ViewController.m文件

import "ViewController.h"

@interface ViewController () <UIScrollViewDelegate>

@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;

@property (nonatomic, weak) UIImageView *imageView;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // 1.创建UIImageView
    UIImage *image = [UIImage imageNamed:@"minion"];
    UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
    [self.scrollView addSubview:imageView];
    self.imageView = imageView;

    // 2.设置contenSize
    self.scrollView.contentSize = image.size;
    self.scrollview.delegate = self;

    // 3.设置缩放比例
    self.scrollView.maximumZoomScale = 2.0;
    self.scrollView.minimumZoomScale = 0.5;
}

#pragma mark - UIScrollViewDelegate
/**
 *  返回需要缩放的子控件(scrollView的子控件)
 */
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return self.imageView;
}

- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
    NSLog(@"scrollViewDidZoom");
}
@end