代理
     self.myScrollView.delegate=self;

     [self.view addSubview:self.myScrollView];

     self.myPageControl=[[UIPageControl alloc] init];
     CGSize PageSize=CGSizeMake(, );
     self.myPageControl.frame=CGRectMake((WIDTH-PageSize.width)/, HEIGHT-PageSize.height-, PageSize.width, PageSize.height);
     self.myPageControl.backgroundColor=[UIColor clearColor];

     // 设置当前页
     self.myPageControl.currentPage=;
     // 分页
     self.myPageControl.numberOfPages=;

     [self.view addSubview:self.myPageControl];

     //  初始化储存图片的集合
     self.imageArray=[NSMutableArray arrayWithCapacity:];
     for (int i=; i<; i++) {
         UIImage *image=[UIImage imageNamed:[NSString stringWithFormat:@"%d",i]];
         [self.imageArray addObject:image];
     }

     self.firstimage =[[UIImageView alloc] init];
     self.secondimage=[[UIImageView alloc] init];
     self.thirimage =[[UIImageView alloc] init];
     //  当前页码
     self.currentPage=;

     [self reloadImage];

 }

 -(void)reloadImage
 {
     // 第一种情况, 第一页
     if (self.currentPage==) {
         self.firstimage.image=[self.imageArray lastObject];
         self.secondimage.image=[self.imageArray objectAtIndex:self.currentPage];
         self.thirimage.image=[self.imageArray objectAtIndex:self.currentPage+];

     }

     // 第二种情况,最后一页
     else if (self.currentPage==self.imageArray.count-){
         self.firstimage.image=[self.imageArray objectAtIndex:self.currentPage-];
         self.secondimage.image=[self.imageArray objectAtIndex:self.currentPage];
         self.thirimage.image=[self.imageArray objectAtIndex:];

     }

     // 第三种情况  中间页
     else{
         self.firstimage.image=[self.imageArray objectAtIndex:self.currentPage-];
         self.secondimage.image=[self.imageArray objectAtIndex:self.currentPage];
         self.thirimage.image=[self.imageArray objectAtIndex:self.currentPage+];
     }

     self.firstimage.frame=CGRectMake(, , WIDTH, HEIGHT);
     self.secondimage.frame=CGRectMake(WIDTH, , WIDTH, HEIGHT);
     self.thirimage.frame=CGRectMake(WIDTH*, , WIDTH, HEIGHT);

     [self.myScrollView addSubview:self.firstimage];
     [self.myScrollView addSubview:self.secondimage];
     [self.myScrollView addSubview:self.thirimage];

     self.myScrollView.contentOffset=CGPointMake(WIDTH, );
 }

 #pragma mark   scrollView  Delegate
 //在滚动结束状态转换
 -(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
 {
     float x=self.myScrollView.contentOffset.x;

     // 向左
     if (x<||x==) {
         if (self.currentPage==) {
             self.currentPage=(int)self.imageArray.count-;
         }else{
             self.currentPage--;
         }
     }

     // 向右
     if (x>*WIDTH||x==*WIDTH) {
         if (self.currentPage==(int)self.imageArray.count-) {
             self.currentPage=;
         }else{
             self.currentPage++;
         }
     }

     self.myPageControl.currentPage=self.currentPage;
     [self reloadImage];
 }