需要实现的效果:
当点击一张图片时,可以扩大到整个屏幕.再次点击时缩小到原来的大小
实现思路:
1.封装一个继承UIImageView的类,再定义一个imageview和scrollview的属性
2.再初始化方法中调用创建子视图的方法(记得给UIImageView打开用户交互),初始化scrollview和Imageview,并且把scrollview添加到self.window上,Imageview添加到scrollview上
3.给self和属性Imagevie 添加手势,两个手势方法控制图片的缩小和放大,图片放大是将scrollview的frame给属性imageview并隐藏self;图片缩小是将self的frame给属性image view并把self的hidden值设置为NO,scrollview也从父视图中移除,当点击self时可实现放大图片,当点击Imageview可实现还原图片.
代码实现:

#import <UIKit/UIKit.h>

@interface ZoomImgView : UIImageView
@property(nonatomic,strong)UIScrollView *scrollView;
@property(nonatomic,strong)UIImageView *imgView;
@end

#import "ZoomImgView.h"

@implementation ZoomImgView

-(instancetype)initWithFrame:(CGRect)frame{
    
    if ([super initWithFrame:frame]) {
        [self _inteTap];
    }
    return self;
}

- (void)_inteTap{
    self.userInteractionEnabled = YES;
    
    //添加手势
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapBig)];
    
    [self addGestureRecognizer:tap];
}

- (void)tapBig{
    //弹出来的视图
    [self creactSubView];
    //放大的动画
    [UIView animateWithDuration:.3 animations:^{
       
        _imgView.frame = _scrollView.frame;
        _scrollView.backgroundColor = [UIColor blackColor];
        self.hidden = YES;
    }];
}

- (void)creactSubView{
    _scrollView = [[UIScrollView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    _scrollView.showsHorizontalScrollIndicator = NO;
    _scrollView.showsVerticalScrollIndicator = NO;
    [self.window addSubview:_scrollView];
   CGRect frame = [self convertRect:self.bounds toView:self.window];
    _imgView = [[UIImageView alloc] initWithFrame:frame];
    
    _imgView.image = self.image;
    
    _imgView.userInteractionEnabled = YES;
    //添加手势
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(smallTap)];
    [_imgView addGestureRecognizer:tap];
    [_scrollView addSubview:_imgView];
    
}
- (void)smallTap{
    
    [UIView animateWithDuration:.3 animations:^{
       
        _imgView.frame = self.frame;
        
    } completion:^(BOOL finished) {
        self.hidden = NO;
        [_scrollView removeFromSuperview];
        
    }];
}
@end

#import "ViewController.h"
#import "ZoomImgView.h"
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    ZoomImgView *imgView = [[ZoomImgView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    imgView.image = [UIImage imageNamed:@"nn.png"];
    [self.view addSubview:imgView];
}
@end

![Uploading 图片放大_952149.gif . . .]