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(0, 0, WIDTH, HEIGHT)];
    self.myScrollView.backgroundColor=[UIColor colorWithRed:0.315 green:0.843 blue:0.892 alpha:1.000];
    self.myScrollView.contentSize=CGSizeMake(3*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(120, 40);
    self.myPageControl.frame=CGRectMake((WIDTH-PageSize.width)/2, HEIGHT-PageSize.height-40, PageSize.width, PageSize.height);
    self.myPageControl.backgroundColor=[UIColor clearColor];

    // 设置当前页
    self.myPageControl.currentPage=0;
    // 分页
    self.myPageControl.numberOfPages=4;

    [self.view addSubview:self.myPageControl];

    //  初始化储存图片的集合
    self.imageArray=[NSMutableArray arrayWithCapacity:1];
    for (int i=1; i<5; 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=0;

    [self reloadImage];

}

-(void)reloadImage
{
    // 第一种情况, 第一页
    if (self.currentPage==0) {
        self.firstimage.image=[self.imageArray lastObject];
        self.secondimage.image=[self.imageArray objectAtIndex:self.currentPage];
        self.thirimage.image=[self.imageArray objectAtIndex:self.currentPage+1];

    }

    // 第二种情况,最后一页
    else if (self.currentPage==self.imageArray.count-1){
        self.firstimage.image=[self.imageArray objectAtIndex:self.currentPage-1];
        self.secondimage.image=[self.imageArray objectAtIndex:self.currentPage];
        self.thirimage.image=[self.imageArray objectAtIndex:0];

    }

    // 第三种情况  中间页
    else{
        self.firstimage.image=[self.imageArray objectAtIndex:self.currentPage-1];
        self.secondimage.image=[self.imageArray objectAtIndex:self.currentPage];
        self.thirimage.image=[self.imageArray objectAtIndex:self.currentPage+1];
    }

    self.firstimage.frame=CGRectMake(0, 0, WIDTH, HEIGHT);
    self.secondimage.frame=CGRectMake(WIDTH, 0, WIDTH, HEIGHT);
    self.thirimage.frame=CGRectMake(WIDTH*2, 0, WIDTH, HEIGHT);

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

    self.myScrollView.contentOffset=CGPointMake(WIDTH, 0);
}

#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<0||x==0) {
        if (self.currentPage==0) {
            self.currentPage=(int)self.imageArray.count-1;
        }else{
            self.currentPage--;
        }
    }

    // 向右
    if (x>2*WIDTH||x==2*WIDTH) {
        if (self.currentPage==(int)self.imageArray.count-1) {
            self.currentPage=0;
        }else{
            self.currentPage++;
        }
    }

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